Dinh dng ngi

Bin tp bi:Nguyn Minh Thy

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Dinh dng ngi

Bin tp bi:Nguyn Minh Thy

Cc tc gi:unknown

Phin bn trc tuyn:http://voer.edu.vn/c/4c53c93b

http://voer.edu.vn/c/4c53c93b

MC LC

1. Dinh dng ngi - Mi quan h gia lng thc - Thc phm, Nng nghip v sckhe

1.1. nh ngha v dinh dng ngi1.2. Vi nt v s pht trin ca khoa hc Dinh dng1.3. Khi nim v cc cht dinh dng v thnh phn lng thc thc phm1.4. Mi quan h gia dinh dng, lng thc - thc phm, nng nghip v sc kho

2. Cu trc c th v nhu cu dinh dng2.1. Cu trc c th ngi2.2. Nhu cu dinh dng2.3. Nhu cu nng lng2.4. Hnh thi nng lng2.5. n v nng lng2.6. Nng lng thc phm2.7. Tiu hao nng lng2.8. Lng cung cp nng lng2.9. Cn bng nng lng2.10. D tr nng lng2.11. Cc bi ton v trao i vt cht2.12. An ninh thc phm

3. Protein3.1. M u3.2. Cu trc v tnh cht l ho hc c bn ca protein3.3. Thnh phn v hm lng protein trong cc nng sn phm chnh (ngun cung

cp protein trong thc phm)3.4. Vai tr v chc nng ca protein trong dinh dng3.5. Nhng thay i xy ra trong c th thiu protein3.6. Cc acid amin v vai tr dinh dng ca chng3.7. Nhng yu t nh hng n gi tr dinh dng ca protein3.8. Cc phng php xc nh gi tr dinh dng ca protein3.9. Nhu cu protein ca c th

4. Lipid4.1. M u4.2. Cu trc v cc tnh cht l ho c bn4.3. Vai tr ca lipid trong dinh dng ngi

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4.4. Cc acid bo4.5. Phosphatide4.6. Sterol v vitamin4.7. Gi tr dinh dng ca cht bo4.8. Hp thu v ng ho cht bo4.9. Nhu cu cht bo

5. Carbohydrate5.1. M u5.2. Vai tr sinh l ca carbohydrate5.3. Carbohydrate tinh ch v carbohydrate bo v5.4. Cc carbohydrate n gin5.5. Polysaccharide5.6. Ngun carbohydrate trong thc n5.7. Tiu ho v hp thu carbohydrate5.8. Nhu cu carbohydrate

6. Vitamin6.1. i cng6.2. Cc vitamin tan trong cht bo6.3. Cc vitamin tan trong nc

7. Cc cht khong7.1. Cc cht khong

8. Khi lun v dinh dng cn i8.1. Mi quan h tng h gia cc dinh dng trong c th8.2. Quan nim v tnh cn i ca khu phn8.3. Tiu chun dinh dng

9. Thc phm v nhu cu dinh dng cho cc i tng khc nhau9.1. Thc phm v nhu cu dinh dng cho cc i tng khc nhau

10. Cc bnh lin quan n dinh dng10.1. Cc bnh lin quan n dinh dng

Tham gia ng gp

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Dinh dng ngi - Mi quan h gia lngthc - Thc phm, Nng nghip v sc khenh ngha v dinh dng ngi

nh ngha v dinh dng ngi

Dinh dng l chc nng m cc c th s dng thc n duy tr s sng, ngha lthc hin cc hot ng sng nh: sinh trng, pht trin, vn ng. Khoa hc v dinhdng nghin cu mi quan h gia cc c th v thc n, ch n ung, sinh l nuidng, bin i bnh l... Thnh ng dinh dng v sc kho cng ng dng chmi quan h gia ch n ung v sc kho hoc bnh tt trong mt phm vi cngng dn s xc nh, vi mc ch u tranh chng cc bnh tt do n ung khng ngcch. Trong khi lun v dinh dng, mi lin quan gia dinh dng vi cc lnh vckhc c th hin:

Dinh dng vi sc kho

Dinh dng vi s sinh trng v pht trin

Dinh dng vi suy lo

Dinh dng vi min dch

Dinh dng vi u sinh

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Vi nt v s pht trin ca khoa hc Dinh dng

Vi nt v s pht trin ca khoa hc Dinh dng

Hypocrate-danh y thi c nu ln vai tr ca n ung trong vic bo v sc kho.Trong vic s dng n ung tr bnh, ng vit: thc n cho bnh nhn phi lmt phng tin iu tr v trong phng tin iu tr phi c cht dinh dng hochn ch v n thiu cht b rt nguy him i vi nhng ngi mc bnh mn tnh.

Sidengai-nh y hc ngi Anh cho rng nhm mc ch iu tr cng nh phngbnh, trong nhiu bnh ch cn cho n nhng khu phn n (diet) thch hp v sng mti sng c t chc hp l.

A.L. Lavoisier l ngi u tin trong nhng nm 1770-1777 chng minh thc n ivo c th v sc vt s b t chy, s dng O2, gii phng CO2 v sinh nhit.

Nm 1783 cng vi Laplace v Ramur chng minh trn thc nghim h hp l mtdng t chy trong c th v o lng c lng oxy tiu th v lng CO2 thi ra ngi khi lao ng, ngh ngi v sau khi n. Nghin cu ca ng t c s chovn tiu hao nng lng, gi tr sinh nng lng ca thc phm v cc nghin cu vchuyn ho.

Giai on th hai bt u t s pht hin cc thnh phn c bn ca thc phm, t chcv dch th. Cng trnh ca nh bc hc c J. Liebig vo gia th k XIX v pht trinbi Voit, Rubner, Atwater v ch ra rng thc n cha ba nhm cht hu c c bn:protein, carbohydrate, lipid v cc cht v c l tro.

Tip theo l thi k tm hiu vai tr ca m trong dinh dng pht trin v pht hins khc nhau v gi tr sinh hc ca chng.

Cui th k XIX v u th k XX, cng trnh ca nh bc hc Nga M. Lunin v nhiungi khc cho bit thm mt s yu t dinh dng m by gi cha bit: cc vitaminv pht hin ra hng lot cc vitamin.

T cui th k 19 ti nay, nhng cng trnh nghin cu v vai tr ca cc axt amin ccvitamin, cc acid bo khng no, cc vi lng dinh dng phm vi t bo, t chc vton c th gp phn hnh thnh, pht trin v a ngnh dinh dng ln thnh mtmn hc. Cng vi nhng nghin cu v bnh suy dinh dng protein nng lng canhiu tc gi nh Gomez (1956), Jelliffe (1959), Welcome (1970), Waterlow (1973).Nhng nghin cu v thiu vi cht nh thiu vitamin A v bnh kh mt (Bitot 1863,M. Collum 1913, Block 1920), thiu mu thiu st, thiu km. Ngoi ra cng c nhiunghin cu gii thch mi quan h nhn qu v cc chng trnh can thip cng ng.

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Ngy nay bit khong 60 cht dinh dng m c th ngi c th s dng c,trong c khong 40 cht c th cn thit tuyt i: 8-10 acid amin, 1-2 ng n,2-3 acid bo cha no, hn 13 nguyn t khong v hn 15 sinh t, v cng c tngi y c s khoa hc cho sn xut, bo qun, ch bin, dinh dng tp th v titch.

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Khi nim v cc cht dinh dng v thnh phn lngthc thc phm

Protein

Nm 1816, Magendie chng minh cc thc phm cha nit cn thit cho s sng-albumin. Nm 1838 nh ho hc H Lan Mulden gi albumin l protein.

Nm 1839 s cn bng nit c Boussingault thc hin Php v ng nhn thy ccloi ng vt khng th s dng trc tip dng nit v c hoc nit khng kh m phin cc thc n cha cc hp cht c nit ca thc vt v ng vt duy tr s sng.

Sau mi n th k 20, bng nhiu cng trnh nghin cu khc nhau ngi ta mipht hin ra protein ca c th khng ch khc nhau v thnh phn, trnh t cc acidamin m cn khc nhau c v cu trc. Cng chnh v vy m n hon thnh cc chcnng c th cho tng loi c th.

Trong tt c cc t bo ng thc vt, s phn chia bt u t nhn, nhn li c tothnh t hai hp cht c lin quan mt thit vi nhau l protein v acid nucleic. Chnh vth m cc qu trnh sng khng th c c nu khng c protein. Ni c th qu trnhdinh dng khng th tin hnh c nu khng c protein hoc thiu vng mt trongcc acid amin khng thay th.

Bnh thiu protein c ngi Php pht hin t nm 1929, gi tn l bouffissuredAnnam, ngi Anh pht hin Chu Phi nm 1932 gi l kwashiorkor. Sau nhngbnh suy dinh dng do thiu protein hoc cc acid amin khng thay th c pht hinvo nm 1959, Jelliffe gi bnh suy dinh dng nng lng, protein hay protein-energy-malnutrition (PEM). y l loi bnh cn tng i nhiu cc nc ang phttrin.

Lipid

S xc nh hai cu t c bn c trong lipid l glycerin v acid bo l do cng caChevreul, ngi Php vo nm 1828. Nm 1845, Boussingault chng minh crng, trong c th carbohydrate c th chuyn thnh lipid. V gi tr dinh dng trongc th ngi:

Cht bo l ngun giu nng lng nht so vi cc hp cht khc nh protein,carbohydrate.

Cht bo tham gia vo thnh phn nguyn sinh cht t bo

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Bo v cho cc c quan khi b chn ng v bo v cho c th khi b lnh

Cht bo cn l dung mi ho tan rt tt cc vitamin tan trong cht bo.

Ngy nay vai tr ca cht bo trong dinh dng ngi c c bit quan tm khi cnhng nghin cu ch ra mi quan lin quan gia s lng v cht lng ca cht botrong khu phn vi bnh tim mch.

Carbohydrate

L cht dinh dng ch yu trong khu phn n ngi Vit Nam. Trong c thcarbohydrate v cc dn xut ca chng hon thnh cc nhim v sau:

Carbohydrate l ngun nng lng cho mi hot ng sng

Carbohydrate cn thit cho s oxy ho bnh thng cc cht bo v protein. Khi thiucarbohydrate th s oxy ho cc cht trn khng th tin hnh n cng.

Carbohydrate l ngun dinh dng d tr, ng thi tham gia vo cu to cc proteinphc tp, mt s enzyme v hooc mon.

Carbohydrate cn ng vai tr bo v c th khi b nhim trng, khi b cc c tthm nhp, n tham gia vo qu trnh th thai v qu trnh phc hi v iu ho phnng enzyme.

Cht khong

Nm 1713 ngi ta pht hin Fe trong mu, nm 1812 phn lp c iode tyrosineca tuyn gip trng. Tuy nhin vo sau na th k XIX, cc nh chn nui mi chngminh c s cn thit ca cht khong trong khu phn, c bit l khi c ch caton b qu trnh trao i cht trong c th ngi c lm sng t th ngi ta cngchng minh cc c th ca cc ion calci, phosphor, magne, ng, coban, km.. trongmi khu cng nh trong ton b qu trnh chuyn ho ca c th. Cc bnh thiu mudinh dng hoc thiu iode cn kh ph bin cc nc ang pht trin ngy nay cngkhng nh vai tr thit yu ca cht khong trong dinh dng ngi.

Vitamin

Nu nh Lind (1753) l ngi u tin pht hin v vai tr ca thc n i vi bnh ttc lin quan vi vitamin (tc dng ca nc chanh i vi bnh hoi huyt) th NicolaiIvanovich Lunin l ngi sng lp ra hc thuyt vitamin. Tip cc cng trnh caHopkin, Eijkman u chng minh vai tr thit yu ca vitamin trong vic chng limt s bnh tt, c bit l vic tch vitamin B1 t cm go ca Funk.

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Cho n nay ngi ta pht hin khong 30 cht thuc vo nhm vitamin nhng trongs ny ch c khong 20 cht c ngha trc tip i vi sc kho v dinh dng ngi.

Nc

Chim khong 55-75% trng lng c th. Nc s dng nh vt liu xy dng trongtt c cc t bo ca c th. M m cha khong 20% nc, c cha khong 75%, huyttng mu cha 90%. Nc trong c th c s dng nh:

Cc dung mi

Mt phn cht bi trn

Cht gy phn ng ho hc

Cht gy iu ho nhit c th

Cht duy tr hnh dng v cu trc c th

Nc phn b trong v gia t bo, trong cc c quan. Nc c a vo c th nhthc phm, ung v qua s trao i cht. N c thi ra khi c th bng nc tiu,phn, m hi v h hp ca phi.

Cht x

C nhiu trong thnh t bo thc vt, n c tc dng lm cho phn o thi nhanh rakhi c th, chng c cc bnh to bn, vim rut tha, tr.. Mt s cht x ho tanc tc dng lm tng chuyn ho cholesterol, trnh c bnh x va ng mch.

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Mi quan h gia dinh dng, lng thc - thc phm,nng nghip v sc kho

Mi quan h gia dinh dng, lng thc - thc phm, nng nghip v sckho

Qu trnh sinh ra, ln ln v tn ti ca mi ngi khng th tch ri s n ung hayl s dinh dng. S dinh dng c quyt nh bi ngun lng thc-thc phm docon ngi to ra. Ngun v nhng c tnh ca lng thc - thc phm do nn sn xutnng nghip chi phi. Tt c nhng iu trn lin quan mt thit ti sc kho ca mic nhn v ca c cng ng. Sc kho nh hng trc tip n ton b h thng snxut nng nghip, quyt nh s lng, cht lng ca nng sn phm lm ra. iu ni ln rng cc yu t dinh dng, lng thc-thc phm, nng nghip v sc kho clin quan hu c, gn b nhau trong mt h thng chung.

3 con ng chnh m thng qua n c chnh sch v chng trnh nng nghip nhhng n tnh trng dinh dng sc kho ca mi c nhn. l:

S tng thu nhp ca mi c nhn v h gia nh s dn n vic tng tiu dng thcphm. Gi c lng thc-thc phm n nh v c phn h thp khi nn nng nghippht trin v c cc chnh sch thch hp v ngc li.

nh hng ti sc kho v v sinh mi trng mc c nhn v cng ng, iu nyc th lm tng hoc gim bnh tt.

nh hng ti s phn b thi gian, c bit l ca cc b m, do c th lm tnghoc gim thi gian nui dng, chm sc tr.

Thc t dinh dng cho thy cn nm c nhu cu dinh dng t da vo khnng sn xut nng nghip, tp tc n ung ca a phng m tnh ra nhu cu thcphm. Cn c vo nhu cu thc phm t k hoch sn xut nng nghip cn i giaxut khu v nhp khu c li cho vic m bo cc nhu cu dinh dng.

