Tôm chua

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TRNG I HC BCH KHOA TP. H CH MINHKHOA CNG NGH HA HC

B MN CNG NGH SINH HC

TIU LUN CNG NGH LN MEN TRUYN THNG

TTMM CCHHUUAAGVHD: C Nguyn Thu Hng

SV: Nguyn Duy Hng

Nguyn Duy NghaLP: HCO2BSH

Nm hc 2005 2006

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Seminar cng ngh ln men truyn thng Nguyn Duy Hng

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Mc lc

M u ------------------------------------------------------------------------------------------------------------ 2I. Tng quan v nguyn liu tm --------------------------------------------------------------------------- 2I.1 Ngun li v tnh hnh thng mi tm trn th gii----------------------------------------- 2

I.1.1 Tm trn th gii --------------------------------------------------------------------------------- 2I.1.2 Ngun li tm Vit Nam ------------------------------------------------------------------------ 3

I.2 Thnh phn ha hc ca tm ----------------------------------------------------------------------- 3II. Mt s quy trnh sn xut tm chua truyn thng------------------------------------------- 5II.1 Quy trnh Hu --------------------------------------------------------------------------------------- 5II.2 Quy trnh ng Hi-------------------------------------------------------------------------------- 6II.3 Quy trnh Nam b ---------------------------------------------------------------------------------- 6

III. Cc qu trnh sinh ha xy ra khi mui tm chua ------------------------------------------------- 7III.1 Qu trnh ln men lactic trong mui tm chua ----------------------------------------------- 7

III.1.1 S bin ng trong qu trnh ln men lactic -------------------------------------------- 7III.1.2 Cc nh hng ln qu trnh ln men lactic -------------------------------------------- 8

III.2 Qu trnh thy phn Protein trong mui tm chua------------------------------------------ 9III.2.1 Qu trnh thy phn protein ------------------------------------------------------------------ 9III.2.2 Cc nh hng ln qu trnh thy phn protein---------------------------------------- 9

IV. Cc hn ch ca quy trnh ln men truyn thng v mt s ci tin ngh -------------10IV.1 Cc hn ch ca quy trnh ln men truyn thng ------------------------------------------10

IV.2 Bin php khc phc ngh--------------------------------------------------------------------10IV.3 Quy trnh sn xut ngh -----------------------------------------------------------------------12V. Kt lun-------------------------------------------------------------------------------------------------------14VI. Ph lc v ti liu tham kho --------------------------------------------------------------------------14

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ti tm chua Nguyn Duy Ngha

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M UTrong cc thc n c truyn ni ting ca dn tc ta, tm chua c gi tr dinh dng

cao v thm ngon c bit. Tm chua c xem l mt c sn ca Vit Nam. Thc chttm chua l mt sn phm ln men lactic v thy phn protein, lm t cc nguyn liu:tm, cm np, mui n v gia v. N l mt thc n thng thy cc tnh pha Nam. THu tr vo tnh no cng mui tm chua, nhng tm chua Hu l thm ngon hn c.

Tuy l mt c sn nhng t trc n nay n cha c nghin cu k v pht trinthnh sn phm cng nghip m ch c sn xut quy m gia nh vi sn lngkhim tn. Nc ta c ngun li v tm rt ln. Tm ngoi tiu th trong nc cn cxut khu ra nc ngoi di dng tm lnh ng. Sn lng tm tuy ln nhng thc tlng tm c phm cht lm lnh ng chim mt t l khng qu 40% sn lngtm ni trn. S tm cn li phi xp vo th phm, cht lng b gim i rt nhiu trongqu trnh bo qun v chuyn ch. Lng tm khng tiu chun xut khu lnhng, cng nh phn phi ti c a vo cc sn phm tm ch bin, trong ctm chua. Vi li th thi gian bo qun di, d dng cho vic lu thng v phn phi,hng v thm ngon, sn phm tm chua nu c u t cho nghin cu v sn xut cth tr thnh mt hng ng gi trong tng lai.

I. Tng quan v nguyn liu tm [2],[3]I.1 Ngun li v tnh hnh thng mi tm trn th gii [2],[3]I.1.1 Tm trn th giiNgun li tm phn b hu ht cc ni trn th gii. Tm phn b c bin v

sng, h. Tuy vy tm bin vn nhiu hn hn. Tm nc ngt ch chim 3-4% ton blng tm khai thc c.

Hin nay trn th gii bit n hng trm loi tm nhng tm c gi tr thngphm ch khong 20 loi. Ngun li tm hu nh phn b khp th gii v c rt nhiuchng loi nhng tr thnh hng ha c gi tr th n b hn ch bi nhiu iu kinnh ging tm, ni sinh sng .

