MNG PROTEIN N C: C TNH V CI THIN TNH CHT CA MNGThawien Wittaya1[1]Prince of Songkla University, Department of Material Product Technology,, Thailand(http://www.intechopen.com/books/structure-and-function-of-food-engineering/protein-based-edible-films-characteristics-and-improvement-of-properties#SEC3)

1. GII THIUCc loi mng protein n c rt quan trng v c ch trong nhng nm gn y v chng em li nhng li ch, bao gm c vic chng c s dng nh nhng bao b cho vt n c, hn mng tng hp. Ngoi ra, cc loi mng protein n c c th s dng cho bao b thc phm c bit l cc sn phm hin nay khng ng gi c, chng hn nh u, cc loi ht v ht iu. Ngoi ra, cc loi mng protein n c ng dng trong nhiu loi thc phm khng c nhiu lp khng ng nht. Chng c th c cu to ngn chn gim thiu s thot nc ca cc thnh phn v tht thot cc cht ha tan trong sn phm v d nh bnh pizza, bnh nng v ko. Hn na, cc loi mng c th n c lm t protein c th hot ng nh mt cht mang khng khun v cht chng oxi ha. Mt ng dng tng t chng cng c s dng b mt ca thc phm kim sot tc khuch tn ca cc cht bo qun t b mt vo bn trong ca thc phm. ng dng khc ca cc loi mng c th n c lm t protein l c s dng trong nhiu lp vt liu ng gi thc phm cng vi mng khng n c. Trong trng hp ny cc loi mng c th n c lm t protein s l cc lp bn trong tip xc trc tip vi nguyn liu thc phm. Qua cc chc nng lin quan n c hc v s ngn cn, cc loi mng protein n c c th thay th mng polymer tng hp. Trong trng thi t nhin, protein tn ti mt trong hai dng l protein dng si v protein dng cu. Loi th nht khng tan trong nc v cung cp cc nguyn liu cu trc chnh ca m ng vt. Protein hnh cu tan trong dung dch nc hoc dung dch axit, baz hoc mui v hot ng rng ri c th sng. Cc protein dng si hon ton m rng v lin kt cht ch vi nhau trong cu trc song song, thng thng qua lin kt hydro, to thnh si. Cc protein hnh cu gp thnh nhng cu trc hnh cu phc tp vi nhau bi mt s kt hp ca hydro, ion, k nc v cng ha tr (disulfide). Cc tnh cht ha hc v vt l ca protein ph thuc vo s lng tng i cc thnh phn acid amin v v tr ca n dc theo chui polymer protein. V cc protein dng si, collagen c ch nht trong vic sn xut cc mng n c. Mt s protein hnh cu, trong c gluten la m, zein ng, protein u nnh, whey protein v protein u xanh, c nghin cu tnh cht mng ca chng.Cc loi mng c th n lm bng protein thng c to thnh t cc dung dch hoc cc cht phn tn ca protein khi bay hi dung mi hoc cht mang. Dung mi hoc cht mang thng b hn ch vi nc, ethanol hoc hn hp nc v ethanol.Thng thng, protein b bin tnh bi nhit, axit, baz, v cc dung mi to thnh cc cu trc m rng hn hnh thnh mng. Sau khi m rng, cc chui protein c th kt hp thng qua lin kt hydro, ion, k nc v cng ha tr. S tng tc chui-n-chui sn xut mng gn kt b nh hng bi mc m rng chui v tnh cht, trnh t cc amino acid. S phn b ng u ca cc nhm phn cc, k nc, v thiol dc theo chui polymer tng kh nng tng tc tng ng. S xc tc ca polymer tng tc chui-n-chui kt qu trong cc mng mnh m hn nhng t linh hot v chng thm, cho kh, hi nc v cc cht lng. Polyme c cha cc nhm c th kt hp thng qua hydro hoc lin kt ion trong cc mng kt qu l ngn cn oxy tuyt vi nhng d b m. Nh vy, cc mng protein c d kin s l mng ngn cn oxy tt ti m tng i thp.Polyme c mt u th ca cc nhm k nc l ro cn oxy thp nhng nhng ro cn m rt tt. Tuy nhin, thc t l cc protein khng hon ton k nc v cha ch yu hydrophillic amino acid lm hn ch tnh cht ro cn m ca chng. Vic to ra cc loi mng c th n c lm t Protein vi tnh thm hi nc thp i hi vic b sung cc thnh phn k nc. iu ny tng t vi tnh hnh vi cc polyme tng hp. y polyme ngn cn oxy- m nhy cm phi l ng polymer vi mt polymer k hoc kp gia cc lp polymer k nc hn ch kh nng a nc. Nhng ci tin ca Cc loi mng Protein n c c nghin cu tm kim cc ng dng ph hp. Chng ny cung cp thng tin chi tit ca mng protein n c v tnh cht ca chng, vic sn xut ca mng protein n c, cc phng php c s dng cho s hnh thnh ca mng protein n c, ci thin tnh cht ca mng protein n c v cc ng dng tim nng ca chng.2. CC LOI MNG PROTEIN N C2.1. Mng collagenCollagen l protein cu trc chnh ca cc m lin kt nh xng, n, gn sn, v dy chng. N chim khong mt phn ba tng s protein trong c th ng vt c v. Collagen c nhiu loi khc nhau. Mi loi c trnh t axit amin ring , nhng tt c u cha mt lng ng k cc cu trc xon ba. Do c tnh sinh hc v li ch ca n, collagen tup I c s dng rng ri nh l mt vt liu sinh hc.N c s dng trong mt lot cc hnh thi vt cht nh bt bin, mng v v mng (Sisken et al., 1993). Collagen c nhng c im nh mt vt liu sinh hc khc bit vi nhng polymer tng hp. Collagen c s dng sn xut mng protein n c thng mi thnh cng nht. Vic s dng mng collagen c mt s li th: n tng thch sinh hc v khng c hi cho hu ht cc m; n c ti liu v kt cu, vt l, ha hc, v cc c tnh min dch; n c th c ch bin bng nhiu hnh thc; v n l d chit xut v tinh ch vi s lng ln. Vic sn xut ca mng collagen t da ng vt c th c thc hin bng cch s dng mt qu trnh kh hoc t vi mt s im tng ng. Chng bao gm: (a) x l kim loi b lng v tch collagen t carbohydrate v protein khc; (b) s trng n axit v ng nht to thnh khong 4.5% gel m (phng php t) hoc ~ 10% bt gel m (qu trnh kh); (c) n thnh mt ng; v (d) trung ha ng p n, ra ng mui, x l ng bng cht lm do v cc mi lin kt cho v lm kh n m 12-14% (theo th t ph thuc vo vic cc qu trnh t hay kh c s dng) (Hood, 1988). 