Cong Nghe Che Bien Dau Mo Tp

8/3/2019 Cong Nghe Che Bien Dau Mo Tp

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TRNG I HC CN TH

KHOA NNG NGHIP & SINH HC NG DNG

GIO TRNH

CNG NGH CH BIN DU MTHC PHM

M s: CB 351

Bin son: Th.s. TRN THANH TRC

NM 2005


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Cng ngh ch bin du thc phm Trn Thanh Trc

i

MC LC

TRANG

CHNG I. THNH PHN V TNH CHT CA DU M...............................................11.1.Tng quan v du m..............................................................................................................11.2.Thnh phn ha hc ca du m............................................................................................21.2.1. Cc thnh phn chnh ............................................................................................................. 2

1.2.2. Cc thnh phn ph ...............................................................................................................6

1. 3. Tnh cht l ha ca du m.............................................................................................11

1.3.1. Tnh cht vt l......................................................................................................................11

1.3.2. Tnh cht ha hc ca du m..............................................................................................11

1.4. Phn loi du mthc phm .............................................................................................13

1.4.1. Nhm cht bo sa..............................................................................................................131.4.2. Nhm acid lauric (du da v du ht c)...........................................................................131.4.3. Nhm bthc vt (bcacao)..............................................................................................131.4.4. Nhm mng vt (mheo) ..............................................................................................131.4.5. Nhm du c (du c v du gan c)...................................................................................131.4.6. Nhm acid oleic v acid linoleic (du olive, du c, du bp, du hng dng)..............141.4.7. Nhm acid linolenic (du u nnh, du ht lanh)..............................................................141.4.8. Nhm acid erulic (C22:1)....................................................................................................141.4.9. Nhm hydroxy acid.............................................................................................................14

CHNG 2. NGUYN LIU CH BIN DU M.................................................................15

2.1. Ht cha du (seed oils) ...........................................................................................................15

2.2.Cy cha du (oils from oil-bearing trees).................................................................................202.3.Mng vt (animal fats)..........................................................................................................222.4.Du tng vt bin (marine oils).............................................................................................23

Chng 3. KHI QUT CNG NGH SN XUT DU TH .............................................25

3.1.Sn xut du tht cha du .................................................................................................253.1.1. Bo qun v sch ht du..................................................................................................253.1.2. Giai on tin x l ht du.................................................................................................323.1.3. Chng sy bt nghin (gia cng nhit m) ..........................................................................383.1.4. Chit tch du bng qu trnh p..........................................................................................40


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3.1.5. Chit tch du bng phng php trch ly ...........................................................................433.2.Sn xut du ttht qu cha du (fruit flesh oil, pulp oil).................................................503.2.1. Du c ..................................................................................................................................503.2.2. Du olive..............................................................................................................................513.3.Tch chit mng vt ...........................................................................................................523.4.Du c........................................................................................................................................52

CHNG 4. K THUT TINH LUYN DU M..................................................................54

4.1.Gii thiu chung.......................................................................................................................544.2.Cc cng on chnh ca qu trnh tinh luyn......................................................................564.2.1. Cc phng php tinh luyn chc.....................................................................................564.2.2. Thy ha du (degumming).................................................................................................584.2.3. Tch sp v ng ha du....................................................................................................614.2.4. Trung ha.............................................................................................................................634.2.5. Ty trng..............................................................................................................................664.2.6. Kh mi ...............................................................................................................................684.3.Tiu chun ca du mthc phm........................................................................................70CHNG 5. CC QU TRNH LM THAY I C TNH DU M.................73

5.1.Khi qut chung.......................................................................................................................735.2.Chit phn on v ng ha du (Fractionation-Winterization) ......................................745.2.1. Gii thiu .............................................................................................................................745.2.2. Csl thuyt ca qu trnh ...............................................................................................745.2.3. K thut chit phn on .....................................................................................................755.2.4. iu kin thc hin..............................................................................................................765.2.5. Sn phm- Kh nng ng dng............................................................................................775.3.Qu trnh hydro ha du (hydrogenation) ............................................................................785.3.1. Gii thiu .............................................................................................................................785.3.2. Csl thuyt ca qu trnh ...............................................................................................785.3.3. Cc yu tnh hng n qu trnh hydro ha ...................................................................805.4.Qu trnh ester ha ni phn t(Interesterification) ...........................................................82CHNG 6. CC SN PHM TDU M...........................................................................85

6.1.Gii thiu chung.......................................................................................................................856.2.Margarine................................................................................................................................85


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6.3.Shortening.................................................................................................................................956.4.Mayonaise.................................................................................................................................966.5.Du chin ..................................................................................................................................986.6.Du salad...................................................................................................................................99

TI LIU THAM KHO .............................................................................................................100


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Cng ngh ch bin du mthc phm Trn Thanh Trc

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CHNG I.

THNH PHN V TNH CHT CA DU M

1.1. TNG QUAN V DU MDu m tng vt v thc vt c s dng trong sn xut cng nh trong isng t rt lu, y cng chnh l mt ngun cung cp nng lng ln. Du mcdng rt ph bin trong qu trnh nu nng hng ngy, xut pht t vn ha ci,nh Trung quc, Ai cp, Hy lp La m c xa. Cho n ngy nay, vic s dng dumtrong qu trnh ch bin thc n vn ng mt vai tr ht sc quan trng, mc dvic thay i tp qun n ung gp phn lm gim sn lng sn xut v s dngthnh phn ny.

Du mc bit n u tin c l t ch Ai cp (nm 1400 trc CN), ngoiphc v cho n ung, vic sn xut x phng t du mcng c ng dng. nhsng ban m ca ngi ci cng c to ra t mng vt cha trong l v mtng sa c s dng nh bc n ngy nay. Ngi La M xa cng bit ch tonn t mng vt trn vi sp ong. Bn cnh , rt nhiu thc vt cng c sdng lm ngun cung cp du: du olive c ngun gc t vng a Trung Hi, ht cidu c s dng ph bin Chu u, du m n v c bit, Trung quc lquc gia bit s dng du sm nht; cho n ngy nay, du u nnh vn c a

chung nc ny. Hin nay, c rt nhiu loi ng thc vt cho du m ckhai thc, mkhng ch thu c t cc ng vt ch yu nh heo, b, cu m mtng vt bin cng c quan tm.

Song song vi qu trnh s dng du m, cng ngh ch bin du cng rt pht trin:t khu chit tch thu du mn k thut tinh luyn gip du mc cht lng caohn. Tuy nhin, bc ngot ln gip nn cng nghip ch bin du mpht trin gnlin vi vic ng dng my nghin p du dng con ln ca Smeaton vo nm 1752.Ti p theo , cng ngh chit tch du c kt h p chng sy cng bc u c

nghin cu trong nhng nm 1795 (Brahma), 1800 (Neubauer), 1891 (Montgolfier).Deiss (1855) th nghim trch ly du thnh cng t dung mi l CS2, sau Irvine,Richardson v Lundy (1864) a ra pht minh cho vic s dng dung mi trch lydu l hydrocarbon v hin vn cn c p dng. Cng vi cng ngh chit tch du,cng ngh tinh luyn du m cng c pht trin song song. Thm vo , cc

phng php kim nh v nh gi cht lng ca du mcng c nghin cu vng dng: khi nim v ch s acid (Merz, 1879), ch s x phng ha (Koettstorfer,1879), ch s iod (Huebl, 1879); vic ng dng phng php sc k trong xc nh gi

tr du mcng c ng dng t nm 1906 (Tswett, sc k ct) v pht trin dn .


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1.2. THNH PHN HA HC CA DU M

1.2.1. Cc thnh phn chnh

(i) Cc acid boHp cht bo c cha cc acid hu cc s nguyn t C trong mch ln hn 4 cgi l acid bo (fatty acid). Ty thuc vo chiu di mch carbon, cc acid bo cchia lm 3 dng chnh: acid bo mch ngn (4-6 Carbon), acid bo mch trung bnh (8-14 C) v acid bo mch di ( 16 C); ngoi ra, ty thuc vo lin kt gia cc nguynt C trong mch, acid bo cng c thc chia thnh 2 loi chnh: acid bo bo hav acid bo cha bo ha. C hn 10 loi acid bo c tm thy ch yu trong thc

phm (bng 1.1).

- Acid bo bo ha: Thut ng bo ha c s dng ch s tha mn v ha

tr ca nguyn t C trong mch acid (ngoi tr C to nn gc acid COOH); nicch khc, lin kt gia cc nguyn t C trong mch l lin kt n (lin kt ).

K hiu: Cx:0 vi x: s nguyn t C trong mch

0: khng c s tn ti ca lin kt i (lin kt ).

- Acid bo khng bo ha: Cc acid bo c cha lin kt i trong mch carbonc gi l acid bo khng bo ha. Trong t nhin, lng acid bo khng bo hachim t l rt ln. Hu ht cc acid bo c xu hng hnh thnh lin kt i vtr C s 9 v s 10 trong mch. Mc d vy, s hnh thnh cc lin kt i khng

bo ha ny cng c thc tm thy tt c cc v tr trn mch C, iu ny lmgia tng ng k lng ng phn ca acid bo khng bo ha. Thm vo , sxut hin ca lin kt i cng gip cho vic hnh thnh cu hnh cis- v trans- caacid bo, nh hng n c tnh sinh hc ca chng. Ngoi tr mt s trng hpc bit, hu ht cc acid bo khng bo ha trong thc phm c cu hnh cis-; tuynhin qu trnh tinh luyn du hay cc qu trnh tc ng lm thay i c tnh dum(ch bin margarine, hydro ha du) c th lm chuyn i cc acid bo khng

bo ha c cu hnh cis- thnh dng ng phn hnh hc trans-, y cng chnh l

mi nguy ln cho vic gia tng bnh xva ng mch v bnh tim.

K hiu:

Cc acid bo khng bo ha c thc k hiu theo hai h thng:- H thng 1: Cx:y, zc (hoc zt) vi: x: s nguyn t C trong mch

y: s lin kt i hin dinz: v tr ca lin kt i trong mch C (nh

s bt u t C k cn nhm COOH)

c,t: cis- hay trans-


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- Theo h thng EEC (End-of-Carbon-Chain): (Cx:y,m) hay (Cx:y,nm); khi hay n: v tr ca lin kt i trong mch C (nh s ngc li h thng 1, C1 l C

bt u ca mch C- nhm CH3).Th d:CH3-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH-CH2-(CH2)6-COOH- Theo danh php IUPAC: 9,12,15-Octadecatrienoic acid- Tn thng thng: -linolenic acid- K hiu theo h thng 1: C18:3,9c,12c,15c

- K hiu h thng EEC: C18:33 hay C18:3n3

Acid oleic (C18:19) l acid bo c 1 ni i chim t l ln trong thnh phn ccacid bo (hn 50%), acid ny c tm thy trong hu ht cc loi du thc vt cngnh mng vt.

Bng 1.1. Cc acid bo ch yu trong thc phm

Acid bo

(theo h thng IUPAC)

Acid bo

(tn thng thng)

Chiu di mch C

(Cx:y,m)

Nhit nng

chy (oC)

Decanoic Capric 10:0 31,6

Dodecanoic Lauric 12:0 44,4

Tetradecanoic Myristic 14:0 54,3Hexadecanoic Palmitic 16:0 62,9

Octadecanoic Stearic 18:0 70,0

9-Octadecanoic Oleic 18:19 13,0

9-trans-Octadecanoic Elaidic 18:19 36,0

13-Docosenoic Erucio 22:19 33,5

9,12-Octadecadienoic Linoleic 18:26,9 -3,0

9,12,15-Octadecatrienoic -Linolenic 18:33,6,9 -11,9

5,8,11,14-Eicosatetraenoic Arachidonic 20:46

5,8,11,14,17-Eicosapentanoic EPA 20:53

4,7,10,13,16,19-Docosahexaenoic

DHA 20:63

- Acid bo khng bo ha mch di 3 v 6

Trong s cc acid bo khng bo ha mch di, acid bo 3 v 6 l hai loi acid bocn thit v c gi tr dinh dng cao nht; cc nghin cu cho thy c th ngi vng vt khng th tng hp cc acid bo ny, m ch yu c cung cp qua ngun


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thc n - du thc vt. Acid linoleic (C18:26) v acid -linolenic (C18:33) l hai

acid quan trng nht i din cho nhm ny. Cc acid bo thuc nhm 3 v 6 cngc thc hnh thnh nhvo qu trnh bin i nh ko di mch carbon hay loi

bo ha (desaturation): acid arachidonic (AA, C20:46), acid eicosapentaenoic (EPA,

C20:53), acid docosahexaenoic (DHA, C22:63) (hnh 1.1)

18:19 18:26 18:33

18:29 18:36 18:43

loi bo ha (desaturase)

ko di mch (elongase)

20:29 20:36 20:43

20:39 20:46 20:53

loi bo ha (desaturase)

ko di mch

22:46 22:53

24:53lo i bo ha

24:63

22:56 22:63

Hnh 1.1. Cc bin i hnh thnh acid bo khng bo ha mch di (polyunsaturated fatty acid)

Trong t nhin, AA cng c th tm c trong tht g v mt sng vt khc, EPAv DHA cng tn ti vi lng ln trong c v mt s hi sn khc.

