Bao Quan Thuc Pham

BO QUN THC PHMI HC QUC GIA THNH PH H CH MINHTRNG I HC KHOA HC T NHINGIO VIN HNG DN: TS. TRNH TH HNG

Zygosaccharomyces Hansenula Clostridium botulinum Pseudomonas Aspergillus flavusMucor

PHNG PHP BO QUNPHNG PHP VT L

PHNG PHP VT LPP LM KH+ PP sy t nhin (phi nng)+ PP sy nhn toPP S DNG NHIT+ PP nhit thp+ PP nhit caoPP S DNG TIA BC XPP HT CHN KHNGPP DNG DNG iN CAO TNPP SIU MPP LC THANH TRNGPP NG GI BNG THAY I KH QUYN (MAP)BO QUN BNG P LC THY TNH CAO

PHNG PHP LM KHNc cn thit cho VSV trao i cht v mi hot ng sngVi khun cn 18% ncNm men __ 20%Nm mc __ 13-16%Ty thuc vo loi thc phmSa bt cha 8% nc VSV pht trin cBt tht __ 10-11%Bt go __ 13-15%Sa bt loi b __ 15%Tinh bt __ 18%Cc loi qu __ 18-25%

Thc phm c m cao mi trng thun li cho VSV pht trinLm kh thc phm VSV khng pht trin thc phm c bo qun lu hn

Cc yu t chnh ca ch syLoi thc phm em syNhit syVn tc lu thng ca khng khThi gian sy m (hm lng nc trong thc phm - m khng kh)

PHNG PHP LM KH

PHNG PHP LM KHPP sy t nhin (phi nng)2.PP sy nhn toSy khSy phunSy thng hoaSy bng bc xSy bng in cao tn

Dng nhit ca nh sng mt tri lm kh sn phmThch hp cho cc loi ht ng cc, cc loi thy sn p mui (c, tm, mc)Cng c th hong kh rau qu m khng cn nng.u imKhng tn km nhin liuC kh nng dit tr cc loi nm mc nh Aspergillus, Penicillium, su mtHn chPh thuc iu kin thi tit khng ch ngTn nhiu cng, khng c gii ha cThi gian t ti m an ton thng diCht lng sn phm khng tt, gim gi tr dinh dng v cm quan.D b m mc khi bo qun.

PHNG PHP LM KHPP sy t nhin (phi nng)

Lm kh lng ln sn phm trong thi gian ngnTin hnh trong thit b nh c tc nhn sy, iu chnh c ch syC nhiu phng php sy: sy kh, sy phun, thng hoa, bc x v in cao tn.u im Sn phm ng nht trn th trngRt ngn thi gian sySn phm c cht lng cao hnHn cht tin v phc tpTn nhiu nhit lng

PHNG PHP LM KH2.PP sy nhn to

Sy kh: (vd cc l sy khoai sn th cng)Dng l sy than, ci lm bay bt hi nc trong thc phm Cht lng sn phm khng cao (cht dinh dng, vitamin b nh hng).Sy phun

PHNG PHP LM KH2.PP sy nhn toDch thc phmC cDng sng m trong bung sy c nhit 95oCNhitSn phm kh & cc VSV b chtdng bt kh (sa bt,)

Sy thng hoa: c trin vng nht

PHNG PHP LM KH2.PP sy nhn toNc trong thc phm (th lng)Th rnHi nc3 giai onu im: Gi nguyn tnh trng sn phm (dinh dng, cm quan), c kh nng phc hi nh ban uHn ch: Phc tp, cn nhiu thit b, cng sut in ln

Sy bng bc xChiu tia hng ngoi (0.75-4m) vo sn phm sn phm nng ln (v 80% cng sut n bin thnh nhit bc x)Dng cc n hng ngoi c cng sut 250-500W.Hn ch: cha s dng rng riHao ph nhiu nng lng (2.5kW/kg cht m)Ch lm nng c b mtPHNG PHP LM KH2.PP sy nhn to

Sy bng in cao tnt sn phm sy vo in trng xoay chiu c tn s dao ng cao (500kHz) cho sn phm kh u v nhanh.Cc sn phm sau khi lm kh lm ngui ngay, bao gi tt, trnh ht m tr li, gi ni kh mt c lu di.

Hn chThit b phc tp, tiu tn nhiu in nng (3.5kWh/kg cht m).

PHNG PHP LM KH2.PP sy nhn to

PHNG PHP S DNG NHITPhng php nhit thp2. Phng php nhit cao

Tc dng ca nhit thpNhit thp khng tiu dit c VSV nhng c ch mi hot ng sng ca chng a s chuyn sang dng tim sinhNhit thp lm gim nng lng hot ng cc cht trong t boLm cc phn ng sinh ha tin hnh kh khn hn.Nhit thch nghi nht: 35-37oCNhit cc tiu: 0-4oC PHNG PHP S DNG NHITPP nhit thp

nh hng nhit thp n cht lng thc phmCht m: ng -20oC, sau 6-12 thng b phn gii nh.Cht bo acid bo; thay i tnh ha tan vitamin A Vitamin thay i ty nhit v thi gian bo qunCarbohydrate t thay i1 t saccharose ng hon nguynCht khong gi nguyn gi tr dinh dngLm lnh t t ng bng t t hnh thi thc phm b bin dng, t bo b ph v gim gi tr dinh dng (sau khi gii lnh).

PHNG PHP S DNG NHITPP nhit thp

a)Lm lnh: ch yu bo qun rau qu tiNhit h xung gn 0oC tinh th nc cha xut hin, h thng men (trong nguyn liu v trong VSV) hot ng yu i km hm nhng bin i v l, ha, sinh; hot ng VSV .C tc dng lm tng phm cht mt s thc phmTht c chn ha hc nn tch t nhiu acid lactic, hng v thm ngonC mui, tht mui c thm mui tt hn v c mu sc ti hnCc loi ru, bia, nc gii kht hp dn khu v ngi tiu dng hn.Bo qun vi ngy vi thng