C th biu th bng s Hnh 1.1 v Hnh 1.2 nh sau:

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Vng xoy trn c nguy him i vi tnh trng sn xut nng nghip km (Harper, 1984)

S biu th mi lin quan gia nng nghip, lng thc thc phm v dinh dng (FAO,1984)

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Cu trc c th v nhu cu dinh dngCu trc c th ngi

Khi qut

Con ngi t khi s sinh n lc trng thnh, cn nng ca c th tng ln n 20 ln. c s pht trin v trng lng nh vy, c th ly cc nguyn liu t thc n, ncung. Nhiu thc nghim chng minh ch n nh hng n cu trc c th. Cutrc ca c th thay i theo tng nhm tui (Bng 2.1) v gii tnh, gene v chng tc.Ngoi ra cc yu t nh dinh dng v tp luyn, lao ng th lc u c nh hng ticu trc c th.

Bng 2.1 nh hng ca qu trnh tng trng, trng thnh v mc bo ph nthnh phn ca c th v m khng cha cht bo (Garrow v cng s, 2000)

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Phng php xc nh cu trc c th

S dng cc s o cu trc c th xc nh v nh gi tnh trng dinh dng trthnh mt trong nhng phng php c p dng rng ri, c ngha thc tin caotrong nghin cu dinh dng v trong vic theo di sc kho. tr em, tng cn l mtbiu hin ca pht trin bnh thng v dinh dng hp l. ngi trng thnh qu25 tui cn nng thng duy tr mc n nh qu bo hay qu gy u khng c lii vi sc khe. Ngi ta thy rng tui th trung bnh ca ngi bo thp hn v t lmc cc bnh tim mch cao hn ngi bnh thng. C nhiu cng thc tnh tnh cnnng "nn c" hoc cc ch s tng ng. Ch s c s dng nhiu v c T chcY t th gii (1985) khuyn dng l ch s khi c th BMI (Body Mass Index):

BMI = WH2

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Trong :

W: Cn nng tnh theo kg

H: Chiu cao tnh theo mt

Theo khuyn ngh ca t chc Y t th gii: ch s BMI ngi bnh thng nn vokhong 18,5 24,99. C th thy s tng ng gia chiu cao v ch s BMI Hnh2.1.

Hnh 2.1 Bng xc nh BMI theo chiu cao v cn nng (http://btc.montana.edu)

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Nhu cu dinh dng

Nhu cu dinh dng

Nhu cu dinh dng va l nhu cu cp bch hng ngy ca i sng, va l nhu cuthing ling bo tn, nhu cu c bn m bo s pht trin bnh thng th lc v trlc ca con ngi, va m bo sc kho, kh nng hc tp sng to, sc lao ng snxut, s pht trin ca x hi. Nhu cu dinh dng gm hai phn: nhu cu nng lngv nhu cu cc cht dinh dng. xc nh nhu cu nng lng, theo t chc Y Tth gii, cn bit cc nhu cu cho chuyn ho c bn v cho cc hot ng th lc khctrong ngy.

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Nhu cu nng lng

Nhu cu nng lng

Nghin cu v nhu cu nng lng l mt ngnh ca khoa dinh dng nhm tm hiunh hng ca cc yu t khc nhau ti cng ca cc qu trnh chuyn ho vt chttrong cc iu kin sinh l.

C th ngi cn nng lng cung cp cho cc hot ng sau:

Cc qu trnh chuyn ho

Hot ng ca c

Gi cn bng nhit ca c th

Nng lng cho hot ng ca no, cc m thn kinh.

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Hnh thi nng lng

Hnh thi nng lng

Trong h thng sinh hc, c rt nhiu dng nng lng:

Nng lng bc x

Nng lng ho hc

Nng lng c hc

Nng lng in

Nng lng nhit

ng vt v thc vt khng loi tr kh nng tun theo nh lut th nht nhit nghc, rng nng lng khng th t sinh ra v mt i m n ch thay i gia cc dngkhc nhau. Tuy nhin khc vi ng vt, thc vt c th s dng ngun nng lngbc x tng hp cc phn t phc tp nh carbohydrate, protein, cht bo, trong khingun nng lng ca ng vt da ch yu vo ngun nng lng ho hc ca thc vtthng qua ngun thc phm (Hnh 2.2). Nng lng ho hc c s dng nh nnglng ca hot ng c (nh s co c), nng lng in (nh duy tr gradient ca ionqua mng) v nng lng ho hc (tng hp cc hp cht phn t lng ln). Tuy nhin,s chuyn ho nng lng thc phm khng phi l mt qu trnh hiu qu hon ton,khong 75% nng lng thc phm c th b hao ph nh l ngun nhit trong qu trnhchuyn ho. Nng lng sinh ra s l ngun duy tr nhit c th trong iu kin khhu thng thng, c bit nu c th c cch nhit tt bng y phc.

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n v nng lng

n v nng lng

n v nng lng theo h SI l joule (J), l nng lng c s dng khi 1 kilogram(kg) di chuyn qua mt metre (m) bng lc 1 Newton (N). Tuy nhin gi tr 1 joule lrt b khi th hin n v nng lng, do trong hu ht khi nim trong dinh dng,n v kJ (= 103 J) hoc MJ (= 106J) c s dng ph bin.

n v nng lng cn c th hin bng calorie, c xc dnh l nng lng cnthit a 1 g nc t 14,5oC tng ln 15,5oC. Trong ng dng thc t ca dinh dnghc, thng ly 1000 calo tc 1 kilo calo (Kcal) lm n v s dng ph bin. C thchuyn ho gia Kcal v kJ nh sau:

1 Kcal = 4,184 kJ; 1 kJ = 0,239 Kcal hay 4,2 kJ = 1 Kcal.

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Ngun nng lng t mt tri n con ngi (http://en.wikipedia.org/wiki)

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Nng lng thc phm

Nng lng thc phm

Nng lng ho hc ca thc phm c th xc nh bng bom calori (Hnh 2.3). Nnglng o c bng cch ny gi l nng lng th (Gross energy) ca thc phm, vn biu th tng nng lng ho hc ca thc phm.

Bom calorie (http://wps.prenhall.com)

Ngun nng lng ch yu cn cho c th c bt ngun t carbohydrate (ng),lipid (m) v protein (m), 3 cht dinh dng ny qua oxy ho trong c th u c thsn sinh ra nng lng, c gi chung l cht dinh dng sinh nhit hoc ngun nhit.Gi tr sinh nng lng ca thc phm lnng lng ho hc ca carbohydrate, lipid,protein v ru chuyn sang nhit khi b t chy. Lng nhit thi ra o bng bomcalorie.

Cc nh ng thc n c t trong khi hnh tr bng thp. Pha trn c dy in nh dng in chy qua. ng cht bom v cho oxy vo vi p sut cao. t bom vothng nc c thnh lm bng cht cch nhit tt. Khi ni dng in, thc phm bt la.Lng nhit thi ra o bng tng nhit ca nc trong thng. Khi t bom calorie:

1g carbohydrate cho 4,1 Kcal (16,74 kJ) glucose 3,9 Kcal

1g lipid cho 9,1 Kcal (37,66 kJ)

1g protein cho 5,65 Kcal (23,64 kJ)

1g ru ethylic cho 7,1 Kcal (gan s dng ru 100 mg/kg cn nng/gi)

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C 3 loi cht dinh dng sinh nhit qua oxy ho trong c th u sinh ra nng lng,v c 3 loi u c th chuyn hon c cho nhau trong qu trnh chuyn ho, nhngkhng th thay th nhau hon ton, trong cc ba n hp l cn phi c s phn b theomt t l tho ng. Tuy nhin khng phi hu ht nng lng ny hin hu trong cth ngi v hai l do:

S tiu ho khng hon ton (ngi kho mnh n hn hp hp thu khong 99%carbohydrate, 95% lipid v 92% protein).

Qu trnh t chy cc dinh dng khng hon ton (nht l m)

- Ur v cc sn phm cha nit khc ra theo ng nc tiu cha khong 1,25 Kcalcho 1g protein.

- Acid hu c, cc sn phm thoi ho carbohydrate v lipid (vi g/ngy).

Bng 2.2 cho bit nng lng thi ra ca cc cht dinh dng chnh c tnh ton biAtwater. Gi tr Kcal/g c gi l h s Atwater v tng i ng cho phn ln ccch n ung thng gp tr khi cha qu nhiu cht khng tiu ho

Bng 2.2 Nng lng chuyn ho ca cc cht dinh dng chnh (Southgate vDurnin, 1970)

Chtdinhdng

Nnglngth (kJ/g)

Phntrmhp thu

Nnglng tiuho(kJ/g)

Mt theonctiu(kJ/g)

Nng lngchuyn ho(kJ/g)

H sAtwater(Kcal/g)

Tinhbt 17,5 99 17,3 - 17,3 4

Glucose 15,6 99 15,4 - 15,4 4

Chtbo 39,1 95 37,1 - 37,1 9

Protein 22,9 92 21,1 5,2 15,9 4

Ru 29,8 100 29,8 Vt 29,8 7

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Ngun nng lng t mt tri n con ngi (http://en.wikipedia.org/wiki)

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Tiu hao nng lng

Chuyn ho c bn (CHCB)

CHCB l nng lng cn thit duy tr s sng con ngi trong iu kin nhn i,hon ton ngh ngi v nhit mi trng thch hp. chnh l nng lng ti thiu duy tr cc chc phn sinh l c bn nh: tun hon, h hp, hot ng cc tuyn nitit, duy tr thn nhit...

Cc yu t nh hng n CHCB:

Tnh trng h thng thn kinh trung ng

Cng hot ng cc h thng ni tit v men (chc phn mt s h thng ni titlm tng CHCB (tuyn gip trng), trong khi hot ng mt s tuyn ni tit khc lmgim CHCB (tuyn yn).

Tui v gii ( ph n thng thp hn nam gii 5 - 10%, CHCB ca tr em thng caohn ngi ln tui, tui cng nh CHCB cng cao. ngi ng tui v gi, CHCBthp dn).

Trong trng hp nhn i hay thiu n, CHCB gim. Tnh trng thiu n nng ko di,CHCB gim ti 50%.

Trong nhng trng hp cn thit, ngi ta o CHCB. n gin nht l cch tnh CHCBbng 1 Kcal cho 1 Kg cn nng trong mt gi. Tuy nhin CHCB cn ph thuc vonhiu yu t khc. Hp l hn l tnh ton CHCB theo tit din da. Tit din da phthuc chiu cao v cn nng c th tnh ton theo cng thc n gin sau:

S = 0,0087 (W + H) 0,26

Trong : S: tit din da (m2)

W: trng lng c th (kg)

H: chiu cao (cm)

Tit din da cn c tnh theo ton tnh din tch da (Hnh 2.3). T ton tnhdin tch da, c th tnh c chuyn ho c bn ca mt ngi theo Bng 2.3

Bng 2.3 Chuyn ho c bn tnh theo kcal/m2 din tch da/gi (Hong Tch Mnh vH Huy Khi, 1977)

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Ngoi ra ngi ta cn c th tnh CHCB theo nhiu phng php khc. Bng 2.4 biuth cch tnh chuyn ho c bn da vo cn nng.

Bng 2.4 Cng thc tnh CHCB da theo cn nng (H Huy Khi, 1996)

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Hnh 2.3. Ton tnh din tch da (Tver and Russell, 1989)

Hot ng th lc

Ngoi chuyn ho c bn ra, hot ng th lc l nhn t ch yu nht nh hng n stiu hao nng lng ca c th. Trong hot ng th lc, trng lng ca c th ngil mt loi ph ti. Hot ng ca c th i hi c bp v cc t chc khc sinh cng.Qu trnh ny, ngoi vic tiu hao c nng ra, t bo v cc c quan t chc c lin quankhi hp thnh nhiu cht mang nng lng nh protein, lipid, glycogen.. cng i hitiu hao nng lng. Hot ng c bp cng mnh v thi gian hot ng cng nhiu thnng lng tiu hao cng ln. Trnh quen vic ca lao ng chn tay cng nh hngn mc tiu hao nng lng. Phng php o chnh xc mc tiu hao nng lng ltng i phc tp, v ch c th dng vo nghin cu khoa hc. Phng php tngi n gin l dng phng php quan st sinh hot c biu th bng tiu hao nnglng cho cc hot ng th lc Bng 2.5.

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Bng 2.5 Tiu hao nng lng tnh theo Kcal/kg cn nng/gi ca ngi trng thnhkhi thc hin cc hot ng khc nhau v ngh ngi (Hong Tch Mnh v H Huy Khi,1977)

Loi lao ng Nng lng tiu hao ngoiCHCB (Kcal/kg/gi)Nng lng tiu hao gp cCHCB (Kcal/kg/gi)

Nm ngh ngi 0,10 1,10

Ngi yn 0,43 1,43

c to 0,50 1,50

ng thoi mi 0,50 1,50

May tay 0,50 1,50

Ng 0,57 1,57

ng nghim 0,63 1,63

an bng que an 0,66 1,66

Ht 0,74 1,74

n cm 0,84 1,84

May my 0,95 1,95

Nghe ging, ghibi 0,96 1,96

nh my chnhanh 1,00 2,00

i qun o (bn i2,5 kg) 1,06 2,06

Ra chn a 1,06 2,06

Qut nh (138ng tc/pht) 1,41 2,41

Bc ba ng gysch 1,43 2,43

Bi tp th dcnh 1,43 2,43

Khu giy 1,57 2,57

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Do chi thong th(4km/gi) 1,86 2,86

Rn luyn th lckh nng 3,14 4,14

Th mc, c kh 2,43 3,43

i kh nhanh (6km/gi) 3,28 4,28

Th 4,71 5,71

Lao ng nng 5,43 6,43

Cht cy 5,43 6,43

Bi 6,14 7,14

Chy (gn 8,5 km/gi) 7,14 8,14

Lao ng rt nng 7,57 8,57

o nng lng tiu hao

Phng php o nng lng trc tip

Phng php o nng lng trc tip gm qu trnh o lng nng lng tiu hao giaion nht nh bng cch o lng nhit mt i t c th ngi. V mt nguyn l, yl phng php o n gin, v s lng phng c thit k xy dng cho qu trnho cho con ngi phi c bo v trnh s mt nhit.