Cc nghin cu gn y cho thy cc acid bo khng bo ha mch di ny cxem l mt trong nhng acid bo cn thit v quan trng nht nhvo s hnh thnhcc hp cht c c tnh sinh hc (eicosanoid) ca chng, gip v hot kh nng sinhcholesterol trong c th ngi. Acid arachidonic c chuyn i nhenzyme thnhcc h p cht nh protaglandin, thromboxan, leukotrien gip c th ngi thc hinmt s chc nng sinh l. Thm vo , cc acid bo ny cn c vai tr cn thit chos pht trin, l hp cht cn bn cho vic thnh lp thnh t bo cng nh hnh thnhhp cht cu trc cn thit ca phospholipid.


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- Cc acid bo c cu trc khngc trng (cu trc him):

Bn cnh cc acid bo bo ha v khng bo ha thng gp, trong thc phm cnxut hin mt lng acid bo vi cu trc t gp hn. Cc acid ny thng khng cvai tr quan trng trong thc phm, v ch tm thy mt s ngun c bit, ch yu

trong cc loi rau. Khc vi cc acid bo thng thng, cc acid bo dng ny thngkhng c cu trc mch thng, chui hydrocarbon c hnh thnh t mt hay nhiunhm methyl v ethyl: acid bo mch nhnh. Cc acid bo mch nhnh hin din chyu trong vi sinh vt v mt lng nhc tm thy trong sa v mca ng vtnhai li (tru, b). Trong s ny, acid ricinoleic (12-hydroxy-9-octadecenoic acid) lhydroxy acid quan trng nht, y l thnh phn chnh ca du hi ly (castor oil).

(ii)TriglyceridTriglycerid l sn phm c to thnh t phn ng ca mt phn t glycerol vi ba

(3) phn t acid bo (hnh 1.2). Ty thuc vo acid bo gn vo cc v tr trn mch Cca glycerol s xc nh c tnh v tnh cht ca triglycerid:

- Triglycerid n gin: to thnh t 3 acid bo ging nhau.

- Triglycerid phc tp: do acid bo khc nhau

Trn thc t, du v mu l sn phm ch yu ca triglycerid phc tp. S phn bca acid bo trong cu trc triglycerid c khm ph v nghin cu trong mt thigian di, rt nhiu hc thuyt khc nhau v kh nng lin kt ny c ngh:

- Thuyt phn b ngu nhin: s phn b acid bo vo cc v tr khc nhautrong triglycerid hon ton theo ngu nhin.

- Thuyt phn b cn bng: cc acid bo c khuynh hng phn b rng ri tt c cc triglycerid.

- Thuyt phn b ngu nhin c gii hn: s phn b acid bo vo cc v trkhc nhau trong triglycerid cng theo quy lut ngu nhin, tuy nhin c mt viim gii hn c bit xy ra trong du thc vt v mng vt . Th d: duthc vt, cc acid bo bo ha c xu hng ester ha v tr s 1 v 3; trong khis gn kt cc acid ny thng xy ra v tr s 2 trong mng vt.

Hnh 1.2. Cu trc triglycerid


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(iii) Cc thnh phn ph

Cc acid bo tdo v mono- , diglycerid

Trong du m, ngoi tr thnh phn chnh l triglycerid cn c s hin din ca mtlng nht nh acid bo t do (khng lin kt vi glycerl) v mono- , diglycerid.

Trong cu to ca cc mono- v diglycerid vn cn s hin din ca hai hay mt nhmhydroxyl (-OH), chng c xem nh du hiu nhm xc nh s tng h p khnghon ton triglycerid sinh hc (qu cha chn, ht) hay du hiu ca qu trnh phngii lipid (lipolysis) sau thu hoch do hot ng ca enzyme. Tuy nhin, ngoi vai trnh cht ch th cht lng, mono- v diglycerid cn c mt vai tr quan trng c

bit nhvo kh nng lin kt mnh ca n vi cc phn t thn du v thn nc;chnh v th mono- v diglycerid c s dng nh mt cht nh ha trong rt nhiuthc phm.

Bn cnh mono- v diglycerid, acid bo t do l sn phm cui trong qu trnh phngii lipid, l gim cht lng du cng nh sn phm thc phm.

Phospholipid

Trong ht du bao gicng c mt phospholipid l mt trong nhng thnh phn lipidphc tp ch yu, bao gm khung glycerophosphate kt hp vi hai chui acid bo di c ester ha v tr C1 v C2, ng thi mt alcohol base gn vo nhm

phosphate (hnh 1.3).

R1, R2: acid bo

Hnh 1.3. Cu trc ca phospholipid


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Phospholipid c phn thnh 5 nhm chnh theo s thay th t nhin (X) trn acidglycerophosphoric:

(1)Phospholipidic acid (PA): khng c thnh phn thay th

(2)Phospholipidyl ethanolamine (cephalin): PE

(3)Phospholipidyl choline (lecithine): PC

(4)Phospholipidyl serine: PS

(5)Phospholipidyl inositol: PI

Phospholipid l cc hp cht cha dinh dng d tr, cung cp nng lng cho ccphn ng trao i cht v tng cng h hp ca ht. Trong cng ngh thc phm,phospholipid c s dng rng ri nh mt cht nh ha , tc nhn kt dnh (anti-spattering) v lm gim nht trong nhiu thc phm. Nhiu hiu quc bit ca

phospholipid c bit n nh ngn cn hay cha khi bnh mt tr nh, vimkhp v hm lng choloseterol trong mu cao. Tuy nhin, cho n ngy nay, cc chli ca phospholipid v mt dinh dng khng c khoa hc chng minh.

Trong ht du, phospholipid nm dng lin kt phc tp vi glucid, protid v ch ckhong 30% dng t do. Do c tnh tan trong cht bo, khi khai thc du thc vt,

phospholipid s c mt trong du.

Cc hp cht khng c tnh x phng ha

Cc hp cht khng c tnh x phng ha thng c mt trong du mvi vai tr quantrng l: sterol, tocopherol, hp cht mu, sp, hydrocarbon v vitamin.

Sterol: h p cht ha tan trong cht bo vi cu trc cn bn t steran(cyclopentanoperhydrophenantrene) (hnh 1.4).


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Hnh 1.4. Cu trc ca steran v sterol

Ty theo ngun gc pht sinh, sterol c chia thnh hai loi chnh: sterol ng vt

(cholesterol) hay sterol thc vt (phytosterol: -sitosterol). Hm lng sterol thay i

trong khong t 0,05-0,60%. Cholseterol c xem nh mt trong nhng nguyn nhnchnh gy nn bnh nhi mu ctim. Chnh v th, rt nhiu bin php lm gim lngcholesterol trong thc phm c nghin cu thnh cng trong nhng nm gn y.Tuy vy, cholesterol vn c mt s chc nng cn thit cho hot ng sng khi n lthnh phn chnh ca mng t bo, cht don cho hot ng ca hormone steroid -hormone cn thit cho qu trnh ln ln v pht trin ca ng vt hu nh cn non.

Tocopherol: Tocopherol l cht chng oxy ha t nhin rt quan trng thuc hphenolic. Tocopherol cng c c tnh tan trong du, thng tn ti dng t do. Ty

thuc vo cu to khc nhau ca tocopherol (hnh 1.5) m c tnh tng ng cngthay i; ph thuc mch C chnh bo ha hay cha 3 lin kt i, v ph thuc vo snhm cng nh v tr nhm methyl gn kt trn mch nhnh; c 4 loi tocopherol khc

nhau: -tocopherol (5,7,8-trimethyl), (5,7-dimethyl), (7,8-dimethyl) v (8-methyl).

Hot tnh chng oxy ha ca cc tocopherol trong du v mph thuc ch yu vonhit v s hin din ca cc hp cht nhim vo h thng. Tuy nhin, hot ngchng oxy ha ca cc tocopherol cng ty thuc vo v tr cu to:

> = >


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Hnh 1.5. Cu trc ha hc ca cc tocopherol

Cc h p cht mu (pigment): S khc nhau vmu sc ca cc loi du v mkhc nhau ph thuc vo lng hp cht mu ha tan trong du. Nhng hp chtmu quan trng nht trong du ml carotene, chlorophyll v gossypol.

- Carotene (hnh 1.6) l ngun cung cp vitamine A - cht c hot tnh chng oxyha v chng ung th. Carotene hin din ch yu trong du c, y chnh l ldo ch yu lm cho du c mu vng, cam hay .

- Chlorophyll cng chnh l nguyn nhn to cho du c mu xanh ti khngmong mun. iu quan trng l s hin din ca chlorophyll torng du lnguyn nhn ch yu lm cho du rt nhy cm vi nh sng quang hp, gynn bin i cht lng. Chnh v th, trong qu trnh tinh luyn cc loi du ccha nhiu chlorophyll (du olive), qu trnh kh mu nhm loi hp cht nyrt c quan tm.

- Gossypol to mu nu trong du ht bng vi (cottonseed oil). Gossypol ccu to l hp cht phenol phc tp, c mi v kh chu, c tnh c. Do , cntch loi hon ton hp cht ny ra khi du v kh du.

Hnh 1.6. Cu trc ha hc ca cc caroten quan trng nht


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Hp cht sp: hin din ch yu trong du bp v ci du. V cu to, sp l ester carc bc mt v t thy i vi ru 2 chc. Sp c nhit nng chy kh cao (tnc >80oC), bn vng v rt kh tiu ha, sp khng c gi tr v mt dinh dng. Trongqu trnh ch bin, s tn ti ca hp cht sp trong du l nguyn nhn ch yu gyc du. Ngay iu kin nhit bnh thng, chng tn ti cc dng tinh th nh

li ti, trong mt thi gian di vn khng lng thnh cn, lm gim gi tr cm quan du.Cc thng sc trng ca sp c cho bng 1.2.

Bng 1.2: Cc thng sc trng ca sp

Thng s Gi tr

Ch s idoine 11,1-17,6

Hm lng acid bo t do (FFA) 2,1-7,3 %

Phosphorus 0,01-0,15 %

im nng chy 75,3-79,9oC

Vic tch sp c thc thc hin bng bin php ng ha du nhit 5oC trckhi lc.

Hp cht mi gc hydrocarbon: bao gm cc alkan, alken (squalene, hnh 1.7) v cchydrocarbon a vng c mi (polycyclic acromatic hydrocarbons PAHs). Cc hpcht alkan (C31-C33) hin din trong du th vi hm lng t 40-100 ppb, gim dn

sau qu trnh tinh luyn. Mt s hp cht mi nh squalene c vai tr rt quan trngtrong cng nghip m phm. Squalene hin din ch yu trong du gan c nhm gc(deep-sea dogfish, Squalus acanthus) v mt s du c khc; olive l du thc vt chyu c s hin din ca squalene. Ngc li, hu ht cc hydrocarbon a vng c mi(PAHs) hin din hm lng ln hn 150 ppb trong hu ht cc du thc vt th,chng ch gim nh sau qu trnh tinh luyn.

Hnh 1.7. Cu trc ha hc ca squalene

Vitamin ha tan trong du: bn cnh vitamin A (retinol) - hin din nhiu nht duc, trong du cn tm thy mt s cc vitamin khc vi lng t hn nh vitamin D,

vitamin E (-tocopherol) v vitamin K (phytoenzymeadion). Cc vitamin ny rt cn

thit cho qu trnh hp thu ca cth ngi.


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1.3. TNH CHT L HA CA DU M

1.3.1. Tnh cht vt l

- Du m nh hn nc, t trng 0,91-0,97. Mc khng no cng ln th t trngcng ln.

- Ch s khc x 1,448-1,474 . Mc khng no cng ln th ch s khc x cng cao.

- C tnh nht kh cao.

- Tan nhiu trong cc dung mi hu cnh eter, benzen, hexan

- im nng chy ca du m th hin khng r rng, ty thuc vo tnh cht canguyn liu to ra du m: Khi dy acid bo cng di, cng no th nng chy catriglycerid cng cao, p sut hi cng km do c t mi . Du mvi cu to chyu l triglycerid dy ngn (du da) th s thy phn s phng thch cc acid bo t

do c khi lng phn t nh, d bay hi, gy mi kh chu. Cng mt chiu di, dycarbon ca acid no c cha nhiu ni kp th c nhit nng chy cng thp.

1.3.2. Tnh cht ha hc ca du m

Tnh cht ha hc ca du mch yu do phn ng ca triglycerid, c tc ng ngkn s thay i cht lng sn phm.

1.3.1.1 Phn ng thy phn v x phng ha

Trong iu kin thch hp, du md b thy phn theo phn ng

C3H5(COOR)3 + 3H2O 3RCOOH + C3H5(OH)3Nu c mt mt lng kim (KOH, NaOH) th sau phn ng thy phn, acid bo tcdng vi cht kim to thnh mui kim (x phng).

RCOOH + NaOH RCOONa + H2O

Phng trnh tng qut:

C3H5(COOR)3 +3NaOH 3RCOONa + C3H5(OH)3

1.3.2.2 Phn ng cng hp

Phn ng ny c tc dng cng hydro vo cc ni i trn dy carbon ca acid bo vis hin din ca cht xc tc thch hp nhm lm gim s ni i trn dy carbon, lmcho du mn nh hn, hn chc cc qu trnh nh oxy ha, trng hp ca dum. Ngoi ra, phn ng ny cn c tc dng gi cho du khng b trmi khi boqun lu.