Tm sng tt c vng bin trn th gii. nhng vng bin su 700 800 m vnc kh nng nh bt c tm. Thc t tm ngon khng nh bt c vng bin sum thng l cc vng bin nng, khong 100m tr li.

Phn loi tm theo khu vc sinh sng th c th chia lm 2 loi chnh l tm hni v tm nhit i.

a) Tm nhit iDo c hon cnh u i nn tm nhit i trng thnh nhanh. Ch trong vi

thng tm nhit i pht dc v sinh si ny n tt, tuy nhin vn i ng, di 1 nm.Tm hn i th ngc li trng thnh chm, nhng vng i di ti 2 - 3 nm.

Tm c vng i cng ngn th gi tr v ngun li thc phm cng cao. Do ccvng t xch o n gip v tuyn Nam - Bc 400 c ngun li tm ln v cht lng tmkh cao

b) Tm hn iBin hn i nh Bc bng dng nng lng thng rt lnh, nhng vo ma

ng nhit nc bin li m hn nhit trong khng kh nn to thnh dng i lutrong bin. y l iu kin thun li cho cc loi thy sn pht trin. Tm hn i a ssng thnh n ven b su khong 10m. Tuy vy cng c th nh bt c tm sng tng nc su (khong 100m nc tr li). Nhng nhn chung loi tm sng ch suhn th gi tr thng phm li km hn

Nh vy, hu ht cc loi tm c gi tr thng phm sng ven b bin, mi

trng ni sinh sng rt a dng do chnh lch v cc iu kin:- Chnh lch v thy triu- Chnh lch nhit ca nc do hi lu.

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- Tnh a dng ca iu kin sng y sng, bin nh ln, nh, ct, bn.- S sai khc v iu kin nhit , nh sng, nng oxyDo tnh a dng ca mi trng lm cho chng loi tm tr nn a dng. Chng loi

tm tuy nhiu nhng loi dng lm thc phm th ch c gii hn bi nhng l do nu trn. iu kin th nht l hng v tht tm phi thm ngon, iu kin th hai l vngi phi ngn. Nhng ging loi tm tha mn c hai iu kin ny th c gi tr trn

thng trng.I.1.2 Ngun li tm Vit NamTm l i tng rt quan trng ca ngnh thy sn nc ta v n chim t l 70-

80% tng kim ngch xut khu ca ngnh. Tm c gi tr dinh dng cao, t chc c thtrn chc, c mi v thm ngon c trng rt hp dn.

Xut pht t nhu cu nn ngh nui tm v khai thc tm nc ta ang cy mnh. Vit Nam c khong 70 loi tm c phn b vng bin xa b, vng binven b v cc thy vc trong ni a.

Cc khu vc c nhiu tm l:- Khu vc vnh Bc B tm tp trung cc ca sng ln nh sng Hng, sng Thi

Bnh, sng Mi tng chnh l tm ro, tm bc. Tm xut hin quanh nm nhngtp trung vo khong thng 3-5 v thng 7-10 hng nm.

- Khu vc Bnh nh, Khnh Ha, i tng khai thc ch yu l tm s, tm v, tmbc, tm rng, tm hm

- Khu vc nam Hong Sa, ch yu l tm rng.- Khu vc Cn Sn c tm v cc loi tm nh thuc h tm gai v h Pandalidae.- Khu vc Ty Nam B ch yu l tm s, tm bc, tm v, tm ro.Hin nay nhu cu v tm ngy cng cao, sn lng tm nh bt c hn v vy

ngh nui tm ang c pht trin mnh c bit l khu vc Nam trung b ko di nng bng sng Cu Long.

Tm s Tm th

Tm cng xanh Tm hmHnh I.1 Mt s loi tm c gi tr ca Vit Nam

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I.2 Thnh phn ha hc ca tm [3]

Thnh phn ha hc ca c tht gm c: Nc, protein, lipid, hydratecarbon, khongcht, vitamin, enzyme, hormon. Nhng thnh phn c hm lng tng i nhiu lnc, protein, lipid v khong cht. Hm lng hydratecarbon trong tm rt t v tn tidi dng glycogen.

Thnh phn ha hc ca tm thng khc nhau ty theo ging loi. Trong cng

mt loi nhng hon cnh sinh sng khc nhau th thnh phn ha hc cng khc nhau.Ngoi ra thnh phn ha hc ca tm cn ph thuc vo trng thi sinh l, ma v, thititS khc nhau v thnh phn ha hc v s bin i ca chng lm nh hng rtln n ma v v gi tr dinh dng ca sn phm, vic bo qun ti nguyn liu vqu trnh ch bin.