2.2. Mng gelatinGelatin l duy nht trong s hydrocolloid vi nhit nng chy gn vi nhit c th, v qu trnh chuyn i gia dng gel v dung dch din ra thun nghch, iu c bit quan trng trong cc ng dng sn phm n c v dc phm. V c bn, gelatin thu c bng cch kim sot qu trnh thy phn t x khng ha tan protein, collagen, c tm thy rng ri trong t nhin nh cc thnh phn chnh ca da, xng v m lin kt. Gelatin bao gm mt chui duy nht ca cc axit amin. Cc c trng ca gelatin l hm lng cc axit amin glycine, proline v hydroxyproline. khong 40oC, dung dch gelatin trng thi keo lng v hnh thnh kt cu gel chu nhit thun nghch khi c c lm mt dn. Trong qu trnh c li, cc chui tri qua mt qu trnh chuyn i trt t ri lon v hnh dng v c xu hng phc hi cu trc collage xon ba (Ross-Murphy, 1992). Gelatin c s dng ng gi thc phm c m thp hoc cc thnh phn thc phm pha du v dc phm. ng gi c tc dng bo v chng li oxy v nh sng, cng nh xc nh s lng thnh phn hoc liu lng thuc. Ngoi ra, mng gelatin c to thnh nh l lp ph trn cc loi tht gim s xm nhp oxy, m v tht thot du (Gennadios et al., 1994). Ngoi ra, gelatin c th to thnh mng r rng v chc chn v c s dng ng gi v cc ch phm vi nang v cc vin nang trong sn xut thc phm v dc phm.Mng gelatin c th c hnh thnh t 20-30% gelatin, 10-30% cht lm do (glycerin hoc sorbitol) v 40-70% nc (Guilbert, 1986). Tuy nhin, mng gelatin cng nh vi hu ht cc mng protein, khng chng thm hi nc, iu ny l hn ch trong ng dng ca n. Tuy nhin, thay i mng li polymer thng qua cc mi lin kt cho ca cc chui polymer c th c p dng ci thin cc chc nng ca mng protein. 2.3. Protein zein t ngZein l protein quan trng nht trong ng. N l mt protein prolamin v do ha tan trong 70-80% ethanol (Dickey & Parris, 2002). Zein l mt loi vt liu tng i k nc v nhit. Bn cht k nc ca zein l do trong thnh phn ca n cha nhiu cc axit amin khng phn cc (Shukla & Cheryan, 2001). V mt k thut, cc mng c lm t mt loi protein ha tan trong ru nh zein, c c tnh chng thm kh tng i cao so vi cc protein khc.Zein l mng hon ho v tnh cht v c th c s dng ch to cc mng phn hy sinh hc. Mng zein c hnh thnh thng qua s pht trin ca ca tng tc k nc v gim cu nidisulfide gia cc chui zein (Guilbert, 1986). S hnh thnh ca mng zein ng c cho l lin quan n s pht trin ca tng tc k nc v hn ch cu ni disulfide gia cc chui zein trong cht nn mng (Gennadios et al., 1994). Mng ny gin v do i hi vic b sung cc cht lm do tng tnh linh hot. Mng zein c kh nng chng thm nc tng i tt so vi nhng mng n c khc (Guilbert, 1986). V zein cng c kh nng lm gim m v gim sn chc v lm chm s thay i mu sc (gim oxy v carbon dioxide) trong tri cy ti. Ngoi ra, zein cng c th tham gia vo cc lp ph nha bao b thng thng. Mc d, zein khng ha tan trong nc c pH trung tnh, n c thm thu hi nc cao so vi cc polyme tng hp in hnh. Tuy nhin, cc c tnh chng thm kh, hi nc c th c ci thin bng cch thm axit bo hoc bng cch s dng mt thuc th lin kt ngang. Tuy nhin, khi cht lin kt cho c s dng, cc tnh n c ca nhng mng sn phm cn thit c xem xt. 2.4. Mng gluten la m Gluten la m l mt protein khng ha tan ca bt m trong bao gm mt hn hp ca cc phn t polypeptide v l protein hnh cu. S c kt v n hi ca gluten to tnh ton vn cho bt m v to iu kin hnh thnh mng. Gluten la m bao gm hai nhm chnh ca cc protein khng ha tan: gliadins, bao gm protein trng lng phn t thp; v glutenins cha protein trng lng phn t cao. Gliadins l cc protein monomeric duy nht trong cc cu ni disulfide hnh thnh bn trong chui protein hoc khng trong khi glutenins to polyme phn t lng cao c duy tr bi lin kt disulfide lin chui. Mng t glutenins chc chn hn v c c tnh chng thm tt hn so vi nhng mng t gliadins hoc gluten. Mng gliadin th hin tnh cht quang hc tt hn nhng kh nng chu nc li km hn. Cc tnh cht ca nhng mng ny i khi lm cho chng nhy cm vi phng php x l nhit, c th dn n thay i tnh cht ca mng. Ngoi ra, gliadin ha tan trong ethanol 70%; glutenin khng hon tan (Gennadios & Weller, 1990). Mc d khng ha tan trong nc t nhin, gluten la m ha tan trong dung dch nc ca pH cao hay thp cng ion thp (Krull & Inglett, 1971). Mng gluten la m c th phn hy sinh hc hon ton sau 36 ngy trong qu trnh ln men hiu kh v trong vng 50 ngy trong t t nng nghip m khng sinh cc sn phm c hi (Domenek et al., 2004).V mt k thut, mng gluten la m c th c hnh thnh bng cch lm kh bng dung dch ethanol. S phn ct lin kt disulfide gc trong vic lm nng dung dch to mng. S hnh thnh ca lin kt disulfide mi trong qu trnh lm kh mng sau c cho l quan trng i vi s hnh thnh ca cu trc mng gluten la m, cng vi lin kt hydro v lin kt k nc (Gennadios & Weller, 1990). Vic b sung cc cht lm do nh glycerin trong mng gluten l cn thit ci thin tnh linh hot ca mng gluten la m. Tuy nhin, tng tnh linh hot mng bng cch tng hm do c th lm gim cc c tnh chng thm nc, n hi ca mng thnh phm. Ngoi ra, tinh khit ca gluten la m cng nh hng n s hnh thnh ca mng v tnh cht c hc; gluten tinh khit hn trong mng th mng cng chc chn hn v r rng hn. Mng gluten la m l mng ngn oxy hiu qu, nhng ngn hi nc km. Tnh chng thm hi nc km ca mng gluten la m l do bn cht a nc ca protein v cht lm do hydrophilic thm vo tng tnh