PHNG PHP S DNG NHITPP nhit thp

b)Lm lnh ng (ng lnh): gi thc phm vi thng n vi nm. Nhit ca thc phm c h thp hn nhit ng bng ca cc dung dch nc trong thc phm phn ln nc trong thc phm b ng bng mng t bo ca vi sinh vt b nn mnh. cc qu trnh sng ca vi sinh vt v hot ng ca cc h thng men b kim ch r rt Nhit lm lnh ng tt nht khi lng nc cn li trong thc phm b ng bng chim khng qu l5%. v vy, ngi ta ch p ng tht, c n -32.-350C, rau qu -20-270C. PHNG PHP S DNG NHITPP nhit thp

b)Lm lnh ng (ng lnh)* u im:Nhiu vi sinh vt khng kp thch nghi vi nhit lnh t ngt mc nhim trng t hn. Lm lnh ng nhanh tinh th nc to ra nh khi lm tan gi, nc trong t bo t chy ra khng hao tn nhiu cht dinh dng phm cht t b bin ibo qun lu vi s lng ln nht v kh nng tin li. tng kh nng iu ha, cung cp thc phm ti sng cho cc thnh ph ln, khu ng dn phc v tt cho vic giao lu hng ho thc phm trong nc v ngoi nc,... * Nhc im ln nht ca phng php ny l t tin v chi ph nng lng v u t thit b cao. PHNG PHP S DNG NHITPP nhit thp

b)Lm lnh ng (ng lnh)PP p nc : gi c thc phm ti trong thi gian ngnNc sch ng trong cc thng cha hoc khoang chaMt s cht thm vo: khng sinh, mui n, mui khongPP lm lnh trong kho lnh: gi na thngGi thc phm nhit cao hn bng im ca dch t boTht sau khi m trong l m phi c lm ngui trc khi lm lnh trnh hin tng phn gii ca thtPHNG PHP S DNG NHITPP nhit thp

Tc dng ca nhit cao: Mi loi vi sinh vt ch c kh nng hot ng trong mt gii hn nhit nht nh, c th chia lm 3 nhm vi sinh vt: Vi sinh vt a lnh (Psychrophile): thng gp vng a cc. Vi sinh vt a m (Mesophile): ph bin nh nm mc, nm men, cc VSV gy bnh cho ngi v ng vt. Vi sinh vt a nng (Thermophile): thng gp cc sui nc nng, ng phn rc . Ngoi ra, mt s vi sinh vt c th sng nhit cao hn, chng l nhng vi sinh vt chu nhit.

PHNG PHP S DNG NHIT2.PP nhit cao: dit vi sinh vt v c bo t ca chng

Thng thng, s dng nhit 60-70oC/ 30 pht c th tiu dit hu ht cc th sinh dng nhit cao gy bin tnh enzyme, mt nc oxy ho cc thnh phn trong t bo. Tnh chu nhit ca cc loi vi sinh vt khc nhaunm men, nm mc cht kh nhanh nhit 50-60oC vi khun chu nhit b tiu dit 80-90oC Nhit cng cao th thi gian tiu dit vi sinh vt cng ngn

PHNG PHP S DNG NHIT2.PP nhit cao

Tc cht ca VSV cn ph thuc vo hm lng nc cha trong t bo. Lng nc cha t sc chu ng toC cao.Hm lng nc trong bo t rt t tnh chu nhit rt cao. Vi sinh vt b tiu dit trong mi trng m nhanh hn trong mi trng kh - khi protein s to thnh nhiu nhm SH t do hn - cc cu ni peptid b ph hu nhanh hn khi c s hin din ca nc. protein d b mt hot tnh trong iu kin c ncPHNG PHP S DNG NHIT2.PP nhit cao

s lng ln vi sinh vt trong thc phm, pH ca mi trng trung tnh hoc kim, cc cht dinh dng trong thc phm (ng, cht m, cht bo...): tnh chu nhit ca vi sinh vt tng thi gian kh trng phi ko di.mui, cc ho cht bo qun, pH acid...: tnh chu nhit ca chng gim. PHNG PHP S DNG NHIT2.PP nhit cao

nh hng ca nhit cao n cht lng thc phm: tiu dit c vi sinh vt trong thc phm, lm thay i trng thi ca thc phm dch thc phm giu dinh dng c th b phn hu mt s cht dinh dng hoc b thay i mu sc, mi, v,... phng php bo qun dng nhit cao phi kt hp vi ch bin c ngay thc phm c ch bin. Vd: hp... PHNG PHP S DNG NHIT2.PP nhit cao

Kh trng Pasteur (gin on v lin tc) Phng php kh trng Pasteur ra i sau khi Louis Pasteur khm ph ra sinh vt gy h hng ru c th b bt hot bi nhit thp hn nhit si. Phng php ny thng dng kh trng sa v cc sn phm t sa. xc nh thi gian v nhit ti thiu trong phng php ny, ngi ta da trn nhng nghin cu v thi gian cht bi nhit ca vi sinh vt gy bnh c kh nng chu nhit nht trong sa. Phng php ny ch dit c t bo sinh dng


Nguyn tc: dng nhit 60-80oC tiu dit vi sinh vt gy bnh c trong thc phm v loi b cc vi sinh vt gy hng thc phm ko di thi gian s dng.Hn chBo t v mt s vi khun chu nhit nh Enterococcus, Microbacterium, Clostridium botulinum, Cl. sporogenes, Cl. putricium vn tn ti lm hng nhanh chng sn phm nhit thng (hin tng sinh hi, ph hy thc phm v lm bt np hp). ngi ta thng kt hp vic gi lnh thc phm vi vic b sung CO2 ko di thi gian s dng. PHNG PHP S DNG NHIT2.PP nhit cao

Do , thanh trng hp ngi ta thng s dng phng php hp kh trng trn 100oC trong thi gian di. Sa 63oC/30 giy, hoc 72oC/16 giy. Thc phm trng ming t sa ng lnh (kem , sa ,...): ti thiu l 69oC/30 giy, hoc ti thiu 80oC/25 giy. Nhng sn phm t sa (kem, sa chocolate...): 66oC/30 giy, hoc 75oC/16 giy. PHNG PHP S DNG NHIT2.PP nhit cao

C 2 phng php kh trng Pasteur: gin on v lin tc. Phng php gin on (Batch method)Phng php ny dng mt l hp Pasteur, bn trong c mt thng cha c bao quanh bi hi nc lu thng. Trong thng cha ny, sa c lm nng v c khuy u trong sut thi gian kh trng. Sau sa c th c lm ngui trong thng cha. Ngoi ra, ngi ta c th lm nng sa mt phn trong mt l hnh ng trc khi a vo thng cha.Phng php ny t dng kh trng sa, thng dng kh trng nhng sn phm t sa hn. Trong cng nghip sn xut kem (ice cream), thng cha trn thng dng khuy trn sn phm nhm t c cht lng sn phm tt hn l bo qun sn phm. PHNG PHP S DNG NHIT2.PP nhit cao

