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Li ni u

Hin nay c nhiu phng php bo qun trng nh bo qun lnh, bo qun bng nc

vi, bo qun bng kh tr v bo qun bng mng (silicate, parafin, chitosan). Trong ,

mng bao lm t chitosan, ph phm ca ng vt thu sn, c tnh khng khun, khngnm, khng thm nc, hn ch mt nc nn thng c nghin cu ng dng bo qun

rau qu, trng gia cm. Kt qu nghin cu ca nhiu tc gi ch ra rng: mng bao

chitosan, trong qu trnh bo qun, nh hng tch cc n cht lng ca trng g ti.

Theo Su Hyun Kim, Cenzig Caner, trng c bo qun bng mng bao chitosan hn ch

ng k s hao ht khi lng, tng ch tiu cht lng lng trng (Haugh units), lng

trng (Yolk index). Nghin cu ca Xian De Liu v cng s cho thy: s dng mng bao

chitosan kt hp vi chiu x gip ci thin cht lng trng g ti trong thi gian boqun. nc ta, tc gi Trn Th Luyn, L Thanh Long cng nghin cu ng dng

mng bao chitosan kt hp vi ph gia bo qun trng g ti.

Tuy nhin, trong cc nghin cu trn, cha c nghin cu no nh gi s bin ng cc

ch tiu ho l ca trng g, nh hm lng protein ho tan, hm lng amoniac, khi ng

dng mng bao chitosan bo qun trng.

Trong nghin cu ny, chng ti tin hnh kho st nh hng ca hm lng chitosan

trong mng bao n mt s tnh cht ho l ca trng g ti trong 30 ngy bo qun nhit thng. T , nh gi ton din hn cht lng ca trng khi ng dng mng

bao chitosan bo qun trng ti.

I.TNG QUAN

I.1 Trng g

Nc ta c nn nng nghip pht trin mnh . Giai on 2007-2010: tc tng n g l

7,8%/nm, tng sn lng tht l 21,9%. Nm 2010, s lng g 233 triu con; sn lng

trng 6.766 triu qu.D kin giai an 2011-2015, tc tng n l 8,5%/nm.Nm

2015 s lng g 350 triu con; sn lng trng 9.236 triu qu.Vi sn lng trng g

ln c bit l trong iu kin kh hu nng m nhit i ca nc ta nn trng d b h

hng trong qu trnh bo qun do tc ng ca hin tng t phn hu, hot ng ca vi

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sinh vt, trao i nc, khng khdo vic tm kim cc phng php bo qun trng

g l mt iu cp thit

I.2 Chitosan

I.2.1 Ngun gc v lch sChitin l mt trong nhng polyme c nhiu

trong thin nhin, c ngun gc t cc loi ng

vt nh tm, cua. Chitin c thi gian phn hy

chm, nn vic x l mt lng ln cht thi trong

cng nghip ch bin hi sn gp nhiu kh khn.

Tn dng ngun nguyn liu chitin ny, chng ta

to ra c chitosan c ng dng trong nhiu lnhvc. V mt lch s, chitin c Braconnot pht

hin u tin vo nm 1821, trong cn dch chit t

mt loi nm. ng t tn cho cht ny l Fungine ghi nh ngun gc ca n. Nm

1823 Odier phn lp c mt cht t b cnh cng m ng gi l chitin hay chiton,

ting Hy lp c ngha l v gip, nhng ng khng pht hin ra s c mt ca nit trong

. Cui cng c Odier v Braconnot u i n kt lun chitin c dng cng thc ging

vi xellulose. Trong ng vt, chitin l mt thnh phn cu trc quan trng ca cc v mts ng vt khng xng sng nh: cn trng, nhuyn th, gip xc v giun trn. Trong

ng vt bc cao monome ca chitin l mt thnh phn ch yu trong m da n gip cho

s ti to v gn lin cc vt thng da. Trong thc vt chitin c thnh t bo nm h

Zygenmyctes, cc sinh khi nm mc, mt s loi to... Chitin c cu trc thuc h

polysaccharide, hnh thi t nhin dng rn. Do , cc phng php nhn dng chitin,

xc nh tnh cht, v phng php ho hc bin tnh chitin cng nh vic s dng v

la chn cc ng dng ca chitin gp nhiu kh khn.