linh hot cho mng. Cc tnh cht ca mng gluten la m c th c ci thin bng cch s dng mt tc nhn lin kt ngang nh glutaraldehyde, hoc x l nhit. 2.5. Mng protein u nnh Protein u nnh t ht u nnh c s dng nh l mt thnh phn trong hu ht mi sn phm thc phm c sn cho ngi tiu dng, v n c cha cht dinh dng cao v c tnh chc nng tuyt vi. Hm lng protein ca u nnh (38-44%) cao hn nhiu so vi hm lng protein trong ht ng cc (8-15%). Cc protein u nnh ln c trng lng phn t khc nhau, 200-600 kDa. Hu ht cc protein u nnh (90%) l globulin, c th c phn on thnh 2S, 7S, 11s v 15s theo h s lng ca chng. 7S v 11s l phn chnh, l khong 37% v 31% tng s protein chit c v c kh nng cho phn ng trng hp (Cho & Rhee, 2004). Protein u nnh bao gm c chui phn cc v khng phn cc. C nhng tng tc ni v ngoi phn t mnh, nh lin kt hydro, cc tng tc lng cc, in tch v k nc. Cc tng tc phn cc v in tch mnh gia chui mch bn ca cc phn t protein u nnh hn ch lun chuyn phn on v tnh di ng phn t, lm tng cng, im hiu sut v bn ko ca mng protein u nnh (Zhang et al., 2001).Protein u nnh rt phong ph, khng tn km, phn hy sinh hc v gi tr dinh dng cao, n cho thy tim nng c pht trin nh l mng n c v phn hy sinh hc. S hnh thnh ca mng t protein u nnh c m t nh l mt qu trnh hai bc: (a) dung dch to mng c lm nng, ph v cc cu trc protein, lin kt gc disulfide b tch ra v cc nhm sulfhydryl v nhm k nc l ra ngoi; (b) s hnh thnh ca lin kt disulfide, k nc v hydrogen mi. Cc protein gp lin kt thng qua tng tc gia cc phn t, chng hn nh lin kt disulfide v cc tng tc k nc, dn n s hnh thnh ca mt mng li xy ra trong qu trnh lm kh. V mt k thut, mng protein n c c th hnh thnh lin kt ti cc v tr khc nhau v hnh thnh mt s lin kt. Tuy nhin, mng protein u nnh cn c c tnh ngn cn kh m thp do tnh a nc ca n v do s lng ng k cc cht lm do a nc c s dng trong qu trnh sn xut mng. Mt phng php c s dng rng ri tng cng cc tnh ngn cn hi nc ca mng l vic p dng cc hp cht k nc nh cht bo vo cc dung dch mng ban u. Ngoi ra, cch khc ci thin cc tnh cht ca mng protein u nnh l sa i cc protein thng qua mng li lin kt cho ca cc chui protein. S hin din ca cc nhm chc nng phn ng trong chui bn axit amin ca protein lm cho lin kt qu trnh ngang c th nh ha cht, enzyme hay x l vt l.2.6. Mng casein Protein sa c th c phn thnh hai loi: casein v whey protein. Casein bao gm ba thnh phn chnh, Casein s, Casein v Casein cng nhau to thnh cc mixen keo trong sa, cha mt s lng ln cc phn t casein v c n nh bng mt cu calcium phosphate (Kinsella, 1984). Cc phn t casein c mt cu trc th cp t c xc nh, thay cho mt cu trc xon ngu nhin m. Casein, trong bao gm 80% protein sa, kt ta khi sa tch kem c axit ha n im ng in casein khong 4.6 (Dalgleish, 1989).S axit ha c kh nng ha tan cc phosphate canxi, do gii phng cc phn t casein ring l, chng kt hp to thnh axit ha tan casein. Cc casein axit c th c chuyn i sang cc mui ca casein ha tan bng cch trung ha bi cht kim. Mng protein n c da trn cc mui ca casein khc nhau c th thu c bng cch ha tan trong nc theo sau phng php c v sy kh.Cc mui ca mng casein c lm t dung dch nc khng qua x l nhit do tnh cht cun xon ngu nhin ca chng. Tng tc trong dung dch to mng c th bao gm k nc, ion, v lin kt hydro (Avena-Bustillos & Krochta, 1993). Mng caseinate trong sut v linh hot, nhng c c tnh ngn cn s thot nc km. iu kin th nghim so snh, mng caseinate ngn cn nc tng t nh mng gluten la m v mng protein u nnh nhng ngn cn m km hn so vi mng zein ng. Casein c nghin cu hnh thnh mng c lp v lp ph trn cc sn phm thc phm. Mng nhiu lp casein bo v tri cy v cc loi rau kh hp th m v oxy ha. H caseinate - lipid thnh cng trong vic gim mt nc t c rt gt v v zucchini (Avena-Bustillos et al., 1993).2.7. Mng protein u xanhu xanh c quan tm nh mt thnh phn tim nng ca mng biopolymeric v hm lng protein cao. Cc ht ging ca u xanh cha khong 25-30% protein. Cc protein t u xanh cha nhiu protein c trng lng phn t (MW) ln gia 24 v 55 kDa vi mt s c t hn 24 kDa. Tuy nhin, c mt lng nh protein gia 14,2 v 24 kDa. Cc thnh phn acid amin ca u xanh chng t l chng rt giu cc axit amin thit yu nh leucine, isoleucine, lysine, phenylalanine v cng rt giu axit amino axit nh axit glutamic v acid aspartic. Tuy nhin, axit amin c cha lu hunh, nh methionine v cysteine cng c pht hin trong protein u xanh (2,75 v 3,62%) (Keereekasetsuk et al., 2009).Bourtoom (2008) chun b v phn tch nhng mng protein t u xanh. Kt qu cho rng cc tnh cht c hc ( bn ko v gin di ti im gy) ca cc mng protein u xanh cao v c tnh ngn cn s hi nc tt. im ny tt hn so vi cc ngun protein khc nh mng casein, mng protein u nnh, mng gluten la m, mng protein u phng v mng protein c tan trong nc. Tuy nhin, nhng mng protein u xanh vn cho thy c tnh cn kh v hi nc thp hn ng k so vi mt s loi polyme tng hp (polyethylene mt cao, polyvinyl chloride, cellulose acetate v polyester).S ngn cn ca cc mng protein u xanh hn ch s thm hi nc thp do cc hydrophilicity vn c ca protein. Vic thm hi nc thng qua mng protein n c cng c h tr bi mt cht lm do a nc, u tin hp ph ca phn t nc. Tuy nhin, cc tnh cht ca mng protein u xanh c th c ci thin bng cch thm cc nguyn liu k nc v cng s dng ha cht v enzyme lin kt cho.

