BÁO CÁO THỰC HÀNH PHỤ GIA-TỔ 3-NHÓM 2-DHTP4

Bo co thc hnh ph gia

GVHD: Th.S Nguyn Th Hong Yn

VIN CNG NGH SINH HC V THC PHM

MN: THC HNH PH GIA THC PHM

BO CO:

THC HNH PH GIAGVHD: Th.S Nguyn Th Hong Yn Lp: DHTP4 Nhm: 2 T: 31. 2. 3.

Nguyn Th Thu Hng Nguyn Th Huyn Nguyn M Linh ng Th Bch Tuyn

08104521 08096211 08234201 08109511

Nguyn Trn Thi Hng 08100391 Nguyn Th Phng Tho 08231591

4. 5. 6.

TP. HCM, THNG 10 NM 2011

T 3 Nhm 2 DHTP4

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MC LC Bi 1: Ph gia chng oxy ha1. TNG QUAN L THUYT...................................................................................8 1.1 Ph gia chng oxy ha............................................................................................8 1.1.1 Gii thiu............................................................................................................8 1.1.2 C ch qu trnh oxy ha cht bo....................................................................10 1.1.3 Tng quan v ph gia chng oxy ha Butyl hydroxytoluen (BHT)..................11 1.2Nguyn liu du thc vt........................................................................................13 1.2.1 Tng quan..........................................................................................................13 1.2.2 c im...........................................................................................................13 1.2.3 Thnh phn........................................................................................................14 1.2.4 Phn loi............................................................................................................16 1.2.5 Bo qun ...........................................................................................................16 1.2.6 c tnh ca mt s loi du n........................................................................17 2. TIN HNH TH NGHIM - KT QU - BN LUN.....................................18 2.1 Xc nh ch s acid..............................................................................................18 2.1.1 nh ngha.......................................................................................................18 2.1.2 Nguyn tc.......................................................................................................19 2.1.3 S tin hnh th nghim..............................................................................19 2.1.4 Thuyt minh quy trnh.....................................................................................20 2.1.5 Kt qu th nghim..........................................................................................21 2.1.6 Nhn xt kt qu..............................................................................................23 2.2 Xc nh ch s Iod bng phng php Wijs........................................................23 2.2.1 nh ngha.........................................................................................................24 2.2.2 Nguyn tc xc nh..........................................................................................24 2.2.3 S quy trnh tin hnh th nghim................................................................24 2.2.4 Thuyt minh quy trnh.......................................................................................25 2.2.5 Kt qu th nghim..........................................................................................26 2.2.6 Nhn xt kt qu..............................................................................................27 2.3 Xc nh ch s peroxyt........................................................................................28 T 3 Nhm 2 DHTP4 Page 2



2.3.1 nh ngha.........................................................................................................28 2.3.2 Nguyn tc........................................................................................................28 2.3.3 Thuyt minh quy trnh.......................................................................................29 2.3.4 Kt qu th nghim............................................................................................30 2.3.5 S quy trnh tin hnh th nghim................................................................30 3. TR LI CU HI..............................................................................................31

Bi 2: Ph gia to nh45I.Tng quan..............................................................................................................45 1. H nh tng...........................................................................................................45 1.1 Khi nim..............................................................................................................45 1.1.1 Phn loi h nh tng.......................................................................................45 1.1.2 S hnh thnh nh tng....................................................................................46 1.2 Cht to nh...........................................................................................................46 1.2.1 nh ngha..........................................................................................................46 1.2.2 Phn loi.............................................................................................................46 1.3 Lecithine................................................................................................................47 1.3.1 c im.............................................................................................................47 1.3.2 Ngun gc..........................................................................................................48 1.3.3 c tnh..............................................................................................................49 1.3.4 C ch tc dng..................................................................................................49 1.4 Lauryl sunfate........................................................................................................50 1.4.1 c im............................................................................................................50 1.4.2 Ngun gc..........................................................................................................51

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1.4.3 c cht..............................................................................................................51 1.4.4 C ch tc dng..................................................................................................52 1.5 Nguyn liu th nghim.........................................................................................52 1.5.1 Du thc vt.......................................................................................................53 1.5.2 Nc...................................................................................................................53 2. Qui trnh tin hnh th nghim.................................................................................54 2.1 Qui trnh chung......................................................................................................54 2.2 Thuyt minh qui trnh............................................................................................55 2.2.1 Th nghim 1: Kho st h du/nc..................................................................55 2.2.2 Th nghim 2: Kho st h nc/du..................................................................56 3. Kt qu - bn lun....................................................................................................56 3.1 3.1.1 3.1.2 3.2 3.2.1 3.2.2 Kt qu............................................................................................................57 Th nghim 1: H du/nc..................................................................57 Th nghim 2: H nc/du..................................................................57 Bn lun..........................................................................................................58 Th nghim 1: H du/nc..................................................................58 Th nghim 2: H nc/du..................................................................58

4.Tr li cu hi..........................................................................................................59

Bi 3: Ph gia ng c1.1

Tng quan v ph gia..................................................................................................651.1 Khi nim..............................................................................................................65 1.2 Gii thiu mt s loi ph gia s dng trong th nghim......................................65

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1.2.1 Triphosphate pentasodium........................................................................65 1.2.2 Pectin.........................................................................................................65 1.2.3 Agar ..........................................................................................................68 1.2.4 Alginat.......................................................................................................69 1.2.5 Carragenan................................................................................................69 1.3 Canxi clorua (CaCl2) ............................................................................................71

2. Tin hnh th nghim ..............................................................................................72 2.1 Th nghim 1..........................................................................................................722.2 Th nghim 2..........................................................................................................74 2.3 Th nghim 3..........................................................................................................75 2.4 Th nghim 4..........................................................................................................75

3. Kt qu - bn lun....................................................................................................75 3.1 Kt qu..................................................................................................................75 3.2 Bn lun.................................................................................................................76 4. Tr li cu hi.........................................................................................................77

Bi 4: Ph gia ci thin bt1. Tng quan v nguyn liu......................................................................................83 1.1 Bt m.................................................................................................................83 1.2 Ph gia ci thin bt m......................................................................................85 1.2.1 1.2.1.1

Vitamin C.......................................................................................................86 Tnh cht v ng dng.................................................................................87 Page 5

T 3 Nhm 2 DHTP4

Bo co thc hnh ph gia1.2.1.2 1.2.2


ng dng trong ci thin cht lng bt m................................................88 Na2S2O3..........................................................................................................89

2. Tin hnh th nghim.............................................................................................89 2.1 2.2

S quy trnh..................................................................................................89 Thuyt minh quy trnh.......................................................................................90

2.2.1 La chn bt m..............................................................................................90 2.2.2 Cn, phi trn..................................................................................................91 2.2.3 Ra gluten ......................................................................................................91 2.2.4 Xc nh cht lng gluten.............................................................................91 3. Kt qu v bn lun...............................................................................................92 3.1 Kt qu................................................................................................................92 3.2 Bn lun..............................................................................................................94 4. Tr li cu hi........................................................................................................94

Bi 5: Enzyme1. Tng quan................................................................................................................98 1.1 Nhm enzyme........................................................................................................98 1.1.1 Gii thiu v Enzyme.........................................................................................98 1.1.2 Vai tr ca enzyme trong ch bin thc phm...................................................98 1.1.3 Nhm cc Enzyme thng c s dng trn th trng..................................99 1.1.4 Enzyme pectinas.................................................................................................99 1.1.4.1 c im..........................................................................................................99 1.1.4.2 Ngun gc.......................................................................................................99 1.2. Nguyn liu da..................................................................................................100 T 3 Nhm 2 DHTP4 Page 6



1.2.1 Ngun gc Phn loi.....................................................................................100 1.2.1 Thnh phn dinh dng....................................................................................101 1.2.2 ch li t da...................................................................................................103 2. Cch tin hnh.......................................................................................................104 2.1 Quy trnh..............................................................................................................104 2.2 Thuyt minh quy trnh.........................................................................................105 2.2.1 X l.................................................................................................................105 2.2.2 Ct nh..............................................................................................................105 2.2.3 Xay nt..............................................................................................................105 2.2.4X l enzyme.....................................................................................................106 2.2.5 Lc....................................................................................................................106 2.2.6 Xc nh V, oBx, nht, pH, mu sc, trong...........................................106 3. Kt qu - Bnh lun................................................................................................107 3.1 Kt qu th nghim..............................................................................................107 3.2 X l kt qu........................................................................................................107 3.3 Nhn xt...............................................................................................................109 4. Tr li cu hi.......................................................................................................110

Ti liu tham kho.......................................................................115

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Bi 1: PH GIA CHNG OXY HA1. TNG QUAN L THUYT 1.1 Ph gia chng oxy ha 1.1.1 Gii thiu Ph gia chng oxy ha l nhng cht cho vo cc sn phm thc phm nhm v hot cc gc t do, t gim tc xy ra qu trnh i ha cht bo. C th l ph gia ny s ko di thi gian hnh thnh nhng hp cht gy ra qu trnh oxi ha. Ngoi ra, ph gia chng oxy ha cn c chc nng v hot peroxide. Khi ch bin, c bit l bo qun cc sn phm thc phm thng xy ra cc qu trnh v cc loi phn ng oxy ha khc nhau lm bin i phm cht v gim gi tr ca thc phm. Cc biu hin thng thy ca s oxy ha cht bo l pht sinh mi v xu, thay i mu sc, thay i nht ca sn phm v lm mt cht dinh dng. Bin php ngn nga s oxi ha: S dng bao b c bit cch ly sn phm giu cht bo vi cc tc nhn lm tng qu trnh oxi ha Rt y, ht chn khng, lm y khng gian t do bng cch s dng cht tr. c bit l s dng ph gia chng oxi ha. Ph gia chng oxi ha l nhng cht cho vo sn phm thc phm nhm ngn chn hay kim hm cc gc oxi ha t do ca ct bo - l nguyn nhn dn n s thay i mu v mi ca sn phm. Ph gia chng oxi ha c hai loi: C bn cht axit: axid citric, acid malic, acid ascorbic C bn cht phenolic: BHA, HBT, TBHQ Phm vi ca bi th nghim l xc nh ch s axit, ch s peroxit, ch s iod ca mu cht bo c b sung ph gia v mu i chng. T 3 Nhm 2 DHTP4 Page 8

Bo co thc hnh ph gia BHA (Butylhydroxyanisoile) BHT (butylated hydroxytoluene) TBHQ (Tert-butylhydroquinone) Tn M t


Tnh tan Du, m, eter,

Nhit

Liu lng s dng

nng chy etanol,

Butyl hydroxyanisol (BHA )

L tinh th mu trng,

propan 1,2 60 65oC i khi hi vng,c diol,... mi thong c trng. Khng tan trong nc. Du, m, ru.

< 0,5 mg/kg th trng

Butyl hydroxytoluen (BHT)

L tinh th trng, hnh

Khng tan trong 69 72oC si, khng v, thong nc v propan mi c trng. 1,2 - diol Tan tt trong L tinh th trng, c Tan khng hon 126.5 128.5oC mi c trng. ton trong nc etanol

< 0,5 mg/kg th trng

Tert

butyl

< 0,5 mg/kg th trng

hydroquinon (TBHQ)

Tc dng ca cht chng oxy ha:

Cht chng oxy ha tc dng vi cc cht xc tc ca phn ng oxy ha nn phn ng khng th xy ra, cht bo khng b oxy ha. V d: acid citric, polyphenol

Cht chng oxy ha tc dng vi cc cht cn bo v, to phc cht bn vng kh b oxy ha

V d: nitrit, nitrat tc dng vi Fe, gi cho Fe (II) khng b oxy ha thnh Fe (III), trnh lm mt mu tht.