Cn chitosan chnh l sn phm bin tnh ca chitin, l mt cht rn, xp, nh, hnh vy,

c th xay nh thnh cc kch c khc nhau. Chitosan c xem l polymer t nhin quan

trng nht. Vi c tnh c th ho tan tt trong mi trng acid, chitosan c ng dng

trong nhiu lnh vc nh thc phm, m phm, dc phm ... Ging nh cellulose,2


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chitosan l cht x, khng ging cht x thc vt, chitosan c kh nng to mng, c cc

tnh cht ca cu trc quang hcChitosan c kh nng tch in dng do n c kh

nng kt hp vi nhng cht tch in m nh cht bo, lipid v acid mt.

Chitosan l polymer khng c, c kh nng phn hy sinh hc v c tnh tng thchv mt sinh hc. Trong nhiu nm qua, cc polymer c ngun gc t chitin c bit l

chitosan c ch c bit nh l mt loi vt liu mi c ng dng c bit trong

cng nghip dc,y hc, x l nc thi v trong cng nghip thc phm nh l tc nhn

kt hp, gel ha, hay tc nhn n nh

Trong cc loi thy sn c bit l trong v tm, cua, gh, hm lng,chitin - chitosan

chim kh cao ao ng t 14 - 35% so vi trng lng kh. V vy v tm, cua, gh l

ngun nguyn liu chnh sn xut chitin - chitosan.Chitosan l mt dng Chitin b kh axetyl, nhng khng ging Chitin, n li tan c

trong dung dch axit. C Chitin v Chitosan u c nhiu ng dng trong cng nghip v

cuc sng, c bit l trong ch bin v bo qun thc phm. Chitin c gc t ch "chiton",

ting Hy Lp c ngha l v gip. Chitin l thnh phn cu trc chnh trong v (b xng

ngoi) ca cc ng vt khng xng sng trong c loi gip xc (tm, cua). Khi ch

bin nhng loi hi sn gip xc, lng cht thi (cha Chitin) chim ti 50% khi lng

u vo v con s ny tnh trn ton th gii l khong 5,11 triu tn/nm. Th nn, nu tndng c Chitin v Chitosan to ra cc sn phm c gi tr th li nng cao c hiu

qu tn dng cc ph phm trong ch bin thy hi sn v bo v mi trng. T Chitin ta

c th iu ch Chitosan v cc dn xut ca chng u c tnh khng khun.

I.2.2 Cu trc ca Chitosan

Chitosan l polymer sinh hc c khi lng phn t ln v rt ging cellulose.

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1. Chitin 2. Chitosan 3. Cellulose

Nh hnh v trn, th s khc bit duy nht gia chitosan v cellulose l nhm amin (-

NH2) v tr C2 ca tritosan thay th nhm hydroxyl (-OH) cellulose. Chitosan tch in

dng do n c kh nng lin kt ha hc vi nhng cht tch in m nh cht bo,

lipid, cholesterol, protein v cc i phn t. Chitin v chitosan rt c li ch v mt thng

mi cng nh l mt ngun vt cht t nhin do tnh cht c bit ca chng nh tnh

tng thch v mt sinh hc, kh nng hp th, kh nng to mng v gi cc ion kim loi.

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Mu ca v gip xc hnh thnh t hp cht ca chitin (dn xut ca4-xeton v 4,4-

dixeton--carotene ). Bt chitosan c dng hi st trong t nhin v mu sc ca n bin

i t vng nht n trng trong khi tinh bt v cellulose li c cu trc mn v mu trng.

I.2.3 Tnh cht ca ChitosanI.2.3.1. Mc deacetyl ha:

Qu trnh deacetyl ha bao gm qu trnh loi nhm acetyl khi chui phn t chitin v

hnh thnh phn t chitosan vi nhm amin hot ng ha hc cao. Mc acetyl ha l

mt c tnh quan trng ca qu trnh sn xut chitosan bi v n nh hng n tnh cht

ha l v kh nng ng dng ca chitosan sau ny. Mc acetyl ha ca chitosan vo

khong 56%-99% (nhn chung l 80%) ph thuc vo loi gip xc v phng php s

dng. Chitin c mc acetyl ha khong 75% tr ln thng c gi l chitosan. C rtnhiu phng php xc nh mc acetyl ha ca chitosan bao gm th ninhydrin,

chun theo in th, quang ph hng ngoi, chun bng HI

Phng php s dng quang ph hng ngoi thng c s dng thit lp cc gi tr

mc acetyl ha ca chitosan. Phng php ny rt nhanh v khng ging nhng phng

php quang ph khc n khng i hi mu phi tinh ch, v khng cn ha tan mu vo

dung dch. Tuy nhin phng php ny s dng ng chun do cch xy dng ng

chun c th nh hng n kt qu. Ngoi ra, khi chun b mu, dng c s dng v cciu kin c th nh hng n vic phn tch mu. Khi mc acetyl ha thp, chitosan

c kh nng ht m ln hn khi mc ny cao do trc khi phn tch chitosan cn

phi sy.

I.2.3.2. Trng lng phn t:

Chitosan l polymer sinh hc c khi lng phn t cao. Ging nh cu to, khi lng

ngun nguyn liu v phng php ch bin. Khi lng chitin thng ln hn 1 triu

Dalton trong khi cc sn phm chitosan thng phm c khi lng khong 100,000-

1,200,000 Dalton, ph thuc qu trnh ch bin v loi sn phm. Thng thng, nhit

cao, s c mt ca oxy v sc ko c th dn n phn hy chitosan. Gii hn nhit l

280C, s phn hy do nhit c th xy ra v mch polymer nhanh chng b ph v, do

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khi lng phn t gim. Nguyn nhn qu trnh depolymer l s dng nhit cao v

acid c nh HCl, H2SO4 dn n thay i khi lng phn t.

Khi lng phn t chitosan c th xc nh bng phng php sc k, phn tn nh

sng hoc o nht.I.2.3.3. nht.

nht l mt nhn t quan trng xc nh khi lng phn t ca chitosan.

Chitosan phn t lng cao thng lm cho dung dch c nht cao, iu ny c th

khng mong mun trong ng gi cng nghip. Nhng chitosan c nht cao thu c

t ph phm ca cc loi gip xc th rt thun tin cho ng gi. Mt s nhn t trong qu

trnh sn xut nh mc deacetyl ha, khi lng nguyn t, nng dung dch,

mnh ca lc ion, pH v nhit nh hng n sn xut chitosan v tnh cht ca n. Vd, nht ca chitosan tng khi thi gian kh khong tng. nht ca chitosan trong

dung dch acid acetic tng khi pH ca dung dch ny gim, tuy nhin n li gim khi pH

ca dung dch HCl gim, vic tng ny a n nh ngha v nht bn trong ca

chitosan, y l mt hm ph thuc vo mc ion ha cng nh lc ion. Qu trnh loi

protein trong dung dch NaOH 3% v s kh trong qu trnh kh khong lm gim nht

ca dung dch chitosan thnh phm. Tng t nh vy, nht ca chitosan b nh hng

ng k bi cc bin php x l vt l (nghin, gia nhit, hp kh trng, siu m) v hahc (s l bng ozon), tr qu trnh lm lnh th n s gim khi thi gian v nhit x l

tng. Dung dch chitosan bo qun 4C c cho l n nh nht.

I.2.3.4. Tnh tan.

Chitin tan trong hu ht cc dung mi hu c, trong khi chitosan tan trong cc dung

dch acid pH di 6.0 . Cc acid hu c nh acetic, formic v lactic thng c s dng

ha tan chitosan. Thng s dng nht l dung dch chitosan 1% ti pH 4.0. Chitosan

cng tan trong dung dch HCl 1% nhng khng tan trong H2SO4 v H3PO4. Dung dch acid

acetic nng cao ti nhit cao c th dn n depolymer ha chitosan. pH cao, c

th xy ra hin tng kt ta hoc ng t nguyn nhn l do hnh thnh hn hp poly_ion

vi cht keo anion. T l nng gia chitosan v acid rt quan trng. nng dung mi

hu c cao hn 50%, chitosan vn hot ng nh l mt cht gy nht gip cho dung dch6


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mn. C mt vi nhn t nh hng n dung dch chitosan bao gm nhit v thi gian

qu trnh deacetyl ha, nng cc cht kim, vic x l s b, kch thc ca cc phn

t. Tuy nhin tnh tan ca dung dch cn b nh hng ca mc acetyl ha, mc

deacetyl ha trn 85% t c tnh tan mong mun.I.2.3.5. T trng:

T trng ca chitin t tm v cua thng l 0.06 v 0.17 g/ml, iu ny cho thy chitin

t tm xp hn t cua. Chitin t nhuyn th xp hn t cua 2.6 ln. Trong mt nghin cu

v dn nhit cho thy t trng ca chitin v tritosan t gip xc rt cao (0.39g/cm3). S so

snh gia t trng ca gip xc v chitin, chitosan thng phm cng ch ra mt vi s

khc bit, iu ny c th do loi gip xc hoc phng php ch bin, ngoi ra, mc

deacetyl ha cng lm tng t trng ca chng.I.2.3.6. Kh nng kt hp vi nc (WBC) v kh nng kt hp vi cht bo

(FBC).

S hp th nc ca chitosan ln hn rt nhiu so vi cellulose hay chitin. Thng

thng, kh nng hp th ca chitosan khong 581-1150% (trung bnh l 702%), v s

thay i trong th t sn xut nh qu trnh kh khong v kh protein cng nh hng

ng k n kh nng gi nc v gi cht bo. S kh protein sau qu trnh kh khong

s lm kh nng gi nc tng. Bn cnh qu trnh kh mu cng l nguyn nhn lmgim kh nng ny ca chitosan hn l chitosan t gip xc khng kh trng. Kh nng

hp th cht bo ca chitin v chitosan trong khong 315-170%, chitosan c kh nng thp

hn rt nhiu chitin. Trong mt nghin cu ch ra rng kh nng gi cht bo trung bnh

ca chitosan t gip xc v chitosan thng phm t cua ln lt l 706% v 587%. Bc

ty trng trong qu trnh sn xut lm gim kh nng ny cng nh ng hng n nht

ca chitosan. Cc bc tin hnh theo th t: kh khong , kh protein, deacetyl ha s

lm tng kh nng ny hn l theo th t kh protein, kh khong, deacetyl ha.

I.2.3.7. Kh nng to mng.

Chitosan c kh nng to mng s dng trong bo qun thc phm nhm hn ch cc tc

nhn gy bnh tm thn trong cc sn phm ng gi trong p sut thay i ca tht, c

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*. Khi dng mng chitosan, d dng iu chnh m, thong khng kh cho thc

phm. Nu dng bao gi bng PE th mc cung cp oxy b hn ch, nc s b ngng ng

to mi trng cho nm mc pht trin.

*. Mng chitosan cng kh dai, kh x rch, c bn tng ng vi mt s cht dovn c dng lm bao gi.

*. Mng chitosan lm chm li qu trnh b thm ca rau qu. Rau qu sau khi thu hoch

s dn dn b thm, lm gim cht lng v gi tr. Rau qu b thm l do qu trnh ln men

to ra cc sn phm polyme ha ca oquinon. Nh bao gi bng mng chitosan m c ch

c hot tnh oxy ha ca cc polyphenol, lm thnh phn ca anthocyamin, flavonoid v

tng lng cc hp cht phenol t bin i, gi cho rau qu ti lu hn. To c ph mng

chitosan c th gi ti trong 6 thng, n cng lm chm qu trnh chn chui hn 30 ngy,chui c mu vng nht khc hn vi mu thm nh bo qun thng thng.

Cch to mng bc chitosan:

- Chitosan c nghin nh bng my gia tng b mt tip xc.

-Pha dung dch chitosan 3% trong dung dch axit axetic 1.5%.

- B sung cht ph gia PEG - EG 10% (t l 1:1) vo v trn u, yn mt lc loi

bt kh.

- em hn hp thu c qut u ln mt ng inox c nung nng nhit 64-65C (ng inox c nng nhit bng hi nc).

- kh mng trong vng 35 pht ri tch mng.