-CH = CH - + H2 - CH2 CH2

Phn ng ny c ngha thc tin quan trng: y chnh l c s l thuyt cho qutrnh chuyn i du t th lng sang th rn s dng trong mt s trng hp c

bit (margarine, shorterning)Ngoi ra, thnh phn acid bo ca du thng cha ng thi acid oleic, acid linoleic,acid linolenic. Mc d acid linolenic c vai tr sinh hc quan trng, nhng n cng l


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nguyn nhn chnh gy nn s trmi ca thc phm, v th qu trnh hydro ha chnlc gim bt hm lng acid linolenic thng c tin hnh trong cng ngh ch

bin du.

1.3.2.3 Phn ngng phn ha

Di tc dng ca baz ha tan trong ru s xy ra sng phn ha (theo c haikiu ng phn hnh hc v v tr, chng 5) cc ni kp trn dy carbon, lm tngtnh kh ca du. Sng phn ha c th thc hin vi cht xc tc Niken, nhit 180oC, Al2O3 tng hot tnh.

1.3.2.4 Phn ng vi ru

y l phn ng cbn bin triglycerid thnh ester metyl ca acid bo nhm phn tch thnh phn ha hc bng sc k kh.

1.3.2.5 Phn ng oxy ha

Nhng du mc cha nhiu acid bo khng no s d b oxy ha bi oxy khng kh.a s cc phn ng xy ra trn cc ni i ca carbon. Du mcha nhiu acid bo noc u im l d bo qun, t b bin i nhng li c h sng ha thp.

Tc tnh l ha ca du mni chung, cc nghin cu v hin tng trmi cadu mkhi chng c tn tr trong thi gian di a ra hai nguyn nhn ch yudn n s bin i ny:

(i) Sthy phn gii phng acid bo ttriglycerid

S thy phn ny c th xy ra khi mch carbon ca triglycerid ngn, hoc ditc dng ca enzyme lipase.

(ii) Si du do phn ng oxy ha ha hc

Phn ng ny xy ra d dng vi dy triglycerid c cha nhiu ni kp. N

thng bt ngun t phn ng cng oxy vo cc ni kp hay xen vo Ci vi nikp to ra cc hydroperoxit. Cc hydroperoxit ny tip tc b phn hy cho racc sn phm sau cng nh cc hp cht carbonyl, aldehyd, aceton, alcohol.

Tng qut :

AldehydCetonAcidEsterAlcohol

Cht bo + O2 hydroperoxit

Vic tm ra nguyn nhn gy bin i mi trong qu trnh bo qun c ngha thc trt quan trng, y chnh l cscho cc nghin cu tip theo nhm lm thay i ctnh du mnh ester ha ni phn t, hydrogen ha(chng 5).


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1.4. PHN LOI DU MTHC PHM

Du v m thc phm c thc phn thnh nhiu loi da vo thnh phn v tnhcht ca cc acid bo. C th chia du mthnh 9 nhm ch yu:

1.4.1. Nhm cht bo sa

Cht bo thuc nhm ny c ngun gc t sa ng vt. Cht bo sa c cu to chyu t cc acid bo mch ngn, khng c ni i (C4:0, C6:0 v C8:0). Ngoi ra, trongcht bo sa vn c s hin din ca cc acid bo bo ha mch di (C16:0 v C18:0)v acid bo khng bo ha c mt ni i (C18:1). Do s hin din a dng ca ccloi acid bo ny m cht bo sa thng c im nng chy thp, khong nhit nng chy rng, thnh phn triglycerid phc tp hn so vi du thc vt. Vi hu htcc ng vt, acid bo tn ti ch yu dng trans-. Cht bo sa c s dng chyu lm ngun thc n cho ngi do gi thnh cao.

1.4.2. Nhm acid lauric (du da v du ht c)

Nhm cht bo ny c tnh cht rt khc bit so vi cc loi du khc do s hin dinvi mc cao ca acid lauric (40-50% C12:0), kn l acid myristic v cc acid

bo bo ha c 8,10 v 14 C. im c trng ca nhm ny l s hin din t l rtthp cc acid bo khng bo ha, tng ng vi im nng chy rt thp. Mc d vy,nhm du da v du c vn c s dng trong cng nghip thc phm v trong ch

bin margarine.

1.4.3. Nhm bthc vt (bcacao)Nhm cht bo ny c thnh phn triglycerid v acid bo rt c bit: ch yu t ccacid bo khng no c 1 ni i nh C18:1, C20:1, C24:3. Bthc vt c gi tr kinh tcao, s dng ch yu trong ch bin chocolate v ko.

1.4.4. Nhm mng vt (mheo)

Mng vt c cu to ch yu t acid bo C16:0, C18:0 v cc acid bo c mc khng bo ha trung bnh. Nhm cht bo ny cha mt t l mong mun catriglycerid bo ha hon ton, tuy nhin nhc im ln nht ca n l s hin din mc rt thp cc acid bo khng bo ha.

1.4.5. Nhm du c (du c v du gan c)

Du c c to thnh t cc acid bo khng no c mch carbon di (cha t nht 6lin kt i). Cht lng du c cao, tuy nhin n l loi du c gi thnh thp nht dokh nng bo qun thp:du c khng c tnh n nh, d bin i do qu trnh oxy hani i v pht sinh mi khng mong mun.


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1.4.6. Nhm acid oleic v acid linoleic (du olive, du c, du b p, du hngdng)

y l nhm du hin din ph bin nht. Acid bo to nn du nhm ny ch yu lC18:1 v C18:2. Lng acid bo bo ha trong nhm du ny ch chim ti a 20%.

1.4.7. Nhm acid linolenic (du u nnh, du ht lanh)

c im quan trng ca du u nnh v du ht lanh l s hin din hm lngcao acid linolenic (C18:3). Do mc khng bo ha cao, cc du ny rt nhy cmvi cc cht oxy ha, iu ny dn n cc bin i khng mong mun v mi v v.

Ngoi tr du u nnh, du ht lanh khng c s dng ph bin cho ch bin thcphm.

1.4.8. Nhm acid erulic (C22:1)

Du thuc nhm ny c hm lng cao (40-50%) acid erulic (C22:1), hin din chyu trong ht bng vi. Mt s gi thit cho rng mt s cc bin i sinh l khngmong mun trong c th ngi do s tham gia ca acid erulic. Chnh v th, vicnghin cu tm cc loi nguyn liu cho du c hm lng erulic thp vn c quantm.

1.4.9. Nhm hydroxy acid

Cc nghin cu cho thy, nhm hydroxy acid ch hin din trong du hi ly (castoroil): triglycerid ca glycerin ch yu (90%) vi acid ricinoleic (12-hydroxyoctadec-9-

enoic acid). Du hi ly khng c s dng cho ch bin thc phm.


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CHNG 2. NGUYN LIU CH BIN DU M

2.1. HT CHA DU (SEED OILS)

c im quan trng ca ht du l m thp, ngn cn s bin i chc v s phhy ca cn trng. Da vo u im ny, du thng khng c tch chit sm rakhi ht du m sc bo qun trong ht nhm ngn cn cc bin i khng mongmun ca du th. Hu ht cc ht rau qu u cha du nhng ch nhng nguynliu c hm lng du cao mi c s dng trong qu trnh sn xut du. Tuy nhin,mt s cc ht li c kh nng s dng cho trch ly du l thnh phn loi ra ca qutrnh sn xut mt sn phm khc (ht c chua trong ch bin nc c chua hay htnho trong sn xut ru vang).

Nhc im ca vic sn xut du t ht du l: Du trong ht du khng nm dngt do, bn ngoi m c nht trong cc khe vch bn trong t bo, qu trnh tchchit du khng th tin hnh trc tip m phi qua cc khu chun b phc tp. Mts ht c hm lng du cao nhng qu trnh trch ly du c th km theo s gii

phng mt s hp cht khng mong mun, kh phn tch khi du.

Mt s ht du s dng ph bin trong qu trnh sn xut du:

2.1.1. Du da

Thu c t cm da kh (Cocos nucifera, h Palmae.). Cy da c th trng v pht

trin vng vnh ai t 20o vBc n 20o vNam ca xch o, nhit thch hpcho qu trnh pht trin l 30oC. Chnh nhvo nhit cao ca nhng vng trngda, ngi ta c th s dng nh nng mt tri cho qu trnh lm kh cm da, ngoira, ngun nhin liu t v da cng c tn dng- y chnh l nguyn nhn lm chodu da thng cha cc h p cht hydrocarbon a vng. Du da thuc nhm acidlauric. Nhvo khi lng phn t ca triglycerid mc trung bnh, du da c nhit nng chy th p (24-27oC). Ngoi ra, mc khng bo ha trong du da thp(


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2.1.4. Bcacao

y l loi b thc vt quan trng nht. Bcacao c mu vng nht, thu c t htca cy cacao nhit i Theobroma cacao (hStercuiliaceae). B cacao c mc acid bo bo ha cao, do bcacao c thng c ngay nhit thng (30-

35

o

C).2.1.5. Cc loi bthc vt khc

Nhm ny ch chim mt lng nh v c s dng nh cht thay th b cacao(cocoa butter equilivalent CBE):

(i) M bomeo (Bomeo tallow; illipe butter): c tch chit t cy Shoreastenoptera Malaysia. Bomeo tallow cn c gi l b xanh do snphm c mu xanh nht. Loi bny c tnh cht gn ging vi bcacaonht khi so snh vi cc loi bkhc.

(ii) Bshea: thu c t cy ht mTy phi (Butyrospermum parkii), c mc acid bo khng bo ha cao hn khi so snh vi b cacao. Vic phntch to stearin t b shea ny c th to ra sn phm thay th b cacao(CBE).

2.1.6. Du hng dng

c chit tch t ht cy hng dng ( Helianthus annuus L., h Compositae).Hng dng thng sng nhng vng kh hu n ha nh M, Chu u v Trung

Quc. Vic trng v ch bin cc sn phm t hng dng c pht trin mnhtrong sut 25 nm qua nhvo s hin din hm lng cao ca acid linoleic thnh

phn dinh dng quan trng cho c th. Trong qu trnh tch chit du, ht hngdng thng phi tri qua qu trnh x l sb nghim ngt, xay xt loi b lp v

bn ngoi ht nhm lm gim ti a thnh phn sp hin din trong du sau qu trnhthu hi. Du hng dng c th thu c bng c hai bin php: p bng sc nc vtrch ly. Qu trnh tinh luyn du hng dng l khu c bit quan trng nhm loi

b cc thnh phn khng mong mun c mt trong du do qu trnh trch ly hay p.

Du hng dng thuc nhm acid oleic-linoleic, cha hn 85% acid bo khng boha, trong hn 2/3 l acid linoleic (C18:2). im ng c ca du hng dng l-15oC, ch s iod t 110-145. Sau qu trnh trch ly, trong kh hay b du hngdng cn cha khong 40-45% protein y l ngun thch hp cho vic ch binthc n gia sc.

2.1.7. Du cy rum (Safflower)

c sn xut nhqu trnh p hay trch ly ht cy rum Carthamus tinctorius L. (hCompositae). Loi cy ny c ngun gc ch yu t Ai cp, ng v mt s vng

pha ty Hoa K, sau c pht trin vi mt thi gian di nhiu ni nhm phcv cho vic sn xut du. Ngy nay, vai tr quan trng ca cy rum thay i ngk, nguyn nhn ch yu do s pht minh ra mu aniline; ng thi mu du sm,


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khc mu vng nht khng cn c a chung. Du rum c gi tr dinh dng rt caodo c hm lng acid linoleic ln nht (>80%), y l ngun quan trng cho vic cungcp acid linoleic tinh khit. Tuy nhin, phn kh v b du rum hu nh khng c gitr dinh dng.

2.1.8. Du ht bng viCh bin t sn phm ph (phn thi) ca qu trnh sn xut bng. Tr lng sn xut

bng trn th gii rt ln, km theo mt lng ln ht bng cha t l du cao cloi ra. Ai Cp, Hoa K, Trung Quc v Nga l nhng nc v ang ch bin dut ht bng vi. Chu u, du ht bng chim t l ln nht. Tuy nhin, do tnh chtca du bng vi c cha gossypol (hnh 2.1) - hp cht a vng to mi v kh chu,khi kt hp vi protein hnh thnh hp cht khng th tiu ha, gy c. Do , victin x l v tinh luyn du bng lun c quan tm. Du bng vi thuc nhm acid

oleic-linoleic; mc d thnh phn du c cha mt t l tng i cao cc acid bokhng bo ha c nhiu ni i, du bng cng cha lng acid bo bo ha cao nhttrong nhm ht du. Du bng vi c thc s dng trong nu nng hng ngy(cooking oil, salad oil) hay trong cng nghip ch bin margarine, shortening.