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Tc dng vi O2 khng kh: oxy phn ng vi cc cht chng oxy ha ch khng phn ng vi cht bo nn cht bo khng b h hng do oxy ha. V d: acid ascorbic, acid erythorbic Ngn chn s tip xc ca O2 vi thc phm

1.1.2 C ch qu trnh oxy ha cht bo S t oxy ha cht bo l phn ng dy chuyn c chm ngi bng s to thnh cc gc t do t cc phn t acid bo. Giai on khi u: RH + O2 Ro + oOOH RH

Ro+ Ho

Bc khi u c th c tng cng bi tc dng ca ngun nng lng nh khi gia nhit hoc chiu sng (c bit l ngun nh sng UV). Ngoi ra, cc hp cht hu c, v c (thng tm thy di dng mui Fe v Cu) cng l nhng cht xc tc c nh hng rt mnh, kch thch qu trnh oxy ha xy ra. Giai on lan truyn: R0 + O2 ROOo + RH

ROO0 (gc peroxide) Ro + ROOH (hydroperoxide)

Giai on kt thc: ROOo + ROOo ROOo + Ro Ro + Ro

ROOR + O2 ROOR R-R

Cc gc alkyl Ro phn ng vi O2 hnh thnh gc peroxide ROOo. Phn ng gia alkyl v O2 xy ra rt nhanh trong iu kin kh quyn. Do , nng ca alkyl rt thp so vi gc peroxide. Gc peroxide hp thu in t t cc phn t lipid khc v phn ng vi in t ny to thnh hydroperoxide ROOH v mt gc peroxide khc. Nhng phn ng ny xc tc cho cc phn ng khc. S t oxy ha lipid c T 3 Nhm 2 DHTP4 Page 10



gi l phn ng gc t do. Khi cc gc t do phn ng vi nhau, cc sn phm khng gc t do s to thnh v phn ng kt thc. Ngoi hin tng t oxy ha, lipid cn c th b oxy ha bng enzyme lipoxygenase. C ch ca cht chng oxy ha: Nhng cht chng oxy ha ngn chn s hnh thnh nhng gc t do (nhng cht c electron ring l) bng cch cho i nguyn t hydro. Khi cho i nguyn t hydro, bn thn nhng cht chng oxy ha cng tr thnh nhng gc t do nhng nhng gc ny hot tnh km hn. Sau gc t do ca lipid (Ro) kt hp vi gc t do ca cht chng oxy ha (Ao) to thnh nhng hp cht bn. Phn ng ca cht chng oxy ha vi gc t do: Ro ROo ROOo Ro ROo ROOo + AH + AH + AH + Ao + Ao + Ao`

RH ROH ROOH + Ao RA ROA ROOA

+ Ao + Ao

V d: BHA, BHT, tocopherol 1.1.3 Tng quan v ph gia chng oxy ha Butyl hydroxytoluen (BHT) - c im + Cng thc ha hc: C15H24O. + Tn ha hc: 2,6-Ditertiary-butyl-p-cresol; 4-methyl-2,6-ditertiary-butylphenol. + Khi lng phn t: 220,36 (dvC).

+ Cng thc cu to:

T 3 Nhm 2 DHTP4

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- BHT l cht rn mu trng, dng tinh th, hnh si, khng v, thong mi c trng. - Tan km trong du, m, ru. Khng tan trong nc v propan 1,2 diol. - Bn nhit, nhit nng chy 69 72oC. - BHT c tc dng chng oxy ha km hn BHA do cu to ca n cng knh hn BHA. S c mt ca st trong mt s sn phm thc phm hay bao b, BHT c th to ra mu vng. - c tnh 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. Khi BHT i vo c th qua ng ming s c hp th nhanh chng qua d dy, rut, sau s c thi ra ngoi theo nc tiu v phn. ngi, s bi tit BHT thng qua thn c th nghim khi cho n vi khu phn c cha 40mg/kg th trng. Nghin cu cho thy 50% liu lng ny c bi tit ra ngoi trong 24 gi u v 25% liu lng cn li c bi tit trong 10 ngy tip theo. S chuyn ha thng qua con ng oxy ha; trong s oxy ha nhm methyl tri loi gm nhm, th v kh, cn s oxy ha nhm tert butyl th tri ngi. Th nghim trn ng vt cho thy, liu lng BHT cao khi a vo c th trong 40 ngy hoc hn s gy c cho cc c quan. T 3 Nhm 2 DHTP4 Page 12



Liu lng BHT cao cc loi vt c th nghim cng gy ra cc nh hung sau: - Lm tng s hp thu iod tuyn gip. - Tng trng lng ca tuyn trn thn. - Gim khi lng ca l lch, lm chm qu trnh vn chuyn cc acid hu c, gy tn thng thn. 1.2 Nguyn liu du thc vt 1.2.1 Tng quan Du n c tinh lc t ngun gc thc vt, nm th lng trong mi trng bnh thng. C kh nhiu loi du c xp vo loi du n c gm: du liu, du c, du nnh, du canola, du ht b ng, du bp, du ht hng dng, du cy rum, du lc, du ht nho, du vng, du argan v du cm go. Nhiu loi du n cng c dng nu n. Thut ng du thc vt c s dng trn nhn ca sn phm du n ch mt hn hp du trn li vi nhau gm du c, bp, du nnh v du hoa hng dng. Du thng c kh mi bng cch nhng vo hn hp hng liu thc phm chng hn nh tho mc ti, tiu, gng trong mt khong thi gian nht nh. Tuy nhin, phi tht cn thn khi tr du kh mi chng pht sinh Clostridium botulinum (mt loi vi khun sn sinh ra cht c c th gy ng c tiu ha). 1.2.2 c im - Du thc vt l loi du c chit xut, chng ct v tinh ch t thc vt. - L hn hp cc triglyxerit c chit xut t thn, ht hoc ci qu ca mt s loi cy c du nh da, hng dng, thu du... Du v cht bo chit xut t thc vt bao gm dng lng nh du canola, dng rn nh b, cacao.

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- Du v cht bo c hyr ha, bao gm hn hp cc triglyxerit c hyr ha nhit v p sut cao. Hyr lin kt vi triglyxerit lm tng phn t khi. Du v cht bo c hyr ha c tng thm kh nng chng oxy ha (i, thiu), hoc tng thm qunh nht hay nhit nng chy. - L cht cung cp nng lng nhiu nht (1g lipid cung cp 9Kcal) v d tr nng lng cho c th. - L dung mi ha tan cc vitamin: A, D, E, K v cc carotenoit trong thc phm cung cp cho c th. - Rt cn cho pht trin c th: tr tu v th lc (c bit l tr em). Theo khuyn ngh ca Vin Dinh dng Vit Nam (giai on 2005 2010) vi khu phn 2.300Kcal/ngi/ngy, cn 25g du, m/ngy. - Khng cha cholesterol. 1.2.3 Thnh phn Thnh phn dinh dng Lng cht bo va trong lng tiu th thc phm hng ngy l ch thng xuyn ca nhng tranh lun. Mt vi cht bo c yu cu phi c trong khu phn n, v cht bo (trong du n) rt cn thit cho nu n. C quan Qun l Dc phm & Thc phm Hoa K (FDA) khuyn co rng phi c 30% hoc t hn lng calori tiu th hng ngy nn t cht bo. Nhng nh dinh dng hc khc li n rng lng calori hng ngy ca 1 ngi m c ngun gc t cht bo khng nn vt qu 10%. Trong mi trng cc lnh, ch n c 2/3 cht bo th c chp nhn v nn nh vy, v l do sinh tn. Trong khi tiu th lng nh cht bo bo ha l rt cn thit th vic tiu th mt lng cht bo vt qu gii hn cho php c chng minh l nguyn nhn dn n bnh nhi mu c tim. Du n l mt loi thc phm cha cht bo bo ha cao gm du da, du c v du nhn c. Du vi lng cht bo bo ha thp hn v

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lng cht bo khng bo ha (hay khng bo ha n) cao hn th c xem nh li cho sc khe hn. Acid bo no Cung cp nng lng v to m d tr nng lng cho c th. Gip gan ch to cholesterol to thnh mui mt. Cc ni tit t v LDLC (cholesterol xu) nu n qu nhiu thc n cha acid bo no s sinh: mt cn bng chuyn ha to ra cc chng bo ph, cholesterol/mu cao. X m ng mch, cao huyt p Acid bo cha no - Acid bo 1 ni i cn gi l omega 9 hay acid oleic. Tng i tt cho sc khe, ngoi ra n cn c tc dng bo no chng bi thc cho ngi n (c trong cc loi du vng, lc, u nnh, hng dng v m ln) khi em chin s t ni i th mt cc tc dng trn. - Acid bo nhiu ni i c gi l cc acid bo thit yu cn cho c th hng ngy, gm c: Acid arachidonic v Acid linoleic c gi chung l omega-6. C tc dng tt cho tim mch. Nu thiu: tr em tng trng chm. Ngi trng thnh: suy gim chc nng sinh sn, gan nhim m, d mc bnh ngoi da. Acid arachidonic l tin cht ca DHA. Acid linoleic l tin cht ca EPA. Alpha linolenic acid (ALA), eicosapentoenoic acid (EPA) v docosahesaenoic acid (DHA) c gi chung l omega 3. ALA khi vo c th nh men delta 6 desaturase chuyn thnh EPA v DHA. - Cc loi du cha nhiu acid bo cha no, khi un nng trn 100oC, s b bin cht, cc vitamin E, A b ph hy, tt c cc dy ni i b ph v bin thnh acid bo no v cc cht c hi, l tc nhn gy ung th, i tho ng v cc bnh tim mch cho ngi n. - Cc acid bo no trong du, m khi un n nhit si (mi loi c 1 nhit si khc nhau) s b phn hy to thnh cc peroxid c hi (bc khi mu xanh), l tc nhn gy nhiu bnh nguy him cho ngi n v ngi chin (rn) thc n. T 3 Nhm 2 DHTP4 Page 15

Bo co thc hnh ph gia 1.2.4 Phn loi


Khi la chn du (nu) n, yu t quan trng cn xem xt l sc chu nng ca du v nn tm loi du ph hp cho tng mn n. - Du ph hp vi nhit nng cao (trn 280C/500F) gm:

Du canola. Du hnh. Du nhn qu m. Du cy rum c axit oleic cao hay du hoa hng dng. Du phng. Du nnh. Du ht nho.

- Du thch hp cho nhit nng trung bnh gm: 2 Du qu c ch. 3 Du hoa hng dng. 4 Du ht vng. - Du cha tinh lc nn hn ch s dng trong nhit di 105C/225F 1.1.5 Bo qun - D c tinh lc hay cha, tt c loi du u nhy cm vi hi nng, nh sng v phi ngoi kh xy. Du b i c mi kh chu v nm rt chua, tt nhin l gi tr dinh dng ca n khng cn na. hn ch qu trnh ny, mt lp kh tr, thng l nit s c bm vo cc bn cha du ngay lp tc sau khi sn xut. y c gi l ph b. Nhng tt hn c l tr du trong t lnh hay ni thong, mt. Du kh m c nhng khi nhit bnh thng, chng s sm tr v th lng. trnh tc T 3 Nhm 2 DHTP4 Page 16



dng xu ca hi nng v nh sang, ngi ta hay ly du ra khi ni cha ng lnh trong khong thi gian s dng ngay, khng lu hn. Du tinh lc c cht bo khng bo ha n cao c th gi c c nm (du liu c th trong vi nm), trong khi nhng loi du c cht bo khng bo ha a cao ch gi c trong 6 thng. Du liu th v cc th c th gi t nht 9 thng sau khi m np. Nhng loi du khng bo ha n c th gi tt ln ti 8 thng hn, du khng bo ha a cha tinh ch c th c phn na thi gian thi. 1.1.6 c tnh ca mt s loi du n Nghin cu cho thy nhng loi du c mu sng (tc l tinh lc nhiu) c im si cao hn. Mc d kt qu ca cuc nghin cu c th khc bit ty vo tng mu du khc nhau (thng hiu, thnh phn, qu trnh ch bin), nhng nhng d liu di y cng rt hu ch trong vic so snh c tnh ca cc loi du khc nhau. im si ch ra ri ro chy n. Khi s dng du nu n, khi thy du c du hiu si, nn vn nh la ngay lp tc. Ni chung, chng ta nn chun b k cng cc dng c cha chy khi nu n, t n gin nh ly np p vo ni hay t hn l dung bnh cha chy. Bo ha (%) 66 65 6 92 13 24 12 41 80 Khng bo Khng bo ha n (%) 30 32% 62 6 25 26 17 47 14 ha a (%) 4 3 32 2 62 50 71 12 16 im si (C) 150 190 250 242 177 236 216 204 138 201 150 Page 17

Du/cht bo B B sa tru lng, b lc Du canola Du da Du bp Du ht bong Du ht nho M ln/heo Macgarin, m T 3 Nhm 2 DHTP4

Bo co thc hnh ph gia Diacyglycerol (DAG) Du liu (cc th) Du liu (th) Du liu (tinh) Du liu (cc trong) Du c Du lc/du phng Du cm go Du rum Du vng (cha tinh) Du vng (bn tinh) Du u tng/du nnh Du hoa hng dng 3.5 14 14 14 14 52 18 20 10 14 14 15 11 37 73 73 73 73 38 49 47 13 43 43 24 20

GVHD: Th.S Nguyn Th Hong Yn 59 11 11 11 11 10 33 33 77 43 43 61 69 215 190 215 225 242 230 231 254 265 177 232 241 246

2

TIN HNH TH NGHIM - KT QU - BN LUN

2.1 Xc nh ch s acid 2.1.1 nh ngha Ch s acid l s mg KOH cn dng trung ha acid bo t do c trong 1g du hoc m. Ch s acid th hin cht lng ca lipid. Nu ch s acid tng th cht lng sn phm gim v ngc li, ch s acid cng thp th du cng tt v c bo qun tt. Di tc dng ca cc enzym thy phn (lipaza, photpholipaza) khi c nc v nhit, triglycerit s b phn ct mi lin kt este v b thy phn thnh acid bo t do. Cc acid khng no hoc c mch ngn (nh du da) d b thy phn hay oxi ha, phng thch cc acid bo t do c khi lng phn t nh d bay hi gy mi kh chu. T 3 Nhm 2 DHTP4 Page 18

Bo co thc hnh ph gia 2.1.2 Nguyn tc -


Di tc dng ca cc enzyme thy phn (lipase, phospholipase), khi c nc v nhit, triglyceride s b phn ct mi lin kt este v b thy phn thnh acid bo t do.