- Lc ny ngi ta thu c mt v bng c mu vng ng, khng mi v, l lp

mng chitosan c nhng tnh nng mi u vit.

ng dng ca chitosan:

Trong thc t ngi ta dng mng chitosan ng v bo qun cc loi rau qu nh

o, da chut, u, qu kiwi v.v... ng dng trong nhiu lnh vc nh: y hc, x l nc

thi, cng nghip nhum, giy, m phm, thc phm...

u im ca mng chitosan:

- Phn hu sinh hc: V tm ph liu l ngun nguyn liu t nhin rt di do, r tin,

c sn quanh nm, nn rt thun tin cho vic cung cp chitin v chitosan.8


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- Tn dng ph thi trong ch bin thy sn bo qun thc phm nc ta. Thnh cng

ny cn gp phn rt ln trong vic gii quyt tnh trng nhim mi trng do cc cht

thi t v tm gy ra.

Tnh khng khun ca Chitosan:Gn y nhng nghin cu v tnh khng khun ca chitosan ch ra rng chitosan c

kh nng c ch s pht trin ca vi khun.

Trong mt nghin cu kh rng v tnh khng khun ca chitosan t tm chng li

E.coli, ngi ta tm ra rng nhit cao v pH acid ca thc n lm tng nh hng ca

chitosan n vi khun. N cng ch ra c ch c ch vi khun ca chitosan l do lin kt

gia chui polymer ca chitosan vi cc ion kim loi trn b mt vi khun lm thay i

tnh thm ca mng t bo. Khi b sung chitosan vo mi trng, t bo vi khun schuyn t tch in m sang tch in dng. Quan st trn knh hin vi hunh quang cho

thy rng chitosan khng trc tip hot ng c ch vi khun E.coli do m l do s kt li

ca cc t bo v s tch in dng mng ca vi khun. Chitosan N-carboxybutyl, mt

polycation t nhin, c th tng tc v hnh thnh polyelectrolyte vi polymer acid tnh c

trn b mt vi khun, do lm dnh kt mt lng vi khun vi nhau.

Cng t th nghim ny ngi ta thy rng c rt nhiu ion kim loi c th nh hng

n c tnh khng khun ca chitosan nh K+, Na+, Mg2+ v Ca2+. Nng ln cc ionkim loi c th khin mt tnh cht ny, ngoi tr nh hng ca Na+ i vi hot ng

khng Staphylococcus aureus. Ngi ta cng thy rng chitosan c th lm yu i chc

nng bo v ca thnh t bo nhiu vi khun. Khi s dng chitosan, th mt lng ln cc

ion K+ vi ATP b r r vi khun Staphylococcus aureus v nm candida albicans. C

chitosan phn t lng 50kDa v 5kDa u khng tt hai loi trn nhng chitosan phn t

lng 50kDa lm mt nhiu gp 2-4 ln ion K+ vi ATP chitosan 5kDa. iu ny th hin

c ch khng khun khc nhau chitosan khi lng phn t thp v cao. Hot ng

khng khun ca chitosan phn t lng khc nhau c nghin cu trn 6 loi vi

khun. V c ch khng khun ny c chng minh a trn vic o tnh thm ca

mng t bo vi khun v quan st s nguyn vn ca t bo. Kt qu ch ra rng kh nng

ny gim khi khi lng nguyn t tng. V n tng cao nng pH thp, gim r rt khi c9


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mt ion Ca2+, Mg2+ . Nng c ch thp nht khong 0.03-0.25%, thay i ty tng loi

vi khun v khi lng phn t ca chitosan. Chitosan cng l nguyn nhn lm thot cc

cht trong t bo v ph hy thnh t bo. Tnh khng khun ny ph thuc vo khi lng

phn t v loi vi khun. i vi vi khun Gram dng, chitosan 470 KDalton c nhhng n hu ht cc loi tr lactobacillus sp. , trong khi vi vi khun Gram m chitosan

c khi lng 1106 KDalton mi c nh hng. Nhn chung, chitosan nng 0.1% c

nh hng mnh hn n vi khun Gram dng nh Listeria monocytogenes, Bacillus

megaterium, B.cereus, Staphylococcus aureus, lactobacillus plantarum, L. brevis v L.

bulgaris hn l vi khun Gram m nh E.coli, Psedomonas fluorescens, Salmonella

typmurium v Vibrio parahaemolyticus. Nghin cu trn vt th nghim cho thy chitin v

chitosan c hot ng c ch vi khun v nm. Mt trong cc ng phn ca chitosan l N-carboxybutyl chitosan c tc dng km hm v tiu dit 298 loi vi sinh vt gy bnh. Khi

c chitosan v chitin trn b mt cc tc nhn gy bnh thc vt, chng c ch s pht

trin ca nhng loi ny. nng 0.1% v pH 5.6 chng khng cc loi nm: Fusarium,

Alternaria, Rhizopus V hot ng khng ny s gim nhng vi sinh vt m trn thnh

t bo c cha chitin, chitosan hoc chitin--glucan.