Hnh 2.1. Cu to ca gossypol

2.1.9. Du thuc h ci du (rapeseed, colza)

Thu c t ht ca cy ci duBrassica napus L. vB. campestis L. (hCruciferae.).Cy ci du pht trin ch yu nhng vng kh hu n i hay kh hu lnh: ng vTy u, Canada, n v Trung Quc. Ci du cha hm lng cao acid erulic, mcd hp cht ny khng c tc hi v dinh dng, tuy nhin cc nghin cu tm cc loidu thuc h ny vi lng acid erulic thp vn c quan tm. Du Canola l loidu t ht ci du ph bin nht hin nay. C 3 kiu ph bin ca du loi ny:

(i) Du c hm lng acid erulic cao: 20-55% acid erulic

(ii) Du c hm lng acid erulic thp: 0-5% acid erulic

(iii) Du khng cha acid erulic


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Mt c im quan trng ca du nhm ny l mc chuyn ha ng thp. B dul ngun thch hp cho vic ch bin thc n gia sc, tuy nhin loi c hm lng aciderulic cao khng thch hp cho cu v gia cm. Hm lng cht xcao cng l mtim c bit ca h ci du.

2.1.10.Du bp (corn oil)

c chit tch t phn phi (ht bp) caZea mays. Du bp th c mu sm dos hin din ca hp cht carotene v xantophyllic. Du bp cha mt lng tng icao (1-3%) phospholipid v nhng hp cht khng c c tnh ca du khc, ch yul sterol ( 1%). Du bp cng thuc nhm acid oleic-linoliec vi mc acid bokhng bo ha cao, c s dng ch yu trong ch bin du n.

2.1.11.Du u nnh (soybean oil)

y l sn phm ca qu trnh p hay trch ly ht u nnh Glycine max (L.) merill(hLeguminosae).u nnh l ngun cung cp du thc vt ch yu cho vic ch binthc phm ca con ngi. u nnh c ngun gc t Trung Quc, nhng ngy nay,ngun cung cp u nnh v du u nnh ch yu t M v cc nc thuc Chu M.Ch bt u trng u nnh t khong nm 1970, hin nay Nam M cung cpkhong 25% sn lng u nnh trn th gii. Mc d qu trnh p du thu c hiusut vn kh cao, tuy nhin qu trnh ny thng i km vi cc bin i khng mongmun v cht lng: mt s thnh phn c hi thu c cng vi du trong qu trnh

p Chnh v th, chit tch du bng bin php trch ly hin ang c s dng rngri, qu trnh p chc tin hnh quy m nh. Du u nnh thuc nhm acidlinilenic; trong thnh phn cha hm lng acid linolenic rt cao khi so snh vi ccloi du khc. Thm vo , qu trnh hydrogen ha du u nnh cng thng cp dng trong ch bin margarine v shortening. B u nnh sau trch ly l nguncung cp protein v cc cht dinh dng cn thit cho gia sc.

2.1.12.Du u phng (peanut oil)

Du phng l mt trong 5 loi du n quan trng nht trn th gii. Du phng thuc nhvo qu trnh tch chit du t nhn ht cy u phng Arachis hypogea-y l loi cy trng ph bin Chu Phi, n v Trung Quc. Du u nnh cs dng ch yu cho nhu cu thc phm: du chin nu, shortening, margarine, dutrn (salad oil). c tnh quan trng ca du phng l s hin din hm lng thpacid bo bo ho, trong khi li rt giu acid bo khng no cha 1 ni i (ch yul acid oleic). Do cc triglycreid ny c nng chy cao, khi nhit du gimxung 5oC, du phng b vn c do s to gel trong du; tuy nhin qu trnh ng hac thc p dng lm trong du. Mt vn nghim trng nh hng n chtlng v gi tr dinh dng ca du l s nhim c t aflatoxin B1, B2, G1 v G2 (hnh2.2) do iu kin mi trng lm pht sinh nm mc. Vic di chuyn c t t bt u


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phng nghin rt kh thc hin do chng c kh nng chu n nhit 300oC; tuynhin s hin din ca cc c t ny trong du c th loi b d dng trong qu trnhtinh luyn.

Hnh 2.2. Aflatoxin

2.1.13.Du ht lanh (linseed oil)

Thu c t ht cy lanh Linium usisitatissimum, c thpht trin hu ht cc vngnhit khc nhau trn th gii, tp trung nhiu nht M, Argentina, n v Nga.Khi gi nhp khu si cotton vo th trng chu u ngy cng gim dn v ging cytrng phi du nhp t M, gi tr kinh t ca si lanh cng suy gim nhanh chng.Chnh v th, vic khai thc gi tr ca ht lanh c quan tm. Du th t ht lanh cth thu c bng c hai bin php: p v trch ly bng dung mi. Do s hin din caacid linolenic trong du lanh hm lng cao (>50%), du ht lanh c s dng chyu nh ngun nguyn liu trong sn xut sn, vecni cng nh cc sn phm cng

nghip khc. Tuy nhin, mt s quc gia, c bit l n , hn 40% du lanh csn xut nhm phc v cho nhu cu tiu th ca con ngi.

2.1.14.Du ht vng (m, sesame oil)

y l loi du c gi tr dinh dng cao do s hin din ca hn 75% acid bo khngbo ha trong du, c bit l t l cn bng ca acid oleic v acid linoleic (Omega 6) .Du vng thu c ch yu nhvo qu trnh p ht vng Sesamum indicum, ctrng v pht trin nhiu n v Trung Quc; mt s ni khc nh Chu u,

Chu M cng s dng ht vng v du vng vi s lng t. y l nguyn nhnchnh lm cho gi du vng thng rt t.

2.1.15.Mt s du tht cho du khng ph bin

Bn cnh cc loi ht du ph bin, mt s nguyn liu khc cng c s dng trongcng ngh ch bin du vi s lng t:

- Du ht nho (Vitis vinifera (L.), hVilaceae): cha hm lng acid linoleic khcao, tnh cht tng t du ht hng dng.


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- Du t ht ph (Hazel-nut Corylus avellana (L.)Gaertn, hBetulaceae) vdu hnh (Prunus dulcis (Mill.) D.A. Webb. hRosaceae): thuc nhm acidoleic linoleic.

- Du bng go (kapok Ceiba pentandra (L.) Gaertn, hBombacaceae): tnh

cht gn nh tng ng vi du ht bng (cottonseed oil).- Du cy c ch (walnut-tree,Juglans regia (L.), hJuglandaceae): thnh vin

ca nhm acid linolenic. Du cy c ch chc sn xut v tiu th rt t, chyu mt s gia nh thng lu.

- Mt s loi du khc vn c sn xut ty vo tp qun tng quc gia nh dumustard, du go, du ht olive

2.1.16.Cc ngun du mi

y chnh l cc nhm du c tm quan trng mi a phng hay khu vc, qucgia, nhng khng c sn xut v tiu th ph bin trn th gii:

- Crambe oil (Crambe abyssinica Hochst. ex R.E. Fries v C. hispanica, hBrassicaceae) vi hm lng cao acid erucic, s dng ch yu cho mc ch kthut.

- Du cy anh tho (evening primrose oil Oenothera biennis hOnagraceae):cha hm lng cao Omega 6 (6,9,12 octatrienic acid).

- Cht bo c ngun gc vi sinh: cha cc thnh phn c bit, c s dng chothc phm v ng dng k thut.

2.2. CY CHA DU (OILS FROM OIL-BEARING TREES)

Du th thuc nhm ny c ngun gc ch yu t phn tht qu ca cc cy cha du.Qu trnh chit tch du t tht qu cn p ng cc yu cu c bit: cht lng duthu c cng cao khi du c chit tch t qu ti, ngay sau thu hoch. Cc tcng chc ln b mt qu sau thu hoch l nguyn nhn chnh lm ph hy mng t

bo, iu ny lm gia tng hot ng ca enzyme, thc y qu trnh thy phn lipidhay cc h hng khc xy ra nhanh chng.

2.2.1. Du olive (olive oil)

y l loi du c sn xut v tiu th rt ph bin trn th gii, c bit l ccquc gia vng a Trung Hi. Du olive thu c do qu trnh tch p phn tht quolive Olea europaea (L.) (hOleaceaei). Trong thnh phn du olive cha hn 80%acid oleic, tuy nhin t l acid bo khng bo ha mch di rt thp. im c bit cadu olive l s thay i ln thnh phn acid bo trong du theo vng trng nguynliu. Mt s du olive t ging nguyn liu tt c th s dng trc tip m khng cn


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qua cng on tinh luyn (virgin state). Ngoi ra, ty thuc vo qu trnh tch p, chtlng du olive thay i khc nhau, c th chia lm 3 nhm:

(i) Hm lng acid bo ti a 1%

(ii) Hm lng acid bo ti a 1,5 %(iii) Hm lng acid bo ti a 3,5 %

2.2.2. Du c (palm oil)

Sn phm t qu ca cy c(Elaeis guineensis), mt trong hai loi cy trng cho duquan trng nht trn th gii (cng vi da). C c ngun gc t Guinea, Ty Phinhng ngy nay, cc trng v pht trin ch yu cc nc nhit i gn ngxch o (ng Nam , Chu Phi, Trung v Nam M). Vic trng c v ch bin du

c gia tng mnh m trong 3 thp nin gn y. Malaysia v Indonesia l 2 quc giasn xut du c hng u th gii. Sn lng sn xut du c hin nay l: 6 tn du c/30 tn bung c ti/ hectar/ nm.

Qu c l ngun nguyn liu c bit trong ch bin du c do tnh cht rt c trngca n: du c thc tch chit t c ht c v phn tht qu (pulp, mesocarp). Mtvn cn quan tm l lng du tch chit cn di chuyn ra ngay, nhm trnh hintng ht du li vo trong nguyn liu. Lng du c thu c trn thc t ch yu

t phn tht qu, du t ht c ch chim t 10-12% tng lng du c thu c.

Thnh phn acid bo ch yu trong du c l acid palmitic v acid oleic (khong 80%tng acid bo trong du). Chnh v thnh phn c bit ny, du c thng b phn tchthnh 2 phn ring bit: lng v rn nhit phng.

Ngoi ra, du c cn rt d b bin i do hat ng ca cc enzyme thy phn trongsut thi gian sau thu hoch v ch bin, nguyn nhn ch yu l do s hin din nng cao cc acid bo t do (20-25%) trong du; vic chit tch du vi k thut

hin i c th lm gim bt lng acid bo t do ny, tuy nhin s hin din cachng trong du c vn cao hn cc loi du khc. Do hm lng carotene cao (0,05-0,2%) nn du c thng c mu cam m. Chnh v l do ny, qu trnh ty trngv trung ha nhm lm gim lng acid bo t do l hai tham s cht lng quantrng nht trong qu trnh tinh luyn du c:

- i vi du c c ngun gc Chu Phi:

+ Ty trng hon ton: hm lng acid bo t do 2,5%

+ Ty trng thng thng: hm lng acid bo t do = 4-5%

- i vi du c c ngun gc tng Nam :


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+ Cht lng c bit: hm lng acid bo t do = 1-2 %

+ Hn ch qu trnh oxy ha mc thp nht: hm lng acid bo t do 2,5%

+ Tiu chun: hm lng acid bo t do = 3-5 %

Du c c tnh cht vt l c bit l trong khong nhit gn 20

o

C, du c s tn ti trng thi bn rn (semi-solid). Chnh v nguyn nhn ny, du c thng c sdng trong ch bin shortening, margarine thc vt c dng lm mi trngtruyn nhit tt cho qu trnh chin mt s loi thc phm bng bin php nhng trongdu, ng thi to gi tr cm quan cho sn phm (gip b mt sn phm kh ro saukhi chin). Ngoi ra, du c cn c s dng trong cng nghip ch bin bnh ko.

Mc d mu nht thng c ngi tiu dng a chung, tuy nhin mt s ni muc trng ca du c do s hin din ca caroten v tocopherol vn c duy tr.

2.2.3. Du bDu b nhn c t phn tht qu ca cy b (Persea gratissima gaertueri), ctrng ch yu vng a Trung Hi v vng pha Nam Hoa K. Ging nh du c,thnh phn acid bo ch yu ca du b l acid palmitic v acid oleic, trong acidoleic chim u th. Tuy vy, du bkhng c tm quan trng trong cng ngh thc

phm, n c ng dng ch yu trong cng ngh m phm.

2.3. MNG VT (ANIMAL FATS)

Mng vt c th phn thnh 2 nhm chnh: msa (cht bo sa) v mnu chyca ng vt.

2.3.1. Cht bo sa

Ngun msa ch yu l cht bo ca sa b. Cc loi sa khc hu nh khng ctm quan trng trong qu trnh cung cp cht bo. Thnh phn acid bo trong msa

b ph thuc vo chn ca con vt. nhng ni b c nui theo kiu cngnghip, mc d ngun thc n c n nh trong sut ma ng, cht lng bmang v bma h vn c s khc bit ln. Ngoi ra, thnh phn msa cng c skhc bit khi lng mtrong cth ca b khc nhau.

2.3.2. Mnu chy (mthng)

y l sn phm ph ca qu trnh ch bin tht. c im quan trng ca mthng ls hin din ca mt lng ln acid bo bo ha, ngoi ra trong mcn cha rt tcht chng oxy ha t nhin v cha hm lng cao cholesterol, iu ny lm cho mrt nhy cm vi s oxy ha, km theo l nhu cu s dng mthng cho thc phmang gim dn.


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- Mheo: Theo nh ngha ca Codex, mheo l phn mthng thu c t phn mmti, c lm sch ca heo c sc kho tt, git mng cch nhm phc vcho nhu cu tiu th ca con ngi, c m bo bi lut thc phm cng nh ccquy nh ca mi quc gia. Phn m mny khng bao gm xng, da, tai, mng, nitng, kh qun, phn mri, mvng, nhng phn tha t m cv mu.