I.2.1 NcC tht ca tm cha khong 70 - 80% nc hm lng ny ph thuc vo ging,

loi tm v tnh trng dinh dng ca tm. Giai on nhn i thng xy ra nhiu loitm trong thi gian trng, lm gim s nng lng d tr trong m c v dn n lmtng hm lng nc trong c th tm.

Trong c v trong cc t bo, nc ng vai tr quan trng lm dung mi cho cccht v c v hu c, to ra mi trng cho cc hot ng sinh ha trong t bo. ngthi nc cng tham gia vo rt nhiu cc phn ng ha hc v c nh hng ln ncc phn ng ca protein. Trng thi ca nc trong c tht tm ph thuc nhiu vo stng tc gia cu trc ca nc v cc cht dinh dng khc trong t bo v c bit lcc protein.

Nhng thay i v hm lng nc trong tht tm gy ra bi qu trnh ch bin cnh hng mnh n tnh thm thu, gi tr dinh dng v cht lng cm quan ca thttm. Nhng thay i ny cng nh hng ln n thi gian bo qun c ca snphm.

I.2.2 Protein

C tht ca tm thng cha khong 13 - 25% protein. Hm lng ny bin thinty thuc vo ging, loi tm, iu kin dinh dng v loi c tht.

C th chia Protein trong m c ca tm nguyn liu thnh 3 nhm sau:- Protein cu trc: 70 - 80% tng hm lng protein- Protein c: (mycoalbumin, globulin, ) chim 23 - 30 % tng hm lng protein- Protein m lin kt: im ng in ca protein tm khong pH = 4,5 - 5,5, gi

tr pH ny cc protein trung ha v in v k nc hn trng thi ion ha. iu cngha kh nng lin kt vi nc v kh nng ha tan thp nht. Nu pH cao hn hocthp hn im ng in th ha tan s tng ln.

Tm l loi thc phm kh giu cc aicd amin. Gi tr dinh dng ca tm cao l

nh cc acid amin ny. Trong thnh phn cc acid amin cha lu hunh cao hn thtnn khi cc acid amin ny b thu phn to ra mi n thi rt kh chu.

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I.2.3 LipidM c ca tm cha khong t 0,01 - 3% lipid m thnh phn ch yu l cc

phospholipid.I.2.4 Cht khong

Tm l loi thc phm rt giu cht khong. Hm lng cht khong c trong thttm bin thin khong t 0,7 - 1,5% khi lng tm. Hm lng cht khong trong tht

tm c c trng theo loi v bin thin theo ma, ng thi hm lng cht khong phthuc rt ln vo iu kin sng ca tm.

I.2.5 H vi sinh vt v enzymeCc loi thu sn c h vi sinh vt t nhin kh cao do sng trong mi trng nc.

Tm c lng vi sinh vt cao nhng t hn c do c v chitosan dy bo v. Cc nhm visinh vt ch yu bao gm

- Nhm vi khun hiu kh trong nc: Pseudomonas sp, Liquefacciens sp.- Trong ni tng (u tm) tp trung cc vi khun ym kh nh: Clostridium sp,

Escherichia coli, Samonella.Cc vi khun ny tham gia qu trnh n thi tm

u tm l ni cha c quan ni tng trong c b my tiu ho. Hai enzymeprotease nh hng n qu trnh mui tm sau ny l trypsin v pepsin.

II. Mt s quy trnh sn xut tm chua truyn thng [1],[4]Trc y nc ta trong dn gian ch c 2 cch mui tm chua, mt Hu v mt

ng Hi. Hin nay min Nam c thm nhiu cch mui tm chua, t hnh thnhcc phng php vi nhng quy trnh cng ngh khc nhau theo tn ca mi a phng.

II.1 Quy trnh Hu

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Tm ti c mui chua vi cm np, mui n, gia v. Gia v gm t, ti, ring,ru. S quy trnh mui tm chua nh sau

Nguyn liu:tm nc ngt, nc l, tm bin cn sng hoc cn ti. Tm c kchthc bng ngn tay t. Tt nht l tm bao t (Penaeus sp.), tm cng (Macro brachumhay Nipponence), tm th (Penseus semiculcatus), tm gn (Penaeus merguinsis ), tmst (Parapenaeppsic harwichii), khng s dng tm chong (Penaeus carinatus), tm ch(Metapenaeusengis) v v qu cng v u d b bin en. Tm b n, tm b gy u,tm b nt, tm ma nc l khng dng mui tm.

