Bai Giang Phu Gia Thuc Pham

Bi ging: Ph gia trong ch bin thc phm

Bin son: Nguyn Ch Linh

TRNG CAO NG CNG NG KIN GIANG KHOA K THUT CNG NGH


Rch gi, nm 2007(Lu hnh ni b)Trng Cao ng cng ng Ki n Giang Trang

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MC LC---------------------------Trang Chng 1: M U 1. NH NGHA PH GIA 2. S PHT TRIN CA PH GIA D NG TRONG BO QUN 3. TM QUAN TRNG CA VIC S DNG PH GIA 4. HP THC HA CA VIC S DNG PH GI A 5. BT HP PHP CA VIC S DNG PH GIA 6. C TNH PH GIA 7. VAI TR, CHC NNG CA PH GIA 7.1. Phn loi theo tnh cht cng ngh 7.1.1. Cht bo qun 7.1.2. Cht cung cp dinh dng 7.1.3. Cht mu 7.1.4. Cht to mi 7.1.5. Cc cht tc ng n tnh cht vt l ca sn phm 7.1.6. Cc cht dng trong ch bin thc phm 7.1.7. Ha cht iu chnh m sn phm 7.1.8. Cht iu chnh pH sn phm 7.1.9. Cc cht khc 7.2. Phn loi theo cu trc ha hc v c tnh 8. CC BC TM KIM MT PH GIA Chng 2: PH GIA DNG TRONG BO QUN THC PHM 1. PH GIA CHNG VI SINH VT 1.1. Tnh cht ca cc cht chng vi sinh vt 1.2. Dy hot ng ca cc cht chng vi sinh vt 1.3. Tnh cht ha hc v vt l ca cc cht chng vi sinh vt 1.4. Tnh cht ca thnh phn thc phm 1.5. Mc nhim vi sinh vt 1.6. Phng php bo qun 2. CHNG OXY HA CHT BO 2.1. M uTrng Cao ng cng ng Ki n Giang

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2.2. Chng oxy ha cht bo 2.2.1. S thy phn cht bo 2.2.2. S oxy ha cht bo 2.2.3. C ch chng oxy ha cht bo 2.2.4. Cc cht chng oxy ha cht bo thng dng 2.2.5. Phng php s dng cht chng oxy ha cht bo 3. CHNG PHN NG HA NU 3.1. Chng phn ng ha nu c s tham gia ca enzyme 3.1.1. C ch phn ng 3.1.2. Phng php kim sot phn ng ha nu c enzyme 3.2. Chng phn ng ha nu khng c enzyme tham gia 3.2.1. C ch ca cc phn ng 3.2.2. Phng php ch ng phn ng ha nu khn g enzyme 4. PH GIA CHNG NH BNH Chng 3: PH GIA LM THAY I CU TRC THC PHM 1. HA CHT IU CHNH M SN PHM 1.1. Ha cht ht m 1.1.1. Ht m theo tnh cht vt l 1.1.2. Ht m theo tnh cht ha hc 1.2. Ha cht gi m 2. HA CHT LM TRONG 2.1. Tch cc cht tan 2.2. Tch cc cht keo 3. CC CHT KEO 3.1. M u 3.2. Gii thiu mt s cht keo thng dng 3.2.1. Acid alginic Alginat 3.2.2. Agar 3.2.3. Cellulose v cc dn sut 3.2.4. Gelatin 3.2.5. Arabic 3.2.6. Pectin 3.2.7. Carrageenan 4. CHT HOT NG B MTTrng Cao ng cng ng Ki n Giang

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4.1. Khi nim 4.2. Phn loi 4.2.1. Cht hot ng b mt loi ion 4.2.2. Cht hot ng b mt lng tnh 4.2.3. Cht hot ng b mt khng ion 4.3. Chc nng ca cht hot ng b mt 4.3.1. Kh nng ty ra 4.3.2. Kh nng to nh 4.3.3. Kh nng to huyn ph 4.3.4. Cn bng k nc a nc 4.4. Cht nh ha 4.4.1. Cc chc nng ca cht nh ha 4.4.2. ng dng cht hot ng b mt trong sn xut thc phm Chng 4: PH GIA DNG TRONG CH BIN THC PHM 1. CI THIN TNH CHT BT V TO N 1.1. Ci thin tnh cht bt nh o 1.1.1. Cht oxy ha 1.1.2. Cc cht kh 1.2. Cc cht gy n 1.2.1. Cht NH4HCO3 1.2.2. Cht NaHCO 3 2. CHT THAM GIA VO SN XUT THC PHM 2.1. Cc cht to c 2.2. Cc cht lm trong 2.3. Cht chng ng bnh 2.4. Cht tr lc 2.5. Cht bi trn, d g 2.6. Cc cht to mng 2.7. Cc cht gip qu trnh to hnh 2.8. Cc photphat 3. HA CHT LM V SINH 3.1. Clorin v cc hp cht cha clorin 3.1.1. Kh nng chng vi sinh vt 3.1.2. c tnh ca cc clorinTrng Cao ng cng ng Ki n Giang

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3.2. Idophor Chng 5: PH GIA LM THAY I TNH CHT CM QUAN CA THC PHM 1. CC CHT TO V 1.1. Cc acid amin 1.1.1. Dch acid amin 1.1.2. Bt ngt 1.2. Cc cht ngt khng ng 1.2.1. Saccharin 1.2.2. Acesulfame Kali 1.2.3. Cyclamate 1.2.4. Aspartame 1.3. Cc cht to v chua 1.4. Cht to v ng 1.5. Cht to v mn 1.6. Cc cht to v khc 1.6.1. t 1.6.2. Ti 1.6.3. Hnh 1.6.4. Rng 1.6.5. Tiu 2. CC CHT MU 2.1. Vai tr ca cht mu 2.2. Phn loi cht mu 2.2.1. Cc cht mu tng hp 2.2.2. Cc cht mu v c 2.2.3. Cc cht mu t nhin 2.3. Cc cht mu hnh thnh trong qu trnh ch bin 3. CC CHT MI 3.1. Cht mi t nhin 3.2. Cht mi tng hp PH LC

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Chng 1

M U1. NH NGHA PH GIA Theo FAO: Ph gia l cht khng dinh dng c thm vo cc sn phm vi cc nh khc nhau. Thng thng cc cht ny c hm lng thp dng ci thin tnh cht cm quan, cu trc, mi v cng nh bo qun sn phm. Theo WHO: Ph gia l mt cht khc hn l thc phm hin din trong thc phm l kt qu ca mt s mt: sn xut, ch bin, bao gi, tn tr...Cc cht n y khng bao gm s nhim bn. Theo y ban Tiu chun ha thc phm quc t (Codex Alimentarius Commisson - CAC): Ph gia l mt cht c hay khng c gi tr dinh d ng, khng c tiu th thng thng nh mt thc phm v cng khng c s dng nh mt thnh phn ca thc phm. Vic b sung chng v o thc phm gii quyt mc ch cng ngh trong sn xut, ch bin, bao gi, bo qun, vn chuyn thc phm, nhm ci thin cu kt hoc c tnh k thut ca thc phm . Ph gia thc phm khng bao gm cc cht nhim hoc cc cht c b sung v o thc phm nhm duy tr hay ci thin thnh phn dinh dng ca thc phm. Theo TCVN: Ph gia thc phm l nhng cht khng c coi l thc phm hay mt thnh phn ch yu ca thc phm, c hoc khng c gi tr dinh d ng, m bo an ton cho sc khe, c ch ng cho vo thc phm vi mt lng nh nhm duy tr cht lng, hnh dng, mi v, kim hoc axt ca thc phm, p ng v y u cu cng ngh trong ch bin, ng gi, vn chuyn v bo qun thc phm. Nh vy, ph gia thc phm khng phi l thc phm m n c b sung mt cch ch , trc tip hoc gin tip v o thc phm, ci thin tnh cht hoc c tnh k thut ca thc phm . Ph gia thc phm tn ti trong thc phm nh mt thnh phn ca thc phm vi mt gii hn ti a cho php c quy nh. Vi s pht trin ca khoa hc cng ngh hin nay gii hn ph gia s dng trong thc phm ng y cng chnh xc hn m bo an ton cho ngi s dng thc phm. Ph gia c s dng trong hu ht cc sn phm thc phm, nhng cht to v, gia v s dng trong ba n hng ngy cng u l ph gia. Do , cn phi nm vng nhng kin thc v ph gia v thng xuyn cp nht nhng pht trin mi v ph gia thc phm m bo an ton khi b sung ph gia vo thc phm.


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2. S PHT TRIN CA PH GIA D NG TRONG BO QUN Vo thi xa xa, khi m thc phm cha c sn xut quy m cng nghip, ph gia cha c th hin r vai tr ca mnh trong thc phm nhng n cng c p dng rt nhiu trong qu trnh bo qun thc phm d tr. C ng vi s pht trin ca x hi v khoa hc cng ngh, ph gia cng pht trin khng ngng nhm p ng nhu cu v dinh dng, v sinh,.nht l khi thc phm c a vo sn xut cng nghip th ph gia mi th hin ht tm quan trng ca n trong thc phm. Qu tr nh pht trin ca ph gia c th tm tt qua cc giai on sau: - Thi tin s: s dng mui v khi bo qun thc phm nh tht, c, - Vn minh Ai Cp: dm, du, mt ong bo qun cc thc phm t ra qu. - Vn minh La M: SO 2 bo qun ru. - Trc nm 1400: pht minh vic l n men rau qu ( Beukels). - Nm 1775: dng Borat (Hofer) - Nm 1810: SO 2 dng trong bo qun tht. - Nm 1833: Creosote dng trong b o qun tht (Reichenbach) - Nm 1858: Khm ph ra c ch chng vi sinh vt ca Sorbi c (Jacques) - Nm 1859: trch ly c Sorbic (Hofman) dng trong cc loi sausage. - Nm 1865: khm ph ra c ch chng vi sinh vt ca Fomic (Jodin) - Nm 1874: khm ph ra c ch chng vi sinh vt ca Salycilic ( Kolbe v Thiersch) - Nm 1875: khm ph ra c ch chng vi sinh vt ca Benzoic (Fleck) - Nm 1907: Formalin v H 2O2 dng trong bo qun sa (Behring) - Nm 1908: Benzoic c dng trong thc phm M. - Nm 1913: hot ng chng vi sinh vt ca p -Cholorobenzoic (Margolius) - Nm 1923: hot ng chng vi sinh vt ca p -Hydroxybenzoic (Sabalistschka) - Nm 1938: Propionic dng trong b o qun cc loi bnh (Hofman, Dalby, Schweitzer) - Nm 1947: Khm ph Dehydroacetic (Coleman, Wolf) - Nm 1950: Xem xt cht bo qun tm c v chng nhn nh l cht bo qun mi. - Nm 1954: sn xut Sorbic thng phm quy m nh. - Nm 1956: khm ph ra diethyl pyrocarbonate (Bernard, Thoma, Genth) - T nm 1980 ti nay: gia tng vic bo qun bng cc hn hp kh.Trng Cao ng cng ng Ki n Giang Trang

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Ngy nay, s tin b ca khoa hc k thut lm phong ph thm, a dng thm vic s dng ph gia trong thc phm. Nhiu ph gia mi c pht hin thay th nhng ph gia khng cn ph hp nng cao cht lng sn phm thc phm. Tuy nhi n, vic s dng ph gia vn cn nhiu tranh lun, mi quc gia c nhng yu cu khc nhau v hm lng cht ph gia s dng gy nh h ng nhiu n vic s dng ph gia. 3. TM QUAN TRNG CA VIC S DNG PH GIA S pht trin ca khoa hc cng ngh gip cho ph gia thc phm ng y cng hon thin v a dng ha, hn 2500 ph gia c s dng trong cng ngh thc phm gp phn quan trng trong vic bo qun v ch bin thc phm. Ph gia c vai tr quan trng trong lnh vc cng ngh thc phm c th l : - Gp phn iu ha ngun nguyn liu cho cc nh my sn xut thc phm, gip nh my c th hot ng quanh nm, gip sn phm c phn phi trn ton th gii. - Ci thin c tnh cht ca sn phm: cht ph gia c b sung thc phm lm thay i tnh cht cm quan nh cu trc, mu sc, ng u,.ca sn phm. - Lm tha mn th hiu ngy cng cao ca ngi tiu dng. Do nhu cu n king ca con ngi t ra i cng nghip sn xut cc thc phm t nng l ng. Nhiu cht to nh v keo t, cc este ca acid bo v cc loi ng gip lm gim mt lng ln cc lipid c trong thc phm - Gp phn lm a dng ha cc sn phm thc phm. Cng vi s xut hin ca ph gia thc phm, thc n nhanh, thc n t nng l ng, cc thc phm thay th khc cng ra i v pht trin p ng nhu cu n ung ngy cng a dng ca con ngi. - Nng cao cht lng thc phm. Cc cht mu, cht mi, cht to v lm gia tng tnh hp dn ca sn phm. - Lm n gin ha cc cng on sn xut. Vic s dng cc ha cht bc v trong ch bin cc loi c gip rt ngn c thi gian bc v trong ch bin. - Lm gim ph liu cho cc cng on sn xut v bo v b mt ca nh my. 4. HP THC HA CA VIC S DNG PH GIA Vic s dng ph gia trong cc sn phm thc phm phi tun th cc lut l v bo v sc khe ngi tiu dng v ch c php cho vo cc sn phm thc phm trong cc trng hp sau: - Ci thin c tnh cht dinh dng ca sn phm. - Tng cht lng sn phm. - Gim ph liu.Trng Cao ng cng ng Ki n Giang Trang

