Mn CNCB Rau Qu

Sy thng hoa

Trng ai Hoc Ky Thut Cng Ngh TP.HCMKhoa Cng Ngh Thc Phm

Bai tp mn CNCB Rau Tri

Nhm SVTH :

1/ Nguyn L Hoang 2/ Hoang Ngoc Duy Quang 3/ Nguyn Thi Kim Vn 4/ L Nguyn Nhn Lun

GVHD : ThS Tn N Minh Nguyt

TP. H Ch Minh 12/20101|Page

Mn CNCB Rau Qu

Sy thng hoa

Mc LcM u............................................................................................3 1. Gii thiu.....................................................................................4 1.1 nh ngha.............................................................................4 1.2 u nhc im ca Sy Thng Hoa......................................4 2. Qu trnh sy thng hoa...............................................................6 2.1 Cc giai on sy thng hoa..................................................6 2.2 Tc truyn nhit trong qu trnh sy thng hoa................8 2.3 Tc truyn khi trong qu trnh sy thng hoa.................8 3. Bin i nguyn liu...................................................................9 4. Thit b sy thng hoa................................................................11 4.1 Yu cu c bn ca thit b Sy thng hoa...........................11 4.2 H thng Sy thng hoa........................................................11 5. ng dng ca Sy thng hoa......................................................15 5.1 Dc phm v cng ngh sinh hc.......................................15 5.2 Cng Ngh Thc Phm........................................................15 Ph lc............................................................................................18 Ti Liu Tham Kho......................................................................19

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Mn CNCB Rau Qu

Sy thng hoa

M uSy l qu trnh tch nc ra khi vt liu nhm gip vt liu trnh c nhng h hng trong qu trnh bo qun. Di thi i cng nghip, sy c xem l mt qu trnh cng ngh c ng dng rt rng ri trong nhiu ngnh cng, nng nghip. Vic tch nc v hi nc ra khi vt liu khng ch n thun l sy thng thng m l c mt qu trnh cng ngh c tnh ton mt cch t m nhm em li sn phm cht lng cao sau khi sy. ng thi phi l mt qu trnh t tiu tn nng lng v chi ph vn hnh thp. Ty tng kiu vt liu m ta c nhng cch sy khc nhau, chnh v th ny sinh nhiu k thut sy ra i nh: h thng sy phun, h thng sy tip xc, h thng sy tng si Bn cnh cc k thut trn, k thut sy thng hoa l mt bc tin mi trong nn cng nghip sy ca nhn loi, n gip con ngi c nhng cch bo qun sn phm c tnh u vit hn trong chi ph v thi gian bo qun vt liu c lu, bo tn c nguyn vn cu trc, mu sc v hnh dng sn phm. Mt yu t quan trong bc nht ca k thut sy thng hoa l khng lm tn thng n cc dng cht d b h hng nh vitamin, protein, hot tnh ca enzyme, sc t Bo tn c trng thi sng ca t bo vi sinh vt.

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Mn CNCB Rau Qu 1. Gii thiu1.1. nh ngha :

Sy thng hoa

- Sy : l qu trnh tch m ra khi vt liu nhm trnh h hng trong qu trnh bo qun, tng bn cho sn phm, gim trng lng, gim chi ph chuyn ch v ng thi n cng lm tng gi tr cm quan cho sn phm. - Sy thng hoa : Sy thng hoa l qu trnh tch m ra khi vt liu bng s thng hoa ca nc. Qu trnh thng hoa l qu trnh chuyn trc tip t th rn sang th hi. iu kin bnh thng, m trong thc phm dng lng, nn thng hoa chng cn c chuyn sang th rn bng phng php lnh ng. Chnh v vy nn cn gi l phng php Sy lnh ng (Freeze Drying hay Lyophillisation). Phng php sy thng hoa do k s G.I.Lappa Stajenhexki pht minh 1921, c ng dng ln u tin Nga.