Ra ct ru chn: tm c loi b rong ru, san h, bn, c, s, c con, mc, utm v c ra tht sch, t 3 - 4 ln. Sau tm c ct ru t mt tr ln v ba ichn trc (bng ko). Tm c ra li v ro nc.

Phun ru: dng ru 400 ngon, phun thnh bi m ln tm (3 - 4%).Mui tm; tm c x l trn c mui vi mui n (mui rang dng bt),

cm np gi nhuyn, ti, t, ring, mng vi.Gi nn: Tm mui c cho vo ang, vi, nn cht, ly l ring y ln, ri gi

nn bng nan tre mng nh trong khi mui da chua. Cui cng y np tht kn. Ang, vitrc phi c ra tht sch, phi kh trc khi mui tm.

Tm chua thnh phm: sau 18 ngy (ma nng) tm chua chn. Tm chua chn cmu ti t nhin, v chua, mi thm c trng ca sn phm ln men lactic. V c ltm khng b gy u, nguyn mnh, dn v khng c vt en. Gia v phi sng p,khng st li nhng ht t, v ti. Phn nc phi c snh, c mu hng nht, khngcn vt ht np, khng lng cn.

Tm chua ct gi ni thong mt thng c 2 tun.

Tm

La chnRa sch

Ct ru chn

Ra

Phun ru

Mui tmLn men

Gi nn

Tm

chua

Ru chn

Ru 40o

Mui, gia v

Ang vi

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II.2 Quy trnh ng HiQu trnh mui tm chua ng Hi c khc mt t so vi mui tm chua Hu,

thng ngi ta s dng thnh v mt t ng thay cm np. Tm chua c mui theot l nh sau: 10 chn tm, 1 chn mui rang, 1 chn thnh go t, 1 tha ng, 1 chngia v (ti, ring, gng), 1 chn ru nh. Trc khi gi nn, ngi ta dng l i ri ln bmt tm. Sau 18 - 20 ngy tm chua bt u n c. Tm chua khng ti v thm

ngon nh tm chua c truyn Hu. Mu ca thnh lm cho mu ca sn phm ti i.II.3 Quy trnh Nam bTm ra sch, b u (trnh hin tng b bin en) mui vi mui n, mt ong, gia

v. Sau 7 ngy cho thm mt t ng vo. Tm chua mui theo phng php ny sau 20ngy th n c. Thnh phm ng trong cc chai x x. im c bit ca phng phpmui tm chua ny l dng cc thanh ma ch mng ci nn tm khi mui.

Qui trnh nh sau:Tm rn la con nh, ra sch ct, ht mt cht trn u v diui, p mui mt m (mt chn tm vi mt tha mui sng). Lc p tm, mun chotm dai th cho vo mt t phn chua tn nh. Ly mt t np vo sch, nu chn. Mng vi,ti, ring, t cc th u nhau, 2 tha ru trng, 1 tha mt ong hoc 1 tha ng, 1 lt

nc mui (10 %), cc th trn chung vi tm cho u nhn vo thu, ly l ring yln, gi kn, bt l ra ngoi.Phng php mui tm chua trong dn gian, ty theo a phng c nhng im

khc nhau nhng nhn chung tm c mui vi mui n (mui rang, dng bt), gia v(ti, i, ring

III. Cc qu trnh sinh ha xy ra khi mui tm chua [2], [3], [5]Trong qu trnh mui tm chua th c 4 qu trnh sinh ha sau y din ra

- Qu trnh sinh trng v pht trin ca vi khun lactic- Qu trnh chuyn ha tinh bt thnh ng ( quy trnh Hu v ng Hi)- Qu trnh chuyn ha ng thnh acid latic

- Qu trnh thy phn proteinHai qu trnh quyt nh n cht lng sn phm l qu trnh ln men lactic (bao

gm hai qu trnh chuyn ha t tinh bt n acid lactic) v qu trnh thy phn protein.

III.1 Qu trnh ln men lactic trong mui tm chuaQu trnh ln men lactic trong mui tm chua xy ra nhiu giai on, to ra nhiu

sn phm trung gian. Trong giai on u ca qu trnh chuyn ha, sn phm chung lacid pyruvic. Sau acid pyruvic b kh thnh acid lactic. Song song vi qu trnh to raacid lactic l qu trnh ln men ru, ln men acid acetic, acid propionic v acid butyric

Theo thi gian mui tm chua, cc hp cht trn c to ra, s phi hp giathnh phn chnh l acid lactic cng vi ru ethylic, acid acetic to ra hng v ctrng cho sn phm. Trong mi trng acid lactic, protein ca tm b bin tnh to cho tmc mu p.