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- Lm tng tnh cm quan thc phm. - Gi phm cht sn phm t thay i. - To d dng cho vic ch bin. - Lm thc phm s dng tin li h n. Khi quyt nh thm mt loi ph gia no vo thc phm, cc chi tit cn ch l : - Mc nguy him i vi ng i tiu dng. - L do tiu dng cn n ph gia. - Tha mn cc yu cu v sc khe. - S cn thit trong ch bin thc phm. - Yu t v kinh t. - C ch tc dng ca cc ph gia. Tht ra khng c ph gia no c th p ng c tt c cc yu cu trn, ty thuc vo trng hp c th s c mt la chn hp l. 5. BT HP PHP CA VIC S DNG PH GIA Theo quy nh ca cc c quan chc nng, ph gia b cm s dng trong cc tr ng hp sau: - C kh nng tng tc vi cc thnh phn trong thc phm lm gim gi tr thc phm. - S dng ph gia ngoi danh mc cho php hoc qu liu l ng cho php. - S dng khng v l do k thut m v l do kinh t. - Che lp h hng. - Che lp cc k thut yu km ca qu tr nh sn xut. - La di ngi tiu dng. 6. C TNH PH GIA c tnh ca ph gia c biu hin bng ch s LD 50 (Lethal Dose) l liu lng ti 50% ng vt dng trong th nghim b cht. Ch s LD 50 cng cao c tnh cng yu. Da vo ch s LD 50 c th chia c tnh ph gia l m 5 mc : + LD50 < 5 mg/Kg Th trng + LD50 = 5 49 mg/Kg Th trngTrng Cao ng cng ng Ki n Giang Trang

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+ LD50 = 50 -499 mg/Kg Th trng + LD50 = 500 - 4999 Th trng + LD50 > 5000 mg/Kg Th trng V d: Gi tr ca ch s LD 50 ca mt s cht chng vi sinh vt khi l m th nghim trn chut nh sau

Ph gia Acid benzoic Mui Nitrat Acid Nitrit Acid Sorbic Acid Propionic Ethanol

Ch s LD50 (mg/Kg th trng) 3000 6000 100-200 10000 4000 9500

Ch s ADI (Acceptable Daily Intake): Lng n vo hng ngy c th chp nhn c tnh theo mg/kg th trng. V d: acid benzoic (0-5 mg/kg th trng/ngy), Nisin (0-3 mg/kg th trng/ngy), acid propionic (Khng gi i hn). i vi mc an ton ca ph gia c th chia ra th nh 5 nhm sau: - Nhm 1: Ph gia an ton tuyt i trong hin ti v tng lai. Cc cht ph gia thuc nhm ny s t tiu chun GMP (Good Manufacturing Practices ): Lng ph gia c php cho vo thc phm va t c yu cu v cng ngh. Do , khng qui nh gii hn ti a v lng ph gia cho vo thc phm cng t cng tt. C khong 350 ph gia t tiu chun nhm 1. - Nhm 2: Ph gia an ton hin ti nhng cn nghin cu thm liu lng cao nh gi an ton ca ph gia s dng. C khong 70 cht t ti u chun nhm 2. - Nhm 3: Ph gia cn nghin cu thm do cha khng nh c an ton khi s dng. - Nhm 4: Ph gia s dng trong cc iu kin an to n. - Nhm 5: Ph gia cm s dng.


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7. VAI TR, CHC NNG CA PH GIA Ph gia dng trong bo qun v ch bin thc phm c vai tr , chc nng lun thay i ty vo loi sn phm. Vic phn loi ph gia gp nhiu kh khn, c th phn loi ph gia theo tnh cht cng ngh hoc theo cu trc ha hc v c tnh. 7.1. Phn loi theo tnh cht cng ngh 7.1.1. Cht bo qun Cc cht ph gia thuc nhm ny c b sung vo thc phm vi mc ch ko di thi gian s dng ca thc phm bng cch ngn chn hay k m hm nhng bin i trong bn thn thc phm do cc qu tr nh bin i sinh ha, ha hc, vt l v vi sinh vt. Cc cht bo qun c chia thnh bn nhm ch yu sau: - Chng vi sinh vt - Chng bin i thnh phn ha hc thc phm - Chng bin i tnh cht vt l ca sn phm - Chng cn trng Tiu biu ca nhm ny l acid bezoic v cc mui Na, K, Ca ca n. Cc este metylic, etylic v propilic c a acid parahydroxybenzoic, a cid sorbic, 7.1.2. Cht cung cp dinh dng Cc cht ny c s dng vi mc ch cng ngh nh ng chng cng c mt gi tr dinh dng nht nh. V d Riboflavin va l cht mu va l vitamin. Ph gia dinh dng thng dng bt, nh ha trong du v c bo v bi cc ph gia bo qun, chng c s dng ring l hay dng chung vi cc ph gia dinh dng khc. Ph gia dinh dng c chia thnh 4 nhm sau: - Vitamin. - Khong cht. - Acid amin. - Cc cht cung cp nng lng. 7.1.3. Cht mu Cht mu thc phm l nhm ph gia c b sung vo thc phm vi mc ch ci thin mu sc ca thc phm nhm l m tng gi tr cm quan ca thc phm. Chng c th l cc cht mu t nhin c chit tch t thc vt hay nhng hp cht m u tng hp.


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- Cht mu t nhin: l cc cht c chit xut t cc nguyn liu hu c thc vt hay ng vt c sn trong t nhi n. V d: Caroten t nhin c chit xut t cc loi rau qu c mu vng, Curcumin c chit xut t ngh, Caramen c to ra t ng,...tuy nhin nhm mu t nhin c nhc im l bn km, s dng vi lng ln nn gi thnh sn phm cao. - Cht mu tng hp: l cc cht mu c to ra bng cc phn ng tng hp ha hc. V d: Amaranth (Mu ), Brilliant blue (Mu xanh), Sunset yellow (Mu vng cam), Tartazine (Mu vng chanh),...l nh ng hp cht mu c tng hp t cc phn ng ha hc. Cc cht mu tng hp c bn cao, vi mt l ng nh t c mu sc yu cu nhng d b ng c nu s dng cc hp cht m u khng nguyn cht. Ngoi ra, trong nhm ny cn g p cc hp cht c tc dng bo v m u t nhin nhm ngn chn cc hin tng bin i mu t nhin ca rau qu v cc cht dng nhum mu. 7.1.4. Cht to mi Cng ging nh hp cht mu, cht mi th hin tnh cht cm quan quan trng ca thc phm, c tc dng sinh l l n h thn kinh, h tiu ha,... Do , trong qu tr nh ch bin thc phm cht mi cn phi c bo v hay tm nhng bin php to ra cht m i mi to tnh hp dn cho sn phm. to m i thm cho cc sn phm thc phm thng thc hin mt trong ba bin php sau: - Dng cc thit b k thut thu hi cht m i b tch ra khi sn phm trong qu trnh ch bin, sau cht mi s c hp th tr li thnh phm. - Chng ct v c c cc cht thm c ngun gc t nhin b sung vo thc phm. - Tng hp cc cht thm nhn to c mi tng ng vi sn phm. Ty theo ngun gc nguyn liu sn xut cht mi b sung vo thc phm v tnh cht cng ngh ca cht mi, c th chia cht mi thnh cc nhm sau: cht mi t nhin, cht mi tng hp, cht bo v mi v lm tng mi. 7.1.5. Cc cht tc ng n tnh cht vt l ca sn phm Nhm ny c s dng rt nhiu trong cng ngh ch bin, n l m thay i cu trc nguyn liu ban u nhm to ra nhng sn phm mi hoc n nh cu trc sn phm. Cc cht ph gia ny c chia thnh cc nhm sau: - Cht lm c - Cc cht hot ng b mt (Lm thay i sc cng b mt ca cht lng)Trng Cao ng cng ng Ki n Giang Trang

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- Cht to bt - Cht n nh huyn ph - Cht to mng 7.1.6. Cc cht dng trong ch bin thc phm Trong cc nh my ch bin thc phm thng s dng nhiu loi ha cht nhm t c cc yu cu v v sinh nh xng, rt ngn thi gian ch bin, to iu kin thun li cho cc qu trnh ch bin tip theo, trnh nhim vi sinh vt vo sn phm,...Cc cht dng trong ch bin thc phm c chia thnh 4 nhm sau: - Ha cht lm v sinh - Ha cht bc v - Ha cht chng bt - Ha cht to kh 7.1.7. Ha cht iu chnh m ca sn phm m sn phm c vai tr quan trng i vi tnh cht cng ngh trong ch bin thc phm, th hin c tnh trng cu trc sn phm, kh nng bo qun sn phm,V th, trong ch bin thc phm cn phi s dng cc cht iu chnh m sn phm theo tnh cht yu cu ca tng sn phm. Cc cht n y bao gm: - Cht chng m - Cht gi m - Cht chng ng bnh- Sp,..

7.1.8. Cc cht iu khin pH ca sn phm Cc cht ny c b sung iu khin cc qu tr nh ch bin sn phm. Vic thay i pH s dn n thay i v tc ln men, bin i sn phm v kh nng bo qun sn phm. Cc cht ny c phn loi thnh 2 nhm sau: - Ha cht lm chn - Ha cht duy tr hot ng sng ca rau qu 7.1.9. Cc cht khc Bn cnh cc ha cht s dng tr n , trong cng nghip thc phm cn s dng cc cht b tr trong qu trnh ch bin nhm to ra nhng sn phm c gi tr cao. V d: khiTrng Cao ng cng ng Ki n Giang Trang

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sn xut nc tri cy cn phi s dng cc cht l m trong sn phm, khi sn xut nc ung c gas ta cn phi b sung kh CO 2, Cc cht ny c th chia thnh 3 nhm sau: - Cht thy phn - Cht gia v - Cc cht kh 7.2. Phn loi theo cu trc ha hc v c tnh Theo c tnh c th phn cc cht ph gia th nh 3 nhm chnh: - Nhm A l cc cht c tnh c yu bao gm 9 nhm phn t: hydrocarbon no mch thng, ng v cc polysacharid, m v cc acid bo, cc mui v c v hu c ca acid bo, cc mui hu c ca kim loi kim (Na, K) v kim loi kim th (Mg, Ca). - Nhm B l cc cht ph gia c cha cc nhm chc mang c tnh cao. C khong 52 dng phn t c xp vo nhm ny chng thng cha nguyn t halogen (khng k mui), cc h thng d vng 3 v tr v cc , lacton khng bo ha. - Nhm C: l cc cht ph gia c c tnh trung gian gia hai nhm tr n.8. CC BC TM KIM MT PH GIA

tm kim mt ph gia a vo sn xut cn thc hin cc b c sau: Bc 1: t ra cc vn trong vic ci thin mt s tnh cht n o ca sn phm Bc 2: p dng ph gia c php dng trong thc phm, p dng ph gia dng trong cc ngnh cng nghi p khc v pht trin cc ph gia mi. Bc 3: nh gi cc ph gia s dng v cc vn thc hin c khi ci thin tnh cht sn phm. Bc 4: Nghin cu c tnh v liu lng s dng ph gia. Bc 5: Nghin cu pht trin cc phng php phn tch v x p loi ph gia va tm c. Bc 6: B sung ph gia vo lut thc phm. Bc 7: S dng ph gia cho thc phm.


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Chng 2

PH GIA DNG TRONG BO QUN THC PHMPh gia dng trong bo qun dng ngn cn, tr hon cc phn ng ha hc, sinh hc v cc bin i vt l lm h hng cc sn phm, nhm n y gm: - Ngn cn cc phn ng sinh hc do vi sinh vt gy ra. - Cht chng oxy ha. - Cht chng phn ng ha nu ca thc phm 1. PH GIA CHNG VI SINH VT Hin nay c khong 30 hp cht chng vi sinh vt c s dng rng ri trong bo qun thc phm. Vi s pht trin khng ngng ca x hi, nhu cu v thc phm ng y cng yu cu cao, sn phm thc phm phi m bo an to n, khng gy c v c thi gian s dng hp l. Do , ph gia chng vi sinh vt c vai tr quan trng trong bo qun thc phm. Vic la chn cc cht chng vi sinh vt t y thuc vo cc yu t sau: - Tnh cht ha hc, hot tnh ca cc cht chng vi sinh vt. - Tnh cht ca thnh phn thc phm. - Phng php bo qun thc phm. - S lng v c tnh ca cc cht chng vi sinh vt. - Gi thnh v hiu qu khi s dng cc cht chng vi sinh vt. 1.1. Tnh cht ca cc cht chng vi sinh vt Cc cht chng vi sinh vt dng trong bo qun thc phm c th l m tr hon hoc tiu dit cc vi sinh vt. Ty thuc vo kiu hot ng chng vi sinh vt ca cc ph gia m chng nh hng ln vi sinh vt di cc hnh thc sau: - nh hng ln AND. - nh hng ln s tng hp protein ca vi sinh vt. - nh hng ln s hot ng ca cc enzim. - nh hng ln tnh thm thu ca mng t bo. - nh hng ln vch t bo. - nh hng ln c ch trao i cc cht dinh d ng.Trng Cao ng cng ng Ki n Giang Trang

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1.2. Dy hot ng ca cc cht chng vi sinh vt Dy hot ng ca cc cht chng vi sinh vt l kh nng tc dng ca n ln h vi sinh vt, cho bit cc cht khc nhau th kh nng tc dng ln cc vi sinh vt khc nhau nh th no. Qua chng ta c th chn c ph gia ph hp cho tng sn phm.Bng 1: nh hng ca mt s cht bo qun tr n vi sinh vt Cht chng vi sinh vt Nitrite Sulfite Acide formic Acide propionic Acide sorbic Acide benzoic Acide esters p-hydroxybenzoic Biphenyl Ghi ch: + ++ +++ Khng tc dng. Tc dng yu. Tc dng trung bnh. Tc dng mnh. Vi khun ++ ++ + + ++ ++ ++ Nm men ++ ++ ++ +++ +++ +++ ++ Nm mc + ++ ++ +++ +++ +++ ++

Hot ng chng vi sinh vt chu nh h ng bi loi thc phm, pH, h m lng mui, kh nng ha ln cc cht vo mi trng. Thng s dng phng php m khun lc sau qu trnh nui cy l c s nh gi dy hot ng chng vi sinh vt. 1.3. Tnh cht ha hc v vt l ca cc cht chng vi sinh vt Ton b dy hot ng, kiu chng vi sinh vt, hiu qu s dng cc cht chng vi sinh vt ph thuc vo tnh cht l ha ca cc ph gia. Trc khi s dng mt ph gia chng ta cn ch cc tnh cht l - ha sau: - Tnh cht tan ca ph gia. - im nng chy, im si ca ph gia (c bit trong tr ng hp c gia nhit trong qu trnh ch bin). - Kh nng ion ha cc cht. - Phn ng ca ph gia vi cc th nh phn thc phm. 1.4. Tnh cht ca thnh phn thc phm S mt hot tnh ca cc cht chng vi sinh vt s xy ra khi cc cht ny tip xc vi cc thnh phn thc phm, kt qu l cht ph gia s gim hoc mt kh chng vi sinh vt.Trng Cao ng cng ng Ki n Giang Trang