Phng php lin tc (Continuous method)Phng php lin tc c nhiu thun li hn phng php gin on, n tit kim c thi gian v nng lng. Trong phng php ny, ngi ta s dng mt l hp Pasteur tit khun nhanh nhit cao. Mi trng lm nng sn phm c th cha hi nc hoc nc nng chn khng. Sa th 4oC c cho chy qua cc tht b ca l hp Pasteur ny, n dc lm nng n nhit kh trng khong 72oC/16 giy. Sau khi kh trng, sa c chy vo mt thit b lm ngui n 4oC hoc thp hn. Sau cng, sa c chuyn vo mt h thng ng gi sn phm. PHNG PHP S DNG NHIT2.PP nhit cao

Phng php UHT (Ultra-high temperature) Phng php UHT kh trng thc phm nhit ln hn 100oC, thc phm c kh trng trc khi ng gi, ri c cho vo cc cha c kh trng trong iu kin v trng. Phng php UHT tiu dit ton b vi sinh vt v bo t, k c vi sinh vt chu nhit c bo t. Thc phm dc x l bng phng php UHT c th c n 6 thng m khng cn lm lnh Mt s sn phm thc phm kh trng bng phng php UHT:Cc sn phm dng lng: sa, nc p hoa qu, kem sa chua, ru, nc st rau x lch. Thc phm c ht nh ring bit: thc phm cho em b, cc sn phm c chua, sp, nc p rau v tri cy. Thc phm c ht ln: cc mn hm.


Nhit cao kt hp p sutgia tng nhit bng hi nc bo ho di mt p sut ln hn p sut bnh thng ca kh quyn. Khi p sut hi nc tng ln th nhit cng tng theo. Di p sut cao v nhit cao, t bo dinh dng v bo t ca vi sinh vt u b tiu dit (Clostridium botulinum). Cn c vo ch s acid ca hp m ngi ta c nhit v thi gian thanh trng thch hp. i vi hp pH>6, cc VSV pht trin c di tc dng ca nhit cao u thuc loi a nng nhit thanh trng ca cc loi hp ny thng l 115-121oC. hp pH 4.5-5, thng c loi vi khun k kh nh Cl. thermosaccharalytium, Bac. stearothermolphilus lm hng thc phm cn c nhit 100-119oC. Cc loi hp c pH

PHNG PHP S DNG TIA BC X

Tc dng ca cc tia bc x: Ngi ta c th s dng cc tia bc x nh: tia t ngoi, tia X, tia gamma, tia beta, tia alpha... trong bo qun thc phm. Tia t ngoi: ngi ta c th s dng n chiu t ngoi chiu vo thc phm. tc dng mnh nhng kh nng m xuyn yu nn ch dng dit khun mt ngoi thc phm, mt ngoi dng c cha ng, khng kh ni sn xut thc phm. lm phn hu mt s cht hu c trong t bolm ng t protein Khi chiu x thi gian kh di, s ph hy protein c th dn n phn gii c chui polipeptide thnh cc gc acid amin, lm enzyme mt hot tnh, dn n ph hu t bo vi sinh vt. sc chu ng ca bo t cao hn 4-5 ln so vi th sinh dng; Mt lng nht nh tia ny c th gy t bin.


Tia ion ho: Cc tia c tn s dao ng cao th c lc m xuyn cao. lm thay i cu trc ca mt s phn t protein ca t bo VSV v lm ion ho dung mi. Hiu qu thanh trng ca tia ion ha tu thuc vo thi gian x l, dy ca thc phm v lng VSV nhim vo thc phm. Cc tia phng x ion c tc dng st trng mnh, khi nh lng m bo y th tit trng hon ton trong vi giy. thc hin mc ch , ngi ta dng cc tia m cc, tia Rnghen v cc tia phng x .. Hin nay, phng php ny ang c nghin cu m bo an ton cho ngi s dng, v ch thanh trng hp l. PHNG PHP S DNG TIA BC X

nh hng ca cc tia bc x n cht lng thc phm Thc phm chiu x thng mt mu, mt mi. Protein v acid amin trong thc phm rt nhy cm vi chiu x. Sn phm do chiu x protein, acid amin, peptide gm: NH3, H2, CO2, H2S v Carbonyl. Cc acid amin c bit nhy cm vi chiu x l : methionin, cysteine, histidine, arginine, tyrosine. Trong d cysteine nhy cm nht. Lipid trong thc phm cng b thay i rt mnh, c bit l trong trng hp c oxy.


Cc loi vitamin nh: thiamin, niacin, pyridoxin, biotin, B12 b ph hu, nhng riboflavin, pantothenic, folic li tng trong qu trnh chiu x. Cc cht pectin v cellulose cng b bin i khi chiu x, kt qu l cc loi rau, qu s tr nn mm hn. trng thi cm quan ca thc phm chiu x b thay i do cht m b ph hu, mi i do m b oxy ho. Nu chiu x mi trng khng c oxy nh chn khng hoc kh oxy, thnh phn dinh dng v tnh cht cm quan t b thay i hn. Trc khi chiu x, ngi ta c th thm vo thc phm cc ho cht bo qun nh cht chng oxy ho, cc cht dinh dng trong thc phm s t b nh hng hn.


ng dng chiu x trong bo qun thc phm v nh hng ca n i vi sc kho ngi tiu dngBo qun cc thc phm nh: khoai ty, hnh, gia v, chui, xoi, ti, ht u, nem chua, tht g, tht vt, tht heo, tht b, tm, i ch... Vi liu thp hn 10 KGy, chiu x thc phm s phng nga v ngn cn s ny mm ca khoai ty, hnh, dit cn trng v ko di thi gian bo qun. Vi liu chiu x 1 n 10 KGy c th gim s nhim vi khun gy bnh nh Salmonella, bo qun tht gia cm, tm, chn ch. Ti mt s nc m qu trnh bo qun thc phm bng chiu x mc lu thng thng mi, nhng cn kh nhiu ngi tiu dng vn gi thi khng chp nhn thc phm chiu x.


PHNG PHP HT CHN KHNG

phng php ny, ngi ta t cc sn phm thc phm trong nhng bao b khng thm kh v ht khng kh trong ra, to ra mt mi trng chn khng. Trong trng hp ny nhng qu trnh oxi ho thng xy ra di tc dng ca khng kh b km hm mnh, lp b mt ca sn phm khng b kh, gi c mu sc v tnh cht ban u ca sn phm. Phng php ny thng c dng kt hp vi cc phng php vt l khc, ch yu l lm lnh v lm lnh ng.