III.1.1 S bin ng trong qu trnh ln men lacticBin ng lng acid lacticTrong qu trnh mui tm chua, lng acid lactic tng ln. Hm lng acid lactic ln

hn 2% c kh nng c ch khng ch nhng vi vi sinh vt c hi m cn c ch c vikhun lactic. Tuy nhin tm chua vi lng acid lactic ln hn 2% c kh nng bo qunc lu.

Bin ng lng acid chungTrong qu trnh ln men lactic khng in hnh, ngoi acid lactic th sn phm cn

kh nhiu acid hu c khc. Theo thi gian ln men, lng acid chung ny cng tng ln.Nu mui tm chua theo phng php dng ng thay cm np s c mi v c

trng ca sn phm ln men lactic. So vi phng php mui tm chua c truyn Hu th

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phng php mui ny c tc ln men lactic nhanh hn. T l acid lactic trong acidchung ca sn phm nhiu hn. Tuy nhin nhiu nh gi cho rng sn phm ln men tng km thm ngon hn t cm np. C th kt lun rng acid lactic khng nm vaitr quyt nh n gi tr cm quan m do h sn phm ca qu trnh ln men. Ngoi rathnh phn ca go np cng cha nhiu hp cht mi gp phn vo hng v chung casn phm.

Bin ng hm lng ru ethylicKhi mui tm chua theo phng php c truyn Hu, ngi ta c phun vo tm

chua mt t ru vi mc ch cho lm cho sn phm thm hng v. Qu trnh ln menlactic d hnh ngoi aicid lactic cn c ru v cc acid khc trong ru ethylic ltrung gian chuyn ho thnh cc acid khc ny . B sung thm ru lm hm lng ccacid khc (ngoi acid lactic) trong sn phm tng ln. Khi kt thc qu trnh ln menlng ru ethylic cn st li mt lng nh cng gp phn to mi thm cho tm chua.

Bin ng ca pHBin ng pH ca tm chua theo xu hng ngy cng gim.III.1.2 Cc nh hng ln qu trnh ln men lactic

Quy trnh ln men lactic trong mui tm chua c nhiu yu t nh hng n.Nhng yu t cng ngh l: lng mui n (c th ly t nc mm), lng cm nphay lng ng thay cm np, lng gia v, nhit ln men

nh hng ca lng mui nMui n c nh hng rt ln n hot ng ca vi khun lactic v s tch ly acid

lactic trong sn phm mui chua. Hm lng mui n khong 6% lm gim i n 30%s hot ng ca vi khun lactic. Tuy vy mui n c tc ng tch cc l km hm cc vikhun gy thi. S dng nc mm thay mui n mui tm chua l mt gii php vnc mm l mt dch giu acid amin v c chc nng n nh v. Tuy nhin n s lmtng gi thnh sn phm v gim mi v c trng ca sn phm.

Vi hm lng mui n s dng khc nhau th lng acid chung to ra trong tmchua khc nhau. Vi hm lng mui n khong 4% th lng acid chung to ra trongtm chua ln nht, hm lng mui n cng thp th lng acid chung to ra do qu trnhln men lactic cng nhiu. Tuy nhin nu hm lng mui n t 2% tr xung, cc vikhun gy thi pht trin mnh lm tm chua b hng.

Trong dn gian khi mui tm chua, hm lng mui n s dng thng rt cao, t10 -15%. Hm lng mui n cao c ch s hot ng ca cc vi khun lactic lm tc ln men chm, kt qu tm chua lu chn. Thng thng, nu mui tm chua vi lngmui n nh trn th n ngy th 18 mi bt u n c.

nh hng ca hm lng ngng l yu t c tnh cht quyt nh n qu trnh ln men lactic. Phi c mt

ca ng, vi khun lactic mi thc hin c qu trnh ln men. Lng ng nhiuhay t nh hng n s tch ly acid lactic trong sn phm.

Khi lng ng tng th tc ln men lactic tng, nhng khi hm lng ngln hn 20% so vi khi lng tm th tc ln men lactic gim dn xung. Vi lngng 14 - 17%, m bo to ra mt lng acid chung va phi, lm cho tm chua c vchua ngt (do lng ng d) thch hp.