1.2. u nhc im ca phng php Sy Thng Hoa :1.2.1 So vi cc phng php bo qun khc Trong k thut sy Nhit l nguyn nhn gy tn tht v hng thm v cht lng dinh dng. Tuy nhin Sy thng hoa lm gim hot ca nc m khng dng nhit tc ng ln thc phm, kt qu l vn gi c hng thm v cht lng sn phm tt hn. Trong sy thng hoa chi ph cho h thng to p sut chn khng v lm lnh rt ln. Vn ny cng vi vn u t ban u lm cho chi ph sy thng hoa v c c thc phm tng cao. Nn cn xem xt li chi ph lin quan trong qu trnh sy thng hoa v t l lm kh. Tuy nhin ngi tiu dng vn s chp nhn nhng sn phm c gi thnh cao m cht lng tt hn vn gi c hng v v cu trc cua sn phm ti (v d: nh c ph, nm c m, tho mc v gia v, nc tri cy, tht, hi sn, rau v khu phn n dinh dng trong qun i hoc tiu dng hng ngy) Ngoi ra, canh trng vi sinh dng trong ch bin thc phm c sy thng hoa ko di thi gian lu tr lu hn. 1.2.2 u nhc im ca phng php Sy thng hoa vi cc phng php sy khc u im : sy thng hoa c u im rt ln so vi cc phng php sy khc l : sn phm c cht lng cao (gi nguyn mu sc, cu trc, hng v, tnh thy ha), gi gn hot tnh sinh hc, khng lm mt cc vitamin. Tiu hao nng lng bay hi hm m thp. Nhc im : gi thnh thit b cao, vn hnh cn c trnh k thut k thut cao; tiu th in nng ln

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Mn CNCB Rau Qu

Sy thng hoa

Bng 1.1 : So snh Sy thng hoa v sy kh truyn thng

Say kho truyen thong -Thc phm sy kh d dng( rau, ng cc).

-Tht ni chung khng cho hiu qu -Khong nhit t 39- 930C -p sut kh quyn -Bc hi nc t b mt thc phm -Lm tn tht cht ha tan, c khi lm cng sn phm -ng sut tc ng trn thc phm rn -t gy thay i cu trc v lam co sn l nguyn nhn nh hng n cu trc phm. v lam co sn phm. -S kh nc chm v khng hon -Kh nc rt nhanh. ton. -Nhng phn sy kh l rn hay l xp -Nhng phn c sy kh va xp c mt thng c mt cao hn nguyn liu. thp hn nguyn liu. -Tn tht hng v. -Hng v c gi li bnh thng. -Sn phm thng sm mu. -Mu bnh thng. -Gi tr dinh dng gim. -Gi c dinh dng. -Gi sn phm thp. -Gi sn phm ni chung cao, c th gp 4 ln sy kh thng thng.

Say thang hoa -Sy c hu ht cc loi thc phm m cc phng php khc khng thc hin c -Rt tt cho ch bin tht chn v sng -Nhit di im ng lnh -Ap sut thp (27-133Pa) -Thng hoa nc t mt nc -S tn tht l ti thiu.

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Mn CNCB Rau Qu 2. Qu trnh sy thng hoa:2.1 Cc giai on sy thng hoa

Sy thng hoa

Qu trnh sy thng hoa tri qua 3 giai on chnh : giai on lm lnh, giai on thng hoa v giai on bc hi m cn li.

Hnh 2.1 : th biu hin trng thi thng hoa im ba th Nu m trong vt liu sy c trng thi ng bng c gia nhit ng p n nhit nht nh th nc th rn s thc hin qu trnh thng hoa. T th cho thy p sut cng thp th nhit thng hoa ca nc cng gim do khi cp nhit cho vt liu sy p sut cng thp th chnh lch nhit gia ngun nhit v vt liu sy cng tng. 2.1.1 Giai on lm lnh (giai on lnh ng) Trong giai on ny vt liu sy c lm lnh t nhit mi trng khong 200C xung nhit (-10 ; -150C). giai on ny khng gian ca bnh thng hoa c ht chn khng v p xut trong bnh gim. Do p sut gim nn phn p sut hi nc trong khng gian bnh thng hoa cng gim so vi phn p sut trong lng vt liu sy iu ny dn ti hin tng thot m t vt liu sy cho nn nhit vt liu sy nh hn im 3 th. C 2 cch lm lnh ng vt liu sy: Cch th nht s dung thit b lm lnh ng thng thng hoc nit lng lm lnh ng sn phm bn ngoi bung sy thng hoa. Cch th hai l vt sy t lnh ng ngay trong bung sy thng hoa khi bung sy c ht chn khng. Trong giai on ny c khong 10 - 15% trn ton b m thot ra khi vt liu sy. Trong giai on ny sn phm cn c lm lnh ng rt nhanh hnh thnh cc tinh th bng nh t gy h hi n cu trc t bo ca sn phm. i vi sn phm dng lng, phng phap lm lnh ng chm c s dng bng to thnh tng lp, cc lp ny to nn cc knh gip cho hi nc dch chuyn d dng.