3. MNG N C TO THNH T PROTEINMng protein c th c hnh thnh bi hai phng php khc nhau: phng php to mng b mt v phng php kt ta.3.1. Phng php to mng b mtMng thu c bng cch lm nng ko di ca dung dch to mng v mng theo nh k c thu hoch t b mt, ro nc v sy kh. Vic s dng phng php ny c m t qu trnh gm hai bc lin quan n s bin tnh nhit ca protein tip theo l s mt nc b mt ca n. Di tc dng ca nhit lm thay i cu trc ba chiu ca protein v cc nhm chc nng hin hu; chng hn nh CO v NH ca lin kt peptid, cc nhm amin mch bn, cc nhm cht k nc, tham gia vo cc ni phn t lin kt hydro v tng tc tnh in (Wang v Damodaran, 1991). Trong qu trnh sy, cc protein dui thng tin li gn nhau v tr thnh lin kt thng qua tng tc gia cc phn t (disulfua v tng tc k nc). iu ny dn n s hnh thnh mt mng li protein by cc thnh phn ca mng, v d nh cc cht lm tng do (Gennadios v Weller, 1991). Mng c to thnh xy ra trong iu kin bin tnh, iu ny c gi nh rng cc protein trong mng vn cn trng thi bin tnh hon ton.Tuy nhin, cc protein bin tnh c th tri qua mt phn un np li, do mt s cu trc th cp quay tr li trong qu trnh to mng. C th hiu rng mc gp np nh vy nh hng n s lng cc nhm chc nng c sn cho tng tc gia cc phn t; do hnh thnh v n nh ca mng li protein (Subirade v cng s 1998). Wu v Bates (1973) nghin cu mng t sa u phng. H bo co rng trong thi gian gia nhit sa u phng, phn t protein c trng lng cao c chia thnh cc phn t c trng lng thp hn. Di tc dng ca nhit, u tin cc conarachin c tch ra sau arachin to thnh cc tiu n v nh ca cm phc hp khng ha tan b mt. Hn na, cc lc ca mt phn gii c th khi s hnh thnh mng li protein bng cch by cc git du v nc thot ra khi b mt to iu kin thun li cho qu trnh ny (Farnum v cng s 1976).3.2. Phng php kt taMng thu c bng phng php ny thng c thc hin bng cch c v lm kh mng trn mt b mt khng dnh. V mt k thut, qu trnh c bao gm lm kh lp dung dch hoc lp trng thi gel vi dy ca mng c kim sot. K thut ny rt hu ch khi lm theo mt s quy trnh cng nghip hnh thnh mng tinh bt bin tnh nh l trng hp ca khun c hoa vn. phng php ny, c dng cho cc mng bc thc phm cng nh cc ng dng phi thc phm; trng thi gel thng c s dng t cc dung dch nng ln mt b mt trong lc lm lnh. Jaynes v Chou (1975) s dng phng php ny sn xut mng protein-lipid u nnh. H tin hnh tch protein pH=6,6; c trn trn cho c m Teflon v lm kh 1000C.Mng c lm t phng php kt ta th ng u hn so vi phng php to mng b mt. dy mng c th c kim sot bi s lng tng cht rn trong lp dung dch khng ging nh trng hp phng php to mng b mt s dng. Trong nhng nm gn y, hu ht cc nh nghin cu s dng k thut kt ta sn xut nhng mng n c. Tuy nhin, c nguyn liu v nhit c c th thay i ty theo trng thi hay loi b mt. Cc k thut kt ta c s dng lm mng protein t gluten la m, zein ca ng, casein, whey protein, protein u nnh v c c protein go.4. CC YU T NH HNG N MNG PROTEIN4.1. Loi nguyn liu ban uTrong dung dch dng to mng nguyn liu c phn loi. Theo c tnh ha tan ca n, chng c phn thnh hai loi: nhm a nc v nhm k nc. Nhm a nc nh protein u nnh, whey protein, protein c ha tan trong nc v protein u xanh tan trong nc. Nhm k nc nh zein ca ng, sp l khng tan trong nc nhng chng tan trong cht lng khng phn cc nh ru. S khc bit v c tnh ha tan ca cc nguyn liu nh hng n nng lng cn thit thu c mng protein kh v s dng n trn cc loi thc phm. Carbohydrate trong cc cht nh alginate, carrageenan, pectin, tinh bt, cellulose v cc dn xut cellulose cung cp mt mng li vng chc. Bn cnh , nhng mng ny c tnh cht chn nc km v n c bn cht a nc (Kester v Fennema, 1986). Protein c tnh cht chn kh tt nhng c tnh chng thm hi nc km. Tuy nhin, mt s mng protein nh mng zein t ng th hin kh nng chng nc tt hn so vi cc mng protein khc bi v zein c cha lng ln cc axit amin mch bn k nc. Mng lipid c lm t nguyn liu k nc nh sp, axit bo, cho thy kh nng cn hi nc rt tt nhng v mt tnh cht c hc th rt km.4.2. Polymer ha hcCc cu trc phn t thng thng c th khuch tn hn cu trc lp th bt thng; trong khi cc phn t phn nhnh biu hin mt cng lin kt cht ch ln hn cc phn t khng phn nhnh. Mt phn nh phn t c trng lng thp hn cho thy mt s lin kt ln hn v s thay i ln trong lin kt khi nhit thay i. Trong polymer cao phn cc nh protein v cellulose, t kt dnh bng cch khuch tn l khng ng k do kh nng linh hot nh v th t c nh ca cc i phn t. iu ny c gy ra bi cc lc ni phn t ca chui polymer. Cellulose c b khung vi mt vng chui cu trc khng linh ng trong khi protein c khuynh hng to thnh cu trc chui xon c (Banker, 1966).Kinsella V Phillips (1989) tm tt cc c im phn t mong mun cho s hnh thnh cc mng protein: 1) phn t ha tan cao thc y s khuch tn nhanh chng; 2) cc phn t ln hn cho php tng tc vi b mt phn gii, kt qu l mng tr nn vng chc hn; 3) cc phn t amphipathic (va c tnh a nc va c tnh k nc) to nn s phn b khng cn xng ca cc gc khng phn cc v c tch in ci thin s tng tc b mt; 4) cc vng linh hot (do) to iu kin thun li cho ng thi pha v s dui ra mt phn gii; 5) phn tn ca cc nhm nh hng n tnh tng tc protein-protein trong cc mng v lc y gia bt kh xung quanh; 6) gc phn cc cung cp cc gc hydrate ha hoc tch in tch ring cc bt kh qua mt bn, lin kt v gi nc; 7) vic duy tr cu trc c th tng s chng cho ln nhau v s tng tc tng on trong mng; 8) vng tng tc c th nh hng n s kt ta ca cc phn on chc nng khc nhau, to iu kin cho cc phn ng ph trong khng kh v pha dung dch.4.3. pHpH ng mt vai tr quan trng trong cc mng protein c lm t nguyn liu protein ha tan trong nc, chng hn nh tch chit protein u nnh; whey protein, nhng kh nng ha tan ca cc protein ph thuc vo im ng in ca chng (pI). Trong qu trnh phn ly ca cc cht i phn t, cc lc lin kt cht ch gia cc phn t cht tan b trung ha bi cc phn t dung mi (Banker, 1966). Chc nng ca cc polymer lin quan n tnh cht ha tan; iu nh hng n c tnh ca mng. Cc nhm ph trch y ln nhau v to ra mt chui polymer tri di khi cc nhm chc nng ca polymer tuyn tnh b ion ha trong thi gian ha tan. S tng tc gia cc phn t polymer v cc phn t ca dung mi tng mnh cng vi s tch in ngy cng tng trn chui. Kh nng ha tan protein ti a thu c ti pH im ng in ca n (pI). Tuy nhin, sn xut mt mng n c ti pH khc nghit, thuc tnh cm quan cng phi c xem xt cng vi cc tnh cht mng khc. Gennadios v cng s (1993) nghin cu nh hng ca pH trn mng khi tch chit protein t u nnh; cho thy rng axit cao (pH 12) u c ch s hnh thnh ca mng protein u nnh. Kinsella v Phillip (1989) bo co rng mng hnh thnh gn im ng in ca protein c m c v vng chc hn.