-

Trung ha lng axt bo t do c trong cht bo bng dung dch KOH phn ng xy ra: RCOOH + KOH RCOOK + H2O

2.1.3 S tin hnh th nghim

100ml cn

PP

Thm ch th

Mu du

Chun bng KOH 0.01N n hng

Cho vo mu du

Lc nh, un cch thy

KOH 0.01N

Chun bng KOH 0.01N n hng Ghi nhn V tiu tn

Tnh ton

Kt qu

T 3 Nhm 2 DHTP4

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Bo co thc hnh ph gia 2.1.4 Thuyt minh quy trnh un si


Trc khi mu c em i xc nh ch s axit th ta tin hnh un si mu du trong khong thi gian 30 pht. Mc ch ca qu trnh un si l cung cp nhit, to iu kin thun li cho cc enzyme thy phn (lipaza, photpholypaza) hot ng thy phn cc triglecerit thnh cc axit bo t do. ng thi di tc dng ca nhit v oxi khng kh s thc y qu trnh oxi ha cht bo to ra cc hp cht peroxit v cc axit bo t do Ta tin hnh un si 3 mu du vi mt mu khng b sung BHT v 2 mu c b sung BHT vi liu lng 0.1% v 0.2%. Vic b sung cc loi ph gia vi liu lng nh vy nhm mc ch so snh thy c hiu qu chng oxy ha ca loi ph gia c s dng. C ch chng oxy ha ca BHT c trnh by phn tng quan. Cho cn vo Cht bo l nhng cht khng ha tan trong nc nhng tan tt trong cc dung mi hu c, v vy trc khi tin hnh chun ta cho cn vo to dung mi ha tan cht bo, gip cho phn ng gia axit bo t do v KOH din ra nhanh v im cui d nhn thy hn, hn ch c sai s. Cn trc khi s dng cn phi iu chnh v mi trng trung tnh bng ch th PP trnh lm nh hng n kt qu thu c. Chun bng KOH Dung dch chun KOH y c s dng trung ha ht acid bo t do c trong mu th c ha tan trong dung mi cn trung tnh vi ch th phenolphthalein.

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im tng ng nhn c khi dung dch t mu vng (c trng cho tng loi du) chuyn sang mu hng nht v bn trong 30 giy. Phng trnh phn ng xy ra nh sau: RCOOH + KOH

RCOOK + H2O

Th tch KOH tiu tn s c ghi li, p dng cng thc v tnh ton c ch s axit ca mu s dng. 2.1.5 Kt qu th nghim

Mu M0 (mL) Ln 1 Ln 2 Trung bnh 8.8 8.5 8.65

Mu M1 (mL) 7.5 7.4 7.45

Mu M2 (mL) 5.6 5.4 5.5

Ch s acid c xc nh theo cng thc:

AV =

56.11 V N K m

Trong : 56.11: Phn t lng ca KOH (vC). V: Th tch dd KOH 0,01N tiu tn (mL). N: Nng ca dung dch KOH (= 0.01N).

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K: H s hiu chnh ca dung dch KOH 0.01N (K = 1). m: Khi lng mu du cn phn tch (g). - Kt qu tnh ton ch s axit:

Mu M0 Kt qu 0.56

Mu M1 0.48

Mu M2 0.35

+ Mu M0: Khng thm ph gia chng oxy ha BHT. + Mu M1: Thm 0.1% BHT vo mu du. + Mu M2: Thm 0.2% BHT vo mu du.

2.1.6 Nhn xt kt qu Ta thy mu trng (khng cho BHA) vo c ch s acid cao nht. Mu c nng BHA cng cao th ch s acid cng thp. Thng thng cc sn phm du m lu s c ch s acid cng cao. Trong cc nh my sn xut du thc vt ch s acid l mt trong cc ch s bt buc phi kim tra m bo cht lng ca sn phm lu thng trn th trng. Nhng iu cn lu khi tin hnh th nghim xc nh ch s acid (AV) - y l phng php chun acid baz nn cn s dng phi trung tnh theo ch th phenolphthalein. - Cn phi un nng tng qu trnh ha tan du. - Chn ch th phenolphthalein v ti im tng ng tn ti RCOOK c tnh kim v pT = 9. - Bnh tam gic phi c ra sch v sy kh. T 3 Nhm 2 DHTP4 Page 22



- Khi cn mu, nu b dnh mu trn thnh bnh th cho dung mi vo ch b dnh. - Qu trnh chun phi lc trn u, trnh bn mu ra ngoi bnh. Thi gian chun khng nn ko di. 2.2 Xc nh ch s Iod bng phng php Wijs 2.2.1 nh ngha -

Ch s iod ca du bo (IV) l s gam iod cn thit cng vo ni kp c cha trong 100g du bo di cc iu kin thao tc theo quy nh. Ch s iod c trng cho mc cha no ca lipid. Lipid cng nhiu ni i th ch s iod cng ln, cng t ni i ch s iod cng thp.

2.2.2 Nguyn tc xc nh Nhng dy ni khng bo ha ca cc acid bo khng no c kh nng gn iod hoc cc halogen khc, do ch s it xc nh tng qut cc acid bo khng no trog cht 10ml du 5ml cloroform 15 ml Wijs bo. R1-CH=CH-R2-COOH + ICl R1-CHI-CHCl-R2-COOH Lc mnh, trong 2 KCl + Ibng ti 45 ICld + KI ph 2NaI + Na2S4O6 I2 + 2Na2S2O3 Cho vo v lc 2.2.3 S quy trnh tin hnh th nghim 10ml KI 10% mnh 30 ml H2O

3 git HTB

Chun bng Na2S2O3 0.01N Ghi nhn V tiu tn

Tnh kt qu T 3 Nhm 2 DHTP4 Kt qu Page 23



2.2.4 Thuyt minh quy trnh un si Mu trc khi em i xc nh cng c tin hnh un si tng t nh trong bi xc nh ch s axit. Mc ch ca giai on ny c trnh by phn trn. B sung cloroform v thuc th Wijs Cloroform l dung mi hu c c kh nng ha tan tt, c cho thm vo ha tan cht bo c trong mu. Trong thnh phn ca thuc th Wijs c hp cht ICl, c cho thm vo cng hp vo cc ni i trong cc phn t bo c ha tan trong cloroform. Lng thuc th Wijs cho vo d s tc dng vi KI gii phng ra iot di dng t do v c nh phn bng dung dch chun Na2S2O3 vi ch th h tinh bt. Thuc th s dng phi d gn bng mt na so vi lng s dng kt qu c c trong php chun c tnh chnh xc cao. Ch l lng KI s dng cng phi d v trong phn ng ny KI va l cht phn ng va l mi trng ha tan

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I2 sinh ra. Nu lng KI dng khng th I2 sinh ra khng c ha tan, n l cht khng bn nn ngay lp tc s b thng hoa nhit thng, gy sai s ln. im tng ng nhn c khi dung dch chuyn t mu tm en sang khng mu. Phng trnh phn ng xy ra: R1-CH=CH-R2-COOH + I R1-CH-CH-R2-COOH I Lc mnh, trong bng ti Lc mnh, trong bng ti 1h to iu kin v c thi gian thuc th tip xc vi cc ni i trong cht bo. Phn ng phi c tin hnh trong iu kin khng c nh sng v trong hp cht ICl, iodua th hin tnh kh, n rt d b oxy khng kh oxy ha v dng I2 theo phn ng 4I- + O2 + 4H+ 2I2 + 2H2O Phn ng ny s c y mnh khi c s hin din ca nh sng. V vy cn phi thc hin phn ng trong bng ti. B sung KI v nc Sau khi thuc th cng hp vo cc ni i th ta s b sung KI vo KI tc dng vi lng thuc th d Phng trnh phn ng ICld + KI KCl + I2 Chun bng Na2S2O3 I2 t do trn s c xc nh thng qua vic ghi nhn li th tch Na2S2O3 tiu tn. Thng s dng Na2S2O3 0.1N chun nhng gim sai s th trong bi th nghim s dng Na2S2O3 0.002N chun. I2 + 2 Na2S2O3

Cl

2NaI

+ Na2S4O6

V mt s nguyn nhn gii thch trn nn trong phng php ny ta cn ch mt s iu sau: + Tin hnh ch ti, trnh nh sng mt tri.

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+ thuc th tip xc vi cht bo trong thi gian cn thit. + Thuc th cn phi tha, lng tha cn phi gn bng na lng cho vo. 2.2.5 Kt qu th nghim Mu M0 (mL) Ln 1 Ln 2 Trung bnh 10.8 10.6 10.7 Mu M1 (mL) 11.2 11.5 11.35 Mu M2 (mL) 12.0 11.9 11.95

Ch s Iod c xc nh theo cng thc:

IV =

0.01269 ( V1 V2 ) N 100 mTrong : 0.01269: S gam Iod ng vi 1mL N2S2O3 0.1N. V1: Th tch N2S2O3 0.01N cho mu trng (mL). V2: Th tch N2S2O3 N2S2O3 0.01N (mL) cho mu th. N: Nng chnh xc ca dung dch KOH (= 0.1N). m: Khi lng mu th (g). - Kt qu tnh ton ch s Iod: Mu M1 Ch s Iod 0.094 Mu M2 0.181

+ Mu M0: Khng thm ph gia chng oxy ha BHT. + Mu M1: Thm 0.1% BHT vo mu du.

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+ Mu M2: Thm 0.2% BHT vo mu du. 2.2.6 Nhn xt kt qu i vi 3 mu du, khi tin hnh th nghim ta nhn thy rng mu 0.02% BHT c th tch Na2S2O3 tiu tn l cao nht, bi v I2 gii phng nhiu nht hay Iod cng vo ni kp l t nht (tng ng vi ch s iod l thp nht). Nhng iu cn lu khi xc nh ch s Iod - Tin hnh ch ti, trnh nh sng mt tri. - thuc th tip xc vi cht bo trong thi gian cn thit. - Thuc th cn phi tha, lng tha cn phi gn bng na lng cho vo. - Mu th phi c cn chnh xc n 0,0001g. Khi lng mu th ca cc ln th khng c chnh lch nhiu trnh sai s. - Cht bo c ha tan trong dung mi (CCl4 : CH3COOH) mu phi khng cha nc, cho tip xc vi thuc th Wijs trong ti. Phn thuc th tha phn ng vi KI 10% gii phng ra Iod t do. nh lng Iod t do bng dung dch Na2S2O3 0.1N vi ch th h tinh bt. - Mu phi chun trong vng 3 pht th kt thc, sau thi gian s phn tch b sai. - Qu trnh chun phi lc mnh, phi chun nhanh. Cho ch th h tinh bt 1% vo chun tip bng Na2S2O3 0,1N n khi dung dch gn mt mu xanh en, lc mnh, chun tng git mt lc mnh. Cho n khi dung dch mt mu xanh en. 2.3 Xc nh ch s peroxyt 2.3.1 nh ngha Ch s peroxyt (PoV) l lng cht c trong mu th c tnh bng mili ng lng oxi hot tnh lm oxi ha KI trn 1kg mu di cc iu kin thao tc theo quy nh T 3 Nhm 2 DHTP4 Page 27

Bo co thc hnh ph gia -


Ch s ny phn nh s i ha ca du m

2.3.2 Nguyn tc Da vo tc dng ca peroxyt vi dung dch KI to ra I 2 t do (trong mi trng acid acetic v cloroform). Sau chun I2 t do bng dung dch chun Na2S2O3 vi ch th h tinh bt. im tng ng nhn c khi dung dch chuyn t mu tm en sang khng mu. Phng trnh phn ngR 1 CH CH R 2 O O + 2KI + 2CH3 COOH R 1 CH CH R 2 O + 2CH3COOK + H 2 O + I2

10ml du 10ml CH3COOH I2 + 2Na2S2O3 2NaI + Na2S4O6 1ml KI bo ha 2.3.3 S quy trnh tin hnh th nghim Cho vo v lc mnh ph