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Mn CNCB Rau Qu2.1.2 Giai on thng hoa

Sy thng hoa

Giai on ny l giai on tch m chnh ca phng php sy thng hoa. y p sut hi nc c gi di 4,58 mmHg (610,5 Pa) v nc dng bng, khi sn phm c cung cp nhit, th bng rn s thng hoa trc tip thnh hi m khng b tan chy. Hi nc tip tc c tch ra khi sn phm bng cch gi cho p sut trong bung sy thng hoa thp hn p sut hi nc trn b mt ca bng, ng thi tch hi nc bng my bm chn khng v ngng t n bng cc ng xon rut g lnh, cc bn dt lnh hoc bng ho cht. Khi qu trnh sy tip din, b mt thng hoa di chuyn vo bn trong sn phm ng lnh, lm sn phm c sy kh. Nhit lng cn thit dch chuyn b mt thng hoa (n nhit thng hoa) c truyn n sn phm do s dn nhit hoc do vi sng cung cp. Hi nc di chuyn ra khi sn phm qua cc knh v n bnh ngng, sau thnh bng bm trn b mt ng. Trong giai on ny nhit vt khng i. Nh vy, nu khng tnh qu trnh mt m trong phng php vt m t lnh ng trong bung sy khi ht chn khng th sn phm c sy trong hai giai on : Trc tin do qu trnh thng hoa xung khong 15% m v sau do bay hi ca phn nc khng ng bng n 2% m bng qu trnh nh m ng nhit. Qu trnh nh m ng nhit (desorption) t c bng cch nng nhit my sy ln gn nhit mi trng xung quanh trong khi vn gi p sut thp ging nh qu trnh sy cc thit b sy chn khng thng thng. ng cong sy Khi ht chn khng, p sut trong bung sy gim xung, m t do bay hi mnh lm gim nhanh nhit ca n xung n nhit ng bng tB ca m ( ng A-B ). Qu trnh ng bng ca m c to nhit nn nhit ca vt sy tng ln mt cht( B C). Qu trnh thng hoa m din ra khc vi qu trnh sy th nht (tc khng i) trong sy i lu l nhit tng ln mt t theo thi gian sy ( on C-D dc ln). iu c gii thch l lp su bn trong vt sy cn c m ang ng bng. Hnh 2.2 ng cong Sy 2.1.3 Giai on bc hi m cn li : L giai on lm bay hi m lin kt, nhit ca vt liu sy tng nhanh. Trong mt s sn phm (v d nc p tri cy, dch chit c ph c c), s hnh thnh nn trng thi thu tinh trong qu trnh ng bng gy ra nhiu kh khn cho vic di chuyn hi nc. V vy, cht lng cn c ng bng dng bt (phng php sy thng hoa bt : vacuum puff freeze drying), hoc l nc p tri cy sy cng vi phn tht (ci). C hai phng php u to nn cc knh nh hi nc c th thot i c. phng php th ba, 7|Page