Dng c o ca Atwater c phng nh ngi c th lu trong vi ngy, c gingnm v xe p ti ch theo di cc ng tc lao ng. Thc n v cht thi ra qual nh. Thnh ngoi cch nhit tt, lng nhit do c th pht ra s do nc chy theocc ng chung quanh hp thu. Da vo nhit ca nc tng ln s tnh c lngnhit thi ra. Mt h thng lun chuyn khng kh khp kn m bo thong kh caphng. Khng kh trong phng i qua cc bnh cha nc cht hp ph CO2, sau O2 c tng cng duy tr n mc bnh thng. Nguyn l ca my o nyn gin nhng thit k v s dng rt kh khn v tn km v thc hnh. Nhc imca phng php o trc tip l ch c th thc hin trong vng vi gi hoc hn, dok thut gi nh rng khng c s tng hoc gim nhit ca c th ngi trong thigian o nng lng.

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Phng php o nng lng gin tip

Phng php ny da vo s oxy ho thc phm trong c th ngi, oxy c tiu thv CO2 c sinh ra. iu ny c th hin t phng trnh ho hc lng php dint s oxy ho 1 mol glucose:

C6H12O6 + 6 O2 6 CO2 + 6 H2O + nhit

(180 g) (6 x 22,4 l) (6 x 22,4 l) (6 x 18 g) (2,78 MJ)

Nng lng to ra t s oxy ho 1 g glucose l 15,4 kJ (2780/180) v do mi lt oxytiu th tng ng vi lng nhit sinh ra l 20,7 kJ (2780/6 x 22,4). V vy nu slng oxygen tiu th c th c o lng th c th tnh ton c lng nhit sinhra. Cc phng trnh tng t c th c vit cho qu trnh oxy ho protein, cht bov alcohol, c biu din Bng 2.6, cho thy nng lng tiu hao cho 1 lit oxy sdng l 19,8, 19,3 v 20,4, tng ng.

Thng s h hp RQ cho mi cht dinh dng c th hin ng thi Bng 2.6,xc nh t l th tch ca CO2 sinh ra v th tch O2 s dng cho qu trnh oxy ho slng cc cht dinh dng c bit.

Bng 2.6 Gi tr oxy ho ca cc cht dinh dng chnh (Brockway, 1987)

Cht dinhdng

O2 tiuth (l/g)

CO2 sinhra (l/g) RQ

+ Nng lng sinhra (kJ/g)

Nng lng sinh ra(kl/1O2)

Tinh bt 0,829 0,8324 0,994 17,49 21,10

Glucose 0,746 0,742 0,995 15,44 20,70

Cht bo 1,975 1,402 0,710 39,12 19,81

Protein 0,962 0,775 0,806 18,52 19,25

Ru 1,429 0,966 0,663 29,75 20,40

+ RQ: Thng s h hp

Nng lng tiu hao c th xc nh chnh xc t qu trnh oxy ho hn hp cc chtdinh dng, Lng CO2 sinh ra cn c o v s nh gi hoc cn thit o lng urto thnh (t s bi tit nit theo ng tit niu). Cng thc ph bin s dng tnh tonnng lng tiu hao ca ngi c pht trin bi Weir (1949) (Cng thc 6.1):

EE (kJ) = 16,489 VCO2 (l) + 4,628 VCO2 (l) 9,079 N (g) (6.1)

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Trong VCO2 v VCO2 l th tch ca O2 tiu th v th tch CO2 sinh ra, tng ngv N l lng bi tit theo ng tit niu. Nu lng nit bi tit ra theo ng titniu khng o c th cng thc tng t (cng thc 6.2) c th c s dng:

EE (kJ) = 16.318 VO2 (l) + 4.602 VCO2 (l) (6.2)

Trong : EE (Energy Expenditure): nng lng tiu hao

VO2 v VCO2 l th tch O2 tiu th v th tch CO2 sinh ra.

N l lng nit bi tit theo nc tiu

Cc cng thc tnh tng t cng c pht trin bi nhiu tc gi khc, vi s khcbit nh t qu trnh tiu th cc cht dinh dng khc nhau nh carbohydrate hocprotein hay lipid.. S khc bit ny dn n s khc bit trong cch tnh ton tiu haonng lng trong khong nh hn 3% di cc iu kin ch n ung thng thng(Brockway 1987).

tnh ton s lng carbohydrate, protein v lipid b oxyho, cc gi tr th hin Bng 2.6 v gi nh 6,25g protein cha 1 g nit c th s dng thit lp cng thcsau:

Oxy ho carbohydrate (g) = 4,707 VCO2 (l) 3,340 VO2 (l) 2,714 N (g)

Oxy ho cht bo (g) = 1,786 VCO2 (l) 1,778 VO2 (l) 2,021 N (g)

Oxy ho protein (g) = 6,25 N (g)

Thit b o nng lng gin tip:

Ti Douglas o chuyn ho nng lng (http://www.nu.ac.za)Thit b s dng o nng lng tiu hao bng phng php gin tip c th thay i tthit b n gin c thit k hot ng trong iu kin iu khin t xa cho ti phngthit k cho ngi phc tp hn.

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H thng n gin nht l dng k thut ti Douglas. Vi k thut ny, cho php olng oxy s dng trong thi gian t 5 n 15 pht. Lng khng kh th ra c tcha vo mt ti nh v mu khng kh ny c a i phn tch (Hnh 2.4)

Nhu cu nng lng c ngy

Hai phng php c th c s dng tnh ton nhu cu nng lng c ngy:

a) Nhu cu nng lng ca ngi trng thnh da vo chuyn ho c bn (CHCB) vc tnh theo h s thuc loi lao ng c th hin Bng 2.7.

Bng 2.7 H s nhu cu nng lng c ngy ca ngi trng thnh t CHCB

Nhu cu nng lng ca nhm lao ng nam la tui 18 - 30, cn nng trung bnh 55kg,loi lao ng nng c tnh nh sau:

Theo Bng 2.7

CHCB = (15,3 x 55) + 679 = 1520,5 Kcal

Nhu cu nng lng c ngy c tnh theo Bng 2.7

1520 x 2,10 = 3193,05 Kcal

b) Nhu cu nng lng c ngy da vo cch tnh gp: bao gm

+ Nhu cu nng lng cho chuyn ho c bn

+ Nhu cu nng lng cho tc dng ng lc c hiu ca thc n

+ Nhu cu nng lng cho hot ng th lc

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Lng cung cp nng lng

Cng lao ng

Lao ng cc nh: cng vic ngi lm l chnh, nh cng vic vn phng, cng viclp t v sa cha my thu thanh, ng h.. c km theo cc hot ng vn th nghipd no ..

Lao ng nh: Cng vic ng hoc i li t nh nhn vin bn hng, thao tc trongphng th nghim, gio vin ging bi..

Lao ng va: nh hot ng thng ngy ca hc sinh, li xe c ng, lp mc in,ct gt gia cng kim loi..

Lao ng nng: lao ng nng nghip phi c gii, luyn thp, nhy ma, vn ng thdc..

Lao ng cc nng: nh cc loi bc vc, cht g, khai thc khong sn v p .. phic gii.

Tnh trng sinh l

Tr em v thanh thiu nin trong thi k sinh trng pht trin, chiu cao, cn nng vlng lao ng tng ln tng ngy, v vy lng cung cp nng lng cng tng lntng ng, nhm p ng nhu cu v sinh trng v pht trin ca chng. Lng cungcp nng lng tng thm cho ngi m ang nui con l mc nng lng dng bp cho vic tit sa.

Kh hu v vc dng

Do c s ci thin v iu kin n mc v , m thng kh hu nh hng khng lnn nhu cu nng lng ca c th. Ch c trong iu kin kh hu nng bc hoc gilnh tng i lu th i hi phi c s iu chnh thch ng (Bng 2.8). Nhng ngic vc dng khc nhau, t l chuyn ho c bn cng khc nhau nn khi hot ng cntng hoc gim lng tiu hao nng lng mt cch tng ng. trnh bo ph hocqu gy, phi iu chnh hp l cho cn nng v chiu cao t c mc chun.

Bng 2.8 Nhu cu nng lng ca ngi ln theo nhit trung bnh hng nm cnnng v tui (Hong Tch Mnh & H Huy Khi, 1977)

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Ngun nng lng t mt tri n con ngi (http://en.wikipedia.org/wiki)

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Cn bng nng lng

Cn bng nng lng

Trong qu trnh trao i cht, s cn bng nng lng theo sau nh lut nhit ng lchc, xc nh rng di nhng iu kin l tng, nng lng lm vic bng vinng lng sn sinh ra. y l ni dung ca lut d tr nng lng. Khi cn bng nnglng c hon ton th khi lng khng thay i. Khi ngun nng lng vt qunng lng tiu dng th nng lng c d tr trong c th di dng m v lm tngtrng lng. Khi ngun nng lng thc phm t hn nhu cu nng lng tiu dng ths dn n tnh trng gim trng lng c th. Trong khu phn n, khi nng lng nhnvo thp hn nng lng s dng th s khc bit c thnh lp bng cch t chycc cht m trong c th v c s mt trng lng cn bng vi s trao i cht bo.

Khi tnh ton cn bng nng lng, nng lng thu nhn vo d dng xc nh bng ccho tng s calori trong thc phm tiu ho. Nng lng dng ht hoc tiu ph thngkh xc nh chnh xc.

Cn bng nng lng = nng lng nhn vo - nng lng sn sinh (s sinh nhit).

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D tr nng lng

D tr nng lng

C th gm ba ngun d tr nng lng chnh, trong d tr ch yu l lipid nmtrong cc t chc m. Bnh thng lipid chim khong 10% trng lng nam v 25% n. Cht bo d tr ch yu nhiu nht di da v trong cc bng. Trong cc t chc,cht bo d tr vn thng c cc trao i ho hc. Khi i c th s dng khong 150g/m/ngy, lng d tr c th trong khong 40 ngy. Lng carbohydrate d trdi dng glycogen gan v c ch khong 100 - 200 g. Phn d tr ch cho c ths dng trong 1 ngy. Trong c th c khong 300 g m dng d tr c ng. Chngtp trung ch yu bo tng t bo v gan. D tr ny c th dng ht trong 4 - 6ngy. Sau m ca cc t chc b phn hy.

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Cc bi ton v trao i vt cht

C th t carbohydrate

180 gr glucose khi b t s dng ht (6 x 22,4 lit) = 134,4 lit Oxy = VCO2

1 lit oxy t c 1,231 g carbohydrate v to ra 5,047 Kcal nhit lng

Mt thanh nin nm ngh 15 pht hp thu 3 lt Oxy v thi 3 lit kh CO2,

S oxy s dng mt gi l : 3 x 4 = 12 lit.

S nng lng dng l : 12 x 5,047 Kcal = 60,56 Kcal

trng thi ngh ngi, mi ngy c th cn: 60,56 x 24 = 1453 Kcal

C th t lipid

Thng s h hp = (18/26) = 0,7

1 g carbohydrate t chy cn 0,83 lit oxy

1 g lipid t chy cn 2,03 lit oxy

1 lit oxy dng t lipid s to ra 4,74 Kcal

* Bi tp: Mt c th nhn i ko di hp thu trong 15 pht mt lng oxy l 3,164lit v o thi 2,215 lit kh carbonic. Hi c th ny s dng ngun d tr no v trong24 gi chi ph bao nhiu nng lng?

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(S dng lng m d tr)

Lng oxy s dng 24 gi c tnh l : 3,164 x 24 x 4 = 303,75 lit,

Nu ch t lipid th oxy ny sinh c : 303,75 x 4,74 = 1440 Kcal

C th dng nng lng t ngun protein

T s carbon (C) thi ra phi, lng oxy phi c to ra kh carbonic (CO2) nh sau:

Lng kh carbonic to ra : 77,52 lit Lng oxy cn : 96,70 lit

Cch tnh n gin

Bng 2.9 Quan h gia thng s h hp v % calo thuc carbohydrate hay lipid

Thng s h hp(CO2/O2)

Mi lt oxy s sinhra (Kcal)

S % calo thuccarbohydrate

S % calothuc lipid

0,70 4,88 0,0 98,9

0,75 4,739 15,6 84,4

0,80 4,801 33,4 66,6

0,85 4,862 50,7 49,3

0,90 4,924 67,5 32,5

0,95 4,985 84,0 16,0

1,00 5,047 100,0 0,0

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Bi tp: Mt c th mi gi hp thu trung bnh 15 lit oxy, thi ra 13,5 lit kh CO2

1) Hi: trong gi , c th s dng bao nhiu nng lng?

Gii: Tnh thng s h hp = 13,5/15 = 0,90

Tra Bng 2.9, bit 1 lit oxy s to ra 4,924 Kcal, vy trong mt gi c th ny tlng thc n c 73,86 Kcal nng lng,

1. Hi: trong s nng lng k trn, carbohydrate ng gp bao nhiu?

Gii: Carbohydrate ng gp 67,5%, tc l (73,86 x 67,5)/100 = 49,86 Kcal

Phn cn li l ca lipid = 24 Kcal

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An ninh thc phm

nh ngha

- C lng thc thc phm (availability)

- C lng thc mi ni, mi lc vi gi c n nh (stability)

- C kh nng tip cn thc phm, c thu nhp, c tin mua thc phm (accessibility).

Theo cng ng Chu u, an ninh thc phm khi vng bng nn i v nn suy dinhdng.

Yu cu

- Thc phm phi m bo s lng

- Cn i v mt cht lng

- Khng l ngun gy bnh

Cn ch i vi cc loi thc phm

Protein ng vt c 8 acid amin thay th t l cn i hoc c d 1 hoc nhiuacid amin. Protein thc vt thng thiu mt hoc nhiu acid amin cn thit hoc c nhng t l khng cn i. Do cn n cc mn n hn hp nhiu loi thc phm.Tht l protein ng vt c s dng ph bin, c gi tr dinh dng cao, nhng khngnn n nhiu nht l khi n khng c rau. i vi tht rang, nng do c p ngnn lm v hiu ho lysine do phn ng Maillard gn lysine vi carbohydrate thnh hpcht kh phn hy bi men tiu ho. Lysine l yu t cn thit cho qu trnh pht trin,do vy khng nn cho tr n cc mn tht nng, rang kh..

Tht heo c kh nng nhim giun xon (tht heo go), tht ch nhi thng hay b snnn phi n chn. Trong da, ph tng ca trng cc c cha cht c buphotoxin gycht ngi. Tht b h hng c histamin (gy d ng) hoc ptomain gy ng c c thcht ngi.

C c hm lng protein cao, cht lng tt, d tiu ho, n gi c sng khng nhngb ng c do vi khun, nhim c sn l gan m cn b thiu vitamin B1 do c sng cmen thiaminase l men phn hy thiamin (B1).

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Tm, ln, cua c nhiu calci v yu t vi lng ng, selenium. Cua ng rang n bdo carbonate calci d tiu ho hp thu hn phosphate calci ca xng.