5ml cloroform

trong ti 5ph

3 git HTB

Cho vo hn hp

30 ml H2O

Chun bng Na2S2O3 0.01N Ghi nhn V tiu tn

Tnh kt qu T 3 Nhm 2 DHTP4 Kt qu Page 28



2.3.4 Thuyt minh quy trnh un si Mc ch ca cng on ny c trnh by phn trn. Cn v erlen nt nhm Phn ng cn phi thc hin trong erlen nt nhm to mi trng kn, gim s bay hi ca iot trong qu trnh thc hin, hn ch sai s. Ha tan B sung thm CH3Cl to mi trng ha tan hon ton cht bo c trong mu. B sung CH3COOH : mc ch l to pH mi trng trong khong 4 6. Phn ng gia KI v peroxyt cn phi tin hnh trong mi trng pH = 4 6 v trong mi trng axit mnh th d sinh ra phn ng oxi ha vi oxy khng kh, do s gy sai s tng i ln. 4I- + O2 + 4H+ 2I2 + 2H2O Trong mi trng kim th I2 s b kh thnh iodua, cng gy sai s khi chun . I2 + OH- IO- + I- + H2O KI c cho thm vo phn ng vi peroxit gii phng ra I2 di dng t do R1-CH-CH-R2 R1-CH-CH-R2 O O + 2KI + 2CH3COOH O + 2CH3COOK + H2O + I2 y bnh, lc mnh Lc mnh nhm ha tan ht cht bo v to iu kin cho phn ng xy ra nhanh hn. Phn ng ny cng cn c thi gian v phi thc hin trong iu kin khng c nh sng. Nguyn nhn gii thch tng t nh bi xc nh ch s Iod. B sung h tinh bt v chun vi Na2S2O3 n mt mu H tinh bt c cho thm vo vi vai tr l cht ch th nhn bit c im tng ng trong php chun gia I2 sinh ra trn vi Na2S2O3. im tng ng nhn c khi mu xanh ca h tinh bt v I2 khng cn na I2 + 2 Na2S2O3 2NaI + Na2S4O6 T 3 Nhm 2 DHTP4 Page 29



Sau khi cho h tinh bt vo cn phi tin hnh chun ngay v iot hp th mnh ln b mt h tinh bt, nu thi gian lu th iot s chui su vo bn trong cu trc ca h tinh bt, do s gy sai s ln. 2.3.5 Kt qu th nghim

Mu M0 (mL) Ln 1 Ln 2 Trung bnh 12.6 12.4 12.5

Mu M1 (mL) 11.8 11.5 11.65

Mu M2 (mL) 8.2 8.4 8.3

Ch s Peroxyt c tnh theo cng thc sau:

P0 V =

(V1 V2 ) N 1000 (meq/kg) mTrong : N Nng chnh xc dd Na2S2O3 (= 0.01N). V2 Th tch Na2S2O3 0.01N cho mu th (mL). V1 Th tch Na2S2O3 0.01N cho mu trng (= 0mL) M Khi lng mu du cn phn tch (= 4.37g).

- Kt qu tnh ton ch s Peroxyt: Mu M1 Ch s Peroxyt 1.95 Mu M2 9.61

2.3.6 Nhn xt kt qu T 3 Nhm 2 DHTP4 Page 30



Ch s peroxyt mu khng c ph gia chng oxy ha l cao nht. Mu c hm lng ph gia 0.02% c ch s thp hn so vi mu c hm lng 0.01%. Mt s nguyn nhn gy sai s c th xy ra: + Ha cht s dng b hng, c bit l vic s dng v bo qun KI. V tuy c ng trong chai nu c nt nhng KI vn b tc ng bi oxi trong khng kh lm cho dung dch KI c mu vng l do: KI + O2 kk I3- + S2O32 I3-(vng) S4O62-+ I-

+ Chnh lng I3- sinh ra phn ng vi S2O32- dn n kt qu sai.V vy trc khi tin hnh ht dung dch KI ta phi kim tra li xem c b vng khng. Nu dung dch b vng nht, ta tin hnh chun li bng cch nh tng git Na2S2O3 n khi mt mu. Nu b vng m ta b dung dch ny v thay dung dch KI khc v phi pha mi lin tc. + Thao tc thc hin cha chun xc. + Khng ng nht gia cc mu tin hnh th nghim (iu kin nh sng, nhit , ng np hay m np trong qu trnh i phn ng xy rac th lm tht thot lng I2 bay ra.) + Mu th nng dn n PV tng + Bnh tam gic nt nhm ra cha sch, d ch cn mt vi vt x phng st li sau khi sy cng lm PV tng hay bin i PV. V vy ta phi chn bnh tht sch. 3 TR LI CU HI

Cu 1. Trnh by ngha ca ch s peroxyt, acid, iod ca du thc vt? - Ch s peroxyt: L s gram Iode c gii phng bi peroxyt c trong 100 gram cht bo. Ch s ny phn nh s i ha ca du m. T 3 Nhm 2 DHTP4 Page 31



Ch s cng gn 1 th cng d b oxi ha. Ch s 75%), lecithin c thm vo l "chng bn tung te" khi chin . l s chp thun ca Thc phm v Dc Hoa K cho ngi tiu dng vi trng thi thng c cng nhn nh an ton. Lecithin c EU tha nhn nh l mt ph gia thc phm, c ch nh bi s E322. C nghin cu cho thy lecithin c ngun gc t u nnh c tc dng ng k vo vic gim cholesterol v cht bo trung tnh, trong khi tng HDL (cholesterol tt) cp trong mu. Tuy nhin, cc nghin cu v lecithin u nnh khng ph hp v mu thun nhau t nhng nm 1920. 1.3.4 C ch tc dng C ch c th ca lecithine xy ra trong h nh tng nh sau. Phn ng ha hc to cc cht mong mun s xy ra khi ta a lecithine vo cc h nh tng ny lm bn h nh tng.

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C 2 cch cc phn t cht phn ng gp nhau: Cch th nht: Cc phn t phn ng ca lecithine thm qua lp mng cht hot ha b mt ra ngoi v gp nhau. Nhng thc t th phn ng theo cch ny l rt nh, khng ng k. Cch th hai: Khi cc ht vi nh tng ca lecithin v phospholipid ca du gp nhau, nu c lc tc ng th 2 ht nh c th to thnh mt ht ln hn. Cc cht phn ng trong 2 ht nh s ha trn, phn ng xy ra trong lng ht ln v sn phm mong mun c to thnh Khi cc phn t lecthine v phospholipid ca du gp nhau s to nn sc cng b mt. Khi 2 cht lng khng tan trn ln vi nhau th gia b mt phn pha ca 2 cht lng ny s xut hin cc ng sut do sc cng b mt to nn. Nng lng b mt l i lng t l thun vi sc cng b mt v din tch phn pha. n nh h nh tng ngi ta cn cho cc cht hot ng b mt nh lecithine. Cc cht ny lm gim sc cng b mt ca nc, gp phn gim nng lng b mt. Do lm bn h nh tng. 1.4 1.4.1 Lauryl sunfate c im

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Cu trc khng gian ca Lauryl Sunfate. Lauryl sulfate l mt cht ty ra v cht hot ng b mt c tm thy trong nhiu sn phm chm sc c nhn ( x phng, du gi u, kem nh rng,) Lauryl sulfate l cht to bt rt hiu qu. Cng thc ha hc ca n l CH3(CH2)10CH2(OCH2CH2)nOSO3-. i khi s i din n c quy nh trong tn, v d lauryl-2 sulfate. Cc sn phm thng mi khng ng nht trong s cc nhm ethoxyl, trong s n l trung bnh, n c ph bin cho cc sn phm thng mi l n = 3. 1.4.2 Ngun gc Lauryl sulfate c iu ch bi ethoxylation ca ru dodecyl. Kt qu cc ethoxylate c chuyn thnh mt este ca axt sulfuric. Lauryl sulfate natri (cn gi l sodium dodecyl sulfate hay SLS) c sn xut tng t, nhng khng c ethoxylation SLS v lauryl sulfate ammonium (ALS) thng c s dng thay th trong cc sn phm tiu dng. Laurylsulfate l cht hot ng b mt c s dng trong nhiu sn phm m phm lm sch kem. N tng t nh x phng. 1.4.3 c cht

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Lauryl sulfate l mt kch thch tng t vi cc cht ty ra, vi cc kch thch tng nng . Lauryl sulfate gy kch ng da ng vt th nghim v trong mt s th nghim trn con ngi. Lauryl sulfate l mt cht kch thch c bit n c lin quan n b mt, v nghin cu cho thy rng laureth sulfate cng c th gy kch ng sau khi tip xc rng mt s ngi. Nghin cu ca OSHA, NTP, v IARC h tr cc kt lun ca cc m phm, Toiletry, v Hip hi Fragrance (CTFA) v Hip hi Ung th M rng SLES khng phi l mt cht gy ung th. Cc C quan Bo v Mi Trng Hoa K phn loi c cht hc 1,4 - dioxane c th l cht gy ung th (c quan st thy s gia tng ca bnh ung th trong cc nghin cu ng vt kim sot, nhng khng phi trong cc nghin cu dch t hc ca ngi bng cch s dng cc hp cht), v c bit n l mt cht kch thch (khng c tc dng mc 400 mg/m3) nng cao hn ng k so vi sn phm thng mi. Theo D Lut 65 ca tiu bang California, 1,4dioxane c phn loi l cht gy ung th. c cht: Dioxane 1,4: cht gy nhim Mt s sn phm c cha SLES c tm thy c cha cc cc cht gy ung th mc thp c bit n dioxane-1,4, cc Cc Qun l dc v thc phm Hoa K ang theo di cc cp ny. FDA khuyn khch cc nh sn xut loi b 1,4 dioxane, mc d n khng phi l yu cu ca lut lin bang. 1.4.4 C ch tc dng Cht hot ng b mt lm gim sc cng b mt ca nc. Cc phn t lauryl sulfate hp ph ln b mt pha lng to thnh mt cht hp ph hydrat ha rt mnh v hnh thnh mt p sut, to cho cc ht du bn vng rt ln, cn tr s kt dnh chng li vi nhau. Lauryl sulfate c cc nhm c cc nh cc hp cht sulfonat hoc etoxysulfat c gn vo cc chui hyrocacbon. Cc nhm tng hp ny mang in m, chng ch lin kt yu vi cc ion (ca st, magi, canxi) trong nc v nh kh nng ca n vn rt tt. 1.5 Nguyn liu th nghim Page 50

T 3 Nhm 2 DHTP4

Bo co thc hnh ph gia 1.5.1


Du thc vt C ngun gc thc vt, nm th lng trong mi trng bnh thng. C kh

nhiu loi du c xp vo loi du n c gm: du liu, du c, du nnh, du canola, du ht b ng, du bp, du ht hng dng, du cy rum, du lc, du ht nho, du vng, du argan v du cm go. Nhiu loi du cng c dng nu n. Lng cht bo va trong lng tiu th thc phm hng ngy l ch thng xuyn ca nhng tranh lun. Mt vi cht bo c yu cu phi c trong khu phn n, v cht bo (trong du n) rt cn thit cho nu n. C quan Qun l Dc phm & Thc phm Hoa K (FDA) khuyn co rng phi c 30% hoc t hn lng calori tiu th hng ngy nn t cht bo. Nhng nh dinh dng hc khc li n rng lng calori hng ngy ca 1 ngi m c ngun gc t cht bo khng nn vt qu 10%. Trong mi trng cc lnh, ch n c 2/3 cht bo th c chp nhn v nn nh vy, v l do sinh tn. Trong khi tiu th lng nh cht bo bo ha l rt cn thit th vic tiu th mt lng cht bo vt qu gii hn cho php c chng minh l nguyn nhn dn n bnh nhi mu c tim. Du n l mt loi thc phm cha cht bo bo ha cao gm du da, du c v du nhn c. Du un nng s lm thay i c tnh ca n. Mt vi loi du rt tt cho sc khe nhit bnh thng nhng s tr nn khng tt khi un nng ti mt nhit no . Khi la chn du, yu t quan trng cn xem xt l sc chu nng ca du, v nn tm loi du ph hp cho tng mn n. Du ph hp vi nhit nng cao (trn 280C/500F). D c tinh lc hay cha, tt c loi du u nhy cm vi hi nng, nh sng v phi ngoi kh xy. Du b i c mi kh chu v nm rt chua, tt nhin l gi tr dinh dng ca n khng cn na. hn ch qu trnh ny, mt lp kh tr, thng l nit s c bm vo cc bn cha du ngay lp tc sau khi sn xut. 1.5.2 Nc Nc l mt hp cht ha hc ca xy v hir, c cng thc ha hc l H2O.