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Trong qu trnh s dng ph gia chng vi sinh vt cn nghi n cu cc c im ca sn phm thc phm, c th cn ch cc im sau: - Gi tr pH ca sn phm c th nh h ng n s ion ha cc cht chng vi sinh vt. - Mt s cht chng vi sinh vt c th b oxi ha, thy phn v to lin kt. - Cht bo c kh nng tc ng l n vi sinh vt ngn cn s nh hng ca cc ph gia. - Cc hp cht khc trong thc phm (khng phi l thnh phn chnh) cng c th nh hng ln hot ng ca ph gia. 1.5. Mc nhim vi sinh vt Vic x l ngun nguyn liu, thc phm trc khi thm ph gia c nh hng trc tip n s lng vi sinh vt. Nu thc phm b nhim l ng vi sinh vt cao th nng ph gia dng phi cao. Vic la chn cc ph gia phi da tr n nguyn tc chng loi vi sinh vt cn chng gi phm cht cc sn phm. 1.6. Phng php bo qun Cc hnh thc bo qun sn phm cng nh h ng n hm lng ph gia thm vo. cc iu kin bo qun khc nhau th nng v loi ph gia b sung vo thc phm cng khc nhau. Do cn phi ch n cc vn sau: - Vi sinh vt c kh nng sinh bo t trong qu trnh bo qun hay khng. - Sn phm c qua qu trnh x l nhit khng. - hot ng ca nc trong sn phm - Bao gi s dng cha ng sn phm. - Sn phm c c bo qun trong mi trng kn hay khng, c ht chn khng trong khi bao gi khng, Da trn s phn tch cc iu kin tr n m chng ta ti u ha vic chn loi v nng ph gia sao cho thch hp, tit kim v hiu qu cao. 2. CHNG OXY HA CHT BO 2.1. M u Cch y na th k, mt nhm ha cht c tm thy v b sung vo nhng sn phm thc phm nhm ngn chn hay kim h m cc gc oxy ha t do ca cht bo l nguyn nhn dn n s thay i mi v v ca sn phm.Trng Cao ng cng ng Ki n Giang Trang

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Trong sut khong thi gian , h ng nghn hp cht chng oxy ha va t nhi n va tng hp c tc dng chng oxy ha hiu qu v an ton i vi ngi s dng. Hin nay, c khong 20 hp cht c php s dng rng ri v c chp nhn nh nhng ph gia thc phm ty theo mi quc gia.Bng 2: S dng cht chng oxy ha du mt s Quc gia Canada Acide ascorbic Palmitate ascorbyl Stearate ascorbyl BHA BHT Acide citric Gum guar Lecithin Citrate monoglycerid Citrate monoizopropil Propyl gallate Acide tartic Tocopherol M BHA BHT Dilauryl thiopropionate Glicine Gum guar Lecithin PG TBHQ THBD Tocopherol Acide thiodipropionic 4-hydroymetyl 2,6 diteriarybutyl phenol EC Acide ascorbic Palmitate ascorbyl BHA BHT Ascorbat canxi Dodecil Octyl gallate Propyl gallate Tocopherol Ascorbat natri

Tuy nhin, hin nay ch yu s dng 5 ph gia c php dng rng ri l: BHA, BHT, Propyl Galate, TBHQ v Tocopherol. Cc ch t ny c th s dng ring r hoc c th kt hp vi mt s cht tr chng oxy ha nh : acide ascorbic, citric nh m gip vic ch bin v bo qun thc phm t hiu qu cao nht. 2.2. Chng oxy ha cht bo Bn cht ha hc ca cht bo l triglycerid, l este ca glycerol v cc acid bo cao phn t. Trong cu trc ha hc ca triglycerid c s hin din ca nhiu acid bo R 1, R2, R3 to este vi glycerol.


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Hu ht cc acid bo tm thy trong thnh phn thc phm c di mch carbon 12 18 carbon, c th l acid bo no hoc acid bo khng no. Ty theo di ca mch carbon v s lng ni i c trong cu to acid b o m cht bo c nhiu tnh cht khc nhau. Cc sn phm cha nhiu cht bo th ng rt d b h hng trong qu trnh bo qun. Thng thng s h hng ca cht bo thng xy ra di 2 hnh thc l: s thy phn v s oxy ha. 2.2.1. S thy phn cht bo S thy phn cht bo l qu trnh phn ng gia nc vi cc triglycerid to th nh glyceryl, cc monoglycerid, diglycerid v cc acide bo t do di tc dng ca enzim lipaza. Qu trnh thy phn cht bo xy ra nhit cao v nc nh: chin sn phm c hm m cao, ch bin cc dng sn phm nh t ng. Kt qu ca qu trnh oxy ha cht bo lm cho sn phm xy ra cc hin t ng sau: - C im bc khi thp. - C s to thnh bt trong qu trnh chin. - n mn cc thit b do s hin din ca cc acide bo. - C v ng, c mi x phng do cc acide bo t o nn. S thy phn cht bo cn xy ra ph bin trong bo qun b v margarin, khi gii phng ra acid butyric v acid c mi r t kh chu. Trong bo qun l ng thc, khi m ca ht cao cng rt d xy ra hin tng oxy ha cht bo. 2.2.2. S oxy ha cht bo Qu trnh xy ra trong sn xut, bo qun v ch bin thc phm c s hin din ca cht bo. S oxy ha cht bo l nguyn nhn hn ch thi gian bo qun ca cc sn phm. S oxy ha cht bo khng no c khi to bng vic to th nh cc gc t do di tc dng ca nh sng, nhit , ion kim loi v oxy. Thng thng phn ng xy ra trn nhm metyl cn k vi ni i ca C=C. C ch phn ng oxy ha cht bo xy ra phc t p, c th chia thnh 3 giai on l: khi to, lan truyn to cc sn phm trung gian v kt thc phn ng. - Khi to.


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- Lan truyn- to cc sn phm trung gian.

- Kt thc phn ng.

Cht bo Peroxyt

Vitamin

Cht mu

Protein

Thay i gi tr dinh dng

Mt mu, lm thay i mu

Thay i cu ni S-S

Oxy ha protein

Aldehyt, alcool, acide, epoxyde, xeton, polyme, oxy ha sterol

Lm gim mi, mu, cu trc, gi tr dinh dng, sinh c tHnh 1: nh hng ca cc sn phm t s oxy ha cht bo n thc phm

Cc biu hin thng thy ca s oxy ha cht bo l: pht sinh mi-v xu, thay i mu sc, lm mt mi t nhin ca cc loi tinh du, thay i nht ca sn phm. S oxy ha cht bo chu nh h ng bi nhiu yu t nh: no ca cht bo, ion kim loi, cht xc tc sinh hc, nhit , k hng kh, cc cht chng oxy ha cht bo, cht tr chng oxy ha cht bo, nm r cc yu t nh h ng n kh nng oxy ha cht bo cn tm hiu cc vn sau:Trng Cao ng cng ng Ki n Giang Trang

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* Thnh phn acid bo Cht bo l hn hp ester ca cc acide bo no v khng no vi glycerin. S hin din ca cc ni i, cc acide bo khng no d b oxy ha h n cc cht bo no. Phn ng s gia tng khi t l ni i cng cao. V d: tc oxy ha (tng i) ca mt s cht bo t l nh sau: Arachidonic : Linolenic : 40 : 20 : Li noleic 10 : : Oleic 1

V tr ni i cng nh v tr hnh hc ca ni i cng c tc dng n tc phn ng. Cc acide dng cis b oxy ha nhanh h n dng trans. Mch acide bo c cc ni i cng hng cng lm tng tc phn ng. S oxy ha cc cht bo no xy ra rt chm ti nhit thng, ti nhit cao (chi n, xo) s oxy ha cht bo no mi c th xy ra. * Acide bo t do Acide bo t do (FFA) b oxy ha rt nhanh so vi cc ester - glycerin. Khi nghin cu cht bo hin din trong thc phm giai on u ti n, hu ht u c s hin din ca cc cht chng oxy ha thin nhin. Trong th nghim nu thm vo 0,1% FFA th hiu qu chng oxy ha ca tocopherol gim r rt v acide bo t do c tc dng xc tc qu tr nh oxy ha. * Nng oxy Ti p sut cao (cung cp oxy khng hn ch) tc oxy ha ca cht bo t y thuc vo p sut O2. Ti p sut thp tc oxy ha t l vi p sut O 2. * Din tch b mt Tc oxy ha cht bo t l vi din tch b mt tip xc ca thc phm vi khng kh. Trong trng hp cc sn phm nh t ng D/N th tc oxy ha cht bo c tnh ton trn c s s khuch tn oxygen qua pha cht bo. * Nhit Thng thng th s oxy ha cht bo gia tng theo nhit . Do s h a tan ca oxy ph thuc vo nhit v vy tc ng ca yu t oxy trong qu tr nh oxy ha ti nhit cao l rt t. S ph thuc ca nhit tr n qu trnh oxy ha cht bo c biu th bng cng thc:


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Trong : K: hng s tc phn ng. A: hng s Entropy (khng ph thuc v o nhit ). Ea: nng lng hot ha. R: hng s kh l tng. T: nhit Kelvin. nhit thp t - 27 n 500C tc oxy ha t thay i. Nhng nhit cao hn tc phn ng gia tng ng k. * m Tc phn ng oxy ha cht bo ph thuc rt nhiu v o m (Aw) ca sn phm. Oxy ha cht bo c th xy ra ti Aw rt nh (Aw < 0.1 trong sa bt), Aw c ng cao th tc oxy ha cht bo cng cao. 2.2.3. C ch chng oxy ha cht bo Gi AH l cht chng oxy ha cht bo. Phn ng chng oxy ha cht bo xy ra theo s sau:

Cht tr chng oxy ha cht bo c thm vo tng hiu qu chng oxy ha. Cc cht quan trng thng c s dng l: acide citric v cc ester monoglycerid citrat, acid ascorbic v ascorbyl palmitat. Cc ester lipophilic ca acide citricm acid ascorbic c kh nng h a tan trong du Thng thng : Citric + cht chng oxy ha tng hp tocopherol

Ascorbic +

Cht tr chng oxy ha cht bo c cc chc nng: - To mi trng acide n nh chng oxy ha cht bo. - Loi b hot tnh cc ion kim loi (to phc v hi)Trng Cao ng cng ng Ki n Giang Trang

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- Loi b oxy (oxy ha ascorbic) - Phc hi chng oxy ha C ch phc hi cht chng oxy ha SH + A AH + S

Xt cho cng cht chng oxy ha cht bo bng ph gia thc cht l : + Ngn chn nguyn nhn gy ra phn ng oxy ha. + Ngn chn cc phn ng lan truyn. 2.2.4. Cc cht chng oxy ha cht bo thng dng a. BHA (Butylated hydroxyanisole) trng thi bt mu trng, d tan trong glycerid v cc dung mi hu c, khng ha tan trong nc, c mi phenol. Hot tnh ca BHA c th b mt khi ch bin nhit cao, tc dng vi kim loi kim cho sn phm m u hng. Hp cht BHA hp thu qua th nh rut non, tn ti trong m t bo, c th tham gia vo qu trnh trao i cht ca ngi v ng vt. y l hp cht t c, vi liu lng 50 100 mg/kg th trng c chuyn sang dng glucuronit hay sulfat v thy ra ngoi theo nc tiu. chut liu lng gy ch l LD50 = 2000 mg/kg th trng.

b. BHT (Butylate hydroxytoluene) dng bt mu trng, khng tan trong nc. Hp cht BHT c hot tnh km h n BHA nhng li bn nhit, c hp thu qua thnh rut v qua qu trnh trao i cht c thi ra ngoi theo phn v nc tiu. L hp cht t c, liu lng 50 mg/kg th trng khng gy nh hng ti sc khe, liu lng gy cht chut LD50 = 1000 mg/kg th trng.


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c. Propyl galat L este ca n-propyl vi acid 3,4,5 trihydroxybenzoic hay acid galic. Propyl galat km chu nhit, tan trong nc v t tan trong cht bo do n c ng dng nhiu tron g thc phm. Hp cht ny khi vo c th c hp th qua ng tiu ha v c chuyn thnh acid 4-octometyl galic thy ra ngoi theo nc tiu. Propyl galat cng t c, liu lng gy cht LD 50 = 1700 -3800 mg/kg th trng. Cc th nghim liu l ng thp 0,117 % khng thy biu hin c nhng khi nng 2,5 % th xut hin ri loi mt s chc nng ng vt.

d. TBHQ (Tert-butyl hydroquinon) Tan tt trong cht bo (10 %) nh ng t tan trong nc (1 %). Cht TBHQ cng c hp thu qua ng rut, tham gia vo qu trnh trao i cht v cui cng c thi ra ngoi theo nc tiu. TBHQ t c, liu lng gy cht chut LD 50 = 700 1000 mg/kg th trng. e. Tocopherol Cc ng phn ca tocopherol u c nhnh b n ging nhau. S khc nhau gia chng l do s lng v v tr ca nhm metyl trong v ng benzopyran (dng betam, gamma, delta). Trong tocopherol c hot tnh cao nht. Cc tocopherol th ng khng c. Tuy nhin nu s dng thng xuyn vi liu lng 1000 UI/ngy s xut hin triu chng ca cc bnh ng rut, vim da, mt mi.


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2.2.5. Phng php s dng cht chng oxy ha cht bo Vic s dng cc cht chng oxy ha cht bo c s dng rng ri trong cng nghip thc phm, c th s dng n l cc hp cht hay kt hp chng vi nhau tng hiu qu chng oxy ha. s dng hiu qu cht chng oxy ha cn ch cc im nh sau: - Kt hp tnh nng ca cc cht chng oxy ha n l. - To iu kin thun li cho chng d d ng s dng. - Kt hp cht chng oxy ha v cc cht tr chng oxy ha tng hiu qu chng oxy ha. - To iu kin cho cht bo tip xc tt vi cht chng oxy ha - Gim ti a cc cht mu ca cc cht chng oxy ha. Vi vai tr quan trng ca mnh, cc cht chng oxy ha cht bo cn ph i c la chn mt cch cn thn tng hiu qu bo qun sn phm v khng lm gim cht lng sn phm. mi iu kin khc nhau v th nh phn, tnh cht ca thc phm cn la chn cht chng oxy ha ph hp. Khi chn cht chng oxy ha cn ch cc vn nh sau: - Kh nng cn t c i vi cc loi sn phm. - Kh nng ha tan v phn tn cc cht chng oxy ha trong sn phm. - Mu sc cht chng oxy ha. - Gi tr pH ca sn phm. - Mi v v ca sn phm. - Lut v tnh hnh lut. - Phng php ch bin thc phm. nh gi hiu qu ca cc cht chng oxy ha s dng trong cc sn phm nhm m bo sn phm khng b bin i m u sc v mi v trong qu trnh bo qun, thng thng thc hin 2 phng php c bn sau: - Phng php oxy hot ng (AOM: active oxygen method) l phng php s dng rng ri trong bo qun thc phm c s hin din cht bo. Ph ng php ny dng nh ga s h hng ca cht bo trng thi lng v phng php thc hin nhit thng. Trong phng php ny O 2 c thi vo cht bo vn tc xc nh thc y qu tr nh oxy ha cht bo, phn tch ch s peroxit, t c th xc nh c ch s peroxit ti hn. V d: 20 meq/kg vi m v 70 meq/kg vi du.