Trng l loi thc phm b dng nhng khng nn n trng sng v lng trng trngcha avidin rt c (c th ph hy bng cch nh bng ln). Trng c th nhim ksinh trng hoc vi sinh vt gy bnh. Trng vt ln cha nhiu ni tit t kch thchchuyn ho c th ngi n.

Sa l loi thc n ton din, ch thiu vitamin C v st. i vi tr em, sa ml tt nht. Sa cc loi ng vt khc tuy protein nhiu hn nhng cha nhiubetalactoglobulin, mt loi protein c phn t lng cao, l i vi tr em, c th gy dng (chy mu rut, chm, hen..). Sa bt tch b cha nhiu lactose, tr em c th hpthu d dng do c men lactase.

Ng cc: trong cc loi ng cc, cht lng protein ca go l tt hn c v t l cc acidamin tng i cn i, sau l bt m v bp. Ng cc ni chung u thiu lysinev methionin, bp cn thiu c tryptophan. Cc cht dinh dng qu u c lp ngoicng ca ht go v trong mm ht.

u c hm lng protein cao, cha nhiu lysine h tr tt cho ng cc. Ch loi unnh v u phng, m va giu protein va giu lipid.

Rau qu:

- l ngun vitamin

- l ngun cht khong

- l ngun khng sinh thc vt

- ngun tinh du hng liu kch thch n ngon ming

- ngun cht cht chng oxy ho (antioxydant) chng li cc gc t do ph hoi ccmng t bo gy ri lon chuyn ho, gy ung th.

- ngun cht x phng to bn, qut sch cc cht c v cholesterol tha ra khi ngtiu ho.

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ProteinM u

M u

Protein ng vai tr c bit i quan trng i vi sc kho con ngi. Nh c chtng v phng x, n nay ngi ta xc nh l mt na cht protein ca c th ci mi trong vng 80 ngy. Mt na protein gan, mu nhanh i mi trong vng 10ngy. Trong mt i ngi, cht protein c th i mi ti 200 ln. Thng qua nhnghu qu trc tip v gin tip, suy dinh dng do thiu protein l nguyn nhn ch yuca tnh trng sc kho km. Tnh trng thiu protein thng i km theo thiu nnglng v cc yu t dinh dng khc cc mc khc nhau.

Suy dinh dng do thiu protein v nng lng c th gp bt k la tui no nhnghay gp nht thi k sau thi b. Ngoi nh hng ti tc ln, thiu protein nhhay trung bnh lm cho tr c bit nhy cm vi ng h hp v ng rut. Nhiunghin cu cn cho thy thiu protein trong hai nm u ca cuc i khng nhng ati tnh trng b nh tui trng thnh m cn lm chm pht trin tr tu.

Thiu protein cn nh hng r rt ti ph n c thai v cho con b. Ngi ta thy cmi lin quan gia ch n thiu ca ngi m vi tnh trng non hay thiu cn catr s sinh. Do bi tit sa nhu cu ca ngi m tng ln rt nhiu. khi n thiu mprotein trong c th m b s dng sn xut sa. Nhiu nh khoa hc cho rng suydinh dng do thiu protein l mt trong nhng vn sc kho hng u v cp thittrong thi i hin nay.

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Cu trc v tnh cht l ho hc c bn ca protein

Cu trc v tnh cht l ho hc c bn ca protein

Cu trc

Cc thnh tu nghin cu v protein cho thy trong phn t protein ngoi cc nguynt carbon, hydro, oxy ging nh glucid, lipid th cn c mt cc nguyn t nit v luhunh. Mt s phn t protein cn cha cc nguyn t khc nh phosphor, st, km,ng.. Cc nguyn t k trn c trong phn t protein theo mt t l xc nh (Bng3.1).

Bng 3.1 T l cc nguyn t ch yu trong protein (L Don Din v V Th Th,1996)

Chng tham gia cu to nn phn t acid amin, trong c th sinh vt thng gp dngacid - amin.

Cng thc tng qut:

C th ngi ch c th ng ho c acid -amin c trong protein v thc n thc vt,cc dng v ? khng c c th ng ho v hp thu.

Acid amin l mt xch c bn to nn phn t protein, chng c lin kt vi nhaubng lin kt peptid ( CO NH ). C th thc vt c th tng hp c tt c ccacid amin t cc hp cht v c c cha nit, nhng ngi v ng vt th khngth tng hp c, cc acid amin u ly t thc vt; ngc li ch c th tng hpmt s acid amin t nhng hp cht hu c khc v c tin hnh gan nh enzymeaminotransferase m nhm ngoi l phosphopyridoxal. Cc -cetoacid c to thnhtrong qu trnh chuyn ho trung gian glucid nh acid pyruvic, c to thnh trong chu

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trnh Krebs nh acid -cetoglutaric, acid oxaloacetic u chu s amin ho bng cchkh to thnh cc acid amin.

T acid pyruvic s to c alanin, acid oxaloacetic s to c acid aspartic, acid

-cetoglutaric s to c acid glutamic

Cc phn t acid amin ny trng hp vi nhau thng qua lin kt peptid to thnh ccpolypeptid. Trong phn t protein c th c mt hay nhiu chui polypeptid.

Thnh phn ho hc

Protein c phn thnh hai loi:

- Protein n gin: trong thnh phn ch cha acid amin. V d prolamin, albumin,globulin..

- Protein phc tp: ngoi acid amin ra, trong phn t ca chng cn cha cc hp chtkhc nh acid nucleic, glucid, lipid (Bng 3.2)..

Bng 3.2 Cc protein phc tp (L Don Din v V Th Th, 1996)

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Thnh phn v hm lng protein trong cc nng snphm chnh (ngun cung cp protein trong thc phm)

Thnh phn v hm lng protein trong cc nng sn phm chnh (nguncung cp protein trong thc phm)

Thc n cung cp cho ngi gm hai nhm ln: ngun thc n ng vt (tht, c, trng,sa..), ngun thc n thc vt (go, khoai ty, bnh m, mt s loi rau, u ..). Ccthc n c ngun gc ng vt c cha hm lng protein nhiu hn thc n thc vt(Bng 3.3). Hm lng protein c trong thc n thng c biu hin bng s phntrm nng lng m protein ca thc n cung cp. Ch dinh dng tt l ch trong protein cung cp khong 10 - 15% nng lng. V th ngi ta phn loi thcphm d vo gi tr nng lng ca protein c trong thc phm (Bng 3.4).

Bng 3.3. Hm lng protein trong mt s loi thc phm quan trng (Norton v cngs, 1978)

Bng 3.4 S phn loi thc phm da vo gi tr nng lng ca protein (L Don Dinv V Th Th, 1996)

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Vai tr v chc nng ca protein trong dinh dng

Vai tr v chc nng ca protein trong dinh dng

Thut ng protein c xut x t ting Hy Lp protos ngha l trc nht, quan trngnht. Protein l thnh phn c bn ca vt cht sng, n tham gia vo thnh phn cami mt t bo v l yu t to hnh chnh. Qu trnh sng l s thoi ha v tn tothng xuyn ca protein.

Protein l thnh phn nguyn sinh cht t bo

nguyn sinh cht t bo khng ngng xy ra qu trnh thoi ho protein cng vi stng hp protein t thc n. Protein cng l thnh phn quan trng ca nhn t bo vcc cht gia t bo. Mt s protein c hiu c vai tr quan trng do s tham gia cachng vo hot ng cc men, ni t, khng th v cc hp cht khc. V d globin thamgia vo thnh phn huyt sc t, miosin v actin m bo qu trnh co c, ?-globulintham gia vo s to thnh rodopsin ca vng mc mt, cht ny gip cho qu trnh cmth nh sng c bnh thng.

Protein cn thit cho s chuyn ho bnh thng ca cc cht dinh dng khc

Mi qu trnh chuyn ho ca glucid, lipid, acid nucleic, vitamin v cht khong u cnc s xc tc ca cc enzyme m bn cht ho hc ca enzyme l protein. Cc qu trnhchuyn ho ca cc cht d l phn gii hay tng hp u cn mt ngun nng lngln, mt phn nng lng ng k do protein cung cp.

Cc qu trnh chuyn ho ca cc cht u lin quan mt thit vi qu trnh chuyn hoprotein, ni cch khc mi qu trnh chuyn ho trong c th u lin quan vi nhau, cth thy s Hnh 3.1.

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Qu trnh chuyn ho ca chui amino acid (http://cwx.prenhall.com)

Glucid qua qu trnh ng phn s to thnh acid pyruvic (CH3CO.COOH). T acidpyruvic khi b kh carboxyl ho bng cch oxy ho, vi s tham gia ca enzymepyruvate decarboxylase th sn phm thu c ca qu trnh ny l acetyl CoA. AcetylCoA l nguyn liu tng hp nn cc acid bo no v cha no trong cht bo.

ng hng bin i th hai ca acetyl CoA l i vo chu trnh Krebs. Trong qutrnh bin i ca chu trnh Krebs th ngoi nng lng c to thnh di dng ccnucleotide kh (NADH2, FADH2), CO2 v H2O, cn to ra hng lot cc sn phmtrung gian, trong qua trng hn c l -Ketoglutarate, oxaloacetate, fumarate. yl cc ketoacid, nu chng b amin ho bng cch kh hoc amin ho trc tip th sto thnh cc acid amin. Cc acid amin thng gp trong trng hp ny l alanine,acid aspartic v acid glutamic. T cc acid amin ban u ny bng ng hng chuynamin ho vi ketoacid vi s tham gia ca enzyme aminotranferase s to thnh hnglot cc acid amin khc-nguyn liu tng hp protein.

Protein tham gia vo cn bng nng lng ca c th

Protein l ngun nng lng quan trng cho c th, cung cp khong 10 - 15% nnglng ca khu phn. Cc acid amin khng tham gia vo tng hp protein hoc cphn gii t protein, t cc on peptid nh enzyme carboxy peptidase hay amino

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peptidase ca rut non s b kh amin ho bng cch oxy ho, kt qu to thnh nhmNH2 v -cetoacid.

Nhm amin phn ln c to thnh ur qua chu trnh ormithin, cn mt phn tn tidi dng amoniac. Cc -cetoacid tip tc b bin i theo ng hng oxy ho to thnh acetyl CoA v nng lng, acetyl CoA li tip tc i vo chu trnh Krebs to ra CO2, H2O, nng lng v cc sn phm trung gian. Nh vy cc acid amin bini theo ng hng kh amin ho s cho ngun nng lng ln. Cc acid amin cngc th b kh carboxyl ho to thnh cc amin hay diamin. Cc amin ny li b oxyho tip tc to thnh NH3, H2O, aldehyde tng ng, ng thi gii phng ngunnng lng ng k. Nh vy khi thiu glucid, lipid th mt phn protein tha c thchuyn ho thnh glucid hay acid bo tham gia vo qu trnh t chy v cung cpnng lng. Khi t chy trong c th, 1 g protein cho 4 Kcal.

Protein iu ho chuyn ho nc v cn bng kim toan trong c th

Protein ng vai tr nh cht m, gi cho pH mu n nh do kh nng lin kt vi H+

v OH-. Cc hot ng ca c th rt nhy cm vi s thay i pH mu, v vy vai trduy tr cn bng pH l rt quan trng. Protein c nhim v ko nc t trong t bo vomch mu, khi lng protein trong mu thp, di p lc co bp ca tim, nc b yvo khong gian bo gy hin tng ph n.

Protein bo v v gii c cho c th

C th con ngi chng li s nhim trng nh h thng min dch. H thng min dchsn xut ra khng th c bn cht l cc protein bo v. Mi khng th gn vi mt phnc hiu ca vi khun hoc yu t l nhm tiu dit hoc trung ho chng. C th c hthng min dch tt khi c cung cp y acid amin cn thit tng hp nn khngth. C th lun b e do bi cc cht c c hp th t thc phm qua h thng tiuho hoc trc tip t mi trng, cc cht c ny s c gan gii c. Khi qu trnhtng hp protein b suy gim do thiu dinh dng th kh nng gii c ca c th gim.

Protein l cht kch thch ngon ming

Do chc nng ny m protein gi vai tr quan trng trong vic tip nhn cc ch nkhc nhau. Trong c th ngi protein l cht c nhiu nht sau nc. Gn 1/2 trnglng kh ca ngi trng thnh l protein v phn phi nh sau: 1/3 c, 1/5 c xng v sn, 1/10 da, phn cn li cc t chc v dch th khc, tr mt v nctiu bnh thng khng cha protein. Protein cn thit cho chuyn ha bnh thng cccht dinh dng khc, c bit l cc vitamin v cht khong. Khi thiu protein, nhiuvitamin khng pht huy y chc nng ca chng mc d khng thiu v s lng.

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Tm li nu khng c protein th khng c s sng. Ba chc phn chnh ca vt chtsng l pht trin, sinh sn v dinh dng u lin quan cht ch vi protein.

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Nhng thay i xy ra trong c th thiu protein

Nhng thay i xy ra trong c th thiu protein

Thiu protein thng dn n tnh trng suy dinh dng. Nu tnh trng ny ko di sdn n tnh trng chung ca c th v pht trin ca n cng nh n s hnh thnh ccc im th cht ca con ngi. Nhng du hiu ca c th thiu protein:

- Chm ln, t ln. y l biu hin ri lon chuyn ho nc v tch cha nc ca cct chc ngho lipid.

- Lon dinh dng, marasmus & kwashiorkor (Hnh 3.2)

+ Lon dinh dng v marasmus l nhng bnh suy dinh dng ni chung trong s thium, nng lng ng vai tr chnh km theo thiu tt c cc cht dinh dng khc.Tnh trng ny thng dn n suy mn m khng gy ph.

+ Kwashiorkor l bnh thiu protein n thun thng gp cc tng lp c i sngthp ca cc nc, nht l cc nc thuc a trc y. Bnh hay gp tr em di 5tui n ch n ch yu l glucid v protein t ngun gc ng vt qu thp. Cc triuchng ca bnh thng gp l:

* Chm ln v chm pht trin

* Bin i mu da

* Bin i tnh trng cc nim mc

* Gim hot ng mi chc phn, c bit l h thng tiu ho dn n ri lon chcphn d dy, rut, kh tiu v tiu chy ko di. cc trng hp bnh nng c th gyph v gim st kh nng hot ng tr tu.

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Cc biu hin bnh thiu protein (http://www.ennonline.net)

- Gim chc nng bo v ca c th:

+ C th km chu ng khi thiu protein v nhy cm i vi cc tc nhn khng thunli ca mi trng bn ngoi, c bit i vi cm lnh v nhim trng.

+ Thiu protein v lng dn n cc bin i bnh l tuyn ni tit (tuyn sinh dc,tuyn yn, tuyn thng thn) v h thp chc phn ca chng. Hm lng adrenalintrong tuyn thng thn b h thp.