PHNG PHP HT CHN KHNG

PHNG PHP DNG DNG IN CAO TN

Sn phm c t trong in trng ca dng in xoay chiu c tn s cao thanh trng. Cc phn t tch in trong sn phm (ion, in t) s dao ng do tc dng ca in nng, chuyn in nng c hp th thnh nhit nng lm cht vi sinh vt. Kh nng hp th in nng tu thuc kch thc bao b ng thc phm, vo in p v tn s ca dng in. Tn s dng in cng ln hay bc sng cng ngn th qu trnh thanh trng cng nhanh. Phng php ny s dng cha ph bin v cn nguy him cho ngi iu khin v gi thnh t (0,3-0,5 kWh/kg sn phm).PHNG PHP DNG DNG IN CAO TN

S bt hot vi sinh bng xung in cao p da trn nhiu nhn t, c th c phn loi thnh

Thng s x l cng xung in v tng thi gian x l hay ngun nng lng u vo l nhng tham s chnh nh hng n s bt hot vi sinh. Nu tng cng xung in hay tng thi gian x l s tng s bt hot vi sinh. Tuy nhin, t s gim chuyn bit v s lng vi sinh , cng xung in s dng phi vt hn gi tr ti hn.


c im vi sinhT bo sinh dng ca vi khun chu ng xung in cao p tt hn nm men hay nm mc. Vi khun gram + chu c xung tt hn gram do s khc nhau v mng v vch t bo. Cc bo t vi khun thng chng chu vi nhng iu kin xung in m bt hot c cc t bo sinh dng. Tnh khng cao vi xung in ca bo t l do kch thc nh v chng trng thi loi nc v khang ha vi lp v v lp ph dy gip bo v nhn bn trong. Bo t men hay mc li d b bt hot bi xung in. T bo pht trin pha log nhy cm vi xung in hn t bo pha tnh. iu ny mt phn l do tnh yu ca mng t bo trong sut s phn chia t bo.


Thng s sn phm dn in ca mu c x l l mt trong nhng tham s sn phm quan trng v n quyt nh trc tip n chng chu ca b phn x l. nh hng ca pH sn phm ln s bt hot vi sinh bi lung xung in thay i v ph thuc vo loi vi sinh cng iu kin x l. pH gim lm tng hiu qu bt hot vi sinh ca xung in. Cc sn phm mang tnh acid thch hp hn vi bo qun bng xung in cao p do pH thp c th trnh c cc t bo tn thng nh phc hi.


u im: bt hot nhanh ca cc vi sinh vt sinh dng gm c chng gy bnh v gy h hng thc phm. Nhc im Ch nhng thc phm lng ng nht khng c bt kh hay cc phn t ln c th x l hu hiu Bo t vi khun khng b bt hotenzyme ch b bt hot mt phn nn hu ht cc thc phm x l bng xung in cn c tr lnh tng thi gian bo qun.S thay i bt li v ha hc c th xy ra nu cht in mi b thng v hin tng ha in khng c qun l.


PHNG PHP SIU M

Siu m l sng m c tn s dao ng cao m con ngi khng cm th c. Di tc dng ca siu m, mi trng lng (sn phm) truyn m b x i y li, b p v to chn khng lin tip sinh ra nhiu khong trng. Lc , cc cht ha tan v hi ca cht lng lp tc dn vo cc khong trng y, gy ra tc dng c hc lm cht vi sinh vt trong mi trng. Mt khc, trong qu trnh y mt phn cht kh ho tan b ion ha to ra nc oxi gi, nitro oxid l nhng cht c i vi vi sinh vt, nht l vi khun.

PHNG PHP SIU M

Cc loi vi sinh vt khc nhau c sc chu ng khc nhau vi sng siu m. Cc t bo ln hn nhy cm hn, dng hnh cu chu ng sng siu m tt hn dng que v nhng loi hiu kh cng chng chu vi sng siu m tt hn k kh. C ch tc ng ca nng lng siu m trn h thng cc cht mi trng lng ch yu cho l do s to l hng v cc lc ny c mt nh hng nguy kch ln h thng sinh hc. S to l do sng m c chia tng qut thnh 2 loi: loi tm thi v loi bn vng. PHNG PHP SIU M

Dng bong bng si trong nc cha y kh hay hi nc, tri qua s dao ng khng u nhau v cui cng n tung. iu ny sinh ra nhit v p xut ti ch cao s phn hy cc t bo sinh hc v lm bin tnh cc enzyme hin din. Cc bong bng n tung vo trong cng sinh ra cc lc bin dng cao v cc tia lng trong dung mi cng c th c nng lng ph hy mng t bo mt cch c hc. C ch tc ng kiu ny cng tng c s dng quy m nh trong vic ty u ngun nc b nhim bo t vi sinh. Dng l n nh lin quan n nhng bt si m dao ng theo mt dng u cho nhiu chu trnh m thanh. Cc bt si cm ng cc vi dng c th gy ra stress trong cc cht lng xung quanh ln s hin din ca vi loi. Tc dng ny do cung cp mt lc ln m khng c s n ca cc bt si. Dng to l trng ny quan trng trn mt lot cc ng dng ca siu m trong cng ngh sinh hc

PHNG PHP SIU M

Hiu qu bt hot ca sng siu m cng c cho l do s pht sinh cc l trng ni bo v ph v cu trc t bo v cc thnh phn chc nng dn n vic phn gii t bo. Bo t chu ng sng siu m tt hn dng t bo sinh dng cc enzyme b bt hot bi sng siu m do tc dng kh trng hp. S to l trng l s hnh thnh, pht trin v thnh thong s n ca cc vi bt to ra trong cht lng khi cc sng siu m truyn qua n. S v ra ca bong bng dn ti s tch t nng lng trong cc im nng. Nhit cao c c do s to l trng Qua cc gc t do c to ra bi s m gii nc Do cc lc to ra bi cc vi dng v sng in PHNG PHP SIU M

Tc dng ca nhit v p sut trn sng m cm ng s ph v t bo S chu ng ca vi sinh vt v cc enzyme vi sng m rt caox l ko di s sinh ra nhng thay i ko di trong thc phm v nh hng ln n cht lng thc phm c x l. S dng sng siu m vi gia nhit va phi c gi l s nhit m Kt hp sng m v p sut va phi c gi l siu m p lcv cui cng s kt hp c 3 loi c gi l nhit siu m p lcthun tin cho s bt hat mt vi enzyme nhit thp.PHNG PHP SIU M