Ngc li, s c ch v lm ngng hot ng ca nm men, nm mc li ph thuc vo

nng chitosan, pH, v nhit . Hot ng c ch vi khun ca chitosan chu nh hngca cc nhn t bn trong cng nh bn ngoi v d loi chitosan, mc polymer ha, c

im dinh dng ca vt ch, cc cht ha hc thnh phn dinh dng v cc iu kin ca

mi trng nh hot ca nc

Chitosan c cho php lm cht ph gia thc phm Nht v Hn Quc ln lt t

nm 1983 v 1995. Chnh hot ng c ch vi khun cao ca chitosan pH thp nn khi

thm chitosan vo nhng thc phm c tnh acid th n c chc nng tng cng hot ng

khng khun nh l mt cht bo qun t nhin. pH 5.5, vi nng 0.5-1% chitosan c

tc dng c ch n cc loi S.aureus, E.coli, Yersinia enterocolitica, Listeria

monocytogenes. pH 6.5 ch c S.aureus b c ch nng trong khi cc loi khc

vn pht trin nng 2.5% (nng cao nht c nghin cu).

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Chitosan phn t nh c tnh khng cc tc nhn gy bnh trn thc vt mnh hn rt

nhiu cc cht phn t ln.

Ngoi ra cc hp cht chitosan lactate v chitosan hydroglutamate cng c s dng

nh l tc nhn c ch E.coli, S.aureus v Saccharomyces cerevisiae. Nng chitosanlactate trong nc ct c nh hng mnh nht nE. coli. Cha n 1h, s lng vi khun

ny gim khong 104, cn S.aureus gim n 106. i vi nm men, chng hon ton

ngng hot ng nng 1mg/ml chitosan lactate sau cha n 17pht.

I.2.4. Phng php xc nh tnh khng khun ca Chitozan

nh gi tc ng trc tip ca Chitozan ln vi khun th nghim bng cch xc nh

phn trm lng vi khun cht khi cho tip xc trc tip vi khun vi Chitozan. Cc bc

tin hnh nh sau :- Chun b dung dch Chitozan v trng : Ho tan Chitozan v trng trong dung

dch 1% axit acetic. iu chnh pH ca dung dch n pH mong mun bng kim long

(khng lm ta Chitozan). Pha long Chitozan n nng thch hp vi thit k th

nghim bng nc mui sinh l v trng.

- Chun b huyn dch vi khun : Nui cy vi khun em th nghim trn mi

trng thch dinh dng (NA) trong vng 24 gi. Chn khun lc in hnh, to huyn

dch vi khun mt chn trc trong nc mui sinh l v trng. c lng lngvi khun ban u, chng ta c th da vo c. Huyn dch vi khun c c 0,5

McLand c chng c khong 108 t bo/ ml. T huyn dch ny chng ta pha long trong

nc mui sinh l c c mt vi khun ban u mong mun.

- T huyn dch vi khun chun b nh trn, chng ta a lng vi khun nht nh

vo cc dung dch Chitozan chun b trn cng vi ng chng l nc mui sinh l.

- Theo thi gian chng ta nh lng vi khun cn sng trong cc dch Chitozan cc

nng khc nhau. nh lng vi khun bng phng php m khun lc.

Cc bc tin hnh nh sau :

Pha long bc 10 mu cn kim tra bng nc mui sinh l v trng.

Mi trng : thng s dng cc mi trng thch hp nh thch dinh

dng (NA), PCA (Plate Count Agar) ...11


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Cy 0,1 ml trn b mt a thch, dng que gt v trng dn dch cy ra

khp b mt mi trng. Mi pha long cy 2 a.