- Ri lon s to thnh choline gan m hu qu l gan b xm nhim m cng ngc ch . S to m gan tng ln khi thiu methionin l mt acid amin cha luhynh v nhm methyl (-CH3). Cht ny gip to thnh choline v do phnggan b nhim m. Khi gan b tch m, gan khng hon thnh c nhim v tng hpalbumin ca huyt thanh v gy ph.

- nh hng n h thng thn kinh trung ng v ngoi bin

- Thnh phn ho hc v cu trc xng cng b thay i. Cu trc c xng yu t,lng lo, gim hng cu, dn n hin tng thiu mu ca c th.

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Cc acid amin v vai tr dinh dng ca chng

Cc acid amin v vai tr dinh dng ca chng

Acid amin l thnh phn chnh ca phn t protein. Do kt hp vi nhau trong nhnglin kt khc nhau, chng to thnh cc phn t khc nhau v thnh phn v tnh cht.Gi tr dinh dng ca protein c quyt nh bi mi lin quan v s lng v chtlng ca cc acid amin khc nhau trong protein . Nh qu trnh tiu ho protein thcn c phn gii thnh acid amin. Cc acid amin t rut vo mu v ti cc t chc,ti y chng c s dng tng hp protein c hiu cho c th.

Cc acid amin cn thit v khng cn thit c trnh by Bng 3.5. Tiu chun xcnh gi tr sinh hc v vai tr sinh l ca cc acid amin l kh nng duy tr s pht trinsc vt ca chng. Mt vi acid amin khi thiu s lm cho sc vt ngng ln, xung cnmc d cc thnh phn khc ca khu phn u y . Cc acid amin ny c gil cc acid amin cn thit hay khng th thay th c v chng khng th t tng hptrong c th hoc tng hp vi tc khng th p ng c nhu cu ca c th mchng phi c a vo y trong m thc n.

Cc acid amin cn thit v khng cn thit (http://en.wikipedia.org)

Nhng acid amin khng cn thit c th tng hp c trong c th. Do khi thiuchng trong c th, c th c th b tr s thiu ht nh cc qu trnh tng hpbn trong. Mt s acid amin c v ngt kiu ng (alanin, valine). Mui natri ca acidglutamic c v ngt kiu m c s dng lm gia v.

Gi tr dinh dng mt loi protein cao khi thnh phn acid amin cn thit trong cni v ngc li. Cc loi protein ngun gc ng vt (tht, c, trng, sa) c gi tr dinhdng cao, cn cc loi protein thc vt c gi tr dinh dng thp hn, nu bit phi

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http://en.wikipedia.org/

hp cc ngun protein thc n hp l s to nn gi tr dinh dng cao ca khu phn.V d go, ng, m ngho lysine cn u tng, lc, vng hm lng lysine cao, khiphi hp go hoc m hoc ng vi u tng, vng, lc s to nn protein khu phnc gi tr dinh dng cao hn cc protein n l.

Gi tr sinh hc ca cc acid amin cn thit

Ngoi 8 acid amin cn thit ph bin, arginine v histidine cng l acid amin cn thiti vi s pht trin ca tr em. Nu thiu mt trong nhng acid amin cn thit s dnn ri lon cn bng m v ri lon s dng tt c cc acid amin cn li. m thcvt nhn chung km gi tr hn m ng vt do thiu hay hon ton khng c mt scc acid amin cn thit. Vai tr ca cc acid amin khng ch gii hn s tham gia cachng vo tng hp m c th m chng cn c nhiu chc phn phc tp v quantrng khc.

* L-histidine (acid -amino -imidasolyl propionic)

C nhiu trong hemoglobin. Khi thiu histidine mc hemoglobin trong mu h thp.Histidine c vai tr quan trng trong s to thnh hemoglobin. Khi cn thit hemoglobinc th b phn gii gii phng histidine.

Kh carboxyl

Hemoglobin Histidine Histamin

Histamin l cht gi vai tr quan trng trong vic lm gin mch mu. Thiu hay thahistidine lm gim st cc hot ng c iu kin.

* L-valine (acid -amino isovalerianic)

Vai tr sinh l ca valine cha c bit r rng nhng cc th nghim trn chut chothy khi thiu valine, chut t n, ri lon vn ng, tng cm gic v cht. Khi b sungvaline vo, cc ri lon trn s khi.

* L-leucine (acid -amino isocapric)

Nhng th nghim trn chut cho thy nu thiu leucine chut ngng ln, xung cn,c cc bin i thn v gip trng.

* L-lysine (acid , diamino propionic)

Lysine l mt trong cc acid amin quan trng nht. y l mt trong b ba acidamin c c bit ch khi nh gi cht lng dinh dng ca khu phn (lysine,tryptophan, methionine). Thiu lysine trong thc n dn n ri lon qu trnh to mu,

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h thp s lng hng cu v hemoglobin. Ngoi ra khi thiu lysine cn bng protein bri lon, c suy mn, qu trnh ct ho b ri lon v c hng lot cc bin i gan vphi.

Lysine c ch yu trong fromage, tht, c, cha khong 1,5 g lysine/100 g thc phmv c nhiu trong sa v cc ch phm ca sa, tht, nhiu nht trong m c-miosin vm mu-hemoglobin. Lysine hin din rt t trong ng cc.

* L-methionine (acid -amino ? -methionine n-butyric)

Methionine thuc loi acid amin cha lu hunh. Lu hynh ca methionine bnvng i vi kim hn cc acid amin c cha lu hunh khc (cystine v cysteine).Methionine c vai tr quan trng trong chuyn ho vt cht, c bit l qu trnh gnv trao i nhm methyl trong c th. Methionine l ngun cung cp chnh cc nhmmethyl d bin trong c th. Cc nhm methyl c s dng tng hp choline, mtcht c hot tnh sinh hc cao. Choline cn l cht tng hp m mnh nht: ngn ngam ho gan. Ngoi ra cn c nh hng c th vo chuyn ho lipid v phosphatid tronggan v gi vai tr quan trng trong vic ngn nga v cha x va ng mch.. Ngunmethionine tt nht l sa, fromage, lng trng trng. Methionine cn hin din trongu nnh, bt m, c thu, tht g, b, th..

* L-threonine (acid -amino -oxybutyric)

Thiu threonine sc vt ngng ln, xung cn v cht.

* L-tryptophan (acid -amino -indolepropionicic)

y l mt trong nhng acid amin quan trng nht m vai tr ca n lin quan cht chvi tng hp t chc, cc qu trnh chuyn ho v pht trin. Tryptophan c nhiu trongtht, sa, trng, fromage..Ngoi ra cn c nhiu trong m la m, u nnh..

* L-phenylalanine (acid -amino -phenylpropionic)

Tham gia vo vic tng hp tyrosine (l cht tin thn ca adrenalin) v l loi acid aminchnh trong vic to thnh m tuyn gip.

Nhu cu ca cc acid amin cn thit

Theo t chc FAO cho thy khi lng m y , cht lng m c quyt nh bitnh cn i ca cc acid amin trong hn l s lng tuyt i ca cc acid amin cnthit khc nhau. Nhng tc dng qua li gia cc acid amin rt nhiu v phc tp. Mthn hp khng cn i c th nh hng xu v mt dinh dng ngay c khi lng acidamin cn thit y cho mt c th bnh thng. Nhu cu ti thiu ca cc acid amincn thit c trnh by Bng 3.6.

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Nhu cu ti thiu ca cc acid amin cn thit ca ngi (Hong Tch Mnh v H Huy Khi,1977)

a. Khi lng cystine y

b. Khi lng tyrosine y

T l cn i gia cc acid amin cn thit theo F.A.O l:

Tryptophane-1, phenylalanine v threonine-2, methionine + cystine, valine-3, isoleucinv leucine-3,4.

Theo Leverton (1959) khi nh gi t l cn i ca cc acid amin cn thit th ch cntnh theo b ba: tryptophane, lysine v acid amin cha lu hynh (methionine + cystine)v t s gia chng nn l 1: 3: 3.

Cc acid amin khng cn thit

Cc acid amin khng cn thit (c th thay th c) chim t l ln trong thnh phnm thc n. C th c th tng hp c nhng qu trnh tng hp bn trong ch png c nhu cu ti thiu ca c th. Do cn a hp l cc acid amin ny vothnh phn m ca thc n. Cc acid amin c th thay th bao gm: alanine, asparagine,acid asparaginic, glycine, glutamin, acid glutamic, oxyprolin, proline, serine, tyrosine,cystine, cysteine.. Acid glutamic tham gia tch cc vo qu trnh chuyn ho m. Mttrong nhng tnh cht ca n l gp phn bi xut cc sn phm c hi ca qu trnhchuyn ho m ra khi c th. Vai tr ca cystine v tyrosine cng khng km phnquan trng. Tyrosine v cystine c th c tng hp trong c th:

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Phenylalanine Tyrosine

Methionine Cystine

Tuy nhin qu trnh ngc li khng th xy ra trong c th. 80 - 90% nhu cu camethionine c th tho mn bng cystine v 70 - 75% nhu cu ca phenylalanine c thc tho mn bng tyrosine. Do cc acid amin khng cn thit c th c t tng hptrong c th nn vic xc nh nhu cu ca chng rt kh khn.

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Nhng yu t nh hng n gi tr dinh dng caprotein

Nhng yu t nh hng n gi tr dinh dng ca protein

Gi tr dinh dng ca protein thc n ph thuc vo cht lng v s lng proteintrong . Cht lng ca protein c quyt nh ch yu bi thnh phn acid amin vmc s dng ca chng trong c th. Nhng yu t sau y nh hng n gi trdinh dng ca protein

nh hng ca nng lng cung cp

Khi nng lng cung cp khng y th hiu qu s dng protein b gim st, triuchng thiu m xut hin nhanh chng khi nng lng cung cp di nhu cu.

nh hng ca vitamin v mui khong

Cc vitamin v mui khong cn thit cho chuyn ho v pht trin, ng thi gi vaitr nht nh trong s dng protein thc n. iu tr tnh trng thiu protein, mt svitamin v cht khong c tm quan trng nh: niacine, kali v phosphor.

Kh nng s dng cc acid amin

C th khng hon ton s dng acid amin c trong thc n. Lng thng gim vnhng l do sau:

- S tiu ho v hp thu khng hon ton

- S c mt ca mt s cht c ch cc men tiu ho mt s thc n

- S bin cht protein v cc acid amin do nhit hoc cc tc dng khc

T l hp thu cc acid amin rt cao phn ln cc protein ng vt nhng proteinthc vt thng km hn. ch n hon ton ngun gc thc vt, lng nit caphn ln ti 20% lng nit n vo hoc hn. Khi cha b nhit lm gim hot tnh, cccht c ch c hiu cc men tiu ho cng lm gim tiu ho v hp thu protein. Tcdng nhit qu mnh cng lm gim mc s dng v hp thu protein. Tc dng nyhay gp nht l thc n giu glucid. Lysine v cc acid amin cha lu hynh chu nhhng nhiu nht.

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Tnh cn i ca cc acid amin trong khu phn - Yu t hn ch

Tt c cc acid amin cn thit phi c mt y , ng lc vi t l thch hp thamgia vo qu trnh tng hp protein. Nu mt trong cc acid amin c vi lng khngy , n to thnh "yu t hn ch", ngha l c th ch s dng tt c cc acid aminkhc mc cn i vi "yu t hn ch" ny, phn cn li s b tiu ph i. "Proteinchun" l protein trong cc acid amin t l cn i nht, thch hp nht cho tnghp t bo, thng chn protein trng lm chun.

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Cc phng php xc nh gi tr dinh dng ca protein

Cc phng php xc nh gi tr dinh dng ca protein

Phng php sinh vt hc

a. H s tng trng lng (Protein efficiency ratio PER)

L trng lng tng thm ca mt con vt ang pht trin chia cho lng Protein n vo.

H s tng trng cng cao chng t m cng tt. Thng thng ng cc = 1 - 2, sa =2.8, trng g ton phn = 3.8.

b. Gi tr sinh vt hc(biological value BV):l t l protein gi li so vi protein hp thu.

B: 75 C: 75 Casein: 75 Sa: 93

Bp: 72 Go: 86 Trng: 100 Bt m: 44

c. H s s dng protein(net protein utilization NPU): l t l protein gi li so viprotein n vo

Cc xt nghim trn ch nh gi v mt cht lng protein. Nhiu tc gi tnh "phntrm nng lng protein s dng" (Net dietary Protein Calories Percent NDpCals%) th hin c v cht v lng protein trong khu phn.

NDpCal% = NPU x % nng lng do protein

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Ch s ho hc (Chemical score CS)

Do c mi lin quan v gi tr sinh vt hc v yu t hn ch ca protein thc n. Do ch s ho hc c tnh l t s gia cc acid amin trong protein nghin cu so vithnh phn tng ng ca chng protein trng trong cng mt lng protein ngangnhau.

a: % hm lng acid amin trong m nghin cu

b: % hm lng acid amin trong m trng

Acid amin c ch s ho hc thp nht s l "yu t hn ch".

Cc gi tr dinh dng ca protein v sp xp gi tr dinh dng ca protein trong thcn c trnh by Bng 3.7 v Bng 3.8.

Cc loi protein thc n (Hong Tch Mnh v H Huy Khi, 1977)

Sp xp protein thc n

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Tiu ho v hp thu protein

Protein cao phn t c hp thu trong rut, di tc dng ca nhiu loi enzyme tiuho (nh pepsin, trypsin ..) phn gii thnh peptide ngn v acid amin trong rut d dy.Sau c hp thu trong rut non, theo tnh mch ch gan, vo trong gan. Mt bphn acid amin trong gan s tin hnh phn gii hoc tng hp protein; mt b phn acidamin khc tip tc theo tun ho mu, phn b n cc t chc c quan, tng hp nncc loi protein m ring bit. Protein khng th c tiu ho hp thu hon ton trongng tiu ho, phn cha c tiu ho di tc dng ca cc vi khun trong rut gis sinh thi ra, sn sinh ra cc cht c nh amoniac, phenol, benzpyrol... Trong ,i b phn theo phn thi ra ngoi c th, mt s t c nim mc rut hp thu, theotun hon mu chuyn vo gan, tin hnh gii c sinh l, sau theo nc tiu thi ra,nh vy mi c th lm c th khng b c.

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Nhu cu protein ca c th

Nhu cu protein ca c th

Cc t chc FAO/OMS thng nht dng phng php ton phn tnh nhu cu.Phng php ny dng tnh gp li cc nhu cu khc nhau gm: lng mt nitkhng trnh khi duy tr v nhu cu cho pht trin, chng cc kch thch.