PHNG PHP LC THANH TRNG

Mng lc xut hin cch y hn 40 nm v ngy cng tr nn quan trng trong cng nghip thc phm, phc v cho vic c c v phn on sn phm C 3 loi mng lc chnh: 1. Mng thm ngc: gi li cc ion n tr trn mng 2. Mng siu lc: gi li cc i phn t nh protein, polysaccharides hay cht bo, ng hay amino acid c th qua mng. ng knh l t 2-20nm 3. Mng vi lc: tch cc loi c kch thc khong 0.1 10nm, gi li cc i phn t PHNG PHP LC THANH TRNG

K thut mng lc gp phn bo qun thc phm bng cch gi li vi sinh vt trn mng v do dch lng thm qua s v khun. S vi lc l mt k thut phng th nghim c s dng tt nht trong vic loi b vi sinh vt (c t bo sinh dng v bo t), do sn phm s c v khun m khng cn x l nhit. K thut vi lc dng ngang (cross-flow MF) c ng dng rng ri trong vic sn xut cc thc ung c lc nh bia, ru vang, nc tri cy. Vi lc di di hu hiu cc t bo v cc cht rn l lng, trnh vic s dng cc tc nhn lm sch nh diatomite hay cc enzyme, m vn gi li c mu.

PHNG PHP LC THANH TRNG

Xu hng tng lai K thut mng to ra nhng tin b ng k trong cc ng dng bo qun thc phm. Tuy nhin, k thut ny cha pht huy ht tim nng ca n do cc l do: Mc tinh sch khng cao u li vi cc k thut khc Vn v dng chy hay s gim v dng trong sut qu trnh ch bin khng c kinh t Nhiu khu vc ca cng nghip thc phm rt truyn thng v chm nm bt cc c hi pht trin k thut mng mi Ch bin mng l mt k thut hon ton vt l, thch hp vi khoa hc sn xut cc thc phm ch bin rt nh v c th tip tc thay th cc k thut phc tp khc lin quan n nhit. Mng lc c th s dng sn xut cc protein tinh khit vi c im chc nng chuyn bit, tinh sch cc oligosaccharide vi c tnh prebiotic hay sa c thi gian bo qun lu m khng cn x l nhit.PHNG PHP LC THANH TRNG

PHNG PHP NG GI BNG THAY I KH QUYN

Tnh nng ca cng ngh bo qun bng cch bao gi sn phm trong kh quyn thay i (MAP) nhm ko di tui th ca thc phm c nhn bit cch y nhiu nm.Ni khi xng ra phng php ny l Vng Quc Anh, bt u t thp nin 1920 cc nh khoa hc nhn thy rng tui th ca nhng qu to c th gia tng bng cch tn tr chng trong mi trng vi nhng nng oxygen thp, kh carbonic li cao, v trong thp nin 30 khi tht b c vn chuyn trong cc mi trng c cha kh carbonic th thi gian bo qun ca chng tng gp hai ln so vi trc. Ngy nay thc phm ng gi trong MA bao gm tht ti v nu chn, tht gia cm v c, rau qu, m si, phomat, cc loi bnh nng t bt m, khoai ty chin, c ph v tr. PHNG PHP NG GI BNG THAY I KH QUYN

Bao gi trong kh quyn iu chnh (CAP) : s bao gi trong mt kh quyn m y thnh phn ca cht kh c lin tc iu chnh trong sut qu trnh bo qun. Bao gi trong kh quyn thay i cn bng (EMA): ng dng ch yu cho rau v tri, bao gi c np y vi hn hp kh cn thit hoc sn phm c ng gi m khng c s thay i ca khng kh bo qun trong bao. S ng gi ny s cho php mt trng kh quyn thay i t c chnh l nh vo s h hp v sau ca sn phm v tnh thm thu ca cht kh trong bao gi. PHNG PHP NG GI BNG THAY I KH QUYN

u im:Tui th c th tng n 400%Tn tht v mt kinh t gim (lu b h hng)Sn phm c th c phn phi n cc ni xa hn v vi t dch v hn, gim chi ph trong phn phiCung ng sn phm vi cht lng caoVic phn loi cc sn phm d dng hnCng tc ng gi c tp trung ho v kim tra tng phn mtTng tnh thm m trong trng bySn phm c nhn thy r rng v quan st c ton bt hoc l khng cn cc ho cht bo qun. PHNG PHP NG GI BNG THAY I KH QUYN

Nhc im: Gi thnh cao Nhit cn phi iu chnhCc cng thc cht kh khc nhau cho tng sn phm i hi thit b c bit v cng tc hun luyn Gia tng th tch bao gi- nh hng trc tip n chi ph vn chuyn v khng gian trong bun bn l.C 3 loi kh chnh c s dng: CO2, N2, v O2. Chng c x dng ring l hay kt hp vi nhau PHNG PHP NG GI BNG THAY I KH QUYN

Dng c bin i khng kh Dng c ny l sn phm ring bit, thng dng ti nh. Cc ti ny c ng gi cng vi sn phm thc phm v s bin i tch cc khng kh trong vt cha cng nh cc sn phm c ng gi v lu tr. Ageless cha cc oxide st, c kh nng gim 02 trong kh quyn vt cha

BO QUN BNG P LC THY TNH CAO

Da trn nguyn tc thy tnh, p lc thy tnh ti mt im cho trc bng nhau mi hng v p lc c truyn i lp tc v ging nhau qua mi trng truyn p lc. Do , hiu qu ca k thut ny th khng ph thuc vo kch thc v hnh dng sn phm Thi gian x l, t l p, nhit v s lng xung rt quan trng i vi hiu qu ca qu trnh. Cc thnh phn thc phm v trng thi sinh l ca vi sinh b bt hot phi c tnh ton khi x l p lc ti a cho tnh an ton v cht lng cao ca thc phm BO QUN BNG P LC THY TNH CAO

nh hng ca p lc cao ln vi sinh vt T bo sinh dng ca prokaryote nh nm men v nm mc nhy cm vi p lc nht vi khun gram dng chu p lc tt hn gram m . vi khun hnh cu chu p lc tt hn hnh que do s thay i hnh thi t hn. Cc chng pht trin trong pha m nhy cm nhiu hn cc chng trong pha log hay pha tnh. Mt s t bo sinh dng b p lc nhiu ln c th tng tnh khng p lc. S nn bng xung hay dao ng p lc cao v chm cng hu hiu trn s bt hot bo t hn l p lc lin tip. S gim p nhanh gia tng lc tc ng trn v bo t nhiu hn s gim p t t to ra s kh trng thch hp ti p lc thp hn. BO QUN BNG P LC THY TNH CAO

PHNG PHP BO QUNPHNG PHP HA HC

BO QUN THC PHM BNG PHNG PHP HA HCS dng cc cht ha hc c ch tc nhn lm bin i cc thnh phn ha hc trong thc phm.

c ch s pht trin ca vi sinh vt cng nh h enzym do chng tit ra.