Nhvo qu trnh ester ha ni phn t, thnh phn ca mheo c thay i mtphn nhm ch bin shorterning, s dng trong cng ngh ch bin bnh.

M heo c khong nhit nng chy rng nh vo s phn b c bit catriglycerid.

Ngoi nhu cu thc phm, mheo cn c s dng trong cng ngh sn xut du bitrn (white grease).

- Mb v cc ng vt nhai li khc: T l acid bo bo ha trong mb cng nhcc ng vt nhai li khc ln hn so vi mheo. Ging nh mth, trong mngvt nhai li cn cha mt lng kh ln cc acid bo c cu trc khng c trng nhacid bo mch nhnh, acid bo c s Carbon l. Chnh v l do ny, mng vt nhaili khng c s dng cho mc ch thc phm, tuy nhin qu trnh chit phn onloi mny c th tch ra c olein v stearin - ng dng trong cng nghip.

2.4. DU TNG VT BIN (MARINE OILS)

Thut ng marine oil: du tng vt bin c s dng ch cc loi du ca ttcng vt sng di nc: c hay ng vt c v khc (c heo). Du tng vt

bin (ch yu l du c) thng l sn phm ph trong qu trnh khai thc v s dngc nh ngun cung cp protein. Tuy nhin, mt s loi c li c khai thc cho mcch chnh l sn xut du. C rt nhiu loi c c kh nng cung cp du: t loi cnh nh c sardine n cc ng vt hu nh c trng lng ln nh c voi. Trongthnh phn ca du c cha mt t l ln acid bo khng no mch di (C 20), chnhv l do ny du c rt nhy cm vi cc phn ng bin i cht lng du. Du c ch

c s dng trong ch bin thc phm sau qu trnh tinh luyn nghim ngt.

- Du c voi: thu c t phn m sn v ni tng ca c voi. Du c voi chacc acid bo khng bo ha cao do c gi tr sinh hc rt ln. Tuy nhin, do

b lut bo vng vt bin, nhm hn ch vic khai thc c voi bng cc binphp sn bn tri php hay c voi b kit sc trn bin do iu kin khch quan:thin taivic s dng du c voi ngy nay khng cn ng vai tr quan trng.

- Du c bin nh: du thu c t cc loi c bin nh ny thng cha nhiuacid bo khng bo ha hn khi so snh vi du c voi. Thnh phn ca duthay i theo ngun nguyn liu. Cc loi du c quan trng nht l du thuc t c sardine vng California (Sardinops sagax caerulea, h Clupeidae),


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c sardine Nht Bn (Sardinops melanostictus, h Clupeidae), du c mi(Brevoortia tyrannus, h Clupeidae) v du c trch (Clupea harengus, hClupeidae).

T l acid bo khng bo ha mch di cng kh cao, ph thuc vo loi c v

mi trng sng: khi nhit mi trng nc cng lnh, hm lng acid bokhng bo ha mch di cng cao. Chnh v s hin din ca acid bo khng bo ha ny, du c thng c lm gia tng cng (to be hardened)trc khi s dng do qu trnh bin i ny s ci thin c kh nng boqun sn phm, lm gim xu hng i ha du.

- Du gan c tuyt: im c bit trong thnh phn du c tuyt (Gadus morhua (L),hGadidae) l s hin din hm lng cao vitamin A v vitamin D


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Chng III. KHI QUT CNG NGH SN XUT DU TH

3.1. SN XUT DU THT CHA DU

3.1.1. Bo qun v sch ht du

3.1.1.1.Nguyn nhn gy hhng ht du trong qu trnh bo qun

Mt trong nhng nguyn liu ch yu dng ch bin du l nhng loi ht c hmlng cht bo cao nh: u phng, u nnh, m, thu du, hng dng,...Tt cnhng loi ht ny u phi qua qu trnh sch v bo qun mi n khu chun b.Trong qu trnh bo qun, nguyn liu c th b h hng do cc nguyn nhn sau:

- S h hp,

- Hot ng ca vi sinh vt, enzyme,

- Do phn ng ha hc,

- Do su mt, chim, chut.

(i) Sh hp ca ht

H hp l biu hin hot ng sng ca ht cng nh bt k cth sng no khc. ychnh l qu trnh trao i cc cht d tr bn trong ht vi mi trng bn ngoi (chyu l khng kh), nh s sng ca ht c duy tr.

Sau thu hoch, qu trnh h hp ca ht vn tip din. Thng qua qu trnh trao icht, cc cht d tr trong ht bt chy, tiu hao dn v gii phng ra nng lng dos oxy ha. Cht d b oxy ha trc tin l cc glucid, sau l protein, cht bo.Qu trnh oxy ha cc cht ny trong ht xy ra phc tp, qua nhiu giai on v sn

phm trung gian. Sn phm cui cng ca qu trnh ny l kh CO2, nc v km theo l mt lng nhit ln c phng thch. Oxy khng kh l tc nhn quan trngnht trong tt c cc phn ng ny. Mc d vy, s h hp ca ht c th xy ra trongc hai iu kin y oxy (h hp hiu kh) hoc thiu oxy (h hp ym kh).

Khi ht c bo qun trong iu kin bnh thng (ng tiu chun), hot ng sngca ht rt yu, s tiu hao cc cht khng ng k. Khi cc hot ng sng ca htc kch thch, tng cng th qu trnh h hp ca ht c tng ln, cht dinhdng ca ht b mt i nhanh chng. theo di tnh trng ht trong qu trnh boqun, hai ch s thng dng l cng h hp v h sh hp.

- Cng h hp: c trng bng lng oxy ht hp th vo v lng CO2 doht thi ra trong mt n v thi gian.

- H sh hp: l t s th tch kh CO2 thi ra v th tch kh oxy ht hp thu votrong mt n v thi gian.


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Hot ng sng ca ht, hay cng h hp ca ht ph thuc vo nhiu yut nhng ch yu l m v nhit .

Thc t cho thy, hot ng sng ca ht bin i rt nhy vi m. Khi htc m chun th cng h hp khng ng k. Khi m ca tng ln th

cng h hp bt u tng nhanh.nh hng ca nhit ti cng h hp ca ht c gii hn hn. Khi htc m thch h p cho hot ng sng th trong khong nhit 50-70oC,cng h hp tng dn.Trn 70oC, cng h hp gim dn, n mt giihn nhit nht nh th ht ngng h hp.

Qu trnh h hp ca cc loi ht din ra theo qui lut chung, mc d vy mi loiht, ty theo thnh phn cc cht (ch yu l du v cht ht nc) m cc qu trnh cth thay i cht t.

(ii) Sph hy do hotng ca vi sinh vt

Sau khi thu hoch, trn b mt lp v ngoi ca ht thng tn ti cc vi sinh vt. Sc mt ca chng l do tt, bi, rc, c,...ln vo theo ht trong qu trnh thu hoch,vn chuyn,... Hot ng ca cc vi sinh vt trong khi ht khng nhng gy nhhng xu m cn l mt nguy c thng xuyn d gy ra s h hng nng cho htdu. Trn ht thng c nhiu loi vi sinh vt hin din nh vi sinh vt hoi sinh, visinh vt gy bnh cho ngi v gia sc..., thng gp nht l cc enzyme, nm mc, vikhun...Vi sinh vt s ph hy ht t ngoi vo trong. Trong qu trnh hot ng v

pht trin, chng s s dng cc cht kh ca ht vo qu trnh trao i cht. Du hiuu tin ca s h hng l lp v ca ht s b sm mu, cu trc v b ph hy... Khilp v bo v b ph hng, cc vi sinh vt s xm nhp vo bn trong, nhanh chnglm h hng v mt cht dinh dng d tr trong ht. Ngoi s mt cht kh, chngcn tit ra cc cht lm gim cht lng sn phm (tit ra cc cht gy mi hi, ng,gy mu sm en cho ht).

S hot ng v pht trin ca vi sinh vt cn c mi trng m cao. Khi mtng th hot ng sng ca ht mnh ln, ta nhit v ta m mnh. T thc ytrli hot ng sng ca vi sinh vt. Qu trnh tc dng thc y nhau gia hot ngca khi ht v vi sinh vt l nguyn nhn thng gy cho c khi ht b bc nng, hhng.

Trng thi nhit ca khi ht cng c nh hng ln n hot ng ca vi sinh vt.Nhit thch hp cho s pht trin ca tng loi khng ging nhau, c th chia lm 3nhm ch yu:

- Nhm a lnh: pht trin nhit gn 0oC.

- Nhm cc vi sinh vta nhit: pht trin nhit gn 50-60oC.


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- Nhm vi sinh pht trin mnh nht: nhit 20-40oC (y l nhm ph binht).

Ngoi m v nhit , mi trng khng kh cng nh hng n hot ng ca visinh vt. Hm lng oxy tng s lm tng hot ng ca vi sinh vt. iu chng t

cc vi sinh vt trong ht thuc loi a kh. Nng CO2 trong mi trng c tc dngkm hm hot ng ca vi sinh vt. V vy, np CO2 vo mi trng bo qun l mtbin php nhm bo qun khi ht.

ngn nga v hn ch s hot ng ca vi sinh vt trn ht, cc bin php thngdng nh lm lnh, to chn khng, np kh CO2... cng t ra kh hu hiu, tuy nhinsy kh ht l bin php n gin, hiu qu v ph bin nht.

(iii) Shhng ht do cc enzyme ph hy

S ph hy ca mt s enzyme c trng thng gp v quan trng l enzyme lipase,phospholipase, lipoxidase...Trong , ph bin nht v thng gy h hng nhiu nhtl enzyme lipase.

- Lipase: c hu ht trong cc loi du. Chng thuc loi enzyme thy phn cnhm hot ng l canxi. Chiu hng v iu kin hot ng ca lipase tythuc vo trng thi sinh l ca ht. Trong qu trnh chn ca ht trn cy,lipase c tc dng kch thch s tng hp t cc acid bo v glycerin thnhglycerid. Tuy nhin, trong qu trnh ch bin v bo qun ht (sau khi thuhoch), lipase li c tc dng ngc li. Chng xc tc qu trnh phn hyglycerid thnh glycerin v cc acid bo t do, lm cho hm lng acid bo tdo trong du tng, ch s acid tng, gim cht lng du. V vy, s thy phnglycerid l tc dng ph hng ch yu ca lipase i vi ht du trong qu trnh

bo qun v ch bin. Lipase ca ht du chu c nhit kh cao. Khi ht 120oC trong 2 gi th lipase ch gim 50% hot tnh hoc 100oC trong30 gith ch mt 40% hot tnh ban u; nhng m cao kt hp vi nhit cao th lipase s nhanh chng b ph hy.Cng nh cc loi enzyme khc,enzyme lipase ch th hin hot tnh cc i mt tr s pH nht nh ca mi

trng. V d: ht thu du, pH ti u l 4,5-5; ht u nnh pH= 5...

- Phospholipase: enzyme thng c trong du, tc dng c hiu l thy phn,ph hy cc phospholipid. Trn thc t, phospholipase tn ti 4 dng A, B, Cv D.

Phospholipase A thy phn lecithin to thnh isolecithin v 1 phn t acid bo.

Dng B thy phn isolecithin thnh 2 acid bo t do.

Dng C phn ct lin kt ester gia acid phosphoric v glycerin.

Dng D phn ct lin kt gia acid phosphoric v baz nit.


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Kt qu cc qu trnh tc dng ca phospholipase lm gim phm cht ca du,ch s acid tng, phospholipid b ph hy.

- Lipoxidase: c tc dng xc tc, thc y phn ng oxy ha cc acid bo khngno bi oxy, to thnh hydroperoxit. Hydroperoxit l cc hp cht khng bn, d

phn hy. Kt qu ca cc phn ng trn to ra trong du cc cht c, lmgim cht lng sn phm. Lipoxidase hot ng tt nht 20-40oC, trn 80oCb mt hot tnh. pH ti u t 6,5- 7,5. Kt qu ny cho thy, qu trnh t nngv gim pH trong ht l bin php loi tr, hn ch s ph hy ca lipoxidase.

(iv) Sph hy do cc phn ng ha hc

Trong ht c du, hu nh c cc nhm cht hu ccng nh v c, y l cchtcho cc phn ng bin i khc nhau c th xy ra. Trong , nhm phn ng ph

bin nht l cc qu trnh ha hc nh cc phn ng oxy ha, thy phn, s bin tnh

nhit ca protein v phn ng bin i mu Maillard.(v) Shhao do su, mt, chim, chut

Trong qu trnh bo qun ht c du, cc loi su, mt, chim, chut d gy ra nhngtn tht ng k. Chng s dng ht lm cht nui sng v tit thi ra trn ht cc cht

bn, hi thi, thm ch c cht gy bnh.

S sng v hot ng ca su mt, cn trng ph thuc vo hm lng m ca ht.Khi ht bm cao, chng s hot ng v pht trin mnh v khi ht kh th hot ng

yu dn v cht. nhit cng nh hng nhiu n hot ng ca cn trng. Phn ln su mt cht 50-60oC. nhit di 0oC, chng cng tn ti nhng hot ng yu hn. Khi nhit thp hn na th chng s b cht dn do s kt tinh ca nguyn sinh cht. Nng oxy v CO2 trong mi trng bao quanh ht cng c nh hng ln n hot ng phhy ca su mt.