Lng mt nit khng trnh khi gm:

- Lng mt nit theo nc tiu Uk: tnh bng cch theo di lng nit ra theo nc tiu ch calo nhng khng c protein, khong 3g nit/ngy tc l khong 46 mg/kgcn nng ngi chun.

- Lng mt nit theo phn Fk: (cng o ch 1g nit/ngy - 20 mg/kg cn nng)

- Lng mt nit theo da P (m hi, mng, tc- khong 20 mg/kg cn nng)

- Nhu cu cho pht trin C: cng trnh ca Holt cho l lng N gi li bng 2.9% trnglng tng thm trong qu trnh pht trin tr em trn mt tui.

nh hng ca cc kch thch

Nhu cu ton b: theo FAO/OMS nhu cu ny c tnh theo mg N/ kg cn nng bngtng s nhu cu trn nhn vi h s 1,1 (tng thm 10% nhu cu) tnh n vic b trtiu ph do cc kch thch hng ngy.

K = (Uk + Fk + P + C) x 1,1

Trong , K: nhu cu N theo kg cn nng/ngy

Uk: lng mt nit khng trnh khi theo nc tiu (mg/kg cn nng/ngy)

Fk: lng mt nit khng trnh khi theo phn (mg/kg cn nng/ngy)

P: lng mt nit theo da (mg/kg cn nng/ngy)

C: lng tng nit trong thi gian pht trin/kg cn nng/ngy

1,1: s tng thm 10% b tr tiu ph do cc kch thch gp trong i sng hng ngy.

Nhu cu theo m chun = K x 6,25

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Tnh theo cng thc trn cho ngi trng thnh:

(46 + 20 + 20) x 1,1 = 95 mg N/kg cn nng

Nhu cu theo m chun = 95 mg x 6.25 = 0,59 g/kg

Thm 20% cho cc thay i c bit 0,71 g/kg cn nng

Phng php tnh trn th hin nhu cu i vi protein chun, ngha l vi protein honton cn i. V th phi iu chnh nhu cu trn khi bit cht lng protein n vo.

Theo FAO:

- Cc nc pht trin: NPU = 70 - 80

- Cc nc ang pht trin: NPU = 60 - 70

- Cc nc c phn n c bn khng phi l ng cc (sn)

NPU = 50 - 60

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LipidM u

M u

Lipid l hp phn quan trng ca khu phn n, c trnh by Hnh 4.1.

Lipid l thnh phn thay i mt cch ng k trong thnh phn v cu trc. Chngc tm thy c hai loi thc phm thc vt v ng vt, v cng thay i rt rngv tnh cht l ho hc. Hu ht cc loi du m t nhin u cha khong 98 - 99%glyceride, phn cn li rt nh bao gm monoglyceride, acid bo t do, phospholipid vcc cht khng x phng ho. Tnh cht l ho hc ca cc cht du m nh hng bikch thc ca ht phn t bo v bi s lng ca cc acid bo bo ho hoc cha boho m chng cha. Thng thng vi cht bo bo ho nhiu v khi lng phn tcao th chng dng rn. Glycolipid hoc cerebroside l nhng hp phn ca acid bovi carbohydrate v cha nitrogen nhng khng c acid phosphoric. Cerebroside ctm thy trong mng ty (myelin) ca si thn kinh trong trng thi kt hp vi lecithin.

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Phospholipid hoc phosphatide cha c hai nitrogen v phosphorus. Cht c bit llecithin rt phong ph trong lng trng. Ngoi ra cn c tm thy trong c, mthn kinh v trong tt c cc t bo ca c th.

Sterol l nhng hp cht monohydroxyalcohol phc c khi lng phn t cao, ctm thy di dng t nhin kt hp vi acid bo. Chng cha carbon, hydrogen v oxy.c bit nhiu nht l cholesterol, phn phi rt rng trong c th, thng hin dintrong ty sng bao bc m thn kinh, trong mu v trong tt c cc t bo ca c th.

Cht bo dng lipid n gin hay phc tp u b hydro ho hoc enzyme phn hythnh dng lipid dn xut. Ba thnh phn quan trng ca nhm ny l: acid bo,glyceride v steroid. Hu ht s tiu ho lipid xy ra ng rut. Mt nh tng hocht bo v chuyn chng thnh dng c th cho php cc qu trnh thy phn bi ngrut v enzyme ca dch ty. Trong qu trnh ny cht bo c th b thy phn thnhacid bo, glycerol v monoglyceride. Mui mt v choline gip cho s nh tng hocc hp cht thy phn ny, sinh ra hp cht hp thu c. Sut qu trnh hp thu chtbo, glycerol v monoglyceride tng hp li thnh cht bo.

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Cu trc v cc tnh cht l ho c bn

Cu trc v cc tnh cht l ho c bn

Cu trc

Du m l hn hp cc ester ca glycerin v cc acid bo (Hnh 4.2).

Phopholipid l diacilglycerin lin kt vi H3PO4 bng lin kt ester v tr nhm OHth 3 ca glycerin, sau gc phosphate b ester ho bi ru cha nhm amin (cholin,etanolamin), acid hydroxyamin (serin)..

Phospholipid c mt bt k t bo thc vt no v n l cu t bt buc ca mngt bo, c bit l cc cy ly du v cc cy h u. Trong quan trng v nhiuhn c l phosphotidinetanolamin (hp cht ph l ethanolamin NH2-CH2-CH2OH) vphosphatidincholin (hp cht ph l cholin: (CH3)3 - N+ - CH2 - CH2OH). Cc hp chtny l thnh phn cu trc ca t bo thn kinh, no, tim, gan, tuyn sinh dc, c bitng vai tr quan trng trong tnh thm mng t bo.

Cc tnh cht ca lipid

Cc ch s c bn phn nh tnh cht ca du v m l:

- Nhit nng chy: ph thuc vo thnh phn ca acid bo. Nu trong thnh phndu v m c nhiu acid bo no th chng c nhit nng chy cao hn v thng

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trng thi rn. Ngc li trong thnh phn c nhiu acid bo cha no th chng c nhit nng chy thp, thng trng thi lng (Bng 4.1). a s du thc vt trng thilng trong iu kin nhit bnh thng.

Tnh cht ca mt s loi du m (L Don Din & V Th Th, 1996)

Khi lng ring ca du thc vt 15oC l 90-98 Kg/m3, ch s chit quang:1,441,48. Nhit ng c ca du thc vt thng l m, cn m c nhit ng c gn 40oC. Do khi lng triglyceride cao nn du thc vt khng bay hi ngayc iu kin chn khng cao. nhit 204 - 250oC, triglyceride s b phn gii thnhcc sn phm bay hi ca s phn hy ho hc.

Trong ht c du khi ny mm hoc trong cc c quan tiu ho ca ngi v ng vt xy ra qu trnh phn gii du v m di tc dng ca enzyme lipase, vi s thamgia ca H2O.

Glycerin v acid bo s c chuyn ho tip tc, to ra mt ngun nng lng khln cung cp cho mi hot ng sng. Glycerin c th c dng tng hp nn ccng 6C hoc b phosphoryl ho ri c phn gii nh glucid.

Cc acid bo s c chuyn ho theo ng hng oxy ho to ra acetyl CoA v ccnucleotide kh (NADH2, FADH2). Acetyl CoA li tip tc i su vo chu trnh Krebscung cp cho c th mt ngun nng lng ln.

Chng hn mt phn t acid bo no b oxy ho qua 1 vng oxy ho gii phng ra 1FADH2, 1 NADH2 v 1 phn t Acetyl CoA, 1 phn t CoA i vo chu trnh Krebs chota 12 ATP. Tng nng lng ca mt vng oxy ho l 17 ATP, tr i 1 ATP dng hot ha ban u cn 16 ATP.

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Nu acid bo c mch Carbon l 16 th phi quay 8 vng oxy ho, nh vy ta c:

8 x 16 ATP = 128 ATP x 12 Kcal = 1536 kcal.

l nguyn nhn d tr v cung cp nng lng ca cht bo.

Thnh phn v hm lng lipid trong mt s nng sn phm chnh

Thnh phn v hm lng lipid hon ton khc nhau cc ngun thc n c ngun gcng vt v thc vt. Trong thc n thc vt: nhm ly tinh bt nh cc loi go, ccloi khoai, ng, sn th ng c hm lng cao hn c khong 3 - 8% v tp trung phnphi ht. Trong la m, i mch v lu go thng c khong 1,6 - 3,2%; khoai lang,khoai ty, sn ti hm lng lipid khng ng k 0,1 - 0,3%. Cc loi rau hu nh chart t lipid, tr cc loi rau u: u H lan, u c-ve, hm lng lipid khong 1 - 2%.Cc loi qu chn, tr gc c hm lng lipid cao, cn li cha khong 0,1 - 0,5% lipid.Ch ring ht v qu cc loi cy ly du l c hm lng lipid rt cao, cao hn bt kloi thc n no, trong phi k n ci da, u phng, m, u nnh, u rng, cdu (Bng 4.2). C th ni nhng thc phm ny l ngun lipid v cng qu gi c thdng lm thc n trc tip, c th l nguyn liu sn xut du thc vt.

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Hm lng lipid tng s trong mt s loi thc n chnh (% khi lng kh)

(*) Theo FAO, 1972 * Theo Norton v cng s, 1978

** Theo bng TPTAVN, 1995

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Vai tr ca lipid trong dinh dng ngi

Vai tr ca lipid trong dinh dng ngi

Cung cp nng lng

Lipid l mt trong ba thnh phn ho hc chnh trong khu phn hng ngy, nhng khcvi protein v glucid, lipid cung cp nng lng nhiu hn (1g lipid cung cp khong9 kcal), gp i so vi mc nng lng do carbohydrate v protein sn sinh ra. Trongkhu phn n hp l, nhu cu nng lng do lipid cung cp khong t 15 -20%. Thcn giu lipid l ngun nng lng m c cn thit cho ngi lao ng nng, cn thitcho s phc hi sc kho i vi ph n sau khi sinh v cc c th mi m dy, chtbo d tr nm di da v m lin kt.

Cu thnh cc t chc

Nh mng t bo l lp m do lipoid, glucolipid v cholesterol.. hp thnh; ty no vcc m thn kinh c cha lipid v glucolipid. Cholesterol l nguyn liu cn thit chto ra steroit hormoon.

Duy tr nhit c th, bo v cc c quan trong c th

Lipid l cht dn nhit khng tt ngn nga s mt nhit di da, c tc dng gi nhit,gip ch cho vic chng rt, ng thi cn lm cho lng nhit bn ngoi c hpthu khng truyn dn vo bn trong c th, c tc dng cch nhit.

Lipid phn b khng u trong c th ngi vi tng hm lng khong 10%. Lngcht bo ch yu tp trung cc t chc di da to thnh lng m d tr c th sdng khi cn thit. Mt phn cht bo cn bao quanh ph tng nh l t chc bo v, ngn nga cc va chm v gip chng v tr ng n. N cn gip c th trnh khicc tc ng bt li ca mi trng ngoi nh nng, lnh. Ngi gy th lp m di damng, do vy m c th km chu ng vi s thay i ca thi tit.

Thc y vic hp thu cc vitamin tan trong cht bo

Vitamin A, D, E, K khng tan trong nc m tan trong cht bo hoc dung mi hotan cht bo. Lipid c trong thc n s lm dung mi thc y s hp thu chng.Nu hm lng lipid trong ba n thp th s nh hng n vic hp thu carotentrong rau xanh (trong c th caroten chuyn thnh vitamin A).

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Lm tng cm gic no bng

Lipid ngng d dy vi thi gian tng i lu, cho nn khi n nhng thc n c hmlng lipid cao s lu b i.

Nng cao gi tr cm quan ca thc n

Thc n c nhiu cht bo s c mi thm v ngon, do vy lm tng s thm n.

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Cc acid bo

Cc acid bo

Tnh cht ca cc acid bo c th hin Bng 4.3

Hm lng cc acid bo trong mt s thc n (Hong Tch Mnh v H Huy Khi, 1977)

Cc acid bo no

Ch yu nm trong thnh phn m ng vt, cc acid bo c trng lng phn t cao(stearic, arachic, palmitic..) th rn. Cc acid bo c trng lng phn t thp (butyric,caprinic..) th lng, trng lng phn t cng cao th nhit tan chy cng cao. Gitr sinh hc ca cc acid bo no km hn cc acid bo cha no do chng c tc dngkhng tt i vi chuyn ho m, chc phn v tnh trng gan v c vai tr ca chngtrong pht trin bnh x va ng mch. Nhiu cng trnh nghin cu cho thy tnhtrng cholesterol qu cao trong mu thng i km vi ch n nng lng cao vnhiu m ng vt.

Cc acid bo cha no

Cc acid bo cha no hin din rng ri trong cht bo n, c bit l cc loi du thcvt (Bng 4.4). Cc acid bo cha no mt, hai hoc ba ni i hay gp nhiu trong thnhphn thc n. Nhng cht bo c hot tnh sinh hc cao l cc cht bo cha cc acidbe c t hai ni i tr ln trong thnh phn ca n. M c v ng vt sng binthng c nhiu acid bo nhiu ni i. Cc acid be cha no rt nhy vi phn ng oxyho v phn ng lin kt nn thng khng bn vng. ng thi thng qua cc phnng ny, cc acid bo cha no chuyn thnh cc acid bo no v tr nn rn.

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Cc acid bo cha no thng gp nht l acid oleic. Acid bo ny c hu nh tt ccc cht bo ng v thc vt, do d dng tho mn nhu cu ca c th. Ngoi ra ccacid bo cha no khc nh: acid linoleic, acid linolenic, acid arachidonic l nhng acidbo c nhiu ni kp v l nhng cht c hot tnh sinh hc r rng nht.

Vai tr sinh hc ca cc acid bo cha no cn thit rt quan trng v a dng. Mt st chc nh tim, gan, no, tuyn sinh dc c nhu cu rt cao v cc acid . Khi thiuchng trong thc n, cc ri lon thng xut hin trc ht cc c quan ny. Vai trsinh hc ca cc acid bo cha no cn thit c th c tm tt nh sau:

? Kt hp vi cholesterol to thnh cc ester c ng, khng bn vng v d dng bixut ra khi c th. iu ny c ngha trong vic ngn nga bnh x va ng mch.Trong trng hp thiu chng, cholesterol s ester ho vi cc acid bo no v tch li thnh mch. Cc acid bo cha no cn thit s to iu kin chuyn cholesterol thnhacid cholic v bi xut chng ra khi c th.

? C tc dng iu ho thnh mch mu

? phng nhi mu c tim v cc ri lon ca h thng tim mch

? Chng ung th

? Cn thit cho chuyn ho cc vitamin nhm B, nht l pyridoxin v thiamin

? phng cc tn thng da (do hot tnh ca men citocromosidase gim).