Vi cc tnh cht l ha c bit (v d nh tnh lng cc, lin kt hir v tnh bt thng ca khi lng ring) nc l mt cht rt quan trng trong nhiu ngnh khoa hc v trong i sng. 70% din tch ca Tri t c nc che ph nhng ch 0,3% T 3 Nhm 2 DHTP4 Page 51



tng lng nc trn Tri t nm trong cc ngun c th khai thc dng lm nc ung. Bn cnh nc "thng thng" cn c nc nng v nc siu nng. cc loi nc ny, cc nguyn t hidro bnh thng c thay th bi cc ng v teri v triti. Nc nng c tnh cht vt l (im nng chy cao hn, nhit si cao hn, khi lng ring cao hn) v ha hc khc vi nc thng. Nc l mt dung mi tt nh vo tnh lng cc. Cc hp cht phn cc hoc c tnh ion nh axt, ru v mui u d tan trong nc. Tnh ha tan ca nc ng vai tr rt quan trng trong sinh hc v nhiu phn ng ha sinh ch xy ra trong dung dch nc. Nc tinh khit khng dn in. Mc d vy, do c tnh ha tan tt, nc hay c tp cht pha ln, thng l cc mui, to ra cc ion t do trong dung dch nc cho php dng in chy qua V mt ha hc, nc l mt cht lng tnh, c th phn ng nh mt axit hay baz. 7 pH (trung tnh) hm lng cc ion hydroxyt (OH-) cn bng vi hm lng ca hydronium (H3O+). Khi phn ng vi mt axit mnh hn th d nh HCl, nc phn ng nh mt cht kim: HCl + H2O H3O+ + ClVi ammoniac nc li phn ng nh mt axit: NH3 + H2O NH4+ + OH2. Qui trnh tin hnh th nghim 2.1 Qui trnh chung

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2.2 2.2.1

Thuyt minh qui trnh Th nghim 1: Kho st h du/nc Chun b 3 mu: M0, M1, M2 cha 45 mL nc. Cho ph gia vo 3 mu theo bng sau M0 Khng ph gia Khuy 5 pht M1 0.1 % Lecithine M2 0.1 % Lauryl sunfate

Cho 5 mL du vo ln lt 3 mu o thi gian t lc ngng khuy n khi tch lp v o chiu cao tng lp.

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2.2.2

Th nghim 2: Kho st h nc/du Chun b 3 mu: M0, M1, M2 cha 45 mL du. Cho ph gia vo 3 mu theo bng sau M0 Khng ph gia Khuy 5 pht M1 0.1 % Lecithine M2 0.1 % Lauryl sunfate

Cho 5 mL nc vo ln lt 3 mu o thi gian t lc ngng khuy n khi tch lp v o chiu cao tng lp.

3. Kt qu - bn lun 3.1 Kt qu Page 54

T 3 Nhm 2 DHTP4

Bo co thc hnh ph gia 3.1.1 Th nghim 1: H du/nc Thi gian Ln 1 2 3 1 2 3 1 2 3 tch lp (s) 6 5 5 11 13 11 19 20 21 Chiu cao lp nc (cm) 2,6 2,7 2,6 2,4 2,5 2,5 2,6 2,4 2,4


Chiu cao lp du (cm) 0,4 0,3 0,4 0,6 0,5 0,5 0,3 0,3 0,4

Chiu cao lp bt (cm) Khng c bt Khng c bt Khng c bt C t bt C t bt C t bt 0,2 0,3 0,2

M0 M1 M2

3.1.2

Th nghim 2: H nc/du Thi gian Ln 1 M0 2 3 1 M1 2 3 1 M2 2 3 Bn lun tch lp (m-s) 02-00 01-47 01-50 15-20 16-38 17-54 17-45 23-10 20-06 Chiu cao lp nc (cm) 0,4 0,5 0,5 0,7 0,7 0,6 0,4 0,2 0,2 Chiu cao lp du (cm) 3,3 3,4 3,5 3,0 3,0 2,9 3,0 3,2 3,2 Chiu cao lp bt (cm) Khng c bt Khng c bt Khng c bt Khng c bt Khng c bt Khng c bt 0,9 0,9 0,8

3.2 3.2.1

Th nghim 1: H du/nc Gi s thi gian tch lp trong cc ln lp th nghim ca cc mu khng c s

khc bit, ta c thi gian tch lp trung bnh ca cc mu nh sau: Mu M0 M1 M2 T 3 Nhm 2 DHTP4 Thi gian tch lp trung bnh (s) 5,3 11,6 20 Page 55



Nh vy ta thy thi gian tch lp ca mu 2 (s dng lauryl sunfate 0.1 %) l cao nht. iu ny c th thy trong h nh tng du/ nc, lauryl sunfate l cht to nh tt hn lecithine vi cng nng s dng. iu ny c th c gii thch nh sau: Lauryl sunfate l mt cht hot ng b mt dng anion, c tnh phn cc mnh nn c kh nng ha tan trong nc cao nn trong h du trong nc vi pha lin tc l nc Lauryl Sulfate ng vai tr l mt cht nh ha tt. Bn cnh Lauryl Sunfate l mt cht c kh nng to bt nn trong qu trnh th nghim chng ta thy c mt lp bt trng xa ni dnh trn b mt dung dch. 3.2.2 Th nghim 2: H nc/du Gi s thi gian tch lp trong cc ln lp th nghim ca cc mu khng c s khc bit, ta c thi gian tch lp trung bnh ca cc mu nh sau: Mu M0 M1 M2 Thi gian tch lp trung bnh (m-s) 01-52 16-37 20-20

Trong h nc/du th thi gian tch lp ca Lauryl sunfate vn cao hn ca Lecithine cng nng s dng. Tuy nhin theo l thuyt th i vi h nc nc/du Lecithine s n nh h nh tng tt hn nhng kt qu thc hin trn th ngc li. Cho nn c l c sai st trong qu trnh th nghim. V lp trong du qu t v do tnh cht nc nng hn nn chm xung y v cng mu vi y pecker, kh o chnh xc thi gian tch lp. 4. Tr li cu hi Cu 1: Nu cc bc hnh thnh h nh tng thc phm, phn loi h nh tng - Cc bc hnh thnh h nh tng thc phm: c s hnh thnh cc git cu c kch thc kh nh ca cht b phn tn trong mt phn kh ln v th tch ca pha lin tc, hin tng ny sy ra do cc gc u bo s co cm vo bn trong l cc T 3 Nhm 2 DHTP4 Page 56



gc u nc bn ngoi (hay ngc li) lm 2 pha khng ha tan trong nhau v c s tch pha hnh thnh nn h nh tng. Vic hnh thnh h nh tng i i vi vic to nn mt b mt lin pha quan trng gia 2 cht lng khng trn ln vo nhau c. B mt chia pha ny s tng theo lut s m khi ng knh ca cc git gim. - Phn loi h nh tng: C rt nhiu h nh tng khc nhau. Trong thc phm, phn loi theo pha phn tn, chng ta thng gp 3 dng: H du trong nc: l h m trong cc git du phn tn trong pha lin tc tc l nc. V d: sa, mayonnaises, kem sa, bnh pht kem(hnh a) H nc trong du: l h m tong cc git nc phn tn trong pha lin tc l du. V d: b, margarine, st dng vi salad,(hnh b) H nc trong du trong nc: h nh tng du trong nc m cc git phn tn ca n c cha nc. y l h kh phc tp trong thc phm v cn nhng nghin cu su hn v h ny. Cu 2: Trnh by c ch hot ng ca ph gia lm bn h nh tng Cht to nh l cht gm 2 gc a nc v k nc, phn k nc s tng tc vi cc cht bo to ra lin kt cu bo v chng li s hp git. Cht lm b nh tng phi c b mt lin pha bn c kh nng chng li mt cch c hc s hp git, phi mt sc cng b mt lin pha ln. 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 ny trong pha lng kia lm tng b mt tip xc, 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 nn 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. 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 hon ton ring l: T 3 Nhm 2 DHTP4 Page 57



- 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 vo nc nh hn lc tng tc gia cc phn t cht lng vi cc phn t nc th khi cho mt lng nh cht lng vo nc, cht lng s lan ra trn b mt thnh mt mng n phn t. Khi cht lng l cht hot ng b mt th nhm phn cc s hng vo nc, cn nhm khng phn cc hng ra khng kh.

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Chn cht nh tng thng gm 2 cht: mt cht rt ho nc v mt cht rt ho du, v tm 2 t l ph hp phi trn s c tc dng lm bn nh tng tt hn nu dng tng cht mt. Cu 3: Trnh by tnh cht v c ch hot ng ca ph gia s dng trong bi Ph gia lecithine c s dng trong bi c 2 u a nc v k nc. u a du s b bao trm bi cc cu bo v u a nc s b bao trm bi cc cu nc gn kt chng li vi nhau tr thnh nh tng. Cu 4: Trnh by tc hi c th xy ra khi s dng sai nhng ph gia trong bi th nghim? Khng t c mc ch ca th nghim. H nh tng to ra khng t yu cu. nh hng n mu sc lm gim gi tr cm quan. Thi gian lm th nghim c th lu. C th s dng loi ph gia c hi vi c th. i vi lauryl sunfate l mt cht gy ung th, kch ng da, lot Aphthous th cng phi cn trng. Cu 5: Nu phng php xc nh lecithine Lecithin l mt phospholipide quan trng. Ngi ta xc nh lecithin bng phn ng v nhng enzyme sau: Phospholipase C: Lecithin + H2O 1-2diglyceride + phosphorylcholine. Alkaline-phosphatase Phosphorylcholine + H2O choline + Pi. Choline kinase:

Choline ATP phosphoryicholine + ADP. Cu 6: K tn vi h nh tng thng gp v ph gia s dng? Nc tng s dng: Gum Xanthan, natri benzoat, caramel. Sa chua s dng: carrageenan, alginet, gelatine. Kem s dng: monoglycerid, polysacchride. Page 59

T 3 Nhm 2 DHTP4

Bo co thc hnh ph gia Chocolate s dng: lecithine, caramel.


Cu 7, 8 : Nu gi tr INS, ADI, ML ca lecithin, lauryl sulphate, mono - &diglycerid ca axid bo? K tn nhng thc phm thng s dng lecithin, lauryl sulphate, mono - &di-glycerid ca axid bo v liu lng c php s dng? INS (international numbering system) l k hiu c u ban Codex v thc phm xc nh cho mi cht ph gia khi xp chng vo danh mc cht ph gia thc phm. ADI (acceptable Daily Intake) l lng xc nh ca mi cht ph gia thc phm c c th n vo hng ngy thng qua thc phm hoc nc ung m khng gy nh hng c hi n sc kho. ADI c tnh theo mg/kg trng lng c th/ngy. ADI c th c biu hin di dng: gi tr xc nh, cha quy nh (CQ) v cha xc nh (CX). ML (MaximumLevel) mc gii hn ti a ca mi cht ph gia s dng trong qu trnh sn xut, ch bin, x l, bo qun, bao gi v vn chuyn sn phm. Lecithin STT 1 2 3 4 5 6 7 8 Tn ting Vit: lecithin Tn ting Anh: lecithins INS: 322 ADI: CX Chc nng: chng oxi hoa, nhu hoa, n inh Nhom thc phm Sa bt, bt kem (nguyn cht) Sa ln men (nguyn kem), khng x ly nhit sau ln men Sa ln men (nguyn kem), co x ly nhit sau ln men Kem thanh trung, x ly nhit cao (UHT), kem tach beo Thit, thit gia cm va thit thu ti dang xay nho Thuy san ti, k ca nhuyn th, giap xac, da gai ti Thuy san, san phm thuy san ng lanh, k ca nhuyn th, giap xac, da gai Thuy san, san phm thuy san hun khoi,sy kh, ln men hoc ML GMP GMP GMP 5000 GMP GMP GMP GMP Page 60

T 3 Nhm 2 DHTP4



9 10 11 12 13

p mui, k ca nhuyn th, giap xac, da gai Mui Du trn, gia vi ( bao gm cac cht tng t mui) Thc n cho tre em di 1 tui Thc n b sung cho tre ang tng trng Ca ph, che, nc ung co dc thao va cac loai ung t ngu cc, khng k nc ung t cacao Mono va diglycerit cua axit beo Tn ting Vit: mono va diglycerit cua axit beo Tn ting Anh: Mono-and-Di-glycerides of Fatty Acids INS: 471 ADI: CX Chc nng:lam day, nhu hoa, n inh, cht n, chng tao bot

GMP GMP GMP 3000 5000

STT 1 2 3 4 5 6 7 8 9 10 11 12

Nhom thc phm Sa va sa b San phm sa ln men va sa co cht rennet (nguyn cht) khng k ung t sa Sa bt, bt kem (nguyn cht) M va du thc vt M ln, m ng vt, du ca va du ng vt khac Thit, thit gia cm va thit thu ti dang xay nho Thuy san va san phm thuy san, k ca nhuyn th, giap xac, da gai a qua ch bin Mui Thc n cho tre em di 1 tui Thc n b sung cho tre ang tng trng Ca ph, che, nc ung co dc thao va cac loai ung t ngu cc, khng k nc ung t cacao Ru vang

ML 2000 100 2500 20000 100000 GMP 5000 5000 5000 15000 GMP 18

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Bi 3: PH GIA NG C1.Tng quan v ph gia 1.1Khi nim Ph gia lm ng c, lm dy l nhng cht c cho vo thc phm nhm lm ng, to keo, lm kt dnh tng khi lng ln, to cu trc, tng dy ca thc phm. Cc cht lm c v to ng rt hu ch v lm cho thc phm c cht lng cao hn. Chng c c tnh nh n nh sn phm, p ng yu cu ca ngi tiu dung. Ngy nay, cc sn phm b sung ph gia loi ny ngy cng ph bin, a dng. 1.2 Gii thiu mt s loi ph gia s dng trong th nghim 1.2.1 Triphosphate pentasodium Sodium triphosphate (STP, i khi STPP hoc natri tripoly hoc TPP) l mt hp cht v c vi cng thc Na5P3O10. y l mui sodium polyphosphate pentaanion, l c s lin hp ca axit triphosphoric.Triphosphate pentasodium c sn xut bng cch nung nng mt hn hp stoichiometric disodium phosphate, Na2HPO4, v bt phosphate, NaH2PO4, trong iu kin kim sot cht ch. 2 Na2HPO4+ NaH2PO4 Na5P3O10+ 2 H2O TPP l mt mui khng mu, m tn ti c dng khan v l hexahydrate. TPP l mt cht bo qun hi sn, tht, gia cm v thc n chn nui. N c ph bin vi s k hiu E451. Trong thc phm, STPP c s dng duy tr m. 1.2.2 Pectin 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 dng l pectin ha tan v protopectin khng ha tan. Di 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% T 3 Nhm 2 DHTP4 Page 62



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.