3.1.1.2. Cc nhn tnh hngn qu trnh bo qun

Nguyn nhn ch yu gy nn s h hng ht du trong qu trnh bo qun l do sh hp ca ht. Cng h hp trong qu trnh bo qun ht ph thuc vo 3 nhn tchnh: hm lng m, nhit v thnh phn khng kh quanh khi ht. Nhng nhnt ny khng nhng nh hng n hm lng du c trong ht m cn nh hng nc cc thnh phn sng khc ca khi ht nh vi khun sng k sinh trong ht hay cctp cht km theo ht, cc loi su b...

(i) m ca ht

m ca ht thay i ph thuc ch yu vo c im v thnh phn v cu to ca

chng, chn ca ht.Cc ht du c cu trc xp hnh thnh do h mao qun i qua gia cc t bo. Trongt bo c cha cc cht dng keo, c i lc ha hc vi nc (c bit l cc cht


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protein), nh ht du c kh nng hp ph hi nc t ngoi vo hoc nh hi nct trong ni bo ra bn ngoi lm thay i m ca chng. Qu trnh ht v nhm(hi nc) ca ht ph thuc vo bo ha hi nc trong khng kh. Khi p sutring phn ca hi nc trn b mt ht th ht hp ph hi nc vo b mt v vo

bn trong (cc mao qun), m ca ht tng ln. Ngc li, khi p sut hi nc

trong khng kh thp hn trn b mt ht, ht nh hi nc ra bn ngoi, m htgim xung. Khi p sut hi nc trong khng kh v trn b mt ht bng nhau thqu trnh ht hoc nhm ngng li, m ca ht khng thay i. Ht du trngthi ny c gi l ht cn bng m. m tng ng gi l m cn bng ca ht.

Qu trnh ht m ca ht thng chia lm 2 giai on:

- Giai on u (giai on htm lin kt): hi nc hp ph vo gia cc b mtnhng phn t dng keo (ht nc) v c gi li trn cc b mt y bng cc

ni lin kt hydro kh bn vng. dng m lin kt, nc t c kh nng thamgia hoc thc y cc qu trnh bin i khng c ch ca ht.

- Giai on hai (htm tdo): Sau khi kt thc giai on mt, ht vn tip tc htm vo gia cc phn t dng keo, nhvo cc lc ht tnh in. Khi dng mt do, nc l yu t quan trng thc y cc qu trnh gy h hng ht, n thamgia trc tip vo cc phn ng ha hc, lm tiu hao lipid trong ht.

m ca ht thi im c nc t do xut hin (kt thc giai on ht m lin kt)gi l m ti hn hay m chun ca ht. ln ca m ti hn ph thuc vo

thnh phn ha hc ca ht. Nu ht c du cao, m ti hn ca ht s gim.Qu trnh bo qun ht du t hiu qu khi m bo qun nh hn m ti hn.

Vi tt c cc loi ht du, m chun c th xc nh bng cng thc:

100

1005,14

MAth

=

Ath : m ti hn (m chun) ca ht (%)

M : Hm lng du trong ht kh tuyt i (%)

14,5 : m dng lin kt ca cc cht ht nc cha trong ht.

(ii) nhit ca ht

Trong qu trnh bo qun cc ht c du, nhit tng s lm tng cng h hpca khi ht. nhit thp s lm cc qu trnh sinh ha trong ht b chm li, nhit cao s thc y qu trnh t bc nng trong khi ht. Tuy nhin, nh hng ca nhit n cng h hp ca ht c gii hn hn. Khi ht c m thch hp chohot ng sng ca n, t nhit thp tng dn ln khong 50 70oC, cng h

hp ca ht tng. Nhng khi tng trn 50 70oC, cng h hp gim dn, nu tiptc tng n mt nhit nht nh, ht ngng h hp (b mt hot ng sng).


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(iii) Thnh phn kh ca khng kh gia khong trng ca ht

iu kin khng c O2, hot ng ca vi sinh vt gim ng k. Li dng tnh chtny, qu trnh bo qun ht t hiu qu, cn to iu kin khng c O2 trong khiht. Qu trnh loi oxy khi khi ht c th tin hnh bng hai cch:

- S dng cc cht kh: CO2, N2, khi... thay th vo cc khong trng ca khiht.

- Phng php ha hc: a ngay vo gia khong trng ca khi ht hi acidpropionic hay cc cht kh bromua metyl, diclo etan... Qu trnh ny t hiu qunhanh tuy nhin n c kh nng thay i phm cht ca lipid.

3.1.1.3. Bo qun v schht du sau thu hoch

Mc ch ca qu trnh ny nhm khc phc cc nguyn nhn gy h hng nh hng

n cht lng ht du.Phng php sch ht du ph thuc vo c im, tnh cht ca ht du cng nhquy m v iu kin sn xut ch bin.

Qu trnh sch ht du tng qut gm cc cng on sau:

Ht ti

Phi sy

Lm sch

Thng g cng bc

Lm ngui

Bo qun

Hnh 3.1. Cc cng on sch ht du sau thu hoch

(i) Lm sch

Tp cht thng l nhng cht v ch trong qu trnh bo qun, ch bin, n cn lngun sn sinh ra cc loi vi sinh vt ph hoi cc iu kin sng bnh thng ca ht.Hn hp tp cht thng lm cho sn phm c mi kh chu. Mc ch ca qu trnh

lm sch ht nhm loi b cc tp cht v cc hi nht, , si, kim loi c tronght du lm tng tro, gim lng lipid v protein trong ht du, gy bn sn phmv h hng my mc trong qu trnh ch bin. Ngoi ra, cn loi cc tp cht hu c


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nh c rc, thn v cy tn ti theo ht du sau thu hoch gy tng m nguyn liu,thc y qu trnh t bc nng v l ngun cung cp vi sinh vt c hi.

Cc phng php lm sch ht thng s dng nh :

- Sng

- S dng sc gi (kh ng lc)

- S dng t tnh (nam chm)

- S dng sng gi

- S dng mi trng lng

(ii) Sy ht

Qu trnh sy ht trc khi bo qun v ch bin gip ht c m an ton, khng hhng trong qu trnh ch bin. Ngoi ra, cn gip dit mt phn ln vi khun, su bk sinh nhnhit sy.

Da vo tnh cht ca qu trnh truyn nhit c th s dng cc phng php nhilu, dn nhit hay bc x nhit lm kh ht. Trong , sy ht nhvo qu trnh ilu nhit ph bin v mang li hiu qu cao. Ngun nhit s dng l khng kh tnng hoc cc sn phm chy ca nhin liu i qua lp ht m. Ty thuc vo mcch sy, m ban u ca nguyn liu, kch thc nguyn liu c th tin hnh sy

cng chiu hay ngc chiu. Phng php sy i lu cng chiu c p dng nhiu.

(iii) Thng gi cng bc

ngha chnh ca qu trnh thng gi cng bc l hc nhit v lm kh mtphn m ca cc ng ht m khng cn phi o trn chng. Ngoi ra thng gicng bc cho ht cn c th s dng tt trong cc phng n tng hp ca cc mysy nhm:

- Sb lm kh ht kho trc khi chuyn i sy,

- Lm ngui ht sau khi sy gip tng hiu sut my sy,

- Gim m ca ht trong qu trnh bo qun,

- Loi tr cc t bc nng ca ht.

(iv) Lm ngui ht

Ht khi ra khi thng sy thng c nhit cao, tin hnh bo qun ngay thng lmtng m ca ht do hi nc trong khng kh ngng t li trn b mt lp ht.

Ngoi ra, qu trnh lm ngui ht thng lm gim thm lng m ca ht khong 1%.


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Nguyn tc chnh ca qu trnh lm ngui ht s dng khng kh mt thi qua cc hpchp v ht th ri pha ngoi chp.

(v) Bo qun ht

bo qun ht kh thng s dng cc xil cha ht. Trong qu trnh bo qun, cn

kim tra thng xuyn tnh trng ht thng qua vic xc nh nhit, m, ch sacid ca ht nhm pht hin v khc phc kp thi tnh trng h hng nu c ca khiht.

3.1.2. Giai on tin xl ht du

Cc ht c du thng cha t 1/ 4 n 3/ 4 lipid. Thnh phn lipid ny khng nm dng t do m c kt hp cht ch vi cc thnh phn khc trong nguyn liu nh

protein, glucid v c gi li trong ni bo ht. Chnh v nguyn nhn ny, ht dutrc khi c tch chit cn phi tri qua qu trnh chun b nhm mc ch:

- Tng hiu sut qu trnh trch ly: Du c di chuyn ra ngoi b mt htqua cc cng on chun b.

- Gip nguyn liu c cu trc tnh cht ph hp cho qu trnh tip theo.

- Gim hao tn nguyn liu.

Hai cng on ch yu trong qu trnh tin x l l tch v ht v nghin ht du.

3.1.2.1. Tch v ht

(i) Mc ch- Tng hm lng du ca nguyn liu ch bin: Du trong m tp trung ch

yu nhn ht, v qu v v ht c mt lng rt t vi thnh phn khngging thnh phn lipid nhn. V vy khi ch bin hu ht cc loi ht ducn tin hnh tch nhn, m cha du ch yu khi lp v ngoi ca htcha t du. Ngoi ra, v qu v v ht c tnh xp, hp thu du, hnh thnhlin kt gi du li v, tng tn tht du.

- Nng cao nng sut thit b cng ngh: V qu v v ht c bn c ln

hn rt nhiu so vi nhn s gy gim hiu sut lm vic ca my, thit b,gy chng mn cc b phn lm vic ca my.

- Tng cht lng du: Lipid ca v ht vi thnh phn ch yu l sp v cccht tng t ln vo du s lm gim gi tr cm quan cng nh cht lngdu.

(ii) Phng php tch v ht

Qu trnh tch v ht bao gm cc bc chnh: ph vv ht, xay xt v phn ly hnhp sau xay.

Ty thuc tnh cht cl ca cc m ht du, my xay xt vc thit k quy trnhlm vic theo cc nguyn l khc nhau. Yu cu i vi cc my xt v l ch ph v


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v, gi cho nhn khng xay xt. Khi xt v, cng c chi dng cho ph v v v giiphng nhn. Di tc ng ca ti trng p ln v ht, v s b ph v.

Cc phng php ph vv ht thng c s dng trong cng ngh sn xut du:

- Ph vv ht do ma st vi bmt nhm

S dng thit b c vnh nhm trn thn hay my xt kh ng hc, chuyn ht vomy vi vn tc xc nh, tip xc b mt ht vi b mt nhm hnh thnh lc cn hmchuyn ng ca ht, v s trc ra khi nhn.

- Ph vv ht do sva p ln bmt rn

Nguyn l: V ht chuyn ng vi vn tc no (khng cnh) va p ln b mtrn chuyn ng, v ht vra tch khi nhn.

Ty thuc loi ht m vn tc dng ht khc nhau. Th d nh trong tch qu trnhtch v ht hng dng, vi vn tc 10 m/s, v bt u trc khi ht, khi tng vn tc

65 m/s, v b ph vhon ton, tuy nhin vi vn tc ny, t l ht b l 25%.Thit b s dng cho qu trnh tch v ht theo phng php ny c th l my xtkiu cnh ba, my xt ly tm.

- Ph vv ht do ct ht bng ccu dao

Nguyn l: Ht ri vo khe gia cc dao chuyn ng v dao tnh, cc li dao b trtrn a quay s xt v, gii phng nhn.

Thit b: My xay da, xay dao.

- Ph vv ht do nn p trong khe gia cc trc quay

Ht ri vo khe trc quay ca my cn 1 i trc, c 2 b mt nhn v mt nhm, rnhkha s b nn, v b x nt ra v tch khi nhn.

(iii) Cc nhn tnh hngn xay xt v ht

-m

Trong trng hp m v < m nhn: khi ph vv kh gin, nhn m dai, ginguyn c hnh dng nhn v d dng tch khi v.

Vi m khi ht khc nhau, v s trc khng u trong qu trnh xay xt. Ty thucloi ht, yu cu m khc nhau. Nhn chung, m ph hp nm trong khong t7%- 8%. m ht thp, chi ph in nng gim nhng ht qu kh, d v.

Khi m ht tng: Nu c ht c chnh ph hp vi vn tc, v d b ph v,lng nhn nguyn cao, nhng chi ph in nng tng. Trng hp cht khng phhp vi vn tc, lng nhn nguyn gim r rt.

- Kch thc ht

Khi ht ng u v kch thc, hiu qu xt v tng, d dng iu chnh chnh xcch lm vic ca my xt.


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Vi khi ht c cng m, ht ln d trc v hn ht b, ng thi vic tiu thinnng cng t hn. Th d: Ht hng dng c m 6-7 %, vi cht 6 mm, vn tcxt 31m/s; vi cht < 6mm, vn tc xt 34 m/s.

- c im ht

Ht c phm cht khc nhau nh kch thc, dy v, t l v/nhn khc nhau, hiuqu xt s khc nhau.

Ht c bn ln, cht nh, khi lng nh, nhn nhiu, vn tc ph vv tng.