Trong c th acid arachidonic l loi c hot tnh sinh hc cao nht, 2 - 3 ln hn acidlinoleic. C th c th chuyn acid linoleic thnh acid arachidonic khi c s hin dinca pyridoxin.

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Hm lng cc acid bo cha no trong mt s du m n (Hong Tch Mnh v H Huy Khi,1977)

Xt v hot tnh sinh hc v hm lng cc acid bo cha no cn thit, c th chia chtbo thnh ba nhm:

? Nhm c hot tnh sinh hc cao: hm lng cc acid bo cha no cn thit khong50 - 80% v vi s lng 15 30 g/ngy c th tho mn nhu cu c th. Thuc nhmny c: du hng dng, u nnh, bp ..

? Nhm c hot tnh sinh hc trung bnh: hm lng acid bo cha no cn thitkhong 15 - 22% v c th cn 50 60 g/ngy m bo nhu cu. Thuc nhm nyc: m ln, m ngng, g v du olive..

? Nhm c hot tnh sinh hc thp: hm lng acid bo cha no cn thit khng qu5 - 6% v v thc t khng p ng c nhu cu c th v cc acid ny, thng gmcc loi: m cu, m b v margarine.

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Phosphatide

Phosphatide

Phosphatide l thnh phn cn thit ca t bo v t chc, tp trung nhiu nht cc tchc thn kinh v t chc no, tim, gan, tuyn sinh dc.. Hm lng ca chng phn bnh sau:

Phosphatide tham gia tch cc vo qu trnh chuyn ho t bo v chuyn ho m, nhhng ti cng hp thu v s dng cht bo trong c th. Ngun phosphatide chyu l lng trng, gan, no.. nhiu cht bo nht l cc loi du thc vt l ngunphosphatide quan trng. Phosphatide hay gp trong thc phm l lecithin (Hnh 4.3)v phn t ph bin hn l cephalin (Hnh 4.4). Lecithin c tc dng iu ho lngcholesterol trong mu, ngn nga tch ly cholesterol, thc y cc qu trnh phn tchv bi xut chng ra khi c th.

Duy tr cn bng sinh hc gia lecithin v cholesterol l yu t quan trng phngv ngn nga x va ng mch. Bnh thng ngi kho t l lecithin/cholesterol =1/1. B l ngun lecithin qu.

Do cc vai tr trn, c th cn cung cp phosphatide y theo thc n. Ngoi cc loidu thc vt cng cn ch b sung cc loi thc phm khc giu lecithin nh trng gton phn.

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Sterol v vitamin

Sterol v vitamin

Sterol

L thnh phn thng xuyn i km theo m. y l cht c cu to phc tp v thucnhm cht khng x phng ho. Trong m ng vt c cholesterol, du thc vt csitosterol. Hm lng sterol trong m ng vt khong 0,2 0,5%, cht bo thc vt cnhiu hn.

1. Sitosterol

1. Cholesterol

Cholesterol b oxy ho gan cho cc acid mt. Cc acid mt c vai tr nh tng ho rut. Cholesterol tham gia vo vic tng hp cc ni tit t v thng thn (testosterol,vitamin D3, ni tit t sinh dc..). Cholesterol l yu t chnh tham gia vo s hnh thnhv pht trin x va ng mch, v vi ch n nhiu cholesterol th cholesterol trongmu tng. Theo nhiu nghin cu cho thy cholesterol huyt gy ng cholesterol thnh mch mu v gy ra cc bin i x va ng mch.

Trong nhng nm gn y ngi ta cng nu ln mi quan h gia cholesterol vi spht trin ca khi u c tnh. cc t bo ung th, lng cholesterol gp 4 ln cao hncc t chc bnh thng. Tuy nhin vn cn ang nghin cu tip tc.

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Vitamin

Cht bo l ngun vitamin A, D v E. Vi lng cht bo s dng y s lm chocc sinh t tan trong du c s dng hon ton v c hiu qu. Cht bo giu cc acidbo cha no cn thit h tr hp thu vitamin A v caroten.

Cc cht bo giu tocopherol kch thch s dng vitamin A v D trong c th. Khi chtbo c cht lng tt v bo qun hp l th lng vitamin trong cng c m bo.Khi cht bo b h hng th cc vitamin trong cng b phn gii.

Vitamin A ch c trong m ng vt, cc loi du thc vt li cha carotene. M ngvt cn cha vitamin nhm D, chng l dn xut ca ergosterol hay cholestetol. V vyc th coi cholesterol l ngun vitamin D chnh trong c th.

Cht bo cng l ngun vitamin E (tocopherol). Mt lng y tocopherol trong ch n gip tch cha vitamin A trong cc ni tng (gan, thn..)

V phng din v sinh, tnh cht chng oxy ho ca vitamin E c bit quan trngtrong vic ngn nga s h hng m. Tocopherol c nhiu trong du thc vt, m ngvt cha t tocopherol nn rt kh bo qun.

Nhu cu vitamin E ph thuc vo lng cc acid bo cha no cn thit trong khu phn. ngn nga biu hin thiu vitamin E, t l vitamin E (theo mg ?-tocopherol) v ccacid bo cha no cn thit (theo gram) s tng ng 0,6.

Cc cht bo thc vt khc ngoi tocopherol cn cha cc cht chng oxy ho t nhinnh sesamol (du m), gosipol (du bng). Tuy nhin gosipol (C30H30O8) l cht ci vi c th vi hm lng khong 0,08 n 2% du bng. Qu trnh tinh ch chophp loi tr cc cht c .

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Gi tr dinh dng ca cht bo

Gi tr dinh dng ca cht bo

nh gi gi tr dinh dng ca cht bo, cc tiu chun sau y c s dng:

? Hm lng vitamin A, D v tocopherol

? Hm lng cc phosphatide (lecithin)

? Hm lng cc acid bo cha no (acid linoleic)

? Hm lng cc sterol, nht l -sitosterin

? D tiu ho v tnh cht cm quan tt

Cht bo ng vt v cht bo thc vt cng khng hon ton p ng c cc nhucu trn. Cc loi m ng vt c vitamin A, D nhng li khng c hoc c rt t ccacid bo cha no cn thit. Cht bo ca sa tuy c c tnh sinh hc cao do trong thnhphn c cha acid arachidonic nhng li rt ngho cc acid bo cha no cn thit khc.Ngc li du thc vt khng c vitamin A, D hay acid arachidonic nhng li c nhiuacid linoleic, phosphatid, tocopherol v sitosterin.

Vic s dng phi hp cc cht bo ng vt v thc vt mi c th to nn ngun chtbo c gi tr sinh hc cao. V mt gi tr sinh hc, t l cht bo ngun gc ng vtnn khong 60 - 70% v ngun gc thc vt 30 - 40%. ngi ng tui, t l du thcvt s dng nn tng.

Tnh cn i ca cc acid bo trong m n cng rt quan trng. T l trong khu phnnn l 10% cc acid bo cha no c nhiu mch kp, 30% cc acid bo no v 60% acidoleic.

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Hp thu v ng ho cht bo

Hp thu v ng ho cht bo

Cht bo trong c th l cht bo trung tnh triglyceride. Cc acid bo trong phn t cachng c cc lin kt khng no khc nhau v c cc chui lin kt vi cc di khcnhau, v vy t l tiu ho hp thu ca chng cng khc nhau.

Cc cht bo d tan chy thng hp thu tt. Cc cht bo tan chy c nhit nngchy trn 40oC u hp thu km.

V mt ng ho c th chia cht bo thnh ba nhm:

? Cc cht bo c tan chy thp hn thn nhit: ng ho 97 - 98%

? Cc cht bo c tan chy trn 37oC: ng ho khong 90%

? Cc cht bo c tan chy trn 50 - 60oC: ng ho 70 - 80%

Tnh cn i v c im cc acid bo trong khu phn nh hng ti hp thu cht bo.Nu trong khu phn n c qu nhiu acid bo no hoc cha no, ng ho u gimxung. Nu hm lng cc acid bo cha no c nhiu ni i cao qu 15%, chng skhng ng ho.

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Vai tr ca mui mt v s tiu ho cht bo

ng (- - - -) biu din s tun hon ca mui mt

TG: triacyl glycerol MG: monoacylglycerol

FA: chui acid bo

Ngun: Harper's Review of Biochemistry, 19th ed., Long Medical Publications, LosAltos, Calif. (1983)

Qu trnh hp thu cht bo c biu din Hnh 4.7. Cht bo c hp thu rutnon. Trong d dy cht bo s c nh tng ho s b v i vo t trng, tc vnhp iu i vo s khc nhau ty thuc vo hm lng ca cht bo trong thc n, t lcng nhiu th thi gian dng li trong d dy cng lu. Khi cht bo vo n t trng,gp mt v enzyme lipase ca tuyn ty s phn gii cc phn t triglyceride, u tinhnh thnh 1-diglyceride v 2-diglyceride v tch 1 phn t acid bo ra, sau tip tc

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phn gii hnh thnh 2 n glyceride v 1 phn t acid bo khc. Tc tc dngphn gii do enzyme cng khc nhau ty theo di ca lin kt cht bo, tc phngii ca acid bo khng no nhanh hn acid bo no.

ng ho ca mt s cht bo nh sau:

B: 93 - 98% M heo: 96 - 98% M b: 80 - 96%

M cu: 80 - 90% Du m: 98% Du u nnh: 97,5%

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Nhu cu cht bo

Nhu cu cht bo

Lng cht bo n hng ngy c cc nc trn th gii rt khc nhau. Nhiu ncChu u, Bc M s dng hn 150 g cht bo hng ngy (theo u ngi). Trong khi cc nc Phi lng cht bo khng qu 15 20 g/u ngi/ngy.

Nhu cu cht bo ph thuc theo tui, tnh cht lao ng, c im dn tc v kh hu(Bng 4.7). x lnh, t l calo do cht bo nn khong 35% tng s calori ca khuphn, vng n i, x nng 15 - 25%.

? ngi tr tui v trung nin, t l m: bo = 1/1

? ng tui: t l m: bo = 1/0,7

? Gi v bo ph: 1/0,5

Bng 4.7 Nhu cu cht bo theo g/kg cn nng

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CarbohydrateM u

M u

Carbohydrate tn gi chung ca nhm phn t hu c v chng cung cp khong 48%nhu cu nng lng ca khu phn. Carbohydrate c phn nhm ty thuc vo slng ca nguyn t carbon trong phn t, nh triose (3 n v carbon), pentose (5 nv carbon), hexose (6 n v carbon). V mt dinh dng loi carbohydrate c tm quantrng l hexose v trong D-glucose l loi quan trng nht. Lng carbohydrate cungcp y s lm gim phn hy protid n mc ti thiu. Trong c th chuyn ho cacc carbohydrate c lin quan cht ch vi chuyn ho lipid v protid.

Cc thc n thc vt l ngun carbohydrate ca khu phn. Cc thc phm ng vt cglycogen v lactose. Glycogen c mt t trong gan, c v cc t chc khc v c ctnh ca tinh bt. Lactose c trong sa trn 5%.

Cc carbohydrate quan trng nht trong thc phm c trnh by Bng 5.1

Monosaccharides Glucose, Fructose

Disaccharides Sucrose, Lactose

Oligosaccharides Raffinose, Stachyose, Fructo-oligosaccharides

Polysaccharides Cellulose, Hemicelluloses, Pectins, -Glucans, Fructans, Gums,Mucilages, Algal polysaccharides

Sugar alcohols Sorbitol, Mannitol, Xylitol, Lactitol, Maltitol

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Vai tr sinh l ca carbohydrate

Vai tr sinh l ca carbohydrate

Cung cp nng lng

L vai tr sinh l ch yu ca carbohydrate. Carbohydrate c trong c bp l ngun nnglng hu hiu nht ca hot ng c. Carbohydrate c oxy ho trong c th c theocon ng hiu kh v k kh.

Carbohydrate v cc ng phn lp th ca chng tham gia vo thnh phn t chcca c th, c chc phn v tnh c hiu cao. Trong dinh dng ngi vai tr chnhca carbohydrate l sinh nng lng. Hn 1/2 nng lng ca khu phn n l docarbohydrate cung cp, 1 g carbohydrate t chy trong c th cho 4 Kcal.

Hot ng ca tim cng ch yu da vo nng lng ca phosphoric acid, glucose vglycogen oxy ho. H thn kinh ngoi glucose ra, khng th s dng c nng lngdo cc cht dinh dng khc cung cp. Glucose trong mu l nng lng duy nht cah thn kinh, khi lng ng huyt thp s xut hin hn m, ngt, thm ch t vong..

Thnh phn cu to nn cc t chc thn kinh

Ngoi vai tr sinh nng lng mc nht nh, carbohydrate cn c vai tr to hnh.Mc d c th lun phn hy carbohydrate cung cp nng lng, mc carbohydratetrong c th vn n nh nu n vo y . Tt c cc t chc v t bo thn kinh uc cha carbohydrate. Desoxyribonucleic acid (DNA) l c s vt cht ca di truynsinh hc c cha ng ribose l loi pentose.

Bo v gan, gii c

Khi glycogen gan c d tr tng i y , gan s c kh nng gii c tngi mnh i vi chng c huyt do mt vi loi ho cht c (nh carbon tetra-chloride, cn, thch tn) v do b nhim cc loi vi sinh vt gy bnh gy nn. V thm bo vic cung cp ng, duy tr trong gan lng glycogen vi mc no s bo v gan trnh c nhng tn hi ca cc tc ng c hi; ng thi s duy trc chc nng gii c bnh thng ca gan.

Chng to th cetone

Lipid oxy ho trong c th s da vo nng lng do carbohydrate cung cp. Khicarbohydrate cung cp khng , c th do b bnh (nh bnh tiu ng) khng thtn dng c ngun carbohydrate, ngun nng lng phn ln cn thit do lipid cung

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cp, v khi lipid oxy ho khng hon ton th s sinh th cetone, y l cht mang tnhacid, nu tch ng trong c th nhiu s dn n ng c acid. V vy c th xemcarbohydrate c tc dng chng to th cetone v phng nga ng c acid.

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Carbohydrate tinh ch v carbohydrate bo v

Carbohydrate tinh ch v carbohydrate bo v

Carbohydrate tinh ch

Carbohydrate tinh ch ch nhng thc phm giu carbohydrate thng qua nhiu mcch bin lm sch, mt ti a cc cht km theo carbohydrate trong thc phm.Mc tinh ch cng cao, lng mt cc thnh phn cu to cng ln, cht x b loitr cng nhiu, hm lng carbohydrate cng tng v thc phm tr nn d tiu hn.Carbohydrate tinh ch l nguyn nhn chnh trong vn gy bo ph, ri lon chuynha m v cholesterol ngi nhiu tui, ngi gi t lao ng chn tay.