Khi mui tm chua theo phng php c truyn Hu, ngi ta s dng cm np(20% so khi lng tm) ln men lactic. So vi ng cm np ln men lactic vi tc chm hn nhng mi v ngon hn.

nh hng ca gia v

Khi mui tm chua, ngi ta dng gia v gm: ti, t, ring, ch yu l ti (80% khilng gia v), sau l t (15%). Lng gia v nhiu hoc t ph thuc vo ngi tiu

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dng, thng l 10% so vi khi lng tm. Cc gia v nh ti, ring c kh nng c chhot ng ca cc vi khun gy thi to iu kin cho vi khun lactic pht trin.

Trong qu trnh mui tm chua, gia v thng b bin mu, ti b xm, ring b en,ch c t , mng vi khng b i mu. Gia v khng nh hng n s to ra acidchung. ti, ring t b bin mu c th cho vo tm chua khi n c (10 ngy saukhi mui tm). t, mng vi cho vo cng vi tm khi mui.

nh hng ca nhit Nhit c nh hng trc tip n qu trnh ln men lactic v cht lng sn

phm. Ma nng tm chua chng chn, ma ma rt lu chn v tm chua mui trong manng c cht lng cao hn, mu sc ti v mi v thm ngon.

Nhit mui tm chua cng cao th qu trnh mui tm chua cng nhanh, lngacid chung tch ly cng nhiu. Nhng nhit cao, mt s vi khun gy thi li c khnng pht trin mnh lm h hng sn phm. Ngoi ra qu trnh ln men butyric xy ramnh trong iu kin ym kh v nhit 30 - 400C do hn ch tm chua ln menbutyric nn mui tm chua nhit di 300C tuy khong nhit ny, tc lnmen lactic khng nhanh nh 350C.

nh hng ca ging vi khun lactic s dng trong mui tm chuaTm chua ch bin theo phng php c truyn Hu, c ln men lactic t nhin,cc vi khun lactic c tr nguyn liu thc vt t khng kh bay vo thc hin qu trnhln men lactic. y l mt qu trnh ln men tp. Do tm chua mui ni ny c mi vthm ngon hn khc ni khc.

S dng cc ging vi khun lactic ng kh ca Hungary thm vo trong qutrnh mui tm chua, lm cho tm chua c mu t nhin, mi thm ngon c trng,lng acid to ra nhiu hn.

III.2 Qu trnh thy phn Proterin trong mui tm chuaIII.2.1 Qu trnh thy phn protein

Khi mui tm chua, tm c nguyn c u s dng protein ni tng catm. Khc vi chp v mm tm, tm sau khi mui vn cn nguyn con, trong khi chpv mm tm yu cu phi nhuyn ra. Qu trnh thu phn protein din ra do s hot ngca protease do cc vi sinh vt t nhin c trong tm to ra v c sn trong ni tng catm. y l mt dng ca qu trnh n thi thng gp thy sn. Qu trnh ny v bncht l khng c li cho sn phm v n to ra cc hp cht amin c mi kh chu. Tuynhin cc hp cht ny nu tn ti mt hm lng nh li to nn hng v c trngcho sn phm, nht l khi phi hp vi cc acid bay hi. V vy vn cn gii quyt caqu trnh mui tm chua chnh l vic khng ch kim sot qu trnh thy phn proteinny.

Cng vi qu trnh thy phn protein l qu trnh bin tnh ca protein di tc ngca ca pH thp do acid lactic gy ra to cho tm c mu p. Trong v tm c chaasthaxanthin mu xanh tm. Khi tm ti th asthaxanthin lin kt cht ch vi protein, Khic tc nhn gy bin tnh hay phn hy (nhit , pH, s thi ra) protein ca tm thasthaxanthin tch ri khi protein v d dng b oxy ha thnh asthaxin c mu gch.Ngoi pH acid th nhit cao cng l nguyn nhn gy bin tnh. nhit trn 40oC thqu trnh bin tnh ny xy ra. V vy qu trnh mui tm chua nu tin hnh nhit cao th tm c mu p.

III.2.2 Cc nh hng ln qu trnh thy phn proteinnh hng ca lng mui n ln qu trnh thy phn protein trong mui tm chuaMui n c nh hng rt ln n hot ng ca qu trnh thy phn protein tm

cng nh s to ra cc hp cht amin trong sn phm tm chua. Mui n c tc dng tchcc l km hm hot ng ca cc vi khun gy thi cng nh gim hot tnh caprotease do chng sinh ra.