Hp cht pectin c c trng bi 2 ch s quan trng l ch s methoxyl MI biu 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.

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- 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.

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 cng 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. Ngoi ra, trong phn t pectin c mang in tch m nn chng c kh nng y ln nhau c kh nng lm gin mch v lm tng nht ca dung dch. Khi lm gim tch in v hydrat ha s lm cho si pectin xch li gn nhau v tng tc vi T 3 Nhm 2 DHTP4 Page 64



nhau to nn mt mng li ba chiu rn cha pha lng bn trong. 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. 1.2.3 Aga c chit t to , ho tan trong nc nng v c tnh chu nhit cao. Bng cch lm lnh c th to thnh gel chuyn ho nhit. Liu dng : khng quy dnh tu thuc vo yu cu ca thc phm dng lm cht to gel v n nh trong cng nghip sn xut trng ming, sa ng, sa scola, nc chm si bt, mn n nh bp, kem, bnh ko .v.v. Liu dng : khng quy dnh tu thuc vo yu cu ca thc phm Cht chit t thn cy. To gel rt bn, cu trc gel cng, dn, trong. Kh nng to gel ph thuc vo nhit , ban u agar pha lin tc v nc pha phn tn. Khi a nhit ln cao ln hn 90oC, agar tr thnh pha phn tn v nc l pha lin tc do lc ny hnh thnh dng dung dch bao gm nhng tiu phn mixen, gia mixen l phn t agar. Khi h nhit xung 35oC cc ht mixen c bao bc xung quanh mt lp nc lin kt li to thnh gel dn n s phn b li din tch trn b mt ca nhng ht mixen. Kh nng hnh thnh gel thun nghch nhit l c im duy nht lm cho agar c mt s kt hp cn thit trong nhiu ng dng. Khi to gel, cc cu ni hydro lm tng tnh bn vng ca cu trc mch agar, chng li mt cch mnh lit s phn ly ca hn hp dch ngay c khi tng kh mnh nhit .

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C ch to gel ca agar 1.2.4 Alginat c chit t to nu, bao gm axit alginic, alginat natri, alginat kali, alginat amn, alginat canxi, alginat propylen-glycol. Phng php s dng : s dng rng ri trong cng nghip sa ng, sa scola, kem, bnh ko, mn n nh bp nu bng c, cc sn phm tht chn. Liu dng: 50mg/kg th trng i vi axit alginic, alginat natri v alginat amn, 25 mg/kg th trng i vi alginat kali v alginat canxi Trong iu kin nhit cao trng thi si v khi lm ngui s to thnh gel. Alginat cng c kh nng kt hp vi ion Ca2+ to gel.

C ch to gel ca Alginat 1.2.5 Carragenan c sn xut thnh cng t loi to bin Rhodophyceae, c cu trc l mt mch thng ca polysaccharide -Sulphat, cha galactose v anhydrogalac tose vi cc lin kt 1 - 3 v 1 - 4. Khi nhit cao, carrageenan s lin kt thun nghch vi ion T 3 Nhm 2 DHTP4 Page 66



kali, ha tan nhit cao v s kt ta cc protein khi iu kin nhit thp. L mt ch phm dng bt mu trng, khng c mi v, c phn chia thnh dng k, , , , trong dng k, ho tan tt trong nc nng v c tc dng to gel rt tt cn dng , , ho tan d dng trong nc lnh v c tc dng to s n nh, tng lin kt ( pessissant ) cho thc phm. Carrageenan c phn loi theo hm lng 3,6 - anhydrogalactose v v tr nhm ester sulfate, to nhiu sn phm c ng khc nhau. Vic thay i thnh phn 3,6 - anhydrogalactose s nh hng n qu trnh hydrat ha, cu trc v bn ca cht ng, nhit ng v nng chy. Nhn chung, carrageenan c ba loi chnh sau: Kappa carrageenan: + Ho tan nhit cao. + To khi ng (gel) cng. + bn ca khi ng tng ln khi c mt ca mui kali. Lota carrageenan: + C th tan mt phn nhit thp. + Ch ha tan hon ton khi un nng dung dch. + bn ca gel tng ln khi c mt ca mui kali. + Hnh thnh khi ng do v n hi. Lambda carrageenan: + C th tan hon ton nhit thp. + To dung dch c nht cao mc d khng to ng.+ Tng tc vi protein to s n nh cho rt nhiu sn phm c ngun gc t

b v pho mt, ch yu c dng lm tng c v ci tin cu trc thc phm. Phm vi ng dng : dng lm cht to gel v n nh trong cng nghip sn xut n trng ming, sa ng, sa scola, nc chm, mn n nh bp, kem, bnh ko .v.v. Liu dng : khng quy dnh tu thuc vo yu cu ca thc phm . T 3 Nhm 2 DHTP4 Page 67



Carrageenan c kh nng to gel nng thp ( nh hn 0.5% ). dng gel cc mch polysaccharide xon vng nh l xo v cng c th xon vi nhau to thnh khung xng khng gian ba chiu vng chc, bn trong c th cha nhiu phn t nc (hay dung mi). S hnh thnh gel c th gy ra bi nhit thp hoc thm cc cation vi mt nng nht nh. Qu trnh to gel din ra phc tp, c thc hin theo hai bc: Bc 1: khi h nhit n mt gii hn no 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 ring. Bc 2: cc phn pht trin y ca chui xon tp hp li to thnh cu trc gel. Cn di iu kin khng to gel, cc nng polymer thp s hnh thnh v hp li ca cc cu trc xon s dn ti tng nht. Nh vy, trc ht l s chuyn i cu hnh t dng cun sang xon l xo, tip l s kt hp cc xon v t hp li to thnh cc xon kp gel. Nh vy do carrageenan to ra l do s tp hp c trt t ca cc cu trc xon.

C ch chuyn i t dung dch sang gel di tc dng ca nhit 1.3 Canxi clorua (CaCl 2)

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L hp cht ion ca canxi v clo. Cht ny tan nhiu trong nc. Ti nhit phng, n l cht rn. Cht ny c th sn xut t vi nhng i vi vic sn xut sn lng ln th ngi ta to n nh l mt sn phm ph ca cng ngh Solvay. Do n c tnh ht m cao,ngi ta phi cha mui ny trong cc dng c y np kn. Clorua canxi c th phc v nh l ngun cung cp ion canxi trong dung dch, chng hn kt ta do nhiu hp cht ca canxi l khng ha tan trong nc. Clorua canxi c s dng ph bin nh l cht in gii v c v cc mn, c tm thy trong cc loi ung dnh cho nhng ngi tp luyn th thao v cc dng ung khc. 3.1 Tin hnh th nghim 2.1 Th nghim 1 Tm tiV, u, chn

X l Ph gia Ngm ph gia 9 Cn mu trc v sau ngm Kt qu Chun b dung dch 200ml TPP 5% v 200ml TPP 10%: cn 10g v 20g TPP dng bt trng cho vo hai becker 250 ml ri thm nc vo cho 200 ml, ta c dung dch TPP 5% v 10%-

Chun b mu: tm ti sau khi mua ch v s c lt b v, u, chn, ui, sau cn 20g cho vo mi mu: M0 : 20g tm + 50g nc M1 : 20g tm + 50g dd TPP 5%

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Bo co thc hnh ph gia M2 : 20g tm + 50g dd TPP 10% Mu trng


TPP 5%

TPP 10%

-

Tin hnh lp li 3 ln cho mu TPP 5% v TPP 10%

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Bo co thc hnh ph gia -


Ta ngm mu trong 30 pht ri ly ra, lau kh v cn li

3.2 Th nghim 2 Chun b dung dch: pha dung dch ng 50%, chnh pH dung dich ng v gi tr 3,5 bng dung dch HCL 5% Thc hin: M0: 50g dd ng 50% M1: 50g dd ng 50% + 1% pectin ( 1% ca 50g dd ng) M2: 50g dd ng 50% + 1% agar ( 1% ca 50g dd ng) M3: 50g dd ng 50% + 1% alginate ( 1% ca 50g dd ng) M4: 50g dd ng 50% + 1% carragenan ( 1% ca 50g dd ng) un nng tt c cc mu cho cc cht tan hon ton, sau ngui v quan st.

Alginate

Carrageenan

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Pectin 2.3 Th nghim 3 M0: 30g nc + 0.5% [Ca2+] t CaCl2 M1: 30g nc +1% pectin + 0.5% [Ca2+] t CaCl2 M2: 30g nc + 1% agar + 0.5% [Ca2+] t CaCl2 M3: 30g nc + 1% alginate + 0.5% [Ca2+] t CaCl2 M4: 30g nc + 1% carragenan + 0.5% [Ca2+] t CaCl2 Ta tnh c s gam CaCl2 cn cho vo l: mCaCl2 = 0.41625g-

Agar

Sau khi cn nc, ta cho pectin, agar, alginate, carragenan ln lt vo cc mu, bc ln bp cho tan hon ton ri mi cho CaCl2 vo.

-

Ch khi cho CaCl2 vo cn phi khuy du v nhanh tay trnh hin tng vn cc. CaCl2 phi c cho vo cc mu di dng dung dch tc l c ha tan trong nc, khng c cho trc tip trnh tan khng hon ton, sau ngui v quan st.