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- Phng php l un: ti nhit cao s thc y qu trnh oxy ha cht bo. y l phng php n gin s dng c cho c cht bo v cht lng. Nhit dng trong phng php ny l 145 0F (62,80C), ri nh gi mi v bng phng php cm quan v cc ch tiu thng thng nh gi h hng cht bo. 3. CHNG PHN NG HA NU Phn ng ha nu xy ra rt ph bin trong ch bin thc phm, l nguyn nhn lm gim phm cht thc phm trong qu tr nh ch bin cng nh bo qun sn phm. nh hng ca s ha nu c th k n l : s thay i mu sc, trng thi cng nh gi tr dinh dng ca sn phm. V d nh trong qu trnh ch bin c ph, bia, bnh mphn ng ha nu cn c kim sot trong trng hp: sn xut nc to, chui khCc phn ng ha nu thng gp trong ch bin l: phn ng Maillard, phn ng caramen ha, s oxy ha acid ascorbic, phn ng do enzyme.Bng 3: C ch phn ng ha nu C ch Yu cu oxygen Phn ng Mailard Phn ng Caramen ha S oxy ha Ascorbic Phn ng do enzim + + i hi nhm A_A Cho khi to phn ng + Kim Kim, acide Acide nh Acide nh PH ti thch

3.1. Chng phn ng ha nu c s tham gia ca enzim Phn ng xy ra khi rau qu b ct gt nh : khoai ty, to, chuido cc hp cht phenol b chuyn ha. Enzim khi to, thc y ch o phn ng ny l polyphenoloxydaza. phn ng c th xy ra th phi c ion kim loi v oxy. Hp cht phenol rt d b oxy ha trong cc iu kin khc nhau: chng c th b oxy ha bnh thng trong mi trng khng kh m, phn ng c tng cng nhit cao v nht l trong mi trng kim. Enzyme polyphenoloxydaza xc tc cho s oxy ha ngng t cc hp cht phenol vi s tham gia ca oxy phn t t khng kh, thc vt c th tn ti 2 dng t do v lin kt Polyphenoloxydaza l nhm enzim oxydoreductaza, c nhiu trong m ng vt, thc vt, nm mcTrng Cao ng cng ng Ki n Giang Trang

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3.1.1. C ch phn ng Nhiu nghin cu trn c ch phn ng ha nu c enzim c thc hin. Ngy nay cc c ch ny c hiu r v chng minh bng phn ng ha hc c th. Nhng phn ng i khi gy bt li cho sn phm i khi li c li cho sn phm t y theo mi loi sn phm. Phn ng ny ph thuc vo 3 yu t chnh: Enzyme hin din trong phn ng, ion kim loi v kh nng tip xc vi oxy. V d 1: S bin i mu sc ca nm rm trong qu trnh bo qun

Bin i mu sc do phn ng ha nu c enz yme

V d 2: Trong cng nghip sn xut ch en, thnh phn ch yu ca ch l hp cht catechin, di tc dng ca enzyme polyphenoloxydaza to cho sn phm c m u ti hoc nu sng c trng cho mu sc ca nc ch. y l phn ng ha nu c li cho sn phm, i vi sn phm cn phi to iu kin thch hp cho phn ng xy ra. S bin i mu ca hp cht tanin to m u cho sn phm ch c th c trnh by theo s bin i sau:Trng Cao ng cng ng Ki n Giang Trang

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Tanin ch (Ch yu l nhm catechin) Peroxydaza + H 2 O2 Polyphenoloxydaza + O2

Octoquinon Peroxydaza Polyphenoloxydaza

Cc sn phm ngng t khng mu

To cht thm, sn phm ngng t c mu ti mu c trng ca nc ch en

3.1.2. Phng php kim sot phn ng ha nu c enzim a. S dng nhit Nhit cao s v hot cc enzim hin din trong cc loi nguy n liu (k c phenolaza). Vic s dng nhit trong chn, nu, s l m hn ch hot tnh ca phenolaza. nh hng ca nhit ln hot tnh phenolaza c th hin th sau:

nh hng ca nhit trn hot tnh phenolase

b. S dng SO 2 hay cc hp cht sinh SO 2 Cc cht nh SO2, sulfit, natrisulfit, natrimetabisulfit l cc h p cht ngn cn phn ng ha nu rt hiu qu. Tuy nhi n, n cng c mt s hn ch trong trng hp c x lTrng Cao ng cng ng Ki n Giang Trang

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nhit s to cu trc km, i khi sinh ra m i v l. Liu lng thng s dng l: 0.01M (s dng cho khoai ty ct ming). Theo nhiu nghi n cu SO2 cng c th ngn cn ha nu enzim mc 1 ppm. nh hng ca thi gian x l nhit n s bin i do phn ng bin i mu c s tham gia ca enzyme vi s c mt ca cc cht sinh SO 2 c th hin th sau:

c. Gim tip xc vi khng kh Phng php ny thng s dng quy m h gia nh, rt hu hiu trong vic ngn cn phn ng ha nu c enzim khi bc v khoai ty tr c khi nu, gt to, trong thi gian ch ch bin, khoai ty c ngm trong nc nh th s hn ch tip xc vi oxy. Khi sn xut quy m ln, khoai ty sau khi gt v, phn loi, ct, nguyn liu c ngm trong nc trc khi chn v chin. S dng bin php ny c mt s khuyt im l nguyn liu tip tc b ha nu khi tip xc li vi khng kh, c bit l trong trng hp yu cu v mi v v mu sc. Trong trng hp vi cc sn phm lnh ng, b mt cc nguy n liu thng c x l vi acide ascorbic (vitaminC), acide n y s t oxy ha trn b mt v to ro cn bo v b mt sn phm. Trong ch bin sn phm tri cy lnh ng, cc cht ngt th ng c s dng nhm gim oxy ha tan trong dung dch, hn ch s khuch tn ca oxy v o cc m nguyn liu. d. Ngn cn bng phng php s dng mui Phng php ny t c s dng, ng dng ch yu l x l tri cy gt v ch ch bin. Mui nng 0.1% bt u ngn cn cc phn ng ha nu trong mt s sn phm.Trng Cao ng cng ng Ki n Giang Trang

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Tc dng ca NaCl n s bin i m u ca to

Khi phi hp nc mui v s dng acide chlorogenic nh l cht m duy tr pH = 5 thng dng trong bo qun to. Tuy vy, nng mui cao t c dng do nh hng v ca mui ln thc phm. e. Dng cc acide y l phng php rt ph bin chng ha nu trong ch bin thc phm. Acide c dng l cc acide rt ph bin c trong m ca rau qu nh : acide citric, malic, photphoric, ascorbict i pH thp tc phn ng ha nu s chm. Quan h gia hot tnh phenolaza v pH c th hin theo th sau:

Qua th trn cho thy pH tt nht cho phn ng l 7 v thp nht ti pH = 3. Acide citric kt hp vi acide ascorbic hay SO 2 c s dng rt lu v c hiu qu cao trong vic chng phn ng ha nu trong ch bin thc phm. Cc nguy n liu thng thng c nhng vo dung dch acide long.Trng Cao ng cng ng Ki n Giang Trang

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Khi i vo mi trng c enzim phenolaza th acide citric cn c th to phc vi Cu ca enzim, t cng l m gim hot tnh ca enzim. f. S dng Borat v cc mui Khi nghin cu nh hng ca borat v cc mui trn phn ng ha nu c s tham gia ca enzim, kt qu cho thy: 1.5% Natri tetraborat v 1.5% Metaborat c th ngn cn hon ton phn ng ha nu c enzim, nh ng cc nng khc th tc dng gim r rt. 3.2. Chng phn ng ha nu khng c enzim tham gia Trong ch bin thc phm, c hin t ng thay i mu sc trong qu trnh gia nhit hay bo qun thc phm. Cc phn ng ha nu n y khng c s tham gia ca cc enzim nn thng gi l phn ng ha nu khng enzim. Cc phn ng ha nu n y thng thy trong ch bin c ph, ca cao, bnh to mi, mu thch hp cho sn phm. Tuy nhin trong mt s trng hp phn ng ny cng cn phi c bin php ngn chn, kim sot gi gi tr dinh dng v cm quan ca cc thc phm. Cc phn ng ha nu c tm thy l: + Phn ng Mailard + Phn ng caramen ha + Phn ng oxy ha acide ascorrbic 3.2.1. C ch ca cc phn ng a. Phn ng Mailard Phn ng ny c khm ph bi nh khoa hc ngi php Maillard (1912), trong qu trnh theo di s to thnh cc cht mu nu (melanoidin) khi gia nhi t glucose vi glycerin. Phn ng Mailard l phn ng gia cc acide amin, amin, protein vi sucrose, aldehyd, xeton y l phn ng rt quan trng trong qu tr nh gia nhit v bo qun sn phm. * Cc bc chnh trong qu trnh chuyn ha ca phn ng Maillard - Phn ng gia nhm alpha amin trong phn t acide amin hay l protein vi nhm carboxyl ca cc loi ng kh (c th gi y l phn ng Carboxylamin). - Cc sn phm ca s trng ngng ny gi l cc Base Schiff, cc sn phm ny s xy ra cc chu trnh k tip thnh lp cc sn phm N-glycosyamin. * Cc iu kin cho phn ng Maillard - Gi tr pH: phn ng Maillard xy ra c trong mi tr ng kim v acide, trong mi trng kim phn ng xy ra tt h n. Mt s nghin cu cho thy tc phn ng tng khiTrng Cao ng cng ng Ki n Giang Trang

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tng pH. Quan h gia pH v tc phn ng rt quan trng trong vic bo qun cc sn phm c acide cao nh: sn phm mui chua, ngm gimTc phn ng maillard gia tng theo ng thng trong phm vi pH = 3 8 v t cc i ti pH = 9 10. - Cht m: vai tr ca cht m trong phn ng ha nu khng enzim c ghi nhn nh sau: tc phn ng cng gia tng nu mi trng c nhiu ion. Mt s nghi n cu cho thy khi b sung Natri photphat v Natri citrat vo hn hp glucose-glycerin th phn ng xy ra nhanh hn iu kin thng. - Nhit : phn ng s tng theo chiu tng ca nhit . Cc nghin cu cho thy tc phn ng xy ra cng nhanh khi tng nhit trong khong 0-900C. - m: phn ng xy ra mnh m trong dung dch, vic l m kh hon ton sn phm c th ngn cn phn ng n y. Cc nghin cu cho thy tc phn ng xy ra rt nhanh ti m ti u v phn ng xy ra chm trong iu kin m qu cao hay qu thp. - ng: ng kh l thnh phn chnh tham gia phn ng Mailard, l cht cung cp nhm carboxyl phn ng vi -amin. * C ch ca phn ng to mu: hai chu trnh to melanoidin

b. Phn ng caramen ha Phn ng caramen l phn ng to mu khi gia nhit ng ti im nng chy. Qu trnh s xy ra trong c mi trng acide v mi trng kim lm cho sn phm ch bin c


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cm quan km (mu ti, v ng, mi xu). Trong sn xut ko, bnh ngt th phn ng ny c kim sot c bit. Phn ng caramen l mt phn ng phc tp, cho d hm lng ng c khc nhau nhng sn phm cui cng l gn nh nhau. Phn ng xy ra theo 2 giai on: - Giai on 1: hnh thnh nn cc alhydric c a glucose, sacarose nh glucozan, fructozan, sacarozan l hp cht khng mu. - Giai on 2: cc hp cht ny trng hp vi nhau to thnh phm vt c mu vng. Sau cc phn ng caramen bin i m u sc: vng vng m nu nu en. Nhiu loi nguyn liu tham gia vo phn ng caramel nh: sucrosem glucose, fructose, mt tinh bt v tinh bt. Nhng iu kin phn ng t y thuc vo cu ca sn phm, tnh ha tan tt trong alcohol,Phn ng t y thuc nhiu yu t nh pH, cht xc tc, nhit , - Khi s dng acid sulfuric (pH = 3,5) nh mt cht xc tc sn phm s c c ng mu mnh, n nh trong acid v khng hnh thnh kt ta vi tannin v alcohol. - Khi s dng sodium hydroxide l m xc tc (pH = 9,5) mu sc c hnh thnh cng c cng mu mnh, n nh trong acid nh ng li kt ta vi tannin hay trong dung dch mui. - Khi dng mui amonium xc tc mu to ra c n nh thp c. Phn ng oxy ha acide ascorbic Acide ascorbic ng vai tr rt quan trng trong qu tr nh ha nu trong cng nghi p sn xut nc rau qu, nc qu c c: nc cam, chanh, qut Phn ng oxy ha acide ascorbic hin nay cng c n nhiu tranh ci nhng nhiu kin cho rng phn ng chnh l s ph hy acide ascorbic thnh lp CO2 sinh cht c mu nu. 3.2.2. Phng php ch ng phn ng ha nu khng Enzim y l vn rt phc tp, ty thuc vo nhiu yu t, nhng cc nh khoa hc a ra mt s bin php c th kim sot s bin m u do phn ng khng enzim. * Kim sot nhit Nhit l yu t quan trng trong vic pht trin m u sc lm h hng sn phm. Nhit cng cao th tc phn ng xy ra cng nhanh. Do phi bo qun sn phm nhit thp thch hp.