Cn tr qu trnh t bin i ca thc phm. Cc cht bo qun tham gia vo qu trnh bt hot cc enzyme c trong thc phm (cc enzyme ny gy bin i cc cht c trong thc phm trong qu trnh bo qun).

YU CU C BN I VI HA CHT BO QUN THC PHM

Phi c tnh khng khun, khng nm mc v khng nm men mnh v phi c tnh cht chng oxy ho xy ra trong bo qun v ch bin lng thc, thc phm.

Khng gy c cho ngi v gia sc.

Khng lm thay i hay lm thay i rt t tnh cht ho l, cm quan ca thc phm.

Khng to ra nhng phn ng ph, nhng sn phm c hi trong thc phm.

Cc cht bo qun thng c s dng dng ha tan.

HA CHT BO QUN THC PHMCht tc ng n s pht trin ca vi sinh vt.

Cht c ch s t bin i ca thc phm (Cht chng oxy ho).

CHT TC NG N S PHT TRIN CA VI SINH VT

C ch s dng

Cc cht bo qun lm thay i cc yu t mi trng, c ch s pht trin ca vi sinh vt.

Cht bo qun tc ng n h thng protein cu trc, enzyme tham gia vo cc qu trnh trao i cht, tiu dit hay c ch s pht trin ca vi sinh vt.

Mt s cht thng dng trong bo qun thc phmSO2Nitrit (NO2) Nitrat (NO3) Acid benzoicAcid sorbic Acid acetic EthylpyrocarbonatCO2 O3Cht gia tng p sut thm thu Khng sinh c sn xut theo phng php ha hc Ethanol H2O2Hp cht ca halogen Cht to mi

Kh SO2 nh hng n cc qu trnh oxy ha trong t bo vi sinh vt, ng thi cng c tc dng tng h vi cc nhm cacboxyl ca cc hp cht c bit c trong thnh phn ca cht nguyn sinh, lm thay i trng thi l, ha hc ca cht nguyn sinh.

Kh SO2 dng trong bo qun rau qu.

Khng dng cc hp cht SO2 bo qun tht, ng cc, u , sa.

Dng s dng: kh SO2, acid sulfurous (H2SO3), cc loi mui nh Natri bisulfite NaHSO3, Kali bisulfite KHSO3, Canxi bisulfile Ca(SO3)2, Natri sulfite Na2SO3, Kali sulfite K2SO3.

SO2 c tc dng bo v nng 0,1-0,2%. SO2 (sulfurous dioxide)

Phng php s dng kh SO2

Phng php sulfite ho t: cho trc tip kh SO2 hoc dung dch axit sulfurous (H2SO3) vo sn phm dng lng: rau qu hoc qu nghin, nc qu.

Phng php sulfite kh (xng khi sulfurous): Qu c ng trong thng hay trong hm kn c cha SO2, SO2 c th ly t bnh thp hoc t lu hunh.

Phng php xng khi cn c dng khi lm v sinh kho.

NaNO3, KNO3

Nitrit c ng dng trong cng nghip ch bin tht.

Mc ch: gi mu cho tht mui mn, lm thuc st khun trong bo qun c, tht v cc ch phm t c, tht (c, tht mui hoc p lnh).

Nitrit (NO2)

Liu lng s dng Nitrit:

- Khng hn ch 0 - 0,4 mg/kg th trng. - C iu kin 0,4 - 0,8 mg/kg th trng. - Dng trn ln vi mui n mui tht th t l khng c ln hn 0,6%. - Khng c dng cho vo thc n ca tr em.

Nitrit c tc dng chuyn hemoglobin thnh methemoglobin, gy hin tng tm ti xm.

Khi n phi thc n cha nhiu nitrit c th gy ng c.

NaNO3, KNO3

S dng lm cht st khun v gi mu cho tht, cc sn phm tht, c v phomt.

Th nghim ngn ngy tru b, gia sc n c kh (cha 1,5% nitrat) b cht do nitrat b vi khun ng rut chuyn ho thnh nitrit.

Liu lng s dng cho ngi : - Khng hn ch 0 - 5 mg/kg th trng- C iu kin 5 - 10 mg/kg th trngTht muiTht hpNitrat (NO3)

c ch mnh nm men v nm mc, c tc dng yu i vi vi khun.

Tc ng ln mng t bo nm, c ch qu trnh h hp ca t bo, c ch qu trnh oxy ha glucose v pyruvate, c ch qu trnh bin dng cc hp cht a lng (N, P,) ca sinh vt.

Mt s loi vi sinh vt c th s dng acid benzoic trong qu trnh trao i cht hay c cc c ch c hiu (cc bm mng) loi b cc cht c ra khi t bo.

Acid benzoic c th tc ng h h hp v h thn kinh trung ng, gy kch ng mt.

Tc dng bo qun ca Acid benzoic v Natri benzoat ch xy ra mi trng acid, pH=2,5-3,5. Acid benzoic, mui benzoat

Nng acid benzoic s dng trong thc phm: 0,05-0,15%.

Nng benzoat trong sn phm c tc dng bo qun l 0,07-0,1%.

Acid benzoic c s dng nhiu trong bo qun tri cy v rau qu. Nu s dng nng cao s lm thay i mi v sn phm, nh hng ti thn ca ngi s dng.

Dng benzoic hoc benzoat trong bo qun sn phm c th lm cho sn phm b thm en, v d nhn bit d v, lm gim ch tiu cm quan ca sn phm.

Liu gy cht ngi: 500 mg/kg.

Dng thng s dng lm cht bo qun: acid sorbic, sorbate natri, sorbate calci, sorbate kali.

Acid sorbic v kali sorbat c tc dng c ch nm mc v nm men, t c tc dng vi vi khun.

Acid sorbic nh hng ti protein trn mng t bo nm mc, gy nh hng n qu trnh vn chuyn cc ion m qua mng: lm chuyn i pH bn ngoi t bo, thay i s vn chuyn ca cc acid amin; lm gim sinh tng hp protein v thay i s tch ly nucleotide trong t bo.