2.4 Th nghim 4 Tin hnh y nh th ngim 3 nhng thay CaCl2 bng 0.1% [K+] t KCl, ta tnh c mKCl = 0,0573g. Sau ngui v quan st.

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3. Kt qu - bn lun 3.1 Kt qu Th nghim 1 Mu Trng 5% TPP (1) 5% TPP (2) 5% TPP (3) 10% TPP (1) 10% TPP (2) 10% TPP (3)

m trc ngm (g) 19,35 19,32 19,68 19,60 19,64 14,49 9,71

m sau ngm (g) 19,36 20,47 19,80 19,73 20,05 14,92 10,13

Th nghim 2 M0: mu M1: 1% pectin M2: 1% agar trng o nht: To gel, do, To gel, cng 1 pht 20 nht giy Th nghim 3 M0: mu M1: 1% pectin trng o nht: Khng to 12 giy gel, nht tng Th nghim 4 M1: 1% pectin M2: 1% agar Tng nht To ng M2: 1% agar Khng to gel, nht tng

M3: 1% alginate M4: 1% carragenan Khng to gel, nht tng To ng, do, n hi

M3: 1% alginate M4: 1% carragenan ng, cng, gin Khng to gel, tng nht

M3: 1% alginate Tng nht

M4: 1% carragenan To gel gin, trong

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Bo co thc hnh ph gia 3.2 Bn lun Th nghim 1


Khi lng tt c cc mu sau khi ngm nc v dung dch TPP u tng ln. Mu ngm nc c khi lng tng ln thp nht, tuy nhin cc mu tng ln khng u nhau v cng khng c s khc bit r rng i vi cc mu 5 v 10% TPP. Th nghim 2 Hin tng xy ra r rng v chnh xc Th nghim 3 Hin tng xy ra ng vi cc mu ch tr agar: mu khng to c gel m ch tng nht. iu ny ch c th c gii thch l c s sai st trong qu trnh thao tc, dn n kt qu sai lch Th nghim 4 Hin tng xy ra r rng v chnh xc. 4. Tr li cu hi Cu 1 : Trnh by tnh cht v c ch hot ng ca ph gia s dng trong bi? Agarose c cu to mch thng , trung tnh, t cc gc beta D-galactopyranose v 3-6- alhidro-L- galactose. C hai gc c s sp xp xen k, bn cc lin kt khc nhau. Lin kt alpha 1-3 d phn hy bng enzyme to thnh neoagarobiose. Lin kt Beta 1-4 d thy phn vi xc tc ca acid v to thnh gc agaragarobiose. Agar-agarobiose lm cho Agar-agar trong mi trng nc c kh nng to gel. Agaropectin c kh nng to gel thp trong nc, cu trc ca n n nay vn cha xc nh r. Ch bit rng n c to nn bi s sp xp xen k gia Dgalactose v L-galactose v chng cha tt c cc nhm phn cc trong agar Acid alginic hay cn gi l Alginate, trong rong Alginic thng dng mui Alginate Ca, Fe, Mg tham gia vo cu trc ca thnh v mng t bo. L mt Copolymer mch thng c cu to t 2 gc Uronat l alpha L- gluronat v Beta Dmannuromat thong qua lin kt 1-4 glucosit. Cu 2 : Trnh by tc hi c th xy ra khi s dng sai nhng ph gia trong bi th nghim ? T 3 Nhm 2 DHTP4 Page 74



Khi s dng qu liu lng nhng ph gia nh pectin, agar, alginate, carrageenan th s khng t c cu trc nh mong mun Cc tc dng tt ca Polyphosphate: - Polyphosphates c s dng nh mt ph gia: cht n nh, cht lm ng, v cht nh ho. - To phc vi ion kim loi - Kh nng gi nc - n nh nh tng - Gy n - Dng lm dung dch m Cc tc dng xu ca Polyphosphate: Tuy nhin polyphosphates cng gy nhng bt li sau (nu s dng qu liu lng). - Lm cho sn phm c cu trc nh cao su. - Hm lng polyphosphates > 0.3 gy v cht. - Lm cho sn phm c v tanh ng, c cm gic nga li. - Hm lng ln nh hng n sc kho: au bng, tiu chy. Cu 3 : Nu phng php xc nh polyphosphate ? Phng php nh lng bng sc k ion : Polyphosphat trong mu sn phm c chit tch bng nc ct kh ion. Dch chit c lm sch bng phng php chit pha rn (SPE) trn ct chit pha rn C18. Hm lng polyphosphat c trong dch chit c xc nh trn my sc k ion s dng h thng phn ng sau ct vi tc cht phn ng l st nitrat trong axit percloric v u d UV ti bc sng l l 330 nm theo phng php ngoi chun. Cu 4 : K tn vi loi thc phm v ph gia lm ng c, lm dy thng gp Axit alginic, Kali alginat, Amoni alginat, Canxi alginat, Propylen glycol alginat, Thch trng (Aga), Carrageenan v mui Na, K, NH4 ca n (bao gm Furcellaran), Gm u Carob , Gm Gua, Gm Tragacanth , Gm Arabic, Gm Xanthan, Gm Karaya, Gm Tara, Gm Gellan, Pectin, Metyl xenluloza, Metyl etyl xenluloza, Natri cacboxy metyl xenluloza, Gelatin thc phm Cu 5: Nu gi tr INS, ADI, ML ca pentasodium triphosphate, gelatin, agar, carrageenan INS (international numbering system) l k hiu c u ban Codex v thc phm xc nh cho mi cht ph gia khi xp chng vo danh mc cht ph gia thc phm. T 3 Nhm 2 DHTP4 Page 75



ADI (acceptable Daily Intake) l lng xc nh ca mi cht ph gia thc phm c c th n vo hng ngy thng qua thc phm hoc nc ung m khng gy nh hng c hi n sc kho. ADI c tnh theo mg/kg trng lng c th/ngy. ADI c th c biu hin di dng: gi tr xc nh, cha quy nh (CQ) v cha xc nh (CX). ML (MaximumLevel) mc gii hn ti a ca mi cht ph gia s dng trong qu trnh sn xut, ch bin, x l, bo qun, bao gi v vn chuyn sn phm. Bng gi tr Gi tr Pentasodium triphosphate Gelatin Agar Carrageenan INS E451i CQ E406 E407 CX Khng gii hn CX Bng Khng gii hn Bng ADI ML

Quy nh ca Vit Nam v mc cho php ca phosphate (theo quyt nh s 3742/2001/Q-BYT ngy 31/8/2001 ca B Y t) Cc cht cho php i vi tng loi sn phm Mc cho php

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Mononatri orthophosphate, Dinatri orthophosphate, Dicanxi orthophosphat , Dikali orthophosphate, Tricanxi orthophosphate, Trinatri orthophosphat Dicanxi diphossphat, Amoni polyphossphat, Monokali orthophosphat Trimagic diphosphat, Monocanxi orthophosphate, Trikali orthophosphate, Dinatri diphosphat, Tetranatri diphosphat, Tetrakali diphosphat Pentanatri diphosphat, Pentakali triphosphat, Natri polyphosphat Kali polyphosphate, Canxi polyphosphat Cho php: cc nhm sn phm thy sn chung gm: - C ti - Nhuyn th, gip xc, da gai ti - Cc sn phm c, ng vt nhuyn th, gip xc, da gai xay nh ng lnh - Thy sn, sn phm thy sn hun khi, sy kh, p mui, k c nhuyn th, gip xc, da gai Ring axit orthophosphoric: cc nhm sn phm thy sn chung v thm: Ring Dikali diphosphat: cho php cc nhm sn phm thy sn chung v thm:

GMP

2200 mg/kg 1100 mg/kg GMP 5000 mg/kg

Thy sn, sn phm thy sn c ch bin dng ln men, 1000mg/kg ng hp, k c nhuyn th, gip xc, da gai - Thy sn, sn phm thy sn ng lnh, k c nhuyn th, gip xc, da gai 5000 mg/kg

Ring Dimagie diphosphat: cho php cc sn phm trn v 5000 thm thy sn, sn phm thy sn x l nhit, k c mg/kg nhuyn th, gip xc, da gai Ring Natri canxi polyphosphat: cho php thy sn v sn phm thy sn k T 3 Nhm 2 DHTP4 1000 mg/kg Page 77



c nhuyn th, gip xc, da gai qua ch bin Ring Diamidon phosphat acetyl ha: Mn amidon phosphat: cho php thy sn, sn phm thy sn xay nh ng lnh, k c nhuyn th, gip xc, da gai Ring Trinatri diphosphat - Thy sn, sn phm thy sn ng lnh, k c nhuyn th, gip xc, da gai - Thy sn, sn phm thy sn ch bin dng ln men, ng hp, k c nhuyn th, gip xc, da gai GMP

cho php 2000 mg/kg 1000 mg/kg

Ghi ch: GMP (theo qui nh ca Quyt nh s 3742/Q-BYT ngy 31/8/2001 ca B Y t) bao gm cc ni dung sau: - Hn ch ti mc thp nht lng ph gia thc phm cn thit phi s dng. - Lng cht ph gia c s dng trong qu trnh sn xut, ch bin, bo qun, bao gi v vn chuyn c th tr thnh mt thnh phn ca thc phm nhng khng nh hng ti tnh cht l ha hay gi tr khc ca thc phm. - Lng ph gia thc phm s dng phi ph hp vi cng b ca nh sn xut c chng nhn ca c quan c thm quyn.Tn ting Vit Tn ting Anh Chc nng Carrageenan v mui Na, K, NH4 ca n (bao gm Furcellaran) Carrageenan and its Na, K, NH4 salts (includes Furcellaran) Lm dy, nh ho, n nh INS: ADI: 407 CX

STT 1 2 3 4

Nhm thc phm Sn phm sa ln men v sa c cht rennet (nguyn cht) khng k ung t sa Sa ln men (nguyn kem), khng x l nhit sau ln men Tht, tht gia cm v tht th ti Thy sn, sn phm thy sn xay nh ng lnh, k c nhuyn th, gip xc, da gai

ML 5000 150 GMP GMP

Ghi ch

21

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Bo co thc hnh ph gia 5 6 7 8 9 10 11 12 13

GVHD: Th.S Nguyn Th Hong YnGMP

Cc sn phm c, ng vt nhuyn th, gip xc, da gai xay nh ng lnh Thy sn, sn phm thy sn hun khi, sy kh, ln men hoc p mui, k c nhuyn th, gip xc, da gai Du trn, gia v (bao gm cc cht tng t mui) Thc n cho tr em di 1 tui Thc n b sung cho tr ang tng trng Nc qu p thanh trng pasteur ng hp hoc ng chai Necta qu thanh trng pasteur ng hp hoc ng chai C ph, ch, nc ung c dc tho v cc loi ung t ng cc, khng k nc ung t cacao Ru vang Gelatin thc phm Gelatin Edible Lm dy, n nh, nh ho

GMP GMP 3000 GMP 3000 1000 GMP GMP INS: ADI: CQ CX

51

Tn ting Vit Tn ting Anh Chc nng STT 1. 2. 3.

Nhm thc phm ung c sa, c hng liu hoc ln men (VD: sa s c la, sa cacao, bia trng, sa chua ung, sa c) Sa ln men (nguyn kem), c x l nhit sau ln men Phomt ch bin

ML 10000 10000 5000

Ghi ch

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Bi 4: PH GIA CI THIN BT1.Tng quan v nguyn liu 1.1 Bt m Bt m l sn phm c ch bin t ht la m bng qu trnh nghin. Trong qu trnh ny v cm v phi c tch ra v phn cn li ca ht la m (ni nh) c nghin nh ti mn thch hp (ra thnh phm l bt m). Bt m hin nay c lm t nhiu loi bt c nghin trn t nhiu loi la khc nhau. Ngi ta gi tn nh bt m loi trng, hay nu, en.. ty vo mu sc ca bt v gi l bt cng hay mm ty vo lng v tnh cht gluten ca bt. Bt m lm bnh m (bread), gluten cao hn v khe hn, lm cho bnh n khe, gi c hnh dng ca bnh sau khi nng. Bt m lm bnh kem xp (cake hay gateaux) c gluten t hn. Bt lm bnh ngt (pastry) c gluten cao hn bnh kem xp cht t, v thp hn bt lm bnh m. Cc cht dinh dng trong bt hng cao th d tiu ha hn, nhng bt m dng thp th c hm lng khong v vitamin cao hn. Bt m gm c gluxit v lipit, c th v thnh phn dinh dng c chia bng di y: Bng phn loi bt m Loi bt v hng bt Bt m ho hng Hng I Hng II Thnh phn ha hc trung bnh tnh bng phn trm cht kh Tinh Cht ng Pentozan Protit Xenluloza Tro bt bo chung 19,5 2,5 3,5 79 77,5 71 12 14 14,5 0,8 1,5 1,9 1,8 2 2,8 0,1 0,3 0,8 0,5 0,7 1,2

Bng ch s cht lng ca bt m ln Cn li trn Lt qua T 3 Nhm 2 DHTP4 Hm lng Page 80

Bo co thc hnh ph gia ry % (t hn)

GVHD: Th.S Nguyn Th Hong Yn ry

Hng bt Thng hng Hng 1 Hng 2 Thng hng Hng 1

tro 0,75 1,10 1,80

gluten % (ln hn) 32 32

Mu sc Hi vng Hi vng nht Hi vng

Bt la m cng 140/3* 260/12* 190/3 43/35

27/2 38/60 25 Bt la mi mm 0,55 260/14 260/14 28 Trng, hi vng 0,75 190/3 43/50 30 Trng, hi vng *: t s l s hiu ry, mu s l % khng lt ry

Cc hng bt khc nhau v tro, trng, mn, acid v hm lng gluten t ( trng v acid khng ph thuc vo ch s tiu chun cht lng bt). tro l ch s c bn xc nh hng ca bt, thm vo ngi ta cn dng trng v mn na. Cn axit v hm lng gluten ti khng th c trng cho hng ca bt v cc ch s ny lun lun bin ng. Cht lng ca bt m c trng bng s lng v cht lng Gluten. Gluten ca bt hng cao hn thng c mu sng hn v ht nc ln hn. Bt c hm lng Gluten cao thng c tnh cht nng bnh cao ph thuc vo cht lng Gluten. Kh nng to kh ca bt c c trng bng lng CO2 thot ra trong mt thi gian nht nh v ng vi mt lng bt nho nht nh. Kh nng to kh ph thuc vo hm lng ng v kh nng sinh ng ca bt. Cc cht dinh dng trong bt hng cao th d tiu ha hn, nhng bt m dng thp th c hm lng khong v vitamin cao hn.Ty tng loi bt khc nhau m hm lng protein khc nhau. N c tng dn theo cht lng bt cao n thp nhng gi tr dinh dng protein bt hng cao c gi tr cao hn. Protein ca bt m c chia lm 4 loi : Albumin: ha tan trong nc Globulin: ha tan trong mui trung tnh Glutelin: ha tan trong dung dch kim 0.2% (trong bt m c tn ring l Glutenin) T 3 Nhm 2 DHTP4 Page 81