Nui cy 370C trong 24-48 gi.

m s khun lc. Chn pha long c s khun lc t 30 n 300khun lc trn 1 a a vo tnh ton. Tnh theo cng thc :

(Vi A l s khun lc trung bnh trn 1 a pha long chn)

- nh gi kh nng khng khun bng cch so snh lng vi khun trong dung dch

Chitozan (CFUchitozan) vi lng vi khun trong ng nc mui sinh l i chng

(CFUchng):

I.2.5 Sn xut Chitosan

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II. VT LIU V PHNG PHP NGHIN CU

II.1 Vt liu th nghim

Trng g ti thu mua ti tnh Bnh Dng, t cht lng tt (khng nt, v, dnhphn) v cn ti (khng qu 24h sau khi ). Chitosan dng vy, mu trng ng, tinh

khit 95%; deacetyl: 86 90%, do trng i hc Thu sn Nha Trang cung cp.

II.2 Phng php nghin cu

X l v chn trng: Loi b nhng qu trng nt, v, dnh nhiu phn. Dng khn

kh, sch lau loi bi bn, rm, rc bm dnh trn v trng.

Chun b dung dch to mng Chitosan c ho tan trong dung dch acid acetic 0.6%

cc mc nng t 1% n 1.6%. n nh dung dch trong 12h sau khi pha. Tinhnh lc, dung dch sau lc thu c chnh l dung dch dng to mng.

Tin hnh to mng: Trng g ti sau khi la chn v lm sch, em nhng ngp vo

dung dch chitosan chun b nh trn trong 15 giy ri vt ra, lm kh t nhin. Sau khi

v trng kh, tip tc nhng trng ln hai tng t nh ln mt.

Bo qun: Sau khi trng kh hon ton, em i bo qun nhit phng. Trong

sut thi gian bo qun (30 ngy), c 5 ngy th tin hnh phn tch cht lng trng (hao

ht khi lng, hm lng protein ho tan, hm lng amoniac).II.2.1 Kho st s hao ht khi lng trng

Sau khi trng c bc bi lp mng Chitosan, mt thi gian cho lp mng kh

hon ton, em i bo qun nhit phng. Trong sut thi gian bo qun (30 ngy), c

5 ngy th tin hnh phn tch cht lng trng (hao ht khi lng, hm lng protein ho

tan, hm lng amoniac).

II.2.2 Kho st s bin i hm lng protein trong trng

Xc nh protein ho tan bng phng php quang ph vi thuc th Biure

II.2.3 Kho st s bin i hm lng amoniac (NH3) trong trng

Xc nh NH3bng phng php chng ct ko hi nc

III. KT QU V BIN LUN

III.1 Kho st s hao ht khi lng trng14


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Chng ta tin hnh xc nh khi lng trng c sau 5 ngy bo qun. Kt qu hao

ht khi lng trng trong 30 ngy bo qun biu din bng 1 v hnh1.

Bng 1. Hao ht khi lng trng (%) theo thi gian bo qun bng mng chitosan

T kt qu th nghim thu c bng 1 v biu din hnh 1, chng ta c th nhn

thy rng: trong 5 ngy u bo qun hao ht khi lng trng c to mng (0.732%

i vi nng chitosan 1.6%) khng c s khc bit ln vi trng khng to mng

chitosan (0.970%). Nng chitosan to mng cng khng nh hng ln n hao ht

khi lng trng trong khong thi gian ny. iu ny c th c gii thch: do trong thi

gian u, khi mng bao t nhin ca v trng cha b phn hu nn cn kh nng khng vi

sinh vt, hn ch s trao i kh v nc vi mi trng bo qun

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Tuy nhin, khi thi gian bo qun cng di th nh hng ca mng bao n hao ht

khi lng trng cng r nt hn. Sau 30 ngy, tr ng c bo qun bng mng chitosan

nng 1.6% ch hao ht 4.750%, trong khi mu i chng ln ti 8,240%.

III.2 Kho st s bin i hm lng protein trong trngBn cnh xc nh hao ht khi lng trng, chng ti cn theo di s bin i hm

lng protein trong trng, thng qua th nghim xc nh hm lng protein ho tan. Kt

qu th nghim c tng hp bng 2 v hnh 2.