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Nhn chung lng mui n cng cao th tc thy phn protein cng chm li. Tuynhin nh ni trn, iu ny cng lm chm qu trnh ln men lactic.

nh hng ca qu trnh ln men lactic ln qu trnh thy phn protein trong muitm chua

ng di tc dng ca vi khun lactic chuyn ng thnh acid lactic v cc acidhu c khc. Cc acid ny to ra mi trng pH thp (4 4.5). Mi trng pH ny c nh

hng n qu trnh thy phn protein. Mt mt n to ra mt mi trng thch hp chocc enzyme protease aicd thy phn protein. Cc protease ny c sn trong tm (trypsin,pepsin) hay do cc vi khun tng hp nn. Mt khc n li c ch hu ht hot ng cacc vi khun gy thi v cng hn ch lun vic tng hp protease ca cc vi khun ny.Nh vy tc ng ny c hai mt.

Vi khun lactic cng c kh nng tng hp protease. Protease ca vi khun lacticcng tham gia thy phn protein trong qu trnh mui tm chua nhng protease ny chm lng t v hot tnh khng cao.

Trong qu trnh mui tm chua, acid lactic to ra lm pH mi trng gim xung,cc protease trong ni tng ca tm nh trypsin hay pepsin cng vi cc protease acid

tnh ca cc vi khun gy thi s c iu kin hot ng.Acid lactic to ra trong qu trnh mui tm chua c kh nng c ch cc hot ngca vi khun gy thi cng nh kh nng tng hp ca cc protease ca chng. Nh vych c protease ca tm ng vai tr chnh trong qu trnh thu phn protein. Nhngprotease ca tm li gim hot tnh mnh trong mi trng c nng mui cao, trong khiprotease vi khun li c kh nng hot ng trong mi trng c nng mui cao mnhhn protease ca tm. V vy qu trnh chn ca tm thng phi ko di.

IV. Cc hn ch ca quy trnh ln men truyn thng v mt s citin ngh [1],[2],[3]

IV.1 Cc hn ch ca quy trnh ln men truyn thng

Quy trnh ln men truyn thng thng gp phi mt s vn kh khn sau- Tm b bin en do phn ng mu ca melanin.- Gia v cng b bin mu c bit l ti v ring (mu vng chuyn sang mu nu

en), t t b bin mu.- S dng hm lng mui qu cao (khong 30% khi lng tm). Lng mui cao

tm khng b thi trong qu trnh ln men lactic. Nhng nhc im vi lng muitrn s c ch hot ng ca protease v ca vi khun lactic lm cho thi gian mui tmchua ko di n 18 - 20 ngy, mt khc lm gim mi v c trng cho sn phm nht lv chua ca acid lactic..

-S dng cm np, thnh ln men lactic tri qua 2 giai on: cm np (hay thnh)

chuyn thnh ng, ng chuyn thnh acid lactic. Nh vy thi gian ln men lactic sko di. Mt khc cm np kh trn u vi tm ln men lactic c u nhngthng lm sn phm c, khng p. Vi thnh thi gian ln men lactic phi ko di,ngoi ra thnh lm cho sn phm c mu nu ti. Ngoi ra khi ln men bng thnh th gia vb bin mu mnh nht. Cc gia v nh ti, t, ring c mu xm en.

-Vic mui tm chua hon ton ph thuc vo thi tit, thin nhn nn khng chng, ma nng tm chua chng chn, ma rt tm chua lu chn.

IV.2 Bin php khc phc nghIV.2.1 Chng hin tng bin en ca tmTm sau khi nh bt ln khi nc, tip xc lu vi khng kh b bin en. Hin

tng ny xy ra c khi mui tm chua. C tc gi cho rng s bin en ca tm l dothyrosin ca tm b xy ha di tc ng ca thyrosinase to thnh cht mu ti gi lmelanin, cc melanin ny tch t li to thnh nhng vng en. Mt s tc gi khc cho

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rng melanin l do phenylalanin b xy ha to thnh. V vy chng hin tng binen c th b u ca tm trc khi mui chua. Nh vy s mt i mt trong hai ngunprotease ca tm thy phn protein. phn ng to melanin khng xy ra c th sdng cc cht chng oxy ha nh acid ascorbic, aicd citric hay cht c ch tyrosinasenh sulfit hay natri sunfit, hoc to iu kin tm khng tip xc vi khng kh. Binphp n gin v c hiu qu nht l cho tm ngp trong nc mui hoc nc mm.

Mt iu ghi nhn l khi mui tm chua vi mui n v cm np hoc mui n ving th tm chua b bin en rt nhiu. Tuy nhin nu s dng nc mm thay mui n mui tm chua th hin tng bin en hu nhkhng xy ra.