4.4. Nhit lm khMng protein n c thng thu c bng phng php c. K thut ny lin quan n vic lm kh ca dung dch keo phc tp gm protein, dung mi v thng thng trc cht lm do c rt vo khun c thch hp. nh hng ca nhit sy ph thuc vo cc c tnh khc nhau ca nguyn liu, chng hn nh s xut hin ca mt khi gel t trc hoc s ng li do nhit xy ra trong qu trnh sy. Hn na, mt hin tng khc c th xy ra nh s chuyn i t dng c sang dng trong sut hoc tch pha (khng tng thch nhit ng lc hc) hoc kt tinh. S tng tc gia cc cht ha l ca polymer sinh hc v iu kin lm kh l rt quan trng (Devani v cng s 2009).Cc lc tng tc trong cc cu trc protein b nh hng bi nhit . Nhit l mt yu t lm bin tnh vng chc cho protein v thm ch c s n nh nhit; cu to ca protein ph thuc vo cc thnh phn acid amin. Trong thi gian lm kh, khi nc c loi b dn, cu trc ca protein s thay i. Ngoi ra, mc dui thng ca mch protein quyt nh loi v t l ng ha tr (lin kt S-S ) hoc khng ng ha tr (tng tc k nc, ion v lin kt hydro); tng tc c th c thit lp gia cc chui protein. c bit, cc mch c th tng tc mnh v d dng hn, c bit l thng qua lin kt disulfua khi cc protein b bin tnh (Mauri v Anon, 2006). Cui cng l s lin kt cht ch ca mng li sau s hnh thnh cc lin kt chc nng. Mng thu c vi cc tnh cht c xc nh.Ngoi ra, cc tng tc a nc tng ln, lin kt hydro v tng tc tnh in gim i khi nhit tng. iu ny l kt qu s h tr ca cht kt dnh gia cc mng polymer v cht nn (Banker, 1966). Nhit cao (70-1000C) nh hng n s to thnh cc cu trc khng linh ng trong dung dch protein v protein bin tnh (Chefel v cng s 1986). Nhit qu nng hoc t l bc hi dung mi qu mc trong qu trnh sn xut c th lm mng khng lin kt cht ch (Guilbert v cng s 1986). Cc protein ha tan trong nc nh protein u nnh, whey protein cn mt nhit cao hn v thi gian di hn to thnh mng so vi nhng mng protein ha tan trong ru nh mng zein t ng hoc gluten la m. Nhit sy cao hn da trn mng tan trong nc c th hn ch s dng ca mng. Tuy nhin, m tng i thp cng c th c s dng to thnh mng nhit thp.

4.5. Nng ca dung dch to mngMng protein to nn t nhng cu trc phc tp. Tng tc protein-protein trong tp hp c th c tnh cht khc nhau (chng hn nh lc tnh in hay k nc, ) t dn n hnh thnh cc loi lin kt khc nhau. iu ny c th nh hng n s di chuyn ca cc protein v kh nng ca n to thnh mng. Nng cc cht trong dung dch to mng nh hng n tnh t dnh ca cc polymer cao phn t v t l ca chng to thnh mng ch phm. Bn cnh , nng protein trong lp dung dch cng c th nh hng n s hnh thnh ca mng protein. nng protein thp hn c t s tng tc gia protein-protein, trong khi nng protein cao hn th chng t khuch tn. nng ti u, vi nht trung gian c th thu c lin kt bn vng gia cc phn t cao nht. Tuy nhin, nng ti u ca mi mng protein i hi khc nhau. Vic sn xut mng t whey protein i hi nng protein tng i cao (> 8%) hnh thnh cu ni S-S trong trong mng protein (Sothornvit v Krochta, 2001). Trong khi , nhng mng c sn xut t protein c vi nng 1,5-2% cho thy mng vng chc hn cc nng khc.4.6. m tng iNc tng tc vi mng protein c xem l mt vn hng u gii thch s thay i thuc tnh vt l gy ra bi s hin din ca m. S hp th nc bng cc vt liu kh thng lin quan n s lin kt ca cc phn t nc vi cc nhm a nc c th, chng hn nh carboxylic, amino, d lng hydroxy v cc nhm peptid. m tng i cao, nhiu phn t hp ph nc lm trng phng v thay i hnh dng trong cu trc phn t. V c bn, cc thuc tnh ca mng protein khc nhau trong thi gian lu tr, c bit nu ta so vi nhng mng tng hp khc, iu ny c th l do nguyn liu ban u khng n nh. Nhng nguyn nhn ny c th nh hng n tnh cht ca mng nh l mt kt qu ca s thay i c tnh. Do , qu trnh oxy ha ca cc nhm sulfhydryl protein c th gy ra s suy thoi ca cc chui polymer (Micard v cng s 2000). Nhng thay i v vt l bao gm s sp xp li chui polymer v c th l do s di chuyn ca cc thnh phn phn t trng lng thp c s dng trong xy dng mng, chng hn nh cht lm do (Anker v cng s 2001). S di chuyn ca cc cht ph gia c th xem l nguyn nhn quan trng nht ca s bt n nh vt l ca mng protein.Cc mi quan h gia m tng i cn bng v hm lng nc trong mng c nh gi bng cch o ng ng nhit hp ph nc. Ngoi ra, s hiu bit v tnh cht hp ph nc l cn thit iu chnh cc ng dng mng. S nh hng ca m tng i v tnh c hc v tnh thm ca mng protein c gii thch bi s gim nhit gy nn mt hin tng do do nc to ra trn mng protein.Cuq v cng s (1996) xc nh nh hng ca m tng i ln c tnh c hc v kh nng cn hi nc ca mng protein t si c. nh hng s ha do ca nc c lin quan n nhng thay i nhanh chng ca tnh cht chc nng mng; kt qu c gii thch bng cch ph v lin kt hydro-polymer. Gim tng i mnh ti lc ph v, c mm do v tnh cht cn hi nc; s gia tng bin dng ti im b gy c quan st khi m tng i tng ln. Pochat-Bohatier cng s (2006) nghin cu nh hng ca m tng i trn carbon dioxide n kh nng thm ca cc mng gluten la m. H bo co rng s gia tng ca tnh thm kh c thy m tng i 96%. iu ny c cho l do s