Kt qu cho thy: sau 30 ngy bo qun, hm lng protein ho tan ca mu i chng

gim r rt (sau 20 ngy bo qun gim 0.428%). iu ny c th l lun rng: trong

thi gian bo qun, s trao i kh, m vi mi trng bn ngoi, to iu kin cho s xm

nhp vi sinh vt lm cho cc phn ng thu phn, phn hu protein din ra mnh lit to

thnh acid amin t do, NH3, H2 vi cc mu trng c bo qun bng mngchitosan th

s bin i hm lng protein ho tan t hn. Nng chitosan mng bao cng nh

hng n hm lng protein ho tan. Sau 30 ngy, hm lng protein ho tan trong trng

vn cn 9.574% (i vi nng chitosan 1.6%).

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Khng s dng mng chitosan ( );Dng mng chitosan nng 1% ( ); 1.2% (

); 1.4% ( ); 1.6% ( ).

III.3 Kho st s bin i hm lng amoniac (NH3) trong trng

Kt qu hm lng amoniac sau 30 ngy bo qun th hin bng 3 v hnh 3.

17


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Qua hnh 3, chng ta c th thy rng hm lng NH3 tng nhiu sau 30 ngy bo qun.

Mu i chng c hm lng cao nht (0.064%). Trong khi , mu trng c bo qun

bng mng nng chitosan 1.6% c hm lng NH3 thp nht (0.021%).

IV. KT LUN V KIN NGH

Nghin cu ny cho thy mng bao chitosan nh hng nhiu n cht lng trng g

ti (hao ht khi lng, hm lng protein ho tan, hm lng amoniac). Nng

chitosan trong dung dch cng nh hng n phm cht ca trng, tuy nhin khng c s

khc bit ln. Do vy nng chitosan thch hp trong dung dch c th thay i t

11.6%. Vi nhng kt qu khi ng dng mng bao chitosan bo qun trng m cc tc gi

khc nghin cu, cng nh nhng kt qu ch ra bi bo ny, cho thy: hon ton c

th s dng mng bao chitosan bo qun trng qui m thng mi v cng nghip.

Cn c gii php x l trong qu trnh sn xut sao cho hn ch n mc thp nht

lng cht thi gy nhim mi trng.

Cn c thm nhiu phng php thc hin vic bo qun sao cho chi ph bo qun l thp

nht h gi thnh sn phm.

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Cn ph bin k thut bo qun trng bng Chitosan n cc trang tri v h gia nh chn

nui gia cm h c th thc hin vic bo qun ti ngun nhm hn ch tn tht

19


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Ti liu tham kho

[1] Cenzig Caner, zge Cansiz, Chitosan coating minimises eggshell breakage and

improves egg quality,Journal of the Science of Food and Agriculture, s 88,2007, 56 61.

[2] S. Bhale, h.k. No, W. Prinyawiwatkul, a.j. Farr, k. Nadarajah, and s.p. Meyers,

Chitosan Coating Improves Shelf Life of Eggs,Journal of food science, s 68,

2003.

[3] Su Hyun Kim, Hong Kyoon No, and Witoon Prinyawiwatkul, Effect of molecular

weight, type of chitosan, and chitosan solution pH on the shelf-life and quality of

coated eggs,Journal of food science, s 72, 2007.[4] S.h. Kim, h.k. No, and w. Prinyawiwatkul, Plasticizer Types and Coating Methods

Affect Quality and Shelf Life of Eggs Coated with Chitosan,Journal of food

science, s 73, 2008.

[5] Su Hyun Kim , Dal Kyoung Youn, Hong Kyoon No, Sang Won Choi, Witoon

Prinyawiwatkul

International Journal of Food Science & Technology

Effects of chitosan coating and storage position on quality andshelf life of eggs, , s 44,

2009, 1351 1359.

[6] Trn Thi Luyn, L Thanh Long, Nghin cu bo qun trng g tui bng mng

bc chitosan kt hp ph gia, Tp ch Khoa hc-Cng ngh Thu sn, s 1, i

hc Nha Trang, 2007.

[7] Nguyn Van Mi, Thc hnh Ho sinh, Nh xut bn Khoa hc K thut, 2001

[8] Xian De Liu, Aera Jang, Dong Hun Kim, Bong Duk Lee, Mooha Lee

and Cheorun

Jo, Effect of combination of chitosan coating and irradiation on physicochemical

and functional properties of chicken egg during room-temperature storage,

Radiation Physics and Chemistry, s 78, 2009, 589591.20

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