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* m Phn ng hot ng tt trong mi trng m, c th kim sot qu tr nh bng cch ly m ra khi vt liu, trong lc bao gi, bo qun cc sn phm kh khng n n cho tip xc vi mi trng m. * Kim sot pH Phn ng Maillard xy ra rt mnh trong mi tr ng kim, v vy khng ch phn ng ny cn thc hin ch pH thp thch hp. V d: vic s dng pH thp trong qu tr nh sy kh trng, cc acide thc phm c thm vo trong qu trnh sy s chng phn ng ha nu. Sau khi ho n thnh sy th dng Na2CO3 n nh li pH ban u. * Bao gi vi khng kh y l phng php c s dng rng ri loi b oxy ra khi mi tr ng bo qun bng cch b sung vo cc loi kh tr, ht chn khng. Qu tr nh ny khng nhng lm hn ch phn ng ha nu m cn hn ch c s bin i cht bo. * Dng cc enzim Enzim glucose oxydaza c s dng nh l cht xc tc chuyn glucose th nh acide gluconic khng phn ng c vi cc amin. S dng glucose oxydaza c u im l loi b oxy, c bit l cc sn phm ng chai s c h m lng oxy rt thp trong khong khng kh tha. * Dng cc ha cht - SO2: y l tc nhn rt tt trong vic ngn chn phn ng ha nu khng enzim. Bisulffit ngn cn s chuyn ha D-glucose thnh 5-hydroxymetylfurfurol cng nh chuyn acide ascorrbic thnh furfurol. - Thiol: vic thm cystein vo trng sy c th ngn cn phn ng ha nu. Tuy nhi n cc thiol thng c mi l nn t c s dng. - Cc mui canxi: c kh nng ngn cn phn ng ha nu. C ch l do tc dng to phc ca canxi vi cc amin. Thc t th cc mui canxi c s sng rt thnh cng trong vic ngn cn phn ng ha nu. Tm li: mc d c nhiu cch ngn chn phn ng ha nu khng enzim nhiu mc khc nhau nhng hu ht cc sn phm u gim gi tr dinh d ng. Vic kim sot phn ng ny giai on khi to rt quan trng trong qu tr nh chng ha nu.


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4. PH GIA CHNG NG BNH Vi cc sn phm dng bt khi bo qun trong thi gian d i s b vn cc, lm gim tnh nng s dng, gim tnh cm quan ca sn phm.Bng 4: Tc dng ca tc nhn ng bnh da tr n trng lng ring v h s nn ca mt s loi bt thc phm Loi bt ng Cc cht ng bnh Khng Stearat canxi SiO2 Tricanxi photphat Nng (%) 0.5 01.5 0.5 T trng bt khng nn 0.7 0.87 0.75 0.76 Ch s nn 0.006 0.039 0.052 0.044

Sp

Khng Silicat Al stearat canxi

2 2

0.7 0.75 0.63

0.27 0.15 0.27

Bt ng cc

Khng stearat canxi SiO2 Tricanxi photphat

1 1 1

0.62 0.59 0.67 0.61

0.109 0.099 0.077 0.062

Protein

Khng stearat canxi SiO2 Tricanxi photphat

1 1 1 1

0.27 0.27 0.27 0.31 0.68 0.7

0.04 0.041 0.036 0.024 0.016

Gelatin

Khng Silicat Al


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Chng 3

PH GIA LM THAY I CU TRC THC PHM1. HA CHT IU CHNH M SN PHM Nguyn liu hay bn thnh phm c m cao s to iu kin tt cho cc vi sinh vt pht trin hoc tc ng lm h hng sn phm. h m nhm ko d i thi gian bo qun sn phm thc phm ng i ta thng dng phng php sy. Tuy nhin, trong mt s trng hp khng th p dng, hoc kh p d ng k thut ny chng ta cn phi dng phng php iu chnh m bng ha cht nhm bo qun sn phm trong thi gian d i. V d: iu chnh m ca cht kh, mi tr ng bo qun sn phm hoc y u cu ch bin sn phm c m thp nh ng khng lm bin i mu sc hay thnh phn sn phm. Vic iu chnh m sn phm bng ha cht da tr n nguyn tc ph bin l ht m v gi m. Ty thuc vo sn phm v iu kin s c ph gia tng ng. 1.1. Ha cht ht m Da vo tnh cht ht m ca ph gia ngi ta chia thnh 2 loi: ht m theo tnh cht vt l v ht m theo tnh cht ha hc. 1.1.1. Ht m theo tnh cht vt l Nguyn tc: ch ht nc, khng gy ra phn ng ha hc. N c ch ngng t trn b mt cc ng mao dn hoc tr n b mt cc cht ht m. Cc cht ny thng c b mt tip xc ln nh: silicgen, alumogel * Dng tinh th khan nc: c kh nng ht nc cn bng vi thnh phn ha hc, cht ny gm: NaSO4 (khan) + 10H 2O CuSO4 (khan) CaCl2 (khan) + 5H 2O + 6H 2O Na 2SO4.10H2O Cu 2SO4.5H2O CaCl 2.6H2O

Kh nng t no nc ty thuc vo iu kin mi trng. Cc cht ny c kh nng ht nc ti nhit bnh thng v cng c th nh m.


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* Cc cht c cu trc xp: chng cha nhiu ng mao dn tr n b mt. Cc cht ny c kh nng ht nc trn cc ng mao dn, thm ch ngay tr n b mt cc cht ht m. Cht thng c s dng l silicagel (H 2SiO2.nH2O)x. Ty vo nh sn sut m 1g silcagel c b mt tip xc khong 300 -800 m2. Silicagel l nhng ht c hnh trn, bu dc, mu trng ti nu. d dng nhn bit Silicagel no nc cha, ngi ta thng cho thm CoCl 2. Khi Silicagel khan c mu xanh, khi Silicagel c mu hng. Ngoi vic s dng Silicagel ra ngi ta cn dng Alumogel(Al 2O3) cng c tnh cht tng t. * Cc cht lng: Cc cht ny ht nc mnh - yu khc nhau, khi ht nc s ta nhiu nhit nh: H2SO4, H3PO4, Cn, Glicerin 1.1.2. Ht m theo tnh cht ha hc Nguyn tc: sau khi ht m to ra cht han ton mi, phn ng ny s ta nhit, i khi lm nng mi trng bo qun. Sau khi dng cc ha cht ny khng th dng tr li. Phng php ny c mt s ha cht c th gy n m n, nh hng n bao b trong qu trnh bo qun. V d: CaO + H 2O Ca(OH) 2 + Q (Kcal)

Thng thng CaO c dng nhiu v r tin, kh nng ht m cao (100g CaO cho vo th tch 15-20 cm3) c th a m mi trng t 80% xung 60% trong v ng 12 gi v gi n nh trong vng 15 ngy. Khi dng th CaO sau khi ht m s r thnh bt v vn tip tc ht m. Khi ht m th tch c th tng gp 3 ln, dng bt d bm v lm n mn bao b. 1.2. Ha cht gi m Trong qu trnh bo qun cc sn phm c s bay h i do chnh lch p sut ring phn trn b mt nguyn liu v mi trng bo qun. iu d gy nt b mt, i khi cn lm bin mu b mt sn phm, lm gim tnh cm quan v dinh dng, iu ny thng xy ra trong bo qun cc sn phm lnh ng, cc sn phm th y sn kh * Cc bin php c th dng chng mt m - S dng cc photphat: dng trong cc sn phm thy sn kh lun gi c mm, chng hin tng cc m trng trn b mt. - Cc enzim: dng proteaza th y phn protein thnh cc acide amin v nc to b mt m. - Dng hn hp: glycerin-gelatin-H2O ph trn b mt cc sn phm tht.Trng Cao ng cng ng Ki n Giang Trang

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- Dng glycerin trong cc s n phm dng si sy kh. 2. HA CHT LM TRONG Do yu cu ca ngi tiu dng cc sn phm lun c iu chnh ph hp vi th hiu. Vi cc sn phm dng lng th hu ht u yu cu cn lm trong (tr cc sn phm yu cu phi c nhiu cht huyn ph th phi c). - p ng nhu cu ngi ta dng cc phng php sau lm trong sn phm: + C hc. + Nhit. + Dng cht ph gia. - Cc bin php c hc khng tch c cc cht keo, cc ion trong cc dung dch. - Dung dch c c nhiu dng: + Huyn ph: cn c hc. + Nh tng: protein, protid, lipid + Cc cht tan: cc ion kim loi. - Cc bin php ha hc khng nhng c th tch cc cn c hc m cn c th loi b cc ion kim loi hay ph v h thng cht keo. 2.1. Tch cc cht tan Nguyn tc: cho cc ion ny tc dng vi cht ph gia to kt ta ln sau d ng cc bin php c hc lm trong. * Tch ion Mg2+ v Ca 2+ Ca2+ + CO 2 Ca2+ + H3PO4 * Tch ion Fe 2+ Fe2+ + Na 2S 2.2. Tch cc cht keo Vn tch cc cht keo th phc tp hn, c nhiu cch c s dng tch cht keo c s dng ph bin nh: - To trng thi tp hp bng cch: + Thay i pH mi trng, a cht keo v im ng in.Trng Cao ng cng ng Ki n Giang Trang

CaCO3 Ca3(PO4)2 Na+ + FeS

(kt ta) (kt ta)

(kt ta)

38



+ Ph v lp v solvat bng cc cht in ly. + Dng nhit lm bin tnh cht keo. - To kt ta th 2 li ko cht keo: th ng dng phng php sulphat ha v carbonat ha. Ngoi ra enzim cng c th dng lm trong cc dung dch. Chng s thy phn cc cc mch cao phn t thnh sn phm ngn mch, ha tan. 3. CC CHT KEO 3.1. M u Theo Sanderson (1981) cc polysacarid dng trong ch bin thc phm gm: Tinh bt, celluloza v cc dn xut, cc cht chit t rong bin, nht thc vt, t ht, t thc vt, t vi sinh vt,cc cht n y tham gia lm cht: dinh dng, to cu trc, lin kt nc, gi m, chu p sut thm thu Theo Glicksman (1969) th cc ch t keo c cc tnh cht sau: + Kh nng lin kt vi nc. + Tnh cht lu bin. + Kh nng to mng hoc to gel. + Kh nng lin kt vi cc cht to mi. + To p sut thm thu. + Ht nc. + To cc phn ng ha hc. + Tng ngt v v. + Kh nng ht nc tr li dng ban u. Cc tnh cht ny c dng trong ch bin thc phm nhm: l m c, nh ha, n nh nh tng, to bt, ci thin tnh chy, cu trc, lm mm, chng vi sinh vt, n nh mi v Trong cng nghip thc phm, cc cht keo c ng dng rt nhiu trong lnh vc ch bin sn phm, pht trin sn phm mi, l m trong sn phm,do vic tm hiu nhng tnh cht c trng ca mt s c trng ca cht keo s gip la chn c nhng cht keo ph hp trong sn phm. Hin nay, c rt nhiu sn phm s dng cc cht keo nh: ko, bnh, mt, b,..


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Bng 1: Phn loi cht keo, ph ng php thu nhn, vai tr Cht keo HM-pectin LMC-pectin LMA-pectin Carrageenan Agar Alginate CMC Guar LBG Xanthan Gellan Gelatin Arabic Casenate Protein u nnh ng vt Ngun gc thc Rong vt bin X X X X X X X X X Vi sinh Phung php trch Trch Nghin Nha ly X X X X X X X X X X X X X X X Chc nng To Lm ng c X X X X X X X X X X X X X X X X X X X n nh X

X X

X X X X X X

X

X

Bng 2: c tnh ca mt s cht keo ph bin Ngun gc Cht keo Dn HM-pectin LMC-pectin LMA-pectin Carrageenan Agar Alginate CMC Guar LBG Xanthan Gellan Gelatin Arabic Casenate Protein u nnh X X X X X X Dnh X X X X D chy X X X X Thun nghch nhit C Khng To gel tc th C X X X X X X X X X X X Khng m X X X X X X X X X X X X X X X in tch O Dng

X X X X X

X X X X X

X X X X X X X X

X X X


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Bng 3: Ch s quc t v chc nng ca mt s cht keo Cht keo Alginic acid Sodium alginate Potassium alginate Ammoginum alginate Calcium alginate Propylene glycol alginate Aga Carrageenan Gum ca u Oat gum Guar gum Tragacanth gum Gum arabic Xanthan gum Karaya gum Gellan gum Konjac mannan Pectin Amidated pectin Cellulose Microcrystalline cellulose Bt cellulose Methyl cellulose Hydroxylpropyl cellulose Hydroxylpropyl methyl cellulose Sodium carboxylmethyl cellulose Ch s quc t 400 401 402 403 404 405 406 407 410 411 412 413 414 415 416 418 E425 440 / E440 E440 460 INS 460 INS 460 / E460 461 463 464 466 Chc nng Cht to c, cht n nh. Cht to c, cht n nh. Cht to c, cht n nh. Cht to c, cht n nh. Cht to c, cht n nh. Cht to c, to nh. Cht to c, cht n nh. To c, to gel, cht n nh, to nh To c, to gel. Cht to c, cht n nh. To c, cht n nh, cht to nh. Cht n nh, cht nh ho v cht phn tn. To c, cht n nh, to nh. To c, to gel, cht n nh, to bt. Cht n nh, cht nh ho v cht phn tn. To c, to gel, cht n nh. To gel, to nh, to c, cht n nh. To gel, to c, cht n nh. To gel, to c, cht n nh. Cht chng vn cc, cht n nh, cht nh ho v cht phn tn. Cht chng vn cc, cht n nh, cht nh ho v cht phn tn. Cht chng vn cc, cht n nh, cht nh ho v cht phn tn. Cht to c, cht n nh. Cht to nh, to c, cht kt dnh, to huyn ph , cht to mng. Cht to c, cht n nh, to nh. Cht to c, cht n nh, to huyn ph .


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3.2. Gii thiu mt s cht keo thng dng 3.2.1. Acid alginic Alginat Acid alginic c Standford pht hin ra nm 1881, l mt acid hu c c trong to nu, trng lng phn t t 32000 200000. Cu to ha hc ca acid alginic gm 2 phn t -D-mannuronic v L guluronic acid lin kt vi nhau bng lin kt 1- 4 glucozid. Acid alginic c chit xut ra t to nu d i dng natri alginat, alginat c trng l ng phn t 20000 60000.