trng phng cc chui polymer vi nc, cho php tng tc ha hc din ra gia cc axit amin v cht kh. Hm lng nc tng ln trong mng l kt qu ca vic thc y mi quan h gia cht kh v b khung protein, dn n gi tr hp ph vt tri ti m tng i cao.4.7. Cht b sung vo mngCc vt liu khc nhau c th c a vo mng protein gy nh hng n cc tnh cht c hc, bo qun, cm quan, hoc dinh dng. Cht lm do l cht ph gia cha mt lp cht quan trng c khi lng phn t hp cht khng bay hi thp c s dng rng ri trong cc ngnh cng nghip polymer. Vai tr chnh ca cc cht l ci thin tnh linh hot v kh nng gia cng ca polyme bng cch h thp nhit xung chuyn sang giai on th hai, thay i nhit trong sut (Tg). Cc hi ng ca IUPAC (The International Union Of Pure and Applied Chemistry) nh ngha cht lm do nh sau ''l mt cht hoc vt liu c kt hp trong mt nguyn liu (thng l nha hoc cht n hi) tng tnh linh hot ca n, kh nng gia cng hoc kh nng trng phng ''Nhng cht ny lm gim sc p ca s bin dng, cng, mt , nht v in tch tnh in ca polymer. ng thi chng lm tng tnh linh hot chui polymer, kh nng chng t gy v hng s in mi. Mt s tnh cht khc cng b nh hng nh mc kt tinh, quang hc, dn in, biu hin s chy v kh nng chng li phn hy sinh hc (Vieira v cng s 2011). Tnh tng thch gia polymer v cht do l mt phn hiu qu ca s ha do; cc thng s khc nhau c th thy tnh nng ny bao gm tnh phn cc, lin kt hydro, hng s in mi v cc thng s tan (Choi v cng s 2004). Ngoi ra, mt yu t tc ng l s solvat ha nh cht lm do vi cc thng s tan ca cc polymer; yu cu t nng lng hn kt hp hoc solvat ha cc polymer. Nhit ca phn ng tng hp hoc s gel ha c lin quan n sc bn vng ca solvat ha cht lm do v kch thc phn t ca n (Rahman v Brazel, 2004).Ni chung, hai loi cht lm do c th phn bit c. S ha do bn trong l mt kt qu ca vic iu chnh cu trc ha hc ca polymer; s ha do bn ngoi thu c bng cch thm mt tc nhn lm bin i cu trc v nng lng trong vic sp xp mng ba chiu ca cc polymer (Banker, 1966). Trong thc t vic b sung mt cht lm do cho mng protein sn xut mng m t c kh nng ph v mng; tr nn linh hot hn v bn vng hn. Vic gim lin kt gia cc ni phn t ca chui polymer; do s lin kt chung, to iu kin cc mng c ko di v lm gim s thay i nhit trong sut ca n. iu ny c th hin bng mt trong cc thuc tnh gim ro cn i vi cc loi kh, hi, mng cht tan (Banker, 1966).Cc cht ho do thng c s dng nht trong cc mng protein l mono-, di-, v oligosaccharides (thng xi-r glucose hoc glucose, fructose trong mt ong), polyols (ch yu glycerol v cc dn xut ca n, polyethylen glycol, v sorbitol), lipid v cc dn xut ca lipid (axit bo, monoglycerides v este ca chng, acetoglycerides, phospholipid v cc cht nh ho khc). Kch thc phn t, cu hnh v tng s cc nhm chc nng ca cht lm do, cng nh kh nng tng thch ca n vi cc polymer, c th nh hng n s tng tc gia cc cht lm do v cc polymer (Yang v Paulson, 2000).Jangchub v Chinnan (1999) bo co rng glycerin c tm thy trong cc cht lm do kt hp vi protein u phng m c khi so snh vi sorbitol, propylene glycol, polyethylene propylene glycol hoc polyethylene glycol. iu cho thy c tnh cht c hc rt km, dn n kim tra tnh thm khng thnh cng. S tp trung ca glycerin m c chim 0,67-1,67% ca protein khng nh hng n tnh thm hi nc v tnh thm kh oxy, nhng nh hng n bn ko v gin di phn trm thuc tnh. Glycerin vi mc ln hn 0,67% ca protein l cn thit c c mt mng protein.Vanin v cng s (2005) tin hnh nghin cu nh hng ca nhiu chng loi v hm lng ca cc cht ho do, cc tnh cht ca mng gelatin. Bn polyol (glycerol-Gly, propylene glycol-PPG, di-DTG v ethylene glycol-ETG) c th nghim cc nng khc nhau. Kt qu cho thy loi cht lm do v hm lng ca n c nh hng ng k n cc tnh cht ca mng dn. nh hng ca s ha do cao hn v tnh cht nhit c tm thy DTG, tip theo l PPG, GLY v ETG, ch yu vi hm lng cht do thp. Lin quan n tnh cht c hc, GLY cho thy s ha do nh hng ln hn v hiu qu hn, nhng nh hng s ha do ca DTG lm bin dng m thng cng l ng k. Cc khng c hc c lin quan n nhit chuyn trong sut ca mng. iu l khng th quan st nh hng ca s ha do v tnh thm hi nc. Tuy nhin, DTG cho thy hiu qu ca s ha do hn, tip theo l Gly v ETG, trong khi mt tc dng ngc c quan st vi s b sung ca PPG.Andreuccetti v cng s (2009) xc nh tc dng ca cc cht lm do k nc c ngun gc t axit citric (tributyl citrat, acetyl tributyl citrat, triethyl citrate, acetyl triethyl citrate) trn cc tnh cht chc nng ca mng gelatin. H pht hin ra rng vic b sung cc dn xut ester citrate trong cng thc mng gelatin da trn cc chng minh tnh kh thi, to ra vt liu c tnh cht linh hot. Vic b sung ngy cng tng cc cht lm do k nc lm gim ng k bn ko. Nhng biu hin tng t nh m t s chun b cc mng vi cht do a nc. V tnh thm hi nc, n c xc nh rng vic s dng cc cht ho do k nc gim nh ging nh khi quan st mng gelatin kt hp vi glycerol v sorbitol5. CI THIN MNG PROTEIN5.1. Hiu chnh mng protein bng phng php ha hcProtein