Thuc loi carbohydrate tinh ch cao c:

- Cc loi ngt, trong lng ng qu 70% nng lng hoc tuy c hm lngng thp (40 - 50%) nhng m cao (30% v hn).

- Bt ng cc t l xay xt cao, hm lng cellulose mc 0,3% hoc thp hn cngthuc loi carbohydrate tinh ch v chng d to m tch cha trong c th.

Ngi nhiu tui, ngi gi, ngi t vn ng th lc nn hn ch lng carbohydratetinh ch di 1/3 tng s carbohydrate khu phn.

Carbohydrate bo v

Gm nhng carbohydrate thc vt ch yu dng tinh bt vi hm lng cellulose caohn 0,4%. Carbohydrate loi ny thng c bo v bi cellulose trc men tiu ho vvy chm tiu, ng ho chm v rt t c s dng to m. Thay th carbohydratetinh ch bng carbohydrate bo v m khng lm thay i cc thnh phn khc trongkhu phn lm tng cm gic no bng.

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Cc carbohydrate n gin

Cc carbohydrate n gin

Thuc loi ny gm c mono v disaccharide. Chng c c tnh chung l d ho tantrong nc, ng ho v s dng nhanh to glycogen. Cc carbohydrate n gin uc v ngt, khi vo c th xut hin tng i nhanh trong mu.

Monosaccharide

Cc monosaccharide thng gp l fructose v glucose. V thnh phn ho hc chngla nhng hexose ngha l trong phn t c 6 nguyn t carbon, ng vi 12 nguyn t Hv 6 nguyn t O (C6H12O6).

a. Glucose

Cu trc ca phn t glucose th hin Hnh 5.1. Glucose c kh nng ng ho nhanhv c s dng nhanh nht trong c th to thnh glycogen. Cht ny cn thit chodinh dng cc c ang hot ng, k c c tim duy tr mc ng huyt v to thnhd tr glycogen gan. Glucose l ngun cung cp nng lng chnh cho h thng thnkinh trung ng. Phn ln carbohydrate a vo c th c chuyn thnh glucose cung cp nng lng cho cc t chc. Glucose c xem l thc n tt nht cho ngisau khi m, m yu hoc b bnh nng.

Hnh 5.1Glucose

Hnh 5.2Fructose

Trong t nhin glucose c nhiu trong cc loi qu. Hm lng ca chng trong mt sloi qu nh sau: chui 4,7%, to 2,5 5,5%, mn 1,4 4,1%.

b. Fructose

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Cu trc phn t ca fructose th hin Hnh 5.2. Fructose c coi l loicarbohydrate thch hp nht cho ngi lao ng tr c ng tui v ngi gi. y cngl loi carbohydrate tt cho cc bnh nhn x va ng mch, cc trng hp ri lonchuyn ho lipid v cholesterol. Fructose nh hng tt n hot ng ca cc vi khunc ch trong rut, c bit ti chc phn ca chng. ngt cao ca fructose cho phps dng vi lng nh t mc cn thit. Ngoi ra cn hn ch c hmlng ng s dng.

Do s lng ca chng bng vi s lng ca glucose t s thy phn ng mann fructose hot ng nh glucose trong vic sn sinh ra glycogen. Glucose vfructose chuyn ho ho hc di tc dng ca dung dch kim v mt cch sinhho hc bi enzyme trong qu trnh chuyn ho qua li cc cht dn xut phosphate,glucose-6-phosphate thnh fructose-6-phosphate.

Cc loi qu l ngun fructose chnh. Ngun fructose t nhin quan trng l mt ong,trong lng fructose ln ti 37,1%. Hm lng fructose trong mt s loi qu nhsau: chui 8,6%, to 6,5 11,8%, mn 0,9 2,7%, m 0,1 - 3%, nho 7,2%.

Disaccharide

Saccharose (ng ma hay c ci ng) v lactose (ng sa) l cc disaccharidechnh c vai tr quan trng trong dinh dng ngi. Tnh cht ca chng l d tantrong nc, d ng ho v s dng to glycogen. Cc disaccharide rt gn vimonosaccharide.

a. Saccharose

Hnh 5.3 SaccharoseHnh 5.4 Lactose

Saccharose (Hnh 5.3) l dng disaccharide ca glucose v fructose. Saccharose didng ng ma hay c ci ng c s dng nhiu nht trong dinh dng ngi.Tuy nhin cn gii hn lng ng s dng i vi ngi ln tui lao ng tr c,nhng ngi c khuynh hng bo... do cc l do sau:

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* Mc s dng ng cao thng khng tch ri vi s tng nng lng chung cakhu phn, y l vic khng tt i vi ngi khng lao ng chn tay.

* Khi tha, saccharose d dng bin thnh m

* Nhiu nghin cu cn cho thy ngi ng tui v gi, tha saccharose c tc dngtng cholesterol trong mu, trong khi tinh bt khng c tnh cht ny.

Ngun saccharose ch yu trong dinh dng ngi l ng ma (10 - 15%) v ngc ci (14 - 18%). Ngoi ra saccharose cn hin din trong mt s loi thc phm khcnh sau: chui 13,7%, m 2,8 - 10%, mn 4,0 9,3%, da hu 5%, c rt 6,4%, to 1,5 5,3%.

b. Lactose (ng sa)

Lactose l mt disaccharide gm 2 monosaccharide to thnh carbohydrate (cu trcphn t c cho Hnh 5.4) trong sa cc loi ng vt c v. Lactose km ngt vkm ho tan hn sucrose, ho tan khong mt phn trong 6 phn nc. Khi hydro hobng nhit vi acid hoc bi enzyme nh lactose ca nc qu ng rut, mi phnt lactose cho mt phn t glucose v mt phn t galactose. Do lactose n vo chp thu. Enzyme thy phn lactose l lactase. Lactase thng mt trong cc c th thanhthiu nin v lm cho cc c th ny khng chu c sa. Qu trnh thy phn lactose ng rut xy ra chm, iu c mt tt v khng tt.

* Mt tt ca vic thy phn chm lactose l nh c th hn ch c cc qu trnhln men rut v bnh thng ho cc hot ng ca vi khun ng rut c ch. S cmt ca lactose kch thch pht trin ca vi sinh vt lm chua sa, c ch cc vi khungy thi. Saccharose khng c tnh cht ca lactose nn khng c tc dng no i vivi khun rut.

* Mt khng tt ca vic thy phn chm lactose l hn ch s dng n to glycogennhanh, do mt ny m khi lao ng nng dng glucose hay saccharose tt hn. Lactosert t s dng trong c th to m v cng khng c tc dng lm tng cholesteroltrong mu. Ngun lactose l sa v cc ch phm ca sa.

c. Maltose (ng mch nha)

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Hnh 5.5 Maltose

Maltose do hai phn t glucose ngng kthp thnh (Hnh 5.5). Trong mm ca ccloi ng cc mi ny mm c hm lngtng i nhiu, c bit l trong mchnha c hm lng cao nht. Thc n ccha tinh bt trong ming di tc dngca amylase trong nc bt, mt phn sc phn gii thnh ng maltose.

ngt ca cc loi ng

ngt ca cc loi ng khc nhau. Nu ly ngt ca saccharose (ma hay c cing) l 100, th ngt ca cc loi ng c sp xp nh sau:

T s liu cho thy ngt nht l ng fructose, t ngt nht l ng lactose. ng ch cc loi ng t lactose phn gii ra, glucose v galactose li ngt hn nhiu (74 v32) so vi lactose (16).

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Polysaccharide

Polysaccharide

Tinh bt

L polysaccharide c cu trc ho hc phc tp. S phc tp ca cu trc phn t ccpolysaccharide l nguyn nhn ca tnh khng ho tan ca chng. Tinh bt c c tnhha tan dng keo. Cc dung dch keo ca tinh bt khng bao gm cc ht tinh bt ringr m l cc mi-xen (micelle) bao gm mt lng ln phn t.

Tinh bt bao gm hai phn t, amylose (thng thng chim 20 - 30%) (Hnh 5.6) vamylopectin (Hnh 5.7) (thng thng chim 70 - 80%). C hai cha hp cht cao phnt ca cc n v -glucose trong cu trc.

Tinh bt l thnh phn dinh dng chnh ca thc phm thc vt, c bit l cc loiht v u cng nh khoai ty. S bin i tinh bt trong c th ng v thc vt khngtch ri vi s to thnh ng. Do c th coi tinh bt l ngun ng quan trng,cn thit cho hot ng ca c th. Nhiu nghin cu chng minh rng thc vt s totinh bt i trc s to thnh ng. Lng tinh bt trong to gim dn trong qu trnhchn v bo qun, ng thi cc loi ng tng ln mt cch tng ng.

Trong c th ngi tinh bt l ngun cung cp glucose chnh. S bin i chm tinhbt thnh glucose to iu kin thun li cho vic s dng chng hon ton nhttrong c th. Trong iu kin tiu hao nng lng trung bnh lng ng cn thit

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ch yu da vo tinh bt. S bin i tinh bt thnh glucose i qua nhiu giai ontrung gian. Do nh hng ca cc men (amylase, diastase) v acid, tinh bt b thyphn to thnh dextrin (bt u l amylodextrin, sau l erytrodextrin, acrodextrin vmaltodextrin). Trong qu trnh , mc ho tan trong nc ca cc dextrin to thnhtng ln. Amylodextrin ch ho tan trong nc nng, cn erytrodextrin c th ho tantrong nc lnh. Acrodextrin v maltodextrin tan d dng trong bt k trng hp no.Phn ng c hiu cho tinh bt cng mt i theo qu trnh trn. Amylodextrin cho muxanh nht, acrodextrin v maltodextrin khng cho phn ng vi iode. Sn phm cuicng ca bin i cc dextrin l ng maltose. y l mt loi ng c y tnhcht ca disaccharide, k c tnh cht d ho tan trong nc. Do nh hng ca cc men,maltose chuyn thnh glucose, cht ny c s dng to glycogen. C th thy qutrnh chuyn ho ca cc disaccharide v polysaccharide theo s Hnh 5.8

Glycogen

ch tn ti trong c th ng vt, l hnh thc carbohydrate tn tr. Glycogen c tngi nhiu gan (ti 20% trng lng ti) v c. Trong c th glycogen c s dng dinh dng cc c, c quan v h thng ang hot ng di dng cht sinh nnglng. S phc hi glycogen xy ra khi ngh ngi nh s ti tng hp glycogen tglucose ca mu.

H thng thn kinh trung ng iu ho vic to thnh v phn gii glycogen trong cth. H thng ni tit t cng tham gia vo iu ho chuyn ho glycogen gan. Khiglucose trong mu cao, insulin ca tuyn ty kch thch tng hp glycogen gan v gyh ng huyt. Khi glucose trong mu thp, adrenalin ca tuyn thng thn gip phngii glycogen gan.

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Hnh 5.8 Qu trnh chuyn ho ca cc disaccharide v polysaccharide

Cc cht pectin

V cu trc ho hc, acid pectinic c cc chui di gm cc anhydric ca acidgalacturonic ni bi cc dy ni glucoside d b phn hy. Do nh hng ca cc tcnhn ho hc (acid, kim) v un nng, cc cht pectin d dng b thy phn. Cc chtpectin cng d dng b phn gii bi cc men c mt trong vi khun, nm v cc t chcthc vt cao cp.

Pectin gm hai dng:

Protopectin

* L nhng pectin nguyn thy ca thc vt khng tan trong nc

* C mt trong cc thc phm thc vt nh: qu, c to thnh cc lp trung gian giacc t bo v cht liu lin kt v cng c thnh t bo.

* Protopectin c nhiu trong cc qu xanh, do qu xanh thng cng. Trong qu trnhprotopectin b phn gii, qu dn tr nn mm. Lng pectin rau qu un chn cao hnrau qu cn ti v mt phn c to thnh t protopectin.

Pectin

* Thuc nhm cht ho tan, ng ho c trong c th. V thnh phn ho hc lcc polygalacturonic phn t cao (trong nguyn t H trong cc nhm carboxyl cthay th bi cc nhm methyl v ion kim loi theo mc khc nhau).

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* Pectin l esther methylic ca acid pectinic. Di nh hng ca enzyme pectinase,pectin b thy phn ti cc thnh phn n gin hn l ng v acid tetra-galacturonic.Do tc dng ca cc enzyme ny nhm methoxyl (OCH3) tch khi pectin. Nh vypectin l acid polygalacturonic c cha cc nhm methoxyl.

Tnh cht ca cc pectin quyt nh vai tr ca chng trong k ngh thc phm l khi cmt ca acid v ng chng to thnh vi nc cc khi ng keo. Ngi ta thy lngru methylic trong pectin cng cao th c tnh ng keo cng tt. Nhiu nghin cucho thy pectin c vai tr trong dinh dng ngi kho v ngi m. Cc cht pectin cch cc vi khun gy thi trong rut v iu ho h vi khun ng rut, ci thin ccqu trnh tiu ho.

Pectin c cng hiu cao trong cc trng hp ng c ngh nghip do ch. nhng nisn xut c nguy him do ch, ch n iu tr, d phng giu pectin c tc dng tt.Nhiu nghin cu ch ra rng vic s dng pectin vo ch n iu tr, d phng giupectin c th p dng cho cc ngh nghip tip xc vi cc cht c khc. Pectin cnthc y qu trnh lin so v c tc dng tt trong iu tr bng lot.

Hiu qu iu tr ca cc thc n thc vt (to, c rt, chui..) trong iu tr cc bnhd dy-rut l do cc cht pectin c nhiu trong . Cc tc dng ny ca pectin chac gii thch y mt cch khoa hc. Ngi ta cho rng tc dng trn c c ldo cc c tnh keo ca pectin v kh nng hp ph cao ca chng. Pectin c nhiu trongcc loi qu, c nh cam 12,4%, m 4 7,1%, mn 3,1 - 8%, to 1,6 5,6%, c rt2,4 4,8%.

Cellulose

Cellulose l thnh phn cu to ca thc vt, v cu trc ho hc rt gn vipolysaccharide (Hnh 5.10).

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Cht lng cellulose c ngha dinh dng quan trng v c chia thnh hai loi:cellulose th v cellulose mn. Loi cng mn cng c kh nng phn gii v ng hocao. Chc nng ca cellulose v cc cht x thc n nh sau:

Phng nga ung th rut kt: Cc thc n c cha hm lng lipid cao s lm cho vikhun k kh trong rut sinh si ny n nhiu khin cho cc ster