Dng thng phm: Acide alginic thu c t alginat dng sn xut cc alginat khc nhau. Ging nh cc polysaccarid khc acide alginic t tan trong n c, v vy thng ch bin thnh cc dng: Na 2CO3 K 2CO3 NH 4OH Acide alginic + MgOH CaCl 2 Propylen oxytTrng Cao ng cng ng Ki n Giang

Na alginat Ka alginat Amon alginat Mg alginat Ca alginat Propylen glycol alginatTrang

42



a. c tnh ca alginat * nht: khi ha tan cc alginat vo nc chng s ngm nc v to dung dch nht. nht ph thuc vo chiu di ca phn t alginat. Bt alginat rt d b gim nu khng c bo qun nhit thp. Ngo i ra, cch sp xp ca phn t alginat cng nh hng n nht ca n.

Bng 4: Phn chia nht ca nng alginat Nng (%) Thp 0.25 0.50 0.75 1.00 1.50 2.00 9 17 33 58 160 375 15 41 93 230 810 2100 nht alginat Trung bnh Cao 21 75 245 540 1950 5200 Rt cao 27 110 355 800 3550 8750

Theo bng trn cho thy s thay i nht so vi nhm alginat. Trong mt s trng hp nht c th gia tng nng thp vi s hin din ca mt s c cht nh: CaSO4, Canxicitrat. Ion canxi lin k t vi alginat to lin kt cho trong phn t gia tng, s lm gia tng trng lng phn t v nht. * S to gel alginat Mt tnh cht quan trng ca alginat l tnh cht to gel ca chng. Trong iu kin nhit cao trng thi si v khi lm ngui s tr thnh dng gel. Thng thng alginat kt hp vi ion Ca 2+ to gel nh hnh v.


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b. K thut to gel alginat Cc alginat c kh nng to gel khi c mt ca ion Ca 2+ v acid. Gel c thnh lp c th kim sot thng qua s gii phng ion Ca 2+, hoc acide trong dung dch alginat. C th to gel acide pH < 4 (khong 3.4) th ng dng kt hp vi vi pectin (HMP). Tham gia to gel cc tng tc tnh in qua cu ni Ca 2+ c vai tr quan trng, v th cc gel ny khng thun nghch vi nhit v t n hi. * To gel trc tip bng cch phun Vi phng php ny, alginat ho c hn hp cha alginat c to gel bng cch nhng hoc phun dung dch c cha ion Ca 2+ vo. Cht thng s dng l CaCl2. Khi c phun vo cc ion Ca 2+ s phn ng vi alginat to dng Box egg. Phng php ny thch hp vi vic ch bin cc sn phm mng v kch thc nh nh to mng bao pha ngoi cho sn phm. Phng php ny dng cc alginat ph n ng mnh vi cc ion Ca 2+ hoc cc alginat c nhiu G.

X l acide: trong phng php ny l to cc mui Caxi khng h a tan pH trung tnh to phn ng vi alginat. Khi cho acide v o chng s tip xc vi b mt vt liu, cc mui ha tan v tip theo l phn ng gia alginat v Ca2+ to gel, iu kin trung tnh v acide: Ca2+ c gii phng trong iu kin thch hp. Khi s dng kt hp alginat, mt mui canxi c ha tan chm v mt phc c Ca 2+ thch hp nh: photphat, citrat cc cht to phc cn thit to li n kt vi Ca 2+ t do v ngn cn qu trnh to mng cht (c tru) trong thi gian ch bin sn phm. Qu tr nh ny c th thc hin pH acide hoc trung tnh. Phng php lm lnh: Alginat c ha tan trong nc vi mt lng nh Ca 2+ v cc cht to phc, gia nhit nhit cao v sn phm s c to thnh do lm ngui to gel Canxi n nh nhit. Gel c th to th nh ti 0-500C nhng cu trc to thnh mm.


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* Kt hp alginat v pectin Khi s dng pectin ring r th ch to c gel nng ng cao v pH thp. Khi alginat Na c thm vo th gel c thnh lp nng cht kh thp h n v khong pH rng hn. Tri cy giu pectin nh to s to gel vi vi alginat natri sau khi ch bin. Mng gel cng thnh lp khi alginat natri cha nhiu dng G, gel mm khi alginat natri cha nhiu dng M. S tr lc pectin-alginat l mt trong nhng ni phn ng quan trng ca alginat vi cht keo khc v l mt trong nhng ch s kinh t quan trng trong khi s dng cc cht keo. Kh nng to gel ca alginat ph thuc v o nhiu yu t nh: ngun canxi, alginat, cht to phc, pH, s ha tan v nhit c. Sn xut alginat Alginat c sn xut theo qui trnh cng ngh sau:Rong bin (Kh hoc ti) Nghin Ra Ha tan vi kim, H 2O v nhit Lm sch Kt ta vi CaCl 2 Alginat Canxi X l acid X l vi Na 2Co3 Alginat Natri Sy kh Nghin Alginat natri kh

Trong thc t, sn xut alginat, u ti n ngm to nu vo dung dch acid sulfuric long chuyn alginat thnh aginic acid v loi b c cc tp cht nh fucoiionm laminarin, manitol, mui v c v mt s cht mu.


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Sau khi ra, nghin nh vi kim hoc mui kim trung h a aginic acid to thnh mt dng mui ha tan tng ng ca aginic acid. Cc th nh phn khng tan nh cenllulose, protein c loi b bng cch gn, lc hoc vt bt ni l n trn. Dung dch alginat thu c, em ty trng bng cch x l vi acid sulfuric kt ta alginic acid. Sau trung h a bng kim hoc baz khc nhau to ra nhng hp cht alginat theo mong mun nh: natri alginat, amon alginat, canxi alginat hay trietanolamin alginat. d. ng dng alginat Cc alginat cng c ng dng rng ri trong cng nghip thc phm. Thng natri alginat c s dng nhiu nht v l hp phn to kt cu cho nhiu sn phm. Trong sn phm natri alginat l cht lm c, lm dy n nh cc bt cng nh to cho nc qu c nhng th c bit. Vi nhng thc phm c acid cao khng th d ng natri alginat c th propylenglycol alginat l cht thay th rt tt v n bn c c trong vng pH = 0 3. Mt hp cht ca acid alginic c t n l lamizell mt alginat kp ca natri v canxi vi mt t lng nht nh. Lamizell to ra c mt nht c bit v cho kh nng n ngon ming cng c quan tm trong sn xut thc phm. Bn cnh , natri alginat cn c dng lm cht bo v kem v n c nhiu tc dng i vi sn phm nh: + Ngn nga to ra tinh th th. + c ch hon ton s to thnh tinh th ca lactose. + Nh ha cc cu bo. + Lm bn bt. + To ra nht cao. + To ra gel c kh nng gi n c tt. + Lm cho kem khng b tan chy. 3.2.2. Agar a. Cu to Agar l mt sulfat polysacarit c tch ra bng nc si t cc loi to (Gelidium sp, Gracilarta). Thnh phn cu to ca mch chnh l -D-galactos v 3,6 anhydro--Lgaclactose xen k vi nhau bng cc lin kt - 1,3 v -1,4. Agar l mt hn hp cc polysacarit c chung mch chnh gm 2 thnh phn ch yu sau:Trng Cao ng cng ng Ki n Giang Trang

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- Agarose l thnh phn to gel chnh ca gar, c khong 1/10 cc n v galactose b ester ha. Hm lng agarose ng vai tr quan trng i vi in tch ca to n phn t v i vi tnh cht ca gel nh : bn, n hi, nhit to gel, nhit nng chy ca gel. - Agaropectin l thnh phn khng to gel, c mc este ha ln h n agarose, ngoi ra cn c acid pyruvic. Nu c mt cu ni gia 2 sulfat gel s trong h n, cu ni ny thng khng bn, d b ph hy nu tip xc vi cc ha cht to phc EDTA, ehxametaphotphat , tripolyphotphat natri...

b. Tnh cht * Tnh tan Agar khng tan trong n c lnh, tan mt t trong ethanol amine v tan c trong nc nng. Agar c kh nng h a tan vi lng nc 30 50 ln khi lng, lng agar trong nc trn 10 % s to nn mt hn hp st. * S to gel ca agar Qu trnh to gel xy ra khi lm lnh dung dch agar. Dung dch agar s to gel nhit khong 40 500C v tan chy nhit khong 80-850C. Gel agar c tnh thun nghch v nhit. Khi un nng polymer to th nh mt khi, khi dung dch ngui i cc chui s bao ly nhau v lin kt vi nhau tng i mt bng li n kt hydro to thnh chui xon kp, to ra mt mng l i khng gian ba chiu nht cc cht kh b n trong do s lng lin kt hydro rt ln . Qu trnh hnh thnh gel v n nh ca gel b nh h ng bi hm lng aga v khi lng phn t ca n. Kch thc l gel khc nhau ph thuc v o nng aga, nng aga cng cao kch thc l gel cng nh. Khi lm kh gel c th to thnh mt mng trong sut, bn c hc v c th bo qun lu di m khng b hng. Kh nng to gel ph thuc v o hm lng ng agarose. S c mt ca ion sunfat lm cho gel b m, c. Do trnh dng nc cng sn xut. Chng c kh nng gi mi v, mu, acid thc phm cao trong khi gel nh nhit nng chy cao (85 -900C). Gel agar chu c nhit ch bin 100 0C, pH 58, c kh nng trng phng v gi nc.Trng Cao ng cng ng Ki n Giang Trang

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Khng dng agar trong mi tr ng pH < 4 v c nhiu cht oxy ha mnh. Agar c th to ng nng thp, y l tnh cht quan trng c ng dng nhiu trong ch bin thc phm.

C u trc gel c a agar

c. ng dng Agar l mt cht to gel rt tt, thng th ng agar c s dng vi hm lng 11,5% khi lng so vi lng ng trong hn hp ko. Jelly c sn xut t loi agar c polysaccharid mch ngn. Agar khng c hp thu vo c th trong qu trnh tiu ha do agar c s dng sn xut cc loi bnh ko cha t nng lng.


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Agar c s dng trong sm phm mt tri cy thay th cho pecti n nhm lm gim hm lng ng trong sn phm v thay th gelatin trong mt s sn phm tht v c. Ngoi ra cn c s dng trong cc sn phm yoghurt, sa chocolate, trong ng nh bnh ko . Agar cn c s dng vo mi trng nui cy vi sinh vt. d. u im khi s dng agar - Kh nng to gel cng ti nng rt thp. - Khng cn bt k cht h tr no, khng nh hng v ca sn phm. - C s khc bit gia nhit nng chy v to gel: 40 0C ng c, 800C nng chy lm cho agar rt d s dng. - C kh nng cnh tranh vi cc cht to ng khc, khng nhng v c tnh k thut m cn c li v kinh t. - Khng cn ng v pH trong qu trnh to ng. - Trong trng hp nng ng cao, agar c th c cc ni phn ng l m tng lc bn gel. - C kh nng chng li cc phn ng phn hy do enzim, d ng lm mi trng nui cy vi sinh vt rt tt. - C kh nng chng li phn hy acide (tr tr ng hp mi trng pH < 4) - Khng mu, khng v nn khng nh hng n v t nhin ca sn phm. e. Quy trnh sn xut agarRong cha agar Lm sch c hc Ra nc Trch ly Lm sch Dch lc To geo Ct gel Sy kh (sau khi lnh ng v tan gi) AgarTrng Cao ng cng ng Ki n Giang Trang

X l kim

(15 -20 ln H2SO4 0,01 0,05 % un si 2 gi)

Lc

B (trch ln 2)

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3.2.3. Cellulose v cc dn xut Cellulose l mt cht hu c tn ti rt nhiu trong t nhi n v l thnh phn chnh cu to nn t bo thc vt. Hp cht ny l mt nguyn liu sn xut ph gia ng dng trong cng nghip thc phm v nhiu lnh vc khc. Hp cht cellulose bao gm nhiu cht nh : methyl cellulose (E461), hydroxypropyl cellulose (E463), hydroxypropyl methyl cellulose (E464), methyl cellulose (E465) v natri carboxymethyl cellulose (E466) hay cn g i tt l CMC. Trong cc hp cht th CMC l mt hp cht c ng dng nhiu nht trong cng nghip thc phm. a. Tnh cht CMC Hp cht CMC c sn xut t vic x l celluloza vi dung dch NaOH v sau l phn ng Williamson: Cell-OH + NaOH + ClCH 2 - COONaMono cloracetatnatri

Cell-O-CH2COONa + H 2O + NaClCMC

ClCH2 - COONa + NaOH

HOCH 2COONa + NaCl

Nh vy CMC l mt dn xut quan trng ca cellulose c cu to t hp cht cellulose kt hp vi Natri

Dng thng phm CMC c dn sut t 0,4 n 1,4. Tuy nhi n cng c loi cao hn s dng cho cc sn phm c bit. Dn sut d i 0,4 CMC khng ha tan trong nc CMC dng trong thc phm c dn sut 0,65 n 0,95 v tinh khit > 99,5 %.