c ha hn l mng vt liu sinh hc vi nhng tnh cht cn kh. Tuy nhin, nhng hn ch chnh ca mng protein tng t nh cc polyme khc l chng thiu bn vng c hc v tnh cn hi nc km v bn cht a nc ca n. Mt phng php rt hiu qu ci thin kh nng chng nc, s lin kt, cng, bn c hc v cc tnh cht cn nc ca cc lin kt ngang trong mng. lm c iu ny cc nhm chc nng khc nhau ca protein c th c s dng. Mng li protein c kh nng tng tc vi mt lot cc hp cht hot ng. iu ny c thc hin thng qua cc nhm chc nng tc ng ln cc nhm ph phn ng vi chng. N c tim nng sa i thng qua lin kt ngang ha hc, vt l hay enzyme tng cng cc tnh nng ca mng.Phng php x l ha hc vi axit, cc cht kim hoc lin kt ngang c s dng rng ri ci thin tnh cht mng. V mt l thuyt, s tng tc protein xy ra nhiu hn vic x l ha hc sau mch cu trc m rng v t thm nc; bn ko ln hn, nn c thu ly. Tuy nhin, theo Brandenburg v cng s (1993) tm thy rng x l bng kim trn protein u nnh khng nh hng n tnh thm hi nc, thm oxy v bn ko nhng x l kim ci thin c b ngoi ca mng (n trong hn, ng u hn v t bt kh) ko di ti im t gy. Ha cht c s dng cho lin kt ngang ca protein bao gm cc aldehyde nh glutaraldehyde, glyoxal hoc formaldehyde, v nhng lin kt ngang t nhin khc. Bi v cc lin kt ngang c s dng trong mng protein; formaldehyde l lin kt ngang n gin nht; c phn ng c hiu rng nht. Ngoi cc nhm amin ca lysine, n phn ng vi cc mch bn ca cysteine, tyrosine, histidine, tryptophan, v arginine. Mc d formaldehyde cha mt nhm chc nng duy nht, nhng n c th phn ng vi c nhm chc nng khc v do hnh thnh lin kt ngang. Glutaraldehyde c trng hn formaldehyde; n c th phn ng vi lysine, cysteine, histidine v tyrosine (Tae, 1983). Lin kt ngang protein bng glyoxal gm cc nhm mch bn lysine v arginine (Marquie, 2001) pH kim.V c bn, qu trnh phn ng gia formaldehyde v protein bao gm hai bc: bc u tin tng ng vi s hnh thnh ca cc hp cht methylol; th hai tng ng vi s hnh thnh ca cc cu methylene l cc lin kt ngang gia cc mch protein. Cc s phn ng c th hin theo hnh 1 nh sau:

Hnh 1. Mch lin kt ngang gia formaldehyde v nhm -amino ca protein (Ngun: GUEGUEN v cng s (1998)Hernandez-Munoz v cng s (2004) nghin cu nh hng ca lin kt ngang bng cch s dng aldehydes vo mng giu glutenin. H bo co rng cc tnh cht thm hi nc ca mng giu glutenin gim khong 30% khi cc lin kt ngang nh formaldehyde, glutaraldehyde v glyoxal c kt hp. Cc gi tr bn ko cao nht thu c khi s dng formaldehyde, tip theo l glutaraldehyde v glyoxal. Ngoi ra, s thay i nhit trong sut ca mng lin kt ngang chuyn sang gi tr cao hn khi lin kt ngang c s dng. V formaldehyde cho thy nhiu hiu qu hn so vi glutaraldehyde v gossypol trong lin kt ngang. Cc tnh cht tt hn ca cc mng protein c x l bng formaldehyde c th l do s mt tnh c hiu ca hp cht ny lin quan n cc nhm mch bn amino acid khc nhau. Ngoi cc amin ra th formaldehyde phn ng vi nhm sulfhydryl, phenolic, imidazolyl, indolyl v guanidin. Hn na, mt s nh nghin cu bo co rng s hnh thnh ca cc cu methylene xy ra gia lysine v tyrosine khi x l bng formaldehyde (Hernandez-Munoz v cng s 2004). Tuy nhin, mc d phn ng mnh vi aldehyde, nhng cng c mt bt li ln chnh l c tnh ca chng. iu ny phi c a vo mc khi tng hp cc vt liu phn hy sinh hc. Tt c cc aldehyde c s dng phi c lin kt ngang trong mng li protein; s tn ti ca aldehyde trong mi trng vo cui thi gian ca vt liu cn c xem xt. Do c tnh ca cc aldehyd, nhiu nh nghin cu c gng s dng lin kt ngang t nhin ci thin cht mng protein. Theo ORLIAC v cng s (2002) xc nh cc tc ng ca t nhin lin kt ngang (tannin v acid gallic) trn tnh cht ca mng c c bng nhit c sn xut t protein ca hoa hng dng. Kt qu cho thy rng s kt hp ca tannin v acid gallic trong cc mng c tnh cht c hc cao hn so vi cc mng i chng, nhng thp hn so vi nhng mng thu c t andehit. y c l l v chng hot ng tng tc yu hn lin kt cng ha tr trong trng hp ca aldehyd. Hn na, bin ng cc k thp nhit x l ngn nga vic loi b cc tannin t do v axit gallic. Sau , Cao v cng s (2007) ci thin cc tnh cht c hc ca mng gelatin bng cch s dng axit ferulic acid tannic. Kt qu cho thy cc axit ferulic v acid tannic hot ng nh lin kt ngang t nhin v c tc dng ln lin kt ngang trn mng gelatin. bn c hc ti a ca mng gelatin c th thu c khi gi tr pH ca dung dch to mng ca axit ferulic bng 7 hoc khi gi tr pH = 9 ca axit tannic. Ngoi ra, cc tnh cht ca mng gelatin c x l bng axit tannic c th tr nn tt hn sau khi c lu tr hn 90 ngy, trong khi thi gian lu tr t nh hng n mng acid ferulic hiu chnh. L do c th l do axit tannic c lin kt ngang vi gelatin trong sut thi gian sy v lu tr.5.2. Hiu chnh mng protein bng phng php enzymec tnh mng protein c tnh chng kh, hi hu c v du tt hn so vi nhng mng tng hp. Tuy nhin, cc c tnh c hc yu v tnh thm nc cao ca mng protein lm gii hn ng dng ca n trong vt liu ng gi. Nhiu nghin cu