Acid sorbic nh hng ti hot tnh ca cc enzyme nht l enzyme dehydrogenase.Acid sorbic (C5H7COOH) Acid sorbic

Acid sorbic v kali sorbat khng c i vi c th con ngi, dng trong bo qun thc phm khng gy ra mi v l, khng lm mt mi t nhin.

S dng cho bo qun sn phm lm nguyn liu cho ch bin: bo qun rau qu cho mui chua, sa lm sa chua.

Dng nhiu trong ch bin rau qu, ru vang, sn xut hp, ch bin sa, bo qun v ch bin c, tht, sn phm bnh m, bo qun nc mm, nc chm, c ngm dm.

Phi hp acid sorbic hoc sorbat vi cc cht bo qun khc:Dng acid sorbic vi natri benzoat trong bo qun nc quDng acid sorbic cho sn phm p ng c th gim mt na lng ng p.Trn 0,1-0,2% acid sorbic (so vi lng mui) vo dung dch mui mui c trc khi hun khi.

Dit nm men, nm mc v vi khun, km hm hot ng ca enzyme.

Ethylpyrocarbonat hon ton khng c i vi ngi, khi tip xc vi nc s phn hy dn dn thnh ethanol v CO2.

Dng trong bo qun nc qu, qu ti.

S dng ethylpyrocarbonat thay th phng php sulfite ho trong bo qun ru nho v nc qu. EthylpyrocarbonatEster diethyl ca acid pyrocarbonic

Carbonic (CO2)

Kh carbonic tc ng ti qu trnh trao i cht ca vi sinh vt, c ch mt vi qu trnh bin dng ca vi sinh vt.

Nm mc nhy cm hn i vi kh carbonic, cn vi khun th t nhy cm hn.

Nng kh carbonic cao c ch s pht trin ca nhng vi khun hiu kh v c vi khun ym kh.

Kh carbonic km hm s oxy ha cht bo ngay c nhng nng nh.Ozon (O3)

Ozon c tnh oxi ha rt mnh, tc ng trc tip ti cc cht sng gy bin i v bt hot cc i phn t sinh hc, gy ri lon cc hot ng sng ca vi sinh vt.

Hiu qu tc dng ca ozon s c nng cao khi h thp nhit v tng m tng i ca khng kh. Kt hp bo qun lnh thc phm vi vic ozon ha khng kh s cho kt qu tt hn.

S dng ng hay mui trong bo qun thc phm lm gia tng p xut thm thu ca mi trng, to p sut thm thu cao nc trong t bo thm ra khi mng t bo cht v gy ra hin tng co nguyn sinh; ng thi t bo vi sinh vt khng th hp thu c cc cht dinh dng, lm c ch hot ng v s pht trin ca vi sinh vt.

S dng nng mui t 5-20% hoc 30%, nng ng 50-60%.

Sn phm in hnh: mt tri cy, tht mui, c mui. Cht gia tng p sut thm thu

Acid acetic lm gim pH ca sn phm, lm cho qu trnh trao i ion ca vi sinh vt khng thc hin c. S thay i qu ln ca nng ion trong v ngoi mng t bo lm ri lon cc qu trnh trao i cht ca vi sinh vt, c ch s pht trin ca vi sinh vt trong thc phm.

Nng acetic acid thng dng: 1,7-2% (pH 2,3-2,5).

Phng php ngm dm thng dng acid acetic, acid citric, tartric.Acid acetic (Ngm dm)

Trc nm 1960, khng sinh c s dng rng ri trong bo qun thc phm do nhng u im ca khng sinh: c ch vi sinh vt mt cch hiu qu, d b bin tnh v phn hu nhit cao.T sau nm 1969 ngi ta thy nhng tn ti trong vic s dng khng sinh lm cht bo qun thc phm:i vi cc khng sinh kh phn hy, d lng trong thc phm s nh hng ti sc kho ca ngi s dng. Lm thay i h vi khun ng rut v s tng hp vitamin rut. Sinh ra s nhy cm i vi khng sinh. Gy ra ng c do cc cht dng chuyn ho ca khng sinh. C hin tng khng khng sinh ca vi sinh vt (ln thuc) lm cho vic iu tr bnh khng hiu qu.Khng sinh c sn xut theo phng php ha hc

Cc cht khng sinh c tc dng ch yu vi vi khun, tc ng yu i vi nm mc, nm men. Lm ngng tng hp thnh t bo vi khun; ph v tnh thm thu ca mng t bo.

nh hng ti qu trnh tng hp protein ca vi khun.

nh hng i vi acid nucleic. Cc cht khng sinh c php dng: biomixin (clotetraxyclin), teramixin, oreomixin,

Nguyn tc s dng khng sinh lm cht bo qun thc phm:Ch s dng nhng khng sinh no khng dng cho cha bnh quan trng, khng gy hin tng khng khng sinh, khng nh hng n vic s dng nhng khng sinh khc trong iu tr bnh.

Khng s dng nhng khng sinh gy hi cho sc kho ngi tiu dng.

Cn xc minh loi khng sinh s dng khng gy hi cho h vi sinh vt ng rut.

Khi s dng khng sinh bo qun, phi m bo khng h thp bt c ch tiu v sinh no khc.

HA CHT BO QUN THC PHMCht tc ng n s pht trin ca vi sinh vt.

Cht c ch s t bin i ca thc phm (Cht chng oxy ho).

CHT CHNG OXY HACc cht chng oxy ha c c tnh d b oxi ha hn so vi cc cht bo c trong thc phm.

S oxi ha cc hp cht chng oxi ha s lm gim s oxi ha ca cc cht bo trong thc phm.

Cc cht chng oxy ha c hai dng nh sau: + Acid (hoc mui hay ester ca chng) nh acid citric, acid ascorbic,...

+ Hp cht phenol lm chm kh nng oxy ha cht bo v du c trong thc phm.

YU CU I VI CHT CHNG OXY HA S DNG TRONG THC PHMKhng c c tnh.

C kh nng ho tan, hoc phn tn ng u trong khi thc phm.

Tng kh nng n nh cht lng sn phm khi hn ch hay loi b qu trnh oxy ha cc cht d b oxy ha trong sn phm.

Cc gi tr dinh dng c bn trong thc phm phi c bo tn.

Bo m cc gi tr cm quan v mu v mi, trng thi ca du m.

Bo m vic tiu th thun li khi s dng cc cht chng oxy ha.