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Vi CMC dn sut 0,95 v nng ti thiu 2 % cho nht 25 Mpa ti 25 0C. C th s dng CMC dng nng hoc lnh. CMC l cc anion polyme mch thng cho cht lng gi l dung dch gi. Dung dch 1% thng thng pH = 7 8,5 cn pH = 5 - 9 dung dch t thay i, pH 7 nht gim t. Dung dch CMC c th b ph hy do cc vi sinh vt hoc enzim kh. G ia nhit 80 C trong 30 pht hoc 100 0C trong 1 pht c th kh tc nhn vi sinh vt m khng nh hng n cht lng CMC. nht CMC gim khi nhit tng, tc dng c tnh thun nghch. S nh hng ca nhit n nht ca CMC 0,7 Ds c th hin gin sau:0

nht ca CMC cn chu nh hng bi cc ion kim loi: + Cation ha tr 1: t tc dng iu kin b nh thng (tr Agar+). + Cation ha tr 2: Ca 2+, Mg2+ lm gim nht. + Cation ha tr 3: Al3+, Cr3+, Fe3+ to gel. Ni chung, tc dng trn nht ca cc loi mui cng t y tuc vo phng php thm vo. CMC c th kt hp d dng vi thnh phn ha hc thc phm nh : ng, protein, tinh bt v hu ht cc polyme trung tnh. b. ng dng CMC v cc dn sut cellulose Cellulose v cc dn sut t cellulose c s dng nhiu trong ch bin thc phm hn 10 nm nay. Hin ti vic s dng khng ngng pht trin khng nhng trong vic ci thin tnh cht sn phm m cn gp phn trong vic sng to cc sn phm m i. Tnh chtTrng Cao ng cng ng Ki n Giang Trang

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tan ca dn sut cellulose trong n c l nguyn nhn lm thay i tnh cht lu bin hc ca thc phm, kt qu l ci thin c cu trc, to dng cho sn phm Ty thuc vo iu kin s dng cc dn sut cellulose c th c cc chc nng sau: gi nc, to c, n nh sn phm, tr phn tn,V vy dng dn sut celluloza cho mt sn phm c mt cng dng hoc nhiu cng dng pht huy c ng lc. Liu lng thng s dng mc nh hn 1% (thng 0.1-0.5 %). Dn sut celluloza s dng nhiu trong cng nghip sn xut nc ung, bnh, sn phm sa, m si, * Dng trong sn xut kem v cc sn phm cng loi Kem cha 10 % cht bo, 11 % sa khng bo, 15 % ng; 0,2 0,3 % cht n nh; 0,25 0,5 % cht nh ha. Cc thnh phn trn thay i ty theo tng Quc gia v tng yu cu sn phm nhng cht n nh khng vt qu 0,5 %. Hin nay cht d ng lm c l CMC, khi ha tan s to dung dch c nht cao, CMC c kh nng l m chm qu trnh kt tinh, lm mn tinh th, ci thin b ng, ngn cn kem chy. * Trong nc ung Vic s dng ring r hoc kt hp vi cc cht keo khc d ng gi n nh cc pha rn trong dung dch. Ngo i ra n cn c kh nng ngn cn phn ly tinh du/n c trong cc sn phm nc qu. Nng thng s dng l 1 %. * Trong sn xut bnh ko v cc sn phm t tinh bt Ci thin c tnh cht bt nho cng nh cc sn phm, c s dng nng 0,1 0,5 % trn trng lng cht kh. Hp cht CMC c tc dng l m mm khi bt nho, gi m, ko di thi gian bo qun, lm sn phm d tr li trng thi ban u, chng dnh... * Trong sn xut cc dng nc st Do CMC to st tt nn CMC c th c dng sn xut cc sn phm nh nc st salad, st c. Cht CMC thch hp cho cc sn phm n y v tnh ha tan tt trong nc lnh ln nc nng, c kh nng lin kt vi nc tt v chu c pH thp. - Nc st salad: CMC thng dng l 7HOF nng 1 % khi thnh phn du l 30 % hay 0,75 % khi thnh phn du khong 50 %. - Nc st c chua: ty theo loi CMC s dng m ta c c cc sn phm c cu trc khc nhau. Loi 7HOF s cho sn phm c cu trc d i, cn loi 7HXFMA s cho sn phm c cu trc ngn hn v mm hn. Nhn chung, CMC l mt hp cht c vai tr quan trng trong cng nghip thc phm, vic pht trin v ci thin tnh cht ca CMC gp phn quan trng i vi cng nghip sn xut thc phm.Trng Cao ng cng ng Ki n Giang Trang

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c. Quy trnh sn xut CMCCelluloza

Cc dn sut ha

Cc dn sut c

Lm gim trng lng

Sy

Ph hy c hc

CMC Celluloza ha tan Bt celluloza Sy Keo CMC Bt CMC

Cht keo Ch bin Sy

CMC

3.2.4. Gelatin a. Ngun gc v cu to Gelatin l sn phm ca qu trnh thy phn mt phn collagen. Collagen c cu to mng v nhng si nh, l cu trc mt b phn trong m ng vt, tn ti trong da, x ng v m lin kt. K thut bin i collagen to gelatin l tng bc ph hy cu trc cc thnh phn thu c dn xut ha tan gelatin. Gelatin l cc polypeptid cao phn t dn sut t collagen, l thnh phn protein chnh trong cc t bo lin kt ca nhiu loi ng vt. Cu to l mt chui acid amin gm 3 acid amin ch yu l glycine, proline v hydroproline. Trong phn t gelatin, cc acid amin lin kt vi nhau to chui xon c c kh nng gi n c. Phn t lng ca gelatin khong vi nghn n vi trm nghn n v Carbon. Thnh phn acid amin c trong gelatin l : Aspartic acid (6 %), Arginine (8 %), Alanine (9 %), Glutamic acid (10 %), Prolin e v Hydroproline (25 %), Glycine (27 %), cc acid amin khc (10 %). Nguyn liu sn xut gelatin ch yu ly t cc l m, nh my ng hp hoc xng thuc da. Ngun nguyn liu ny cn phi c ngm mui hoc vi bo qun.


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b. S chuyn dng t collagen sang gelatin S chuyn dng t collagen th nh gelatin ca cc nguyn liu cha hm lng collagen cao (thng khng tan trong nc) l qu trnh chuyn sang dng ha tan trong nc (do s gim phn t). Mc d c nhiu phng php hin i sn xut gelatin nhng qu trnh sn xut vn ph thuc nhiu v o kinh nghim. Qu trnh ch bin bao gm: thy phn vi acide hoc kim to th nh cc gelatin ha tan trong nc (c khi s dng kt hp c enzim). Ph ng php n gin nht l lm bin tnh nhit trong mi trng acide nh vi nhit khong 40 0C. Ti ch x l ny cc si collagen b mt lin kt hydrogen v hydrophobic (thnh phn to xon ca cc phn t collagen). Giai on tip theo l s dui thng ca mch gip gelatin h a tan. Qu trnh thy phn s to nn: 3 dy t do, 1chui , 1 chui v to chui . S khc bit gia cc chui , , l trng lng phn t = 80.000-125.000 vC, = 160.000 - 250.000 vC v = 240.000 375.000 vC. c. Tnh cht gelatin * C ch to gel Gelatin trng n khi cho vo nc lnh, lng nc hp thu gp 5-10 ln th tch chnh n. Khi gia nhit n b nng chy, ha tan v thnh lp gel khi lm lnh. S chuyn dng t sol sang dng gel c tnh thun nghch v c th lp i lp li nhiu ln. y chnh l tnh cht c bit c ng dng nhiu trong thc phm. Gelatin c nhit nng chy thp 27-340C. tan ca gel gelatin ph thuc v o cc yu t nh nhit v kch thc ca ht gelatin. Gelatin tan trong r u v cc dung mi hu c. * bn gel bn gel c tnh theo gi tr lc cn to ra mt bin dng nht nh hay s bin dng c gy ra bi mt lc nht nh. bn gel ca gelatin c th c biu dinTrng Cao ng cng ng Ki n Giang Trang

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theo mt s n v khc nhau ty thuc vo tng phng thc kim tra khc nhau. Gelatin c kh to gel m khng cn phi hp vi cht no khc. Lc bn gel c nh ngha l trng lng (g) cn thit t l n b mt gel (ng knh 21.7 mm) lm bin dng 4 mm. Ngoi ra, st ca gelatin cng l mt tnh cht c quan tm c bit, st ca gel s tan khi nng gelatin tng v nhit gim. S thay i nht theo nng c biu din trn th sau:

d. Quy trnh sn xut gelatin

Lng

Xng

Da

Nghin

Tch khong

X l vi

X l acide

Trung ha

Trch ly nc nng

Lc

C c

Tit trng

Lm lnh

Sy kh

Bao giTrng Cao ng cng ng Ki n Giang

Phi trn

NghinTrang

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e. ng dng gelatin Gelatin c ng dng rt ph bin trong cng nghip ch bin ko, sa l n men, phomat v cc sn phm trng ming. Mt s lnh vc ph bin s dng gelatin trong sn phm l: - Sn xut kem: c tc dng kim ch s h nh thnh tinh th ca kem v ng, nng thng dng l 0,25 % - Ko do: s dng vi nng 1,5 % ngn cn s h nh thnh tinh th. Rt thch hp trong cc sn phm bnh ko np kh CO 2 nh ko do hay bnh xp v gelatin c tnh st gip n nh bt trong sut qu tr nh x l, vn chuyn v d tr. - Cng ngh bnh ko nng lng thp: do c nng lng thp 14,7 KJ/g nn c nghin cu ng dng trong sn xut thc phm c gi tr nng l ng thp. - Trong y hc: gelatin c s dng trong sn xut bao thuc ca cc dng thuc vi n hnh thoi, vi nng 1 % gip cho bao thuc c dai cn thit. Bn cnh , gelatin cn c ng dng trong nhiu ng nh cng nghip ch bin khc nh cng ngh ch bin tht, lm nc st, lm trong ru, f. Mt s lu khi s dng gelatin Vic chun b gelatin trong sn xut th ng gp kh khn khi sn phm y u cu c hm lng gelatin 10 % l cht lng c nht cao v c tnh cht lu bin phi Newton. S thay i nht theo nng arabic c biu din bng th sau:

Arabic tan c trong nc, khng tan trong cht bo, c nht thp. nht ph thuc vo pH v nng mui. nng cao l cht keo kt hp vi cc qu trnh sy sn phm rt hiu qu. Arabic rt n nh trong mi trng acide, v vy arabic s dng rt tt cho vic n nh mi ca nc qu. Gi tr pH t nhin ca dung dch Arabic l 3,9 - 4,9 l do s hin din ca acide gluconic. Khi thm acide hoc kim c th lm thay i nht v din tch tip xc ca dch keo, pH thp th nht thp v ngc li. nht t ti a khi pH= 5,5. Hp cht arabic thng c s dng gi mi cho cc sn phm dng nh tng, gi mi cho cc sn phm bao gi, gi nc v chng s kt tinh ng. 3.2.6. Pectin a. Ngun gc v cu to Pectin l mt polysaccharide tn ti ph bin trong thc vt, l thnh phn tham gia xy dng cu trc t bo thc vt. thc vt pectin tn ti ch yu 2 d ng l pectin ha tan v protopectin khng ha tan. D i tc dng ca acid, enzyme protopectinaza hoc khi gia nhit th protopectin chuyn thnh pectin. Pectin l hp cht cao phn t polygalactoronic c n phn t l galactoronic v ru metylic. Trng lng phn t t 20.000 - 200.000 vC. Hm lng pectin 1% trong dung dch c nht cao, nu b sung 60 % ng v iu chnh pH mi trng t 3,1-3,4 sn phm s to ng. Cu to phn t pectin l mt dn sut ca acid pectic, acid pectic l mt polymer ca acid D-galacturonic lin kt vi nhau bng lin kt 1-4-glycozide.Trng Cao ng cng ng Ki n Giang Trang

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Hp cht pectin c c trng bi 2 ch s quan trng l ch hin cho phn trm khi lng nhm methoxyl OCH3 c trong phn t pectin v ch s este ha DE th hin mc este ha ca cc phn t acid galactoronic trong phn t pectin. Da trn mc methoxy ha v este ha, trong thng mi chia pectin thnh 2 loi: pectin c methoxyl ha cao v pectin c methoxyl ha thp. - Pectin methoxyl ha cao (High Methoxyl Pectin HMP): DE >50 % hay MI > 7%. Cht ny c th lm tng nht cho sn phm. Mun to ng cn phi c iu kin pH = 3,1 3,4 v nng ng trn 60 %.

- Pectin methoxyl ha thp (Low Methoxyl Pectin LMP): DE < 50 % hay MI < 7%. c sn xut bng cch gim nhm methoxyl trong phn t pectin. Pectin methoxy thp c th to ng trong mi trng khng c ng. Chng thng c dng lm mng bao bc cc sn phm.


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Trong qu trnh bo qun c th b tch nc hoc lo ha. Qu trnh to ng ph thuc vo nhiu yu t: ngun pectin, mc methoxy ha c ng cao th kh nng to ng cng cao. Khi s dng cn phi ha tan pectin vo nc, khi pectin ht nc th mi s dng cng on cui ch bin. Cc pectin u l nhng cht keo ho nc nn c kh nng hydrat ha cao nh s gn cc phn t nc vo nhm hydroxyl ca chui polymethyl galacturonic. Ngo i ra, trong phn t pectin c mang in tch m n n chng c kh nng y ln nhau c kh nng lm gin mch v lm tng nht ca dung dch. Khi l m gim tch in v hydrat ha s lm cho si pectin xch li gn nhau v tng tc vi nhau to nn mt mng li ba chiu rn cha pha lng b n trong. b. ng dng Pectin l cht to gel quan trng nht c s dng to ra cu trc gel cho thc phm. Kh nng to gel ca n c s dng trong nhng thc phm cn c s n nh ca nhiu pha. Tc dng to gel ca pectin c s dng ch yu trong cc sn phm mt tri cy v mt ng. Tc dng ca pectin l to ra cu trc mt ng v mt tri cy khng b thay i trong qu trnh vn chuyn, to ra mi v thm ngon cho sn phm v gim s ph v cu trc. Trong mt s trng hp, pectin cn c s dng vi carageenan tng hiu qu to gel. 3.2.7. Carrageenan a. Lch s pht hin ra Carrageenan Carrageenan bt u c s dng hn 600 nm trc y, c chit xut t ru Irish moss (Loi rong Chondrus crispus) ti mt ngi lng trn b bin pha Nam Ireland trong mt ngi lng mang tn Carraghen. Vo nhng nm 30 ca th k XX, carrageenan c s dng trong cng nghip bia v h si. Cng trong thi k n y nhng khm ph v cu trc ha hc ca carrageenan c tin hnh mnh m. Sau ny, carrageenan c chit xut t mt s lo i rong khc nh Gigartina stelata thuc chi rong Gigartina. Nhiu loi rong khc cng c nghin cu trong vic chit tch carrageenan ng dng trong nhiu lnh vc khc nhau. Ngy nay, sn xut cng nghip carrageenan khng c n gii hn vo chit tch t Irish moss, m rt nhiu loi rong thuc ngnh Rhodophyta c s dng. Nhng loi ny gi chung l Carrageenophyte. Qua nhi u nghin cu, c hng chc loi rong bin c khai thc t nhin hay nui trng sn xut carrageenan.Trng Cao ng cng ng Ki n Giang Trang

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b. Cu to ca carrageenan Carrageenan l mt polysaccharide ca galactose galactan. Ngoi mch polysaccharide chnh cn c th c cc nhm sulfat c gn vo carrageenan nhng v tr v s lng khc nhau. V vy, carrageenan khng phi ch l mt polysaccharid n l, c cu trc nht nh m l cc galactan sulfat. Mi galactan sulfat l mt dng ring ca carrageenan v c k hiu ring. V d: , , , carrageenan. Trong qu trnh chit tch, do tc ng ca mi tr ng kim cc -,-,-carrageenan d chuyn ha thnh -, -, - carrageenan tng ng. Cc carrageenan c mc sulfat ha khc nhau, th d carrageenan (25 % sulfat), carrageenan (32 % sulfat), carrageenan (35 % sulfat). Cc sn phm ny c thng mi ha, chim v tr quan trng trong th trng polysaccharide.