c thc hin ci thin hiu qu cc mng protein. K thut ci thin cc chc nng ca mng protein l hiu chnh mng polymer thng qua cc lin kt ngang ca n. Mt k thut hiu qu ci thin cc c tnh cn kh v tnh vng chc c hc ca mng protein l k thut lin kt ngang bng phng php enzyme. Mt s enzyme c s dng cho cc protein lin kt ngang bao gm transglutaminase (TGase; EC.2.3.2.13), lipoxygenase, lysyl oxidase, polyphenol oxidase v peroxidase. Tuy nhin, transglutaminase l mt loi enzyme c th xc tc cho phn ng lin kt ngang ng ha tr gia cc protein to thnh polyme c phn t lng cao (MW).De Jong v Koppelman (2002) bo co rng transglutaminase xc tc cc phn ng gia cc nhm acyltransfer -cacboxamit ca gc glutamine (acyl donor) v nhm -amino ca gc lysine (acyl acceptor), kt qu l s to thnh - ( -glutaminyl) lysine v cc protein lin kt ngang trong phn t. Cc phn ng xc tc ca glutamyl transferase c th hin trong hnh 2 (Yee v cng s 1994). Phn ng trng hp khi s dng transglutaminase c nghin cu vi cc ngun protein khc nhau bao gm casein, protein u nnh v gelatin, ni phn ng khc nhau trong vng chc ca gel u ph thuc vo iu kin phn ng v cc ngun protein khc nhau (Sakamoto v cng s 1994). Tng cng lc gel ca protein trong qu trnh hot ng ca transglutaminase ph thuc vo th t v cng m theo enzyme to ra cc lin kt ngang v mc m cc lin kt cng ha tr mi ny c th cn tr cc lin kt ngang t nhin xut hin trong qu trnh hnh thnh v bo ton xon bc ba khi to gel (Babin v Dickinson 2001). Larre v cng s (2000) bo co rng transglutaminase l c hiu qu khi lin kt cng ha tr trong mng thu c t gluten c kh nh amide. Vic thit lp cc lin kt cng ha tr to ra s hnh thnh cc polyme c trng lng phn t cao l nguyn nhn chnh lm cho mng khng tan cao hn; b mt a nc cng c gim. Tnh cht c hc ca chng cho thy rng vic b sung thm cc lin kt cng ha tr ca transglutaminase lm tng tnh hon thin ca mng.

Hnh 2. Cc phn ng xc tc ca glutamyltransferases (Yee v cng s 1994)Ni chung, cc mi lin kt ngang ca transglutaminase ci thin sc bn ko ca mng protein, trong khi n lm gim gin ti im gy v kh nng ha tan. Trong mt s trng hp, chng hn nh vi protein u nnh v mng gluten kh amide khi x l transglutaminase tnh k nc ca b mt mng tng ln ng k (Tang v cng s 2005).Tuy nhin, c rt nhiu vn lin quan n k thut lin kt ngang ny, vn phi c nghin cu trc khi cc thng mi ha p dng cho cc mng. V d, iu ny khng chc chn rng khi lin kt ngang bng enzyme c th ci thin tnh cht ca mng c c t nhiu protein thc phm khc nhau. Hn na, i vi mt s protein c cc thng s ch bin ti u c c hiu qu tt nht trong vic ci thin. S ci thin cc thuc tnh ca mng protein bng cch s dng enzyme thng thng ph thuc vo cc loi protein cht nn v mt s thng s ch bin, chng hn nh s lng enzyme yu cu. V vy, n c d kin rng s ci thin cc thuc tnh ca mng protein bng cch x l enzyme cng b nh hng bi nng enzyme v lm ng t hoc tp hp li lm gim tnh cht c hc ca mng protein.Jiang v cng s (2007) bo co rng tnh cht ca mng protein u nnh c bit l bn ko v tnh k nc c th c thay i bi transglutaminase. Tuy nhin, h ch ra rng vic thay i cc thuc tnh ca cc mng protein u nnh bi transglutaminase l n mt mc no ; ph thuc vo nhiu thng s ch bin. Chng bao gm cc nng enzyme, iu kin ca dung dch to mng v nhit khng kh lm kh. S nh hng ca cc thng s x l c th gii thch cho s tng hp ca mng protein u nnh gy ra bi transglutaminase. V vy, vic ci thin bn ko ca mng protein u nnh t transglutaminase c th t c bng cch c ch hoc tr hon s xut hin ca cc tp hp.5.3. Hiu chnh mng protein bng phng php chiu xMc d protein c bit n c kh nng to mng tt; cc mng protein c tnh cht ro cn kh tt. Do , mt nhu cu cn thit l tm kim cht mi v quy trnh mi c c sn phm tt hn. Lin kt ngang c tm thy thng qua s dng chiu x l mt phng php hiu qu ci thin tnh chng thm v tnh cht c hc ca mng protein. Ni chung, chiu x nh hng n protein bng cch gy ra nhng thay i v hnh dng, qu trnh oxy ha cc axit amin, lm t lin kt cng ha tr v s hnh thnh ca cc gc khng c protein (Cheftel v cng s 1985). Protein c th chuyn i phn t c trng lng cao hn thng qua vic to ra cc phn ng lin kt ngang, tng tc k nc, lc tnh in, v s hnh thnh lin kt disulfua (Davies v Delsignore, 1987). V d, cc gc hydroxyl v superoxide anion c to ra bi chiu x ca dung dch to mng lm thay i cc thuc tnh phn t ca protein. iu ny c th dn n nhng thay i ca cc mng protein bi lin kt ngang ng ha tr c to thnh trong dung dch protein sau khi chiu x (Garrison, 1987). S to thnh tp hp cc phn t c trng lng cao l khng ng k phm vi liu lng chiu x thp, nhng tng ng k vi liu lng cao hn. Phng php chiu x lm mng protein c ci thin, chng hn nh chiu x gamma c s dng rng ri thay i protein. Ouattara v cng s (2002) s dng chiu x gamma to lin kt ngang ci thin kh nng thm hi nc v s n nh ha hc ca mng protein sa. Kt qu cho thy chiu x gamma vi mc ngha (p