- ng lc ph vv ht

V ht chu tc dng ca ngoi lc do cnh ba ca tay quay va p ln ht- lc nny, lc ma st gia cc ht vi nhau, ma st gia ht v thit b. Ngoi ra, ht cnchu tc ng ca ni lc l lc un cong, lc bin dng n hi ca ht. Ht chu nnng hc mt i mi lin h bn vng gia nhn v v, ht b rn nt, nhn tch khi

v ht.V ht cn do cnh bin ca cc cnh ba lm vhoc b vtrong lc bay t mt cnh

ba vo thnh trong lng my.

Nhng ht khi ba p khng lc lm vv, khi vng vo mt rp ca lng my sb vtip tc.

(iv) Phn ly hn hp xay

Thnh phn hn hp sau xay ch yu gm:

- Nhn nguyn, nhn na,

- Mnh nhn vln, nh, trung bnh,

- V nguyn, nt,

- Bi du (cm).

3.1.2.2. Phng php tch v khi nhnSau qu trnh xay, c th tch ring tng thnh phn trong hn hp ra khi nhau,

qu trnh phn ly bng sng phn loi kch thc hay s dng tnh cht kh ng hcca cc thnh phn phn ly nhqut gi c ng dng.

Cc thit b phn ly thng dng nh:

- Sng qut

Nhim v ch yu ca my sng qut l loi b trit v khi nhn vi tn tht dutheo v t nht.

My sng qut lm vic bnh thng khi sn xut kh du c v thp, t l v cho

php trong nhn khng ln hn 1,6%, thng thng khng vt qu 3%. Khi dngnhn trch ly, t l v cho php trong nhn khng ln hn 8% nhm trgip cho


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qu trnh khuch tn du. Hm lng du trong v thi khng vt qu 0,5%. Nngsut: 50-60 tn ht/ngy.

- Sngin

My sng in gm 2 phn: phn tnh in (in cc) v phn khung sng phn tch

nhn v v da trn s khc bit tnh cht vt l v in l ca chng. Nng sut 200tn ht/ngy. T l nhn ln theo v


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Cc loi my nghin thng s dng: nghin trc (my cn trc), nghin ba, nghina... Trong , my nghin trc c s dng ph bin nht.

Ty thuc loi nguyn liu, iu kin nghin khc nhau:

-u phng

- m trc khi nghin < 8,5%.- S dng my nghin 2 i trc.

- Mc ph vnhn (lng bt lt sng cc ng knh khc nhau): Ving knh d= 1mm l 10-15%, d= 2 mm t 70-80%.

- Da

Ci da c hm lng du cao, kch thc dy v di. Do , trc khi nghin cn ctci da thnh tng mnh c chiu di 20- 25 mm.

Nghin qua 2 thit b :

- Nghin ba n kch thc lt qua l ry d=1 mm l 15%.

- Nghin nh bng my nghin 2 i trc.

-u nnh (u tng)

u nnh c hm lng du tng i cao, kch thc ht nh, thng s dng mynghin 2 i trc hay 1 trc, c rnh kha. Mc ph vnhn d= 1mm xp x 60%.

(iii) Sbin i tnh cht ca nguyn liu trong qu trnh nghin

-Sph hy cu trc tbou im khi tin hnh nghin cc ht cha du l cu trc cc m t bo b ph v,du t bn trong ni bo gii phng ra ngoi b mt, tng hiu sut qu trnh p haytrch ly. Tuy nhin, qu trnh ny lm cho b mt t do ca nguyn liu trnn ln,du trn b mt nguyn liu tip xc vi khng kh, qu trnh oxy ha du (i ha)din ra nhanh chng.

Trong qu trnh nghin, mt phn du trong t bo c thot ra trn b mt v nmli di tc dng ca lc lin kt phn t, mt phn du cn st li s nm yn

trong cc mnh t bo b ph hy, gy tn tht du. Nu lc nghin cng nh th hmlng du gi li trong nguyn liu cng nhiu.

- Bin i ha hc v sinh ha ca ht khi nghin

Du trong ni bo sau khi gii phng ra do vic ph vcu trc t bo khi nghin, hpph trn mt din tch rng ln b mt cc ht bt. Trong qu trnh , nguyn liunguyn liu c nhng bin i ha hc v sinh ha nht nh.

Nguyn nhn ch yu do:

- Tc ng chc ca lc nghin.- Tc ng ca nhit sinh ra do ma st gia nguyn liu vi b mt nghin v

gia nguyn liu vi nguyn liu.


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S bin i sinh ha thng xy ra trong qu trnh nghin ch yu l do s bin tnhprotein vi mc khc nhau do tc ng ccng nh tc ng nhit. Tuy nhin, sbin tnh ny khng su sc do thi gian tc ng ca lc nghin v nhit ln nguynliu khng di. Ngoi ra, qu trnh nghin ht cn l nguyn nhn lm cho cc henzyme trong t bo b ph v gim mt phn hot tnh, sau khi b ph vcu trc,

to kh nng tip xc gia du v oxy, khng kh m ca kh quyn, cc qu trnh oxyha v thy phn du s din ra, cng h hp ca ht tng. Trn b mt bt, c s

pht trin mnh cc h vi sinh vt, gy mt du v cc thnh phn khc nh protein,glucid.

Cng cc qu trnh ph hy xy ra trong bt cng mnh khi du c gii phngra di dng mt lp mng mng, phb mt bn trong cng nh mt ngoi ht bt.

(iv) Cc yu tnh hngn qu trnh nghin

- m nguyn liu

Ht m do hn nhng t dn hn ht kh, lm cho s bin dng do tng khi mht tng. Ht m, khi nghin s b cn dp, khng bp v, d bt vo trc nghin,

bt nghin thot ra khi khe trc c dng dt, trong khi t ht kh s thu c btti mn, nhiu cm, tm.

m ca ht v nhn nh hng ln n hiu sut nghin: m thch hp cho qutrnh nghin ty thuc vo loi nguyn liu, hm lng du trong tng loi nguyn

liu. i vi ht c cha hm lng du cao, m nguyn liu cng thp, v ngcli, ht c hm lng du thp, m c th cao hn.

Th d : i vi u phng, m gii hn l 6- 7%.

i vi da, m gii hn l 7-8 %.

- Hm lng du trong nguyn liu

Ht c hm lng du cao, nht cao, khi vo khe trc, u tin b cc trc nn duthot ra v bi trn b mt nghin, gim ma st nguyn liu v b mt nghin, cc trc

cun bt vo khe rt kh, lm gim hiu sut nghin.

- Nhit nghin

Khi nhit tng, tnh do ca nguyn liu cng tng, kh nghin t yu cu thchhp. Vi m thch hp, nhit nghin khng ln hn nhiu so vi nhit khngkh. Nhit nghin thch hp 25-45oC.

(v) Cc chtiu vbt nghin

- nh v mng: Bt nghin cng mng cng nh, du trong nguyn liud dng tch ra khi p hay trch ly, khi bt d ti p xc vi nhit v hi


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nc trong ni chng. Bt qu vn d vn cc, cnh khuy kh lm vic,hi khng thot ra khi chng v sy.

- T lv ln trong bt: V cng nhiu t l tn tht du theo kh du cngln, cht lng du v kh du cng km. T l v ln trong bt c xcnh hm lng xtrong bt nghin v nhn ht.

- acid v mi: y l ch tiu quan trng trong trng hp bt nghinkhng c s dng ngay. Bt c acid, mi mc hc cn em ch binring (thnh phm c cht lng xu).

Mc d vy, khi bt sau khi nghin rt kh t c sng u cao. Nguyn nhnch yu do bn ca bn thn vt th phn b khng u nhau trn ton b cu trcca ht. Chnh v th, khi c ngoi lc tc ng vo th s phn hy xy ra nhngkhu vc c s phn khng yu hn. Mt khc, ngoi lc tc ng ln vt th cng

phn b khng u nhau v cng v phng ca lc. nhng gc cnh, vt thrn chu tc dng ca lc ln, do , s phn hy xy ra mnh. my nghin trc,hin tng ny din ra phc tp hn v khi ht ri vo gia khe trc th v tr ca htnm khe trc khng ging nhau nn chu tc ng ca lc khng u nhau. Hn na,

bn thn nguyn liu c kch thc khc nhau nn di tc ng c hc ca lcnghin, nguyn liu b vthnh tng mnh c kch thc khc nhau.

Ngoi ra, do nhng thay i v ha hc v sinh ha nn bt nghin d b chua, ch sacid tng cao, kh bo qun. Cn tin hnh nghin v chng sy song song, trnh victhay i cht lng du v hiu qu tch du.

3.1.3. Chng sy bt nghin (gia cng nhit m)

3.1.3.1. Mc ch

- Chng sy bt nghin l qu trnh gia cng nhit m cho khi ht nhm mc chch yu l to sng u cho khi ht v to iu kin tt cho qu trnh tchchit du t hiu qu cao nht. Qu trnh chng sy s ph v lin kt t nhingia phn bo v phn khng bo, gip du thot ra dng t do di tc dng

ca nc v nhit.- Ngoi ra, nhvo cc tc ng ny to cho du c nht thch hp (thp

nht), to tnh linh ng cho du.

- V hot enzyme khng mong mun, xc tc qu trnh phn hy du (lipase,lipoxygenase, phospholipase).

- Lm mt tnh c ca nguyn liu nu nguyn liu c cha c t.

- Mt khc, chng sy cn lm thay i mt phn v mt ha hc theo chiu hngtch cc cho cc giai on k ti p nhm m bo cht lng sn phm cui:

Protein b bin tnh nhit nn tnh do ca bt p tng, tiu ha ca kh du tthn.


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3.1.3.2 Cc bin i bt nghin khi chng sy

Do nh hng ca nhit v hi nc khi chng sy, cc cht trong khi bt nghin cnhng thay i v tnh cht vt l, ho, sinh

(i) Cc bin i vt l

Trong giai on lm m, cc cht phi lipid s trng n. Nhqu trnh lm m cthc hin nhit khng cao (50-600C) nn bt chtrng thi lin kt v trng nnhng khng b h ha, iu ny gip cho tnh do ca bt tng ln.

Trong cc ht bt trng nmi lin h gia du v cc thnh phn phi lipid byu i, chiu dy cc mng du tng dn v chuyn ln trn b mt cc ht bt. Do

phn a nc ht nc trng n, th tch ca bt cng tng ln. Khi du t bntrong cc khe vch chuyn ra pha mt ngoi. Tc trng n lc mi bt u htnc ln, sau gim dn v n cui qu trnh th bt khng cn ht nc na. Tc

thm nc ca bt ph thuc vo:- iu kin lm m, ch yu l so trn,

- Tnh cht ho nc trong nguyn liu,

- Khi lng nc lm m,

- Hm lng du trong nguyn liu.

giai on sy, nhit tng n 105oC nhm bc thot bt mt phn nc, iu nydn n s bin tnh protein lm thay i c tnh bt, bt trnn cng v c tnh nhi. S bin tnh ca protein gip cho lin kt vi du gim, nht du gim lm

tng tnh linh ng ca du, du d dng thot ra khi pNu nhit tip tc tng n 150-180oC, bt chng sy trnn chy lng, mc dprotein bin tnh su sc.

(ii) Bin i ho hc

Cc cht protein trong bt chng sy nhit 75-80oC v m 10% b bin tnhsu sc. Mc bin tnh ca cc cht protein trong thi gian gia cng nhit m phthuc vo nhit v thi gian chng sy.

Di tc dng ca nhit , cc glucid v protein s tng tc theo phn ng caramelv Melanoidin. Hai phn ng ny to ra cc sn phm c mu sm lm cho kh du vdu cng b sm mu, gy nh hng n cht lng du v kh du.

Qu trnh gia nhit cn lm cho lin kt ca phospholipid vi cc thnh phn khc bct t, gii phng phospholipid t do. Phospholipid t do d ha tan trong du lmcho hm lng phospholipid trong du tng. Nhit cn l nguyn nhn thc ycc qu trnh oxy ha du lm gim cht lng du.

(iii) Cc bin i sinh ho

giai on u chng sy, nhit khng cao (50-60o

C), ng thi m tng nncng hot ng ca cc enzyme thy phn du tng. Song song , s sng vhot ng ca cc vi sinh vt cng tng lm nh hng khng tt n cht lng bt


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chng sy. nhit cao hn, trong giai on sy, hot ng ca cc enzyme v ccvi sinh vt bc ch v protein b bin tnh.

3.1.3.3.Yu cu c tnh kthut ca bt chng sy

Bt chng sy phi c c tnh k thut ph hp vi iu kin lm vic ca my p

hoc trch ly. Ty theo tng loi nguyn liu, ccu ca thit b m bt chng sy cnhng c tnh k thut khc nhau, nhng yu cu chung quan trng l mc ngnht ca khi bt.

- Mc ng nht chung: khi bt phi c tnh ng nht v kch thc, hnhdng, m, tnh do, n hi...

- Mc ng nht ni ti: ng nht vc tnh b mt v c tnh bn trong cacc phn t bt.

Nu bt khng t ng nht chung cng nhng nht nt ti th hiu qu thot

du s gim. Tuy nhin, trong thc t sn xut kh t c c hai ng nht ny.m ca khi bt sau chng sy thng t 8-12%.