c. Tnh cht * tan Carrageenan tan trong n c nhng tan ca n ph thuc v o dng, nhit , pH, nng ca ion v cc cht tan khc. Nhm carrageenan c cu ni 3,6-anhydro khng a nc, do cc carrageenan ny khng tan trong nc. Nhm carrageenan khng c cu ni th d tan hn. Th d nh carrageenan khng c cu ni 3,6-anhydro v c thm 3 nhm sulfat a n c nn n tanTrng Cao ng cng ng Ki n Giang Trang

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trong nc iu kin bt k. i vi carrageenan th c tan trung bnh, mui natri ca carrageenan tan trong n c lnh nhng mui kali ca carrageenan ch tan trong nc nng. * nht nht ca cc dung dch carrageenan ph thuc v o nhit , dng, trng lng phn t v s hin din ca cc ion khc tr ong dung dch. Khi nhit v lc ion ca dung dch tng th nht ca dung dch gim. Cc carrageenan to th nh dung dch c nht t 25 500 Mpa, ring carrageenan c th to dung dch c nht ti 2000 Mpa. S lin quan t l thun gia nht v trng lng phn t ca carrageenan c th m t bng cng thc cn bng ca Mark -Houwink nh sau:

[] = K(M w)Trong : : nht Mw: trng lng phn t trung bnh K v : hng s ph thuc vo dng ca carrageenan v dung mi ha tan * Tng tc gia carrageenan vi protein y l mt trong nhng tnh cht quan trng ca carrageenan v cng l c trng cho tt c cc cht to gel cng nh cc cht khng to gel l xut hin phn ng vi protein. Phn ng ny xy ra nh cc cation c mt trong cc nhm protein tch in tc dng vi nhm sulfat mang in m ca carrageenan v c tnh quyt nh n bn c hc ca gel. Trong cng nghip sa, nh vo tnh cht lin kt vi cc protein trong sa m carrageenan c s dng (vi nng 0,015 0,025 %) lm tc nhn ngn chn s tch lng v lm n nh cc ht coca trong sa scla.


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* To gel Carrageenan c mt tnh cht v cng quan trng l to gel nng thp (nh h n 0,5 %). dng gel cc mch polysaccharide xon v ng nh l xo v cng c th xon vi nhau to thnh khung xng khng gian ba chi u vng cht, bn trong c th cha nhiu phn t nc (hay dung mi). T dng dung dch chuyn sang dng gel l do tng tc gia cc phn t polyme ha tan vi cc phn t dung mi bn trong, nh tng tc ny m gel to thnh c bn c hc cao. Phn xon vng l xo chnh l nhng mm to gel, chng li ko cc phn t dung mi vo vng lin kt. S hnh thnh gel c th gy ra bi nhit thp hoc th m cc cation vi mt nng nht nh. Qu trnh hnh thnh gel din ra phc tp, c thc hin theo hai bc: - Bc 1: khi h nhit n mt gii hn n o trong phn t carrageenan c s chuyn cu hnh t dng cun ngu nhin khng c trt t sang dng xon c trt t. Nhit ca qu trnh chuyn i ny ph thuc vo dng v cu trc cc carrageenan, cng nh ph thuc vo dng v nng ca mui thm vo dung dch carrageenan. Do , mi mt dng carrageenan c mt im nhit to gel ri ng. - Bc 2: gel ca cc polyme xon c th thc hin cc cp xon. Trong tr ng hp u, s phn nhnh v kt hp li s xut hin cp xon thng qua s h nh thnh khng y ca xon kp, theo h ng mi chui tham gia v o xon kp vi hn mt chui khc. Trong trng hp th hai, cc phn pht trin y ca a xon t hp li to thnh gel. Cn di cc iu kin khng to gel, cc nng polyme thp s h nh thnh v hp li ca cc xon s dn n tng nht. Qua , c th m t c ch to gel nh sau: trc ht l xut hin s chuyn i cu hnh t dng cun sang xon l xo, tip sau l s kt hp cc xon v t hp li c trt t to thnh xon kp gel. Nh vy, gel l tp hp cc xon c trt t hay c n gi l xon kp.

d. ng dng Carrageenan c s dng nhiu dng khc nhau trong nhiu sn phm m chng ta s dng hng ngy, nht l trong lnh vc thc phm v bnh ko.Trng Cao ng cng ng Ki n Giang Trang

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Cc sn phm c s dng carrageenan c s dng ph bin trong nhiu th k. Nhiu nghin cu chng minh an ton ca carrgeenan, n khng gy c, khng c du hiu gy vim lot trn c th v c th s dng trong thc phm vi mt l ng khng gii hn. T chc FDA ca M xp carrageenan vo danh mc cc cht an ton i vi cc sn phm thc phm. Tnh ph bin ca carrageenan c th hin 4 c im sau: - Tham gia nh mt cht to ng i vi mt s sn phm nh : kem, sa, b, pho mt. - Lm bn nh tng, gip cho dung dch trng thi nh tng cn bng vi nhau m khng b tch lp. - C th thay i kt cu ca sn phm vi tnh cht ha l, c hc mong mun, to ra cc sn phm ng c c bn dai. - Gip n nh cc tinh th trong cc sn phm bnh, ko ngn chn ng v nc b kt tinh. Chnh v vy, carrageenan c ng dng rng ri trong cc ngnh kinh t quc dn. Gp phn a dng ha cc sn phm thc phm.T l s dng carrageenan trong cc sn phm khc nhauCc sn phm khc, 3.29% Kem nh rng, 7.84% Nc dng gel, 14.71%

Tht v gia cm, 30.39%

B sa, 43.14%

* ng dng trong cng nghip sa Carrageenan c kh nng lin kt vi protein ca sa, l m cho ht nh tng sa nc bn vng. Chnh v tnh cht ny m carrageenan khng th thiu c trong cng nghip ch bin sa. Sa nng c cha carrageenan c lm lnh s to gel, gi cho nh tng ca sa vi nc c bn vng, khng b phn lp. Tc nhn chnh trong qu tr nh to gel l do lin kt gi cc ion sulfat vi cc ui mang in ca cc phn t protein v cc cation Ca 2+, K+ c mt trong sa.Trng Cao ng cng ng Ki n Giang Trang

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Mc to gel ca carrageenan vi sa cng khc nhau: carrageenan v carrageenan khng tan trong s a lnh, carrageenan tan trong sa lnh. Chnh v vy, carrageenan c ng dng nhiu hn trong cng ngh ch bin sa. * ng dng trong cc ngnh thc phm khc Carrageenan c ng dng trong nhiu lnh vc ch bin thc phm khc nhau nh : kem, phomat, bnh pudding, si r, ung lnh, mt t ng v sa chua. Cc cng ty ch bin tht cng s dng carrageenan trong ch bin tht v carrageenan c kh nng tng hiu sut cc sn phm bng cch gi n c bn trong sn phm. Ngoi ra, carrageenan cn c thm vo bia hoc ru to phc protein v kt lng chng lm cho sn phm c trong hn. 4. CC CHT HOT NG B MT 4.1. Khi nim Cht hot ng b mt l cht c kh nng lm thay i nng lng b mt m n tip xc. Tnh hot ng b mt c th dn n hai hiu ng ho n ton ring l: - Lm gim sc cng b mt phn chia pha ca h thng - Bn ha b mt phn chia pha bi s to th nh nhng lp hp ph. Cht hot ng b mt gm hai phn: phn c i lc vi n c hay phn u (head hyprophilic) v phn k nc hay phn ui (tail hyprophilic).

Nu lc tng tc gia cc phn t ca mt cht lng khng tan v o nc nh hn lc tng tc gia cc phn t cht lng vi cc phn t n c th khi cho mt lng nh cht lng vo nc, cht lng s lan ra tr n b mt thnh mt mng n phn t. Khi cht64


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lng l cht hot ng b mt th nhm phn cc s hng vo nc, cn nhm khng phn cc hng ra khng kh.

4.2. Phn loi 4.2.1. Cht hot ng b mt loi ion a. Cht hot ng b mt loi anion Cht hot ng b mt anion l nhng cht hot ng b mt m trong dung dch nc phn ly thnh gc mang in tch m. V d: + Alkyl sulfate natri (Lauryl sulfate Natri) C 11H23CH2OSO3Na + Alkyl aryl sulfonate: C11H23CH2OSO3- + Na+

b. Cht hot ng b mt cation Cht hot ng b mt cation l nhng cht hot ng khi phn ly trong n c to thnh cc ion dng. Lp cht hot ng b mt cation u ti n l nhng mui amin bo (mui amonium): Trong : R: gc hydro carbon mch di X: ion halogenua, sufate ho c methyl sulfate. a, b, c: hydro, nhm alkyl ng n hoc alkyl aryl.


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4.2.2. Cht hot ng b mt lng tnh Cht hot ng b mt c trng l vic cha c nhm anion v nhm cation trong cng phn t. Nhm anion thng l acid cacboxylic, acid sulfonic, ho c gc sulfat. Nhm cation thng l Nitro bc 4, nhm amino. in tch ca cht hot ng b mt l ng tnh c quyt nh bi pH ca dung dch. Trong mi tr ng kim n c tnh cht anion; trong mi trng acid n c tnh cht cation. Hu ht cc cht hot ng b mt l ng cc hon ton tng hp vi cht hot ng cation, anion v nonion V d: Akyl amido propyl betai n

4.2.3. Cht hot ng b mt khng ion Cht hot ng b mt khng ion khc vi cc cht hot ng b mt khc ch : phn i nc ln hn cht hot ng b mt anionic v mt s cationic. Cht hot ng b mt khng ion c mi trng s dng rng nh: nc cng, phn, cht in li pH thp v khng b ta, gim tnh hot ng b mt khng ng k. Cht hot ng b mt khng ion cng c cu to t phn k n c v phn a nc. - Phn k nc : l hydrocacbon mch di c H linh ng nh alkyl phenol, amin, alcol, amid. - Phn a nc : propylen oxid, etylen oxid, poly glycol, glucose, glycerin. 4.3. Chc nng ca cht hot ng b mt 4.3.1. Kh nng ty ra Kh nng ty ra ca mt ha cht rt phc tp, n khng ch ph thuc v o s gim sc cng lin din, kh nng to micell m cn ph thuc vo mt s yu t khc nh: kh nng thm t, kh nng nh ha ca cht ty git, bn cht vt liu ty ra cht d v cch ty git. Cht hot ng b mt lm gim sc cng b mt ca n c, v vy dung dch cht ty ra d thm t si vi v ngm vo mao qun ca si vi bn trong khi n c khng c kh nng ngm vo trong mao qun ca si vi v nc c sc cng b mt ln. Cc phn t cht ty ra hp ph ln b mt si vi v b mt cc ht bn rn hay lng to thnh mt cht hp ph hydrat ha rt mnh v hnh thnh mt p sut, tch nhng ht bn ra khi b mt si vi, r i chuyn chng vo dung dch ty ra, nhng mng hp phTrng Cao ng cng ng Ki n Giang Trang

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trn b mt ht bn, to cho cc ht bn vng rt ln, cn tr s kt dnh chng li vi nhau trn b mt si vi. Mt khc, do dung dch cht ty d to bt, mt phn cht bn s tch vo bt, nht l nhng ht bn thm t km s dnh vo cc bt kh nh trong qu trnh tuyn ni khi lm giu qung. 4.3.2. Kh nng to nh Nh l mt hn hp tng i n nh ca mt cht lng trong mt cht lng, hai cht lng ny khng tan vo nhau. Khi t o nh, s khuch tn pha lng n y trong pha lng kia lm tng lin din rt nhiu, ngha l lm tng nng lng t do ca h thng. V vy, khi c cht hot ng b mt, chng l m gim sc cng b mt phn chia pha, tc l lm gim nng lng t do b mt, do lm tc kt dnh ca cc ht chm li n n h tr nn bn hn v mt nhit ng. Cht hot ng b mt c kh nng to nh (bn nh) l do chng c kh nng di chuyn n v cht cha trn b mt phn chia pha gia hai cht lng m trong trng hp ny l b mt cc ht micell. 4.3.3. Kh nng to huyn ph Huyn ph l mt h l lng cc ht rn phn tn trong mt cht lng. Kh nng to huyn ph ca cht hot ng b mt l kh nng ngn cc ht rn dnh kt vi nhau. cht hot ng b mt phn tn u trong nc, ngn cn khng cho t, cht bn bm tr li b mt ca vt ty ra. bn vng ca huyn ph ph thuc vo bn cht ca cht hot ng b mt (cht phn tn, to huyn ph ), nht pha lng, lc tnh in gia cc ht, nhit 4.3.4. Cn bng k nc a nc (HLB: Hydrophilie Lipophilie - Balance) Cn bng k nc a nc HLB l t l gia tnh a nc v k nc. Gi tr HLB cng thp (1 40): cht hot ng b mt c tnh a du, HLB cng cao (>40), cht hot ng b mt c tnh a nc. Cc phng php xc nh gi tr ca HLB: - Cng thc ca KAWAKAMI: HLB = 7+11,7 log(Mn/Md) Trong : Mn: khi lng phn t a nc trong phn t. Md: khi lng phn t a du trong phn t. - Cng thc tnh este ca acid bo v ancol a chc: HLB = 20(1-S/A) Trong : S: ch s x phng ha ca ester A: ch s acid ca acid bo.Trng Cao ng cng ng Ki n Giang Trang

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- Tnh trn nhm a n c, nhm k nc: HLB = 7+HLB

nhm a nc -

HLB nhm k nc

- Nu hn hp c nhiu cht hot ng b mt: HLBhh =x1.HLB1

Vi x1: % khi lng trong tng lng cht hot ng b mt. Hin ti da vo cn bng thn du - nc ngi ta chia HLB ra thang t 0 - 20. S ha tan ca cc cht hot ng b mt da tr n cn bn ca HLB cho trong bng sau:Bng 5: Lin h HLB v kh nng phn tn v ha tan ca cc cht hot ng b mt

Trng thi cc cht hot ng b mt trong n

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