Mt s cht chng oxy ho dng v c trin vng dng nc ta:

Acid ascorbic (vitamin C): bo qun tht ng thng; hoa qu ng l, lm cht chng oxy ho du m Acid citric, acid limonic: bo qun sn phm sa, ko, nc gii kht -tocopherol (vitamin E): l cht chng oxi ha t nhin, c trong mt s du m t nhin nh du u tng, du ht bng, du mm ng cc. Trong k thut bo qun, ngi ta dng dung dch pha trong du, khng cha t hn 31% tocopherol Acid tartric

Kt hp gia cht chng oxy ha v cc k thut bo qun khc lnh: bo qun du tinh ch t cy ci du vi liu lng 500 mg tocopherol/kg 400C trong 2-4 tun. Nu du 100C, c th bo qun hn 15 thng.

Nu rt ht khng kh hay bm kh tr vo bao gi thc phm c th gim 50% lng cht chng oxy ha.

PHNG PHP BO QUNPHNG PHP SINH HC

Phng php sinh hc

1/ Phng php ln men (mui chua)2/ Phng php dng bacteriocin3/ Phng php dng enzyme

1/ Phng php ln men (mui chua) S dng cc vi sinh vt ln men to ra acid lm thay i pH mi trng c ch s pht trin ca vi sinh vt gy h hng thc phm v ko di thi gian bo qun thc phm.

Vi khun sinh acid lactic (LAB) l mt nhm vi khun a dngc sn phm trao i cht cui cng l acid lactic.

Phn loi: Da trn sn phm cui: nhm vi khun ln menlactic ng hnh v nhm vi khun ln men lacticd hnh Da trn kh nng chu nhit: nhm chu nhit cao,nhm chu nhit trung tnh, nhm a lnh

LactococcusLactobacillusLeuconostocPediococcus

Trong qu trnh ln men cc vi khun ny tit ra acid lactic v acid acetic lm acid ha mi trng gp phn km hm v tiu dit vi khun gy h hng thc phm. Ngoi ra cc vi khun sinh lactic cn tit ra cc bacteriocin khng khun

2/ Phng php s dng bacteriocin Bacteriocin l cc protein c tnh khng mt s gy h hng v gy ng c thc phm, n c cc vi sinh vt ch yu l nhm vi khun sinh lactic tit ra. Bacteriocin lp I c ph khng khun kh rngEnterococcusLactobacillusBacteriocin lp IIa li c ph khng khun hpL.monocytogenesS.aureus Streptococcus

Tin trnh thng s dng ng dngbacteriocin trong bo qun thc phm

Nui cy LAB trnthc phm vikhun pht trin vto bacteriocin B sung bacteriocintinh khit haybn tinh khit vothc phmS dng cc snphm ln men bichng to bacteriocinlm thnh phnch bin thc phm

Nisin l mt bacteriocin c sinh ra bi Lactococcus lactis v Streptococcus lactis. Nisin lin kt vi anion phospholipid di chuyn vo t bo gy ri lon qu trnh trao i ion v lm cht vi sinh vtLactococcus lactisStreptococcus lactisNisin

Nisin b ph hy pH=8,0 nhit 37oC t 15-30 pht N c dng trong cng nghip ch bin pho mt, bo qun hp, nc p qu ng hp, rau qu ti Liu dng trong thc phm l 20 U.I/g thc phm Nisin c tc dng vi mt s vi khun (Enterococcus, Listeriamonocytogenes, Staphylococcus aureus, Bacillus cereus,Clostridium botulinum..), nhng khng c tc dng vi nm men,nm mc.

EnterococcusL.monocytogenesS.aureus C.botulinumB.cereus

3/ Phng php s dng enzyme

CM N C V CC BN LNG NGHE!

Nhit sy rau qu: 65-80 C, c: 60-65 C.Sy nhit cao; Pr bin tnh, caramen ha, vit b ph hy, mt cht thm. m khng kh thch hp bo qun thc phm l 70%.Loi bt m trc khi sy bng pp c hc: p, lc, ly tmVi sinh vt b tiu dit trong mi trng m nhanh hn trong mi trng kh:do protein d b mt hot tnh trong iu kin c nc hn, khi protein s to thnh nhiu nhm SH t do hn v cc cu ni peptid b ph hu nhanh hn khi c s hin din ca nc.

Cn tr qu trnh t bin i ca thc phm. Cc cht bo qun tham gia vo qu trnh bt hot cc enzyme (c tc dng gy bin i cc cht c trong thc phm trong qu trnh bo qun) c trong thc phm.Cc cht ny c tc dng c ch s pht trin ca vi sinh vt hoc tiu dit vi sinh vt. Cc cht bo qun thuc nhiu nhm cht khc nhau tc ng vo nhng nhn t khc nhau trong qu trnh pht trin ca VSV

SO2 l mt cht st khun mnh. Vic xng khi rau qu bng kh SO2 s nng cao tnh bn ca chng v ngn cn qu trnh pht trin ca nm mc, hn ch qu trnh thi ra ca rau qu.

mt s loi vi sinh vt c th s dng benzoic acid trong qu trnh trao i cht hay c cc c ch c hiu l cc bm mng loi b cc cht c ra khi t bo. Cc nng ny trong nc qu, rau qu nghin, nc mm, nc chm... khng c hi n sc kho con ngi.Dng benzoic hoc benzoat trong bo qun sn phm c th lm cho sn phm b thm en, v d nhn bit d v, lm gim ch tiu cm quan ca sn phm.

ATP binding cassette transporterNm mc nhy cm hn i vi kh carbonic, cn vi khun th t nhy cm hn. S dng ng hay mui trong bo qun thc phm lm gia tng p xut thm thu ca mi trng, to p sut thm thu cao, nc trong t bo c chiu hng thm ra khi mng t bo cht v sinh ra hin tng co nguyn sinh; ng thi t bo vi sinh vt khng th hp thu c cc cht dinh dng. iu ny lm c ch hot ng v s pht trin ca vi sinh vt.

Tc dng ca khng sinh biu hin 3 hng chnh: nng cao n c tnh st khun do tc dng bin tnh cc protein mng t bo lm vi sinh vt cht.

Thioure: cm s dngC kh nng ho tan, hoc phn tn ng u trong khi thc phm lm cho tc dng chng oxy ho c chc chn. Tng kh nng n nh cht lng sn phm khi hn ch hay loi b qu trnh oxy ha cc cht d b oxy ha trong sn phm.

Acid ascorbic (vitamin C): bo qun tht ng thng; hoa qu ng l, lm cht chng oxy ho du m

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