Mn CNCB Rau Qu

Sy thng hoa

nc tri cy sau khi ng bng c nghin thnh cc, nh sy nhanh hn v cho php kim sot kch c ca ht bt tt hn. Tc sy ph thuc phn ln vo tnh cn tr nhit ca sn phm v mc thp hn vo cn tr dng hi (dch chuyn khi) ra khi b mt thng hoa. Sau giai on thng hoa do trng thi ca nc trong vt liu nm trn im 3 th nn m trn vt liu tr v dng lng. V khi p sut trong bnh thng hoa vn c duy tr b hn p sut kh tri nh bm chn khng v vt liu sy vn tip tc c gia nhit nn m vn khng ngng bin t dng lng sang dng hi v i vo khng gian bnh thng hoa. Nh vy giai on bc hi m cn li chnh l qu trnh sy chn khng bnh thng. Qu trnh dch chuyn m trong sy thng hoa khc vi qu trnh dch chuyn m trong h thng sy khc lm vic p sut kh quyn. Khi thng hoa cc phn t nc khng va chm nhau nh m sy thng hoa c mt u im ln l bo ton c cht lng sinh hc ca sn phm sy

2.2 Tc truyn nhit trong qu trnh Sy thng hoa :C ba phng php truyn nhit n b mt thng hoa. Nhit truyn xuyn qua cc lp ng bng. Tc truyn nhit ph thuc vo dy v dn nhit ca lp bng. Khi qu trnh sy xy ra, chiu dy ca lp bng gim xung v tc truyn nhit tng ln.Nhit b mt ca thit b cp nhit c gii hn trnh lm tan bng. Nhit truyn qua lp kh. Tc truyn nhit n b mt thng hoa ph thuc vo chiu dy v din tch b mt ca sn phm, dn nhit ca lp kh v chnh lch nhit gia b mt ca sn phm v b mt bng. Khi p sut bung sy khng i, nhit ca b mt bng duy tr khng i. Lp kh ca sn phm c dn nhit rt thp (tng t nh vt liu cch nhit) v v th gy ra s cn tr ln vi dng nhit. Khi qu trnh sy tip din, lp ny tr nn dy hn v s cn tr nhit tng ln. Lm gim kch thc nguyn liu v tng chnh lch nhit s lm tng tc truyn nhit. Tuy nhin, sy thng hoa, nhit b mt b gii hn n 40-650C trnh s bin tnh protein v cc thay i ho hc khc, c th lm gim cht lng ca sn phm. Truyn nhit bng vi sng. Nhit c to ra trn b mt bng v tc truyn nhit khng b nh hng bi dn nhit ca bng v cht kh hay dy ca lp kh. Tuy nhin, nhit vi sng kh kim sot v c nguy c b tnh trng qa nng cc b dn n s tan chy bng.

2.3 Tc truyn khi trong qu trnh Sy thng hoa:Khi nhit truyn ti b mt thng hoa, nhit v p sut hi nc ca bng c tng ln. Hi nc di chuyn xuyn qua cht kh n vng c p sut hi thp trong bung sy. p sut 67 Pa, 1g bng hnh thnh 2m3 hi v do , my sy thng hoa cn phi ly i hng trm mt khi hi trong 1 giy qua cc l hng ca cht kh. Cc yu t kim sot chnh lch p sut hi nc l : - p sut trong bung sy - Nhit ca thit b ngng t hi, c hai cn thp n mc chi ph cho php. 8|Page

Mn CNCB Rau Qu

Sy thng hoa

- Nhit ca bng b mt thng hoa, cn cng cao cng tt nhng khng tan chy. Trong thc t m bo tnh kinh t, p sut bung sy thp nht vo khong 13 Pa v nhit thit b ngng t thp nht l khong -350C V l thuyt, nhit ca bng cn nng ln mc ch va di im ng bng. Tuy nhin, trn mt nhit ti hn nht nh, gi l nhit sp (collapse temperature), cu trc sn phm s b ph hy ngay lp tc. Trong thc t, v th tn ti nhit bng ti a, nhit ngng t ti thiu v p sut bung sy ti thiu v nhng thng s ny kim sot tc chuyn khi. Trong qu trnh sy, m h xung t mc ban u rt cao trong vng lnh ng n mc thp hn lp kh, ph thuc vo p sut hi nc trong bung sy. Khi nhit chuyn qua lp kh, quan h gia p sut trong bung sy v p sut trn b mt bng l : kd Pi =Ps + b.s Trong , Pi (Pa) l p sut ring phn ca hi nc b mt thng hoa, Ps (Pa) p sut ring phn ca hi nc b mt, kd (Wm-1K-1) : dn nhit ca lp kh, b(kg.s-1.m-1) thm ca ca lp kh, s (J.kg-1) : n nhit thng hoa, ts (0C) : nhit bmt v ti (0C) nhit ti b mt thng hoa. Thi gian sy c thM ) tnh bng cng thc sau : x2 (M c1 2 2