3.1.4. Chit tch du bng qu trnh p

3.1.4.1. Csl thuyt ca qu trnh p duKhi u ca qu trnh chit tch du c tin hnh bng bin php p s dng hinc, tin trnh ny c thc hin theo bin php th cng, gin on (batch). nnm 1092, qu trnh tch chit du lin tc bng thit b p trc vt c Anderson

pht minh v a vo s dng. Cch p tch bng trc vt ny da trn vic thit kcu to th tch gim dn ca vt Archimede trong lng ng. Ngay lp tc, cch nyc ng dng nh mt phng php tiu chun v ph bin nht cho qu trnh chittch du ca hu ht nguyn liu. Thit b cbn ban u ny c ci tin v honthin dn, gip hiu sut tch du ngy cng nng cao.

Nh thit kc bit ca vt ti, du c gii phng ra khi bt nghin do s tothnh p lc trong my p - do s nn nguyn liu v sc phn khng ca nguyn liu:

Bt chng sy sau khi c chun b c cu trc n hi v c l nht nh, phn

protein ca bt c tnh do rt cao, d dng bin dng khng phc hi v trng thi c.Du phn b trong cc khe vch v trn mt cc ht bt l cht lng, nht nhnhit cao. Khi bt b p trong lng my, p lc hnh thnh gip du t cc khe vchthot ra.

S thay i p lc ln hay nh ph thuc vo cu to lng p, trc vt v c tnh clca bt p.

- Cu to thit b: S thay i ng knh lng p, chiu di bc vt, thanh gt ca ra kh.

- c tnh cl ca bt p:

+ Bt nho, nc c, my khng to p lc.


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+ Bt kh, trc vt khng quay c, gy h my. Trng hp thit b c thlm vic c, p lc to thnh thng rt cao, nhit p cao, bt sm mu,kh du c mu nu xm.

Nu p lc tng cao, tnh chy do ca bt cng tng, lm tc khe cn thot du.

3.1.4.2. Cc yu tnh hngn hiu sut tch du

(i) Mc nghin ht

Bt chng sy khng ng u, kh nng ht m vi lng cn thit cng khng ngu v tc , lng m phn phi khng ng nht ton khi bt, hiu sut chittch gim.

Ngoi ra, cu trc bt nghin phi c ph vmc ti a v nu bt nghin c kchthc ln, ng i ca du di nn du kh thot ra di tc dng ca lc khuy.

(ii) Slng v ln trong khi bt nghin

V ln trong khi bt nhiu, lng nc lm m cng tng, thi gian, ngoi ra v cthnh phn ch yu l cellulose kh nng ht du cao lm gim hiu sut.

(iii) Mc lm m v nhit chng sy

Mc lm m v nhit chng sy phi thch hp bt c tnh cht c l thchhp (do, n hi). trng thi ny, di tc ng ca cnh khuy, du thot ra ddng.

- Nu bt qu kh khi chng sy bt khng do, khng b vn thnh cc c kchthc nht nh. Khi p, bt ri rc, du khng thot ra c.

- Nu bt qu nho, du c gi li trong cc khe vch t bo, cc t bo li linkt cht ch vi nhau do bt qu t, lm tc cc ng thot du.

(iv) Thi gian thot du

ng vi mi thit b (c th tch, tc khuy, din tch v nhng v tr nhng l lithot du khc nhau) cn thi gian thot du nht nh.

Thi gian thot du c tnh bng hiu s gia thi gian t lc bt i vo n khi kh

du thot ra. Chnh v th, nu thi gian thot du ngn, du thot ra cha ht; ngcli, thi gian thot du di, nng sut gim.

(v) Cu to thit b

Mc tch kit du t bt cn ph thuc vo nhng nt c bit ca kt cu lng p,chnh gn vt, bc vt...

3.1.4.3. Cc bin php p du cbn

Ty thuc vo tnh cht nguyn liu, vic chit tch du t ht du c thc hin theocc bin php khc nhau: Chit tch theo 2 giai on (p sb trc khi p kit haytrch ly) hay p trc tip (1 giai on).


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- p sb: s dng thit b p du c p sut to thnh thp, iu ny dn nlng du cn st li trong bnh du khong 15-25%. Lng du cn li ctch chit bng bin php trch ly hay s dng thit b p kit.

- p trc tip: my p c thit k vi p sut to thnh trong p cao hn, du

c chit tch ra khi nguyn liu vi hiu sut cao, lng du cn li trong khdu dao ng trong khong 4-7%. K thut ny yu cu nng lng s dng lnhn, ng thi nhit ca bnh du gia tng trong sut tin trnh p. iu nyc th l nguyn nhn lm cho du d b oxy ha v i ha, ng thi xy ra cc

bin i lm gim phm cht du. Chnh v th, vic lm lnh h thng trong sutqu trnh p cn thit phi c tin hnh nhm ngn cn tc ng xu ca nhit.

Cho n trc nm 1990, qu trnh tch chit du bng p kit mt ln t khi s dng

do lng du st li sau khi p vn cao. Tuy nhin, do vn bo v mi trng, qutrnh p kit c p dng rng ri hn nhm hn ch lng dung mi s dng v thiloi.

Ngoi bin php p trc vt thng thng, mt s loi du c cht lng cao nh duolive thng c tch chit bng p lnh. phng php ny, khng c giai on xl nhit c p dng cho nguyn liu trc khi tch chit thit b p trc vt. Qutrnh p lnh c s dng nhm mc ch ngn cn qu trnh pht sinh mi trong du.

S tng qut ca qu trnh chit tch du t ht cha du c tng hp hnh 3.2.

Ht du, thu hochNguyn liu

Tin x l Lm sch, sy kh

Ht du, bo qun

Gim kch thc Tch v, nghin

X l nhit - m Chng sy bt nghin

Chit tch du 1p s b

Nghin ti

Giai on trung gian Bnh du Bt (flakes)

Chit tch du 2 p kit Trch ly

Sau x l

Sn phm cui Duth

Bnhdu

Bdu

Toasting Loi dung mi

Thy ha

Du th 2 Lecithin

Hnh 3.2. S chit tch du tht du


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3.1.5. Chit tch du bng phng php trch ly

Trch ly du c thc hin da trn c tnh ha tan tt ca du thc vt trong ccdung mi hu ckhng cc nh xng, hecxan, dicloetan ..., ch yu l hexan. Vicchuyn du phn b bn trong cng nh mt ngoi cc cu trc vt th rn nh ht, bt

chng sy, kh du vo pha lng ca dung mi l mt qu trnh truyn khi xy ratrong lp chuyn ng, da vo s chnh lch nng u trong nguyn liu v dngchy bn ngoi.

Khai thc du bng phng php trch ly em li hiu qu kinh t cao, c nhiunc trn th gii p dng do c nhiu u im:

- My mc thit bc cgii ha v tng ha hon ton nn quy trnh snxut lin tc, nng sut thit b cao, thao tc d dng, hiu sut lao ng cao.

- Trch c trit hm lng du t nguyn liu, hm lng du cn li trong

b rt thp (0,1- 0,3%). Do , du tn tht trong qu trnh sn xut khng ngk.

- i vi cc loi nguyn liu c cha hm lng du th p (17- 18%) v loinguyn liu cha du qu th ch dng phng php trch ly c hiu qu khaithc cao.

Tuy nhin, qu trnh trch ly i hi h thng trch ly phi m bo, trnh hin tngchy n do dung mi c nhit si thp, dung mi s dng c cht lng cao, phhp vi tng loi nguyn liu nhm trnh tn tht cng nh gim pht cht ca du.

3.1.5.1. Bn cht ha l ca qu trnh trch lyBn cht ca qu trnh trch ly l qu trnh ngm chit du trong dung mi hu c. yl kt qu ca 4 qu trnh kt hp:

- S di chuyn vt l ca du t ht,

- Kh dung mi v ht tch du: sn phm l kh du c s dng trongch bin thc n gia sc,

- Tch loi dung mi t du trch ly,

- Thu hi dung mi cho cc qu trnh s dng li.

Vic chuyn du t nguyn liu vo dung mi c thc hin nh vo qu trnhkhuch tn, trong :

- Khuch tn phn t(20%): Chuyn du t ni tm nguyn liu vo dung mi.

- Khuch tn i lu (80%): Chuyn du t b mt nguyn liu vo dung mi.

Qu trnh trch ly du thc vt din ra theo 2 giai on:

Giai on u(Khuch tn i lu ca du thc vt vo dung mi)

Trc tin din ra s thm t dung mi trn b mt nguyn liu, sau thm suvo bn trong nguyn liu to ra mixen (dung dch du trong dung mi). Sau khi ycc bc khng kh trong khe vch t bo ra ngoi, mixen chim y cc khe vch trng


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v thc hin ha tan du trn lp b mt. Sau nhdung mi thm su vo cclp bn trong, tip tc ha tan du phn b trong cc ng mao dn bc kn. Qutrnh ha tan du vo dung mi tip tc din ra n khi t s cn bng nng mixen lp bn trong vi lp mt ngoi ca nguyn liu. Vic to mc chnh lch thngxuyn n nh gia nng mixen trong nguyn liu v bn ngoi nhdng dung mi

chuyn ng mang nguyn liu trch ly.

Giai on hai(Khuch tn phn tca du thc vt vo dung mi)

Dung mi tip tc thm su qua cc thnh t bo cha b ph vv ha tan du trongcc khe vch t bo. Lng du cn st li trong ni tm nguyn liu ch chimkhong 20% do dung mi thm rt kh khn vo cc t bo cha b ph vny.

ha tan cc cht ph thuc vo lc tng tc gia cc phn t dung mi v chttan. Cng lc tng tc ny do thm in mi quyt nh, th hin mc phncc ca cc thnh phn hp thnh phn t cht . Do cc loi du thc vt s hatan tt trong cc dung mi c thm in mi gn vi thm in mi ca du thcvt ( thm in mi ca cc loi du thc vt nm trong khong 3,0- 3,2). Cc dungmi c thm in mi >20 c kh nng ha ln trong nc (bng 3.1).

Bng 3.1. thm in mi ca mt s dung mi hu c(nhit 20oC)

Dung mi hu c thm in mi

Xng

Hexan

Benzen

Dicloetan

Axeton

2,00

1,89

2,20

10,36

21,50

Ngoi ra, trong du thc vt cn c mt lng acid bo t do, s lng acid bo t dotng, tnh ha tan ca du trong dung mi tng.

Du trong cc dung mi hu c to thnh dung dch phn t (dung dch tht: lipid,acid bo t do cn thit, vitamin tan trong du,lipid mang sc t...), trong lc , duchit t nguyn liu c du trong iu kin sn xut bao gicng ko theo vi du mtlng cc hp cht khng c tnh bo (phospholipid, sp, cn x phng) chuyn vodung mi lm cho mixen c tnh keo. V vy, mixen va l dung dch c c tnh phntva c c tnh keo.

3.1.5.2. Cc dng thit btrch ly du

Thit b trch ly thng c cu to phc tp do m bo tnh an ton. Ty thuc tngloi nguyn liu m cc qu trnh trch ly khc nhau c p dng. Hin ti c hai loi

thit b trch ly c s dng ph bin: Thit b trch ly ngm chit (Percolationextractor) v thit b trch ly kiu nhng (Immersion extractors)


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(i) Thit b trch ly ngm chit (Percolation extractor)

- Dung mi c bm vo h thng v phn phi thng qua h thng bngchuyn ca bnh du, c chiu dy thay i theo kiu trch ly ngc dng.

- Kiu thit k khc nhau ty thuc vo hng thit k, qu trnh sn xut.

(ii) Thit b trch ly kiu nhng (Immersion extractors)

- Ht c ngm hon ton trong dung mi.

- Qu trnh trch ly cn khuy o lin tc nhm trch vic hnh thnh nng

dung mi cc bmt s v tr. Trong trng hp ny, s hnh thnh nhngphn t nh tng.

- Thit b hot ng lin tc hoc gin on. Thit b trch ly Hildebrandt c sdng ph bin nht trong qu trnh trch ly kiu nhng (hnh 3.3).

Dung mi

B du sau trch ly

Nguyn liutrch ly

Hnh 3.3.Thit b trch ly Hildebrandt

3.1.5.3. Dung mi trch ly du

(i) Cc loi dung mi thng dng

Xng: Cu to gm mt chui nhng hydrocacbon mch thng, cha no hay dnxut ca hexobenzen v cc ng ng. Ngoi ra, trong thnh phn ca xng cn ccc hydrocacbon no. Nhit si khong 70- 120oC. Xng khng tan trong nc. Khnng ha tan du mca xng l 1:5, kh nng ha tan du mtng khi tng phn nhc nhit si thp.

n- hexan: Cht lng, d bay hi, nhit si t 66,7- 69,3oC. Khi lng ring 663kg/m3 15oC. n- hecxan l mt loi xng trong thnh phn khng ln hydrocacboncha no v thm, c kh nng ha tan du v mbt k t l no.


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Propan v butan: Dung mi tin tin, khi s dng di p sut d 0,4- 1,2 MPa srt ngn c qu trnh trch ly 2- 3 ln. Dung mi ny ch ha tan mt lng rt nhcc cht khng c c tnh bo.

Ru etylic: Cht lng, nhit si 78,3oC, nhit bt la 404oC. Ru tan trong

nc bt k t l no. Tuy nhin, c th dng ru etylic 96% trch ly du nnh.

Axeton: Cht lng, c mi c trng, nhit si 5

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