Prolamin: ha tan trong ru (trong bt m c tn ring l Gliadin) bt m hm lng Glutenin v Gliadin chim 80% v t l ca mi loi l nh nhau. Khi chng c nho trn vi nc to thnh mt khi dnh hay cn gi l mng phn b u trong khi bt nho c tnh cht va dai va n hi, c tc dng gi kh lm khi bt nho n c gi l gluten. Sau khi ra lng tinh bt tri i cn li khi n hi do gi l khi gluten t. Trong gluten t c khong 60-70% nc. nh gi cht lng bt m ta nh gi qua cht lng gluten. nh gi gluten c cht lng tt hay xu ngi ta da vo mu sc, n hi, chu ko. Hm lng gluten t trong bt m dao ng trong phm vi rt ln, t 15 n 55%. Khi bt m c cht lng bnh thng th t l gluten t ph thuc vo hm lng protit ca bt. Vi cc loi bt m sn xut t ht b hng, su bnh, ny mm, do sy nhit qu cao th hm lng gluten t gim v tnh ht nc ca protit b thay i. Hm lng v cht lng Gluten bt m ph thuc vo ging la m, iu kin trng trt, ch sy ht, ch gia cng nc nhit, ch bo qun Gluten ca bt m cht lng cao thng c n hi tt, chu ko va phi. Cn nu dng bt m cht lng cao v chu ko nh th bt nho thng b chy khng t yu cu. Chnh v cht lng ca Gluten c nh hng ln n qu trnh ch bin v cht lng sn phm nh vy nn trong sn xut ta thng dng nhng cht ph gia ci to bt m. 1.2 Ph gia ci thin bt m Ph gia ci to cht lng bt m l loi ph gia lm tng cht lng cu trc bt v dai, n, kh nng gi kh,... to iu kin thun li cho qu trnh ch bin, tng gi tr cm quan cho thc phm tng cht lng gluten, ngi ta thng tng thm cc tc nhn oxi ha nh Vitamin C, Kali Bromat, Canxi peroxyt, Canxi bromat, Kali v canxi iodate...Cc cht nh ha lm mm rut bnh v lm mnh bt nho nh Sodium Stearoyl-2-

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lactylate, ethocylated mono...cc enzyme nh protease, amylase...ngc li nhng cht kh s lm gim cht lng gluten. 1.2.1 Vitamin C Vitamin C tn ti trong thin nhin di dng ph bin l axit ascorbic, axit dehydroascorbic v dng lin kt ascorbigen. N ch tn ti dng L trong cc sn phm thin nhin. Cho ti nay ngi ta pht hin c 14 ng phn v ng ng ca vitamin C c hot tnh chng bnh hoi huyt v 15 cht ng phn khng c hot tnh. Cc cht ny phn bit nhau bi s lng nguyn t cacbon, s sp xp ca cc nhm nguyn t cc nguyn t cacbon bt i v dng kh hoc dng oxy ha. Cng thc cu to ca vitamin C cho thy n l mt dn xut ca ng:

-

Khi lng phn t: 176,13 g/mol. C dng: bt mu trng n vng nht (khan). S CAS: [50-81-7]. Nhit nng chy: 1930C (phn hy). pKa : pKa1 = 4,17, pKa2 = 11,56. Kh nng ha tan trong nc cao.

1.2.1.1Tnh cht v ng dng

L cht chng oxy ha, to v chua. Thng dng tinh th khng mu hoc mu trng, i mu khi phi ngoi khng kh hoc iu kin m t. Vitamin C khng mi, c v chua ca axit. Tan trong nc, etanol v acetol. Khng tan trong

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chlorofom, ester. Vi vitamin C, cn ch ti s d phn hy ca n. Nhit phn hy t 191 194 oC. Tnh cht kh mnh ca vitamin C ph thuc vo s c mt ca nhm dienol trong phn t ca n. Chnh v vy m dung dch Feling, bc nitrat hoc mt s hp cht c mu, c bit cht 2,6-diclophenolindophenol b kh bi axit ascorbic ngay nhit thng. Trong thc phm c cc cht n nh vitamin nh protein trng, tht, gan, tinh bt, mui n... Dng ascorbigen ca vitamin C l dng lin kt ca n vi polypeptid. Trong thc vt n chim ti 70% tng lng vitamin C. Dng ascorbigen bn vi cc cht oxy ha nhng hot tnh ch bng mt na vitamin t do. Ngoi dng lin kt vi polypeptid cn c cc dng lin kt khc v d dng lin kt vi Fe v axit nucleic, vi polyphenol. Vitamin C c tng hp d dng thc vt. a s ng vt, tr chut bch, kh v ngi, u c kh nng tng hp vitamin C t ng glucoza. S d ngi khng c kh nng c l v thiu cc enzyme c hiu xc tc cho s chuyn ha glucoza thnh vitamin C Trong mi trng axit, vitamin C kh n nh, v vy khi chit rt mnh vitamin C t cc nguyn liu, ngi ta thng dng cc axit tricloaxetic hoc metaphosphoric. Nhn chung, khi bo qun qu nhit 0 4oC s gim st v vitamin C khng ng k. mt s dch qu, ngi ta nhn thy vitamin C c th b oxy ha gin tip bi enzyme phenoloxydaza. Chnh v vy khi c mt vitamin C, dch qu s sm mu chm hn ( do qu trnh ngng t cc hp cht quinol)

Da vo tnh cht chng oxy ha ca axit ascorbic ngi ta thng thm n vo dch qu ngn cn qu trnh sm mu. Tnh cht chng oxy ha ca n cn c s dng bo v tocopherol v c vitamin A tht khi bo qun, v axit ascorbic l ngun d tr hydro, n c th nhng hydro trc tip cho cc peroxyt. gi c vitamin C, ngi ta thm mt s cht n nh, v d, ng saccarose, axit hu c, sorbitol, glixerin hoc mt s hp cht ca antoxian, flavonoit 1.2.1.2ng dng trong ci thin cht lng bt m T 3 Nhm 2 DHTP4 Page 84



Vitamin C lm tng kh nng gi kh ca khung mng gluten, lm tng cng v n hi ca bt nho v t duy tr hnh dng ca bt nho sau khi v to hnh, kt qu tng th tch, tng xp, tng cu trc cho sn phm. Cu trc phn t protid c nh hng ti cht lng gluten, cht lng ca gluten nh hng quyt nh ti cht lng ca bt m. Nu trong thnh phn ca protid c cha nhiu axit amin cistein (c nhm SH) th khi c cht oxi ha vo s chuyn lin kt -SH thnh lin kt -S-S-. T l mi lin kt disulfua tri hn ngha l protid c cu trc bc ba v bc bn nhiu hn th gluten ca bt cht hn, sc cng ln hn, kh nng to khung mng gluten bn cht hn, cu trc c ci thin hn. R-SH + R-SH O ____________ RS RS + H2O

Bn cnh cht oxi ha cn c tc dng lm hn ch s hot ng ca h enzyme -amylase thy phn tinh bt thnh dextrin nh hng n cht lng bt nho. Phn ng oxy ha xy ra gia axit ascorbic vi lin kt SH trong cystein ca protein bt nho, cc phn t c a v dng L- dehydroascobic axit, do axit ascorbic chuyn ha trong qu trnh oxy ha. C ch oxy ha ny c tm thy do vic hnh thnh cc axit dehydroascorbic do s hin din ca oxy v cht oxy ha ascorbic. Phn ng tip theo l s gim Hydro ca axit dehydroascorbic. Phn ng ny hon tt khi oxy ha ht cc nhm SH trong phn t protein do s hin din ca dehydroascorbic m c th l h thng phn ng NADH + H+ oxy ha nonenzymatic nh superoxidant.1.2.2 Na2S2O3

NAD.

Tc dng ca acid ascorbic c th l do cc sn phm trung gian ca cc gc

Cng thc phn t: Na2S2O3 + Nhit nng chy: 48,30C + Nhit si : 1000C + tan trong nc : 20,9 g / 100ml (200C) T 3 Nhm 2 DHTP4 Page 85



+ L tinh th khng mu, thng tn ti dng Na2S2O3.5H2O C ch tc ng: tc ng ch yu ln thnh phn cystein trong cu trc protein to thnh cystin tng cu trc khung mng gluten thng qua cc cu ni isunfua gia cc phn t protein. 2 Tin hnh th nghim. 2.1 S quy trnh

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Bt m

Cn

Phi trn

Ra gluten Dung dch Iod

Kim tra tinh bt

V trn

Ngm nc

Xc nh cht lng

Kt qu

2.2 Thuyt minh quy trnh 2.2.1 La chn bt m T 3 Nhm 2 DHTP4 Page 87



La chn bt k loi bt m no c sn trn th trng tin hnh xc nh cht lng. Bt m khng c ln tp cht, c kch thc ht ng u. 2.2.2 Cn, phi trn Cn 25g bt m cho vo 15 ly nha nh ( 3 ly k hiu l Mo, 3 ly M1, 3 ly M2, 3 ly M3, 3 ly M4) Chun b 50ml dung dch vitamin C 0,1%, 50 ml dung dch vitamin C 0,2%, 50ml dung dch Na2S2O3 0,1%, 50ml dung dch Na2S2O3 0,2%. Phi trn vo 15 ly bt m vi hm lng nh sau: + 3 mu u (Mo): 15ml nc ct/ mu+ + + +

3 mu tip theo (M1): 15ml vitamin C 0,1%/ mu 3 mu tip theo (M2): 15ml vitamin C 0,2%/ mu 3 mu tip theo (M3): 15ml Na2S2O3 0,1%/ mu 3 mu tip theo (M4): 15ml Na2S2O3 0,2%/ mu

Trn u cc mu cho n khi khi bt khng dnh vo ly na. Khi nho trn vi nc thnh phn protein khng ha tan l glutelin v gliadin ht nc trng n to thnh cu trc khung mng gluten. Gluten l thnh phn quan trng to cu trc cho sn phm. trong 20 pht cho gluten ht nc trng n, n nh cht lng bt nho. 2.2.3 Ra gluten Mc ch: lm tri i lng tinh bt thu c khi do n hi gi l gluten t xc nh cht lng. Tin hnh: sau khi 20 pht, ra khi bt nho di vi nc chy nh, cho khi bt vo lng bn tay, t pha di 1 ry trnh mt gluten, ra n khi nc ra tht trong. Kim tra bng cch cho vo nc ra mt t dung dch iod, nu sau khi cho iod vo dung dch c mu xanh tm chng t vn cn tinh bt, ta tip tc ra. Nu dung dch khng i mu l t. 2.2.4 Xc nh cht lng gluten T 3 Nhm 2 DHTP4 Page 88

Bo co thc hnh ph gia Xc nh cng t.


Cn 4g gluten, v thnh hnh cu ri ngm trong nc khong 15 pht. Sau nc ra, lau kh. Xc nh cng t bng cch dng hai tay ko di khi gluten trn thc chia milimet cho ti khi t,tnh chiu di t lc t. Thi gian ko 10 giy. Khi ko khng c xon si gluten. cng t biu th nh sau: + cng ngn: 10cm + cng trung bnh: 10 20 cm + cng di: ln hn 20cm Xc nh n hi nh gi n hi, dng khi lng cn li sau khi xc nh cng t. Dng tay c nh hnh dng khi gluten khong 2cm, sau ko di ming gluten trn thc khong 5cm ri bung ra. Nhn nh n hi ca gluten theo 3 mc sau: + Gluten n hi tt : gluten c kh nng phc hi hon ton chiu di v hnh dng ban u sau khi ko hay nn. + Gluten n hi km: hon ton khng tr li trng thi ban u v b st sau khi ko. + Gluten n hi trung bnh: gluten c nhng c tnh gia hai loi trn. Ty theo mc n hi v cng t cht lng gluten c chia thnh ba nhm: + Tt : gluten c n hi tt, cng t trung bnh. + Trung bnh: gluten c n hi tt, cng ngn hoc c n hi trung bnh, cng t trung bnh. + Km : c n hi km, b vn, b t khi cng. 3 Kt qu v bn lun 3.1 Kt qu Bng kt qu T 3 Nhm 2 DHTP4 Page 89


GVHD: Th.S Nguyn T

BÁO CÁO THỰC HÀNH PHỤ GIA-TỔ 3-NHÓM 2-DHTP4

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Transcript of BÁO CÁO THỰC HÀNH PHỤ GIA-TỔ 3-NHÓM 2-DHTP4