(ts ti)

Td = 8kd (ts ti) Trong : td (giy) l thi gian sy, x (m) : chiu dy ca sn phm, ( (kg.m-3) : t trng ca cht kh, M1 : m ban u v M2 : m cui cng. Ch rng : thi gian sy t l vi bnh phng dy ca sn phm : do gp i chiu dy sn phm s ko di thi gian sy gp 4 ln.

3. Bin i nguyn liu :Sn phm sy thng hoa c thi hn s dng rt lu trong iu kin bao gi ph hp v co th c bo qun nhit phng. Bi v hot nc trong sn phm thng rt thp (di 0,3). Vi hot ca nc thp nh vy, cc enzyme v vi sinh vt gn nh b c ch hon ton. Thi gian bo qun ca mt s sn phm sy thng hoa c cng b trn th trng c th ln n vi chc nm. C bit c sn phm c bo co c thi hn s dng ln n 50 nm (nh tht heo sy thng hoa M, c s dng trong qun i). Cc sn phm cui cng gi li 98% cht dinh dng v cn nng t hn nhiu so vi trc khi sy. Thc phm sy thng hoa gn nh gi li c cc c tnh ca nguyn liu ban u ng thi s tn tht v mt cht lng thng mc thp nht. San phm chng nhng gi li ti a cc c tnh v cht lng (mu sc, mi v, trng thi) m cc hp cht c hot tnh sinh hc (vitamin, enzyme, omage-3 axt) cng c bo v mt cch tt nht (tt nhin khng phi 100%). Nghin cu trn sn phm c hi sy thng hoa ch ra rng sn phm c t l co rt th tch di 10% (chp nhn c), mu sc c gim sau sy thng hoa nhng sau khi ht nc c s phc hi li mu sc ng k, sn phm c tc ht nc cc nhanh ch trong 9|Page

Mn CNCB Rau Qu

Sy thng hoa

khong 5-10 giy t c t l ht nc ti a nhit 80 0C (iu ny rt thun li khi s dng nh l mt thnh phn thc phm dng soup). C cu trc xp, dn ph hp vi san phm snack n lin. nhng sn phm phai c kh cao va cn ha tan tt nh sa bt thi vi phng php sy thng hoa, m sn phm cn li 4 - 6%, v hnh dng ban u vn c gi nguyn, khng c s thay i v kch thc r rt Sn phm sy thng hoa lu li rt tt cc c tnh cm quan v cht lng dinh dng. Cc cht d bay hi khng b cun vo hi nc sinh ra trong qu trnh thng hoa m b mc li trong khung sn phm. Kt qu l 80-90 % mi c gi li. Kt cu ca sn phm tt : t b co ngt v khng b hin tng cng v. Cu trc xp cho php qu trnh lm t tr li nhanh chng v hon ton, nhng n d v v cn bo v trnh b h hi c hc. Ch c nhng thay i nh v cht lng protein, tinh bt v cc hydrocacbon khc. Tuy nhin cu trc xp ca sn phm c th cho oxy xm nhp v gy oxy ho lipit. V vy, sn phm cn c bao gi trong kh tr. Nhng thay i ca thiamin v axit ascorbic trong qu trnh sy thng hoa mc va phi v s tht thot ca cc vitamin khc khng ng k (xem bng). Tuy nhin, s tht thot cc cht dinh dng do cc qu trnh chun b trc khi sy, c bit l chn hp rau c th nh hng ng k n cht lng dinh dng ca sn phm sy thng hoa. Bng 3.1 : Tn tht vitamin trong qu trnh Sy Thng Hoa Thc Phm Vitamin Vitamin Thiamin C A 26 - 60 0 - 24 8 - 30 5 0 3 3-5 2