IV.2.2 Chng bin i mu ca gia vTrong qu trnh mui tm chua, mt s gia v b bin i mu nh ti, ring, gng

lm cho cht lng ca tm chua b gim i. Do khi mui tm chua khng nn cho ti,ring vo ngay t u m sau khi tm chua n c mi cho vo. t, mng vi chovo cng vi tm khi mui m bo qu trnh ln men lactic ca tm chua.

IV.2.3 Rt ngn thi gian mui tm chua rt ngn thi gian mui tm chua, s dng cc bin php tng nhanh qu trnh

ln men lactic v thy phn protein.Dng ng thay cm np rt ngn thi gian ln men. Nu mun s dng cmnp th c th b sung thm amylse tng cng qu trnh thu phn tinh bt thnhng.

S dng cc ging vi khun lactic c nng sut cao.S dng ch phm trypsin, bromelin, papain rt ngn thi gian thy phn protein

(5% so khi lng tm). Tt nht l s dng ch phm protease vi khun v hot ngc trong iu kin nng mui cao.

IV.2.4 Gim lng mui s dngGim lng mui s dng v b sung mt s ph gia c ch vi sinh vt nh acid

ascorbic hay acid citric hn ch vi khun gy thi.Tin hnh ra bt mui trc khi cy ging vi khun lacitc

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IV.3 Quy trnh sn xut ngh

Tm

La chnRa sch

Ct ru chn

Ra

p mui

Ra mui ro

Ln men

Vo hp

Tmchua

Lc bt cnB bt mt s

thnh phn

Rt dch

Ru chn

30oC , 10 ng

Cn

Mui 15 20 %

Ging vi khunlactic Gia v

Dch rt

Nc mui

Rau trnn km

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Thuyt minh quy trnho Nguyn liuTm nc ngt, nc l, tm bin cn ti. V ngoi mu t nhin, nh sng u

dnh cht vo thn, khng b v gch, mt cng trn, bng en. Tht chc, c mu trnghay trng nht, n hi, kh tch ri khi v, mi tanh t nhin, khng c mi ha chtbo qun.

o Ra schTtm c ra sch di vi nc chy. Nht sch cc tp cht, rong bin, tm

n, u tm. C th ra tm my ra thi kh v cho tm chy trn bng ti chuynng vi vn tc 0,1 m/s.

o Ct ru chn, raTm c ct sch ru t mt tr ln v 3 i chn trc bng ko. Tm c ra

li tht sch v ro 10 pht.o p muiTm x l c hc, c ngm nc mui 15 20 % trong 12 gi. Vt ra ra

sch bng nc v ro.o Ln menS dng ging Strep. cremoris, Strep. lactis cy trn lactose ln men dch ng

300C trong 6 gi. Cho dch ng ln men vo tm gi nn vi t l 5% so khilng tm.

Gia v s dng bao gm: t, ti, ring pha trong nc sch c nng mui khong5 7 %. Mui s dng l mui n hay ly t nc mm. B sung thm ch phmprotease vi khun hay trypsin, bromelin t da, papain t u .

Thi gian ln men 10 ngy 300C. Tm c cho vo ang hoc thng thp khngr ln men. Kt thc qu trnh ln men pH dch ln men t 3,8 4, tm chua c mu ti, thm ngon c mi c trng ca sn phm ln men lactic.

Lc bt cn v b bt mt s thnh phn nguyn liu khng t chunDch ln men s c c do mt s m c ca tm cng nh m thc vt ca gia

v b tch ri khi nguyn liu. ng thi sinh khi ca vi khun lactic cng lm c dungdch. Lc s b gip loi b bt thnh phn gy c, lm dung dch trong, gi tr cm quantng.

Mt s thnh phn nguyn liu b bin mu nh tm b bin en, ti, gng b honu, cc ht t cng cn c loi b.

o Vo hp, rt dchDch ln men sau khi lc s b c cho vo bnh thu tinh v rt dch b sungThnh phn ca dch rt bao gm: ng, mui hay nc mm, acid lactic hay acid

acetic gia v nh ti, t, ring, cht to st (tinh bt bin tnh hay pectin), phm mu ()thc phm v cc ho cht bo qun. T l cc cht trong dch rt cng nh t l dch rt :dch ln men trong bnh tu thuc vo thnh phn dch ln men v khu v ngi tiudng.

Cui cng mt s loi rau trn c b sung vo lm a dng sn phm. Ccloi rau thng dng l bn bn, ng sen

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V. Kt lunTm chua l mt sn phm ln men truyn thng c trng ca Vit Nam. Nu

chng ta bit vn dng sn phm ny tr thnh mt mt hng c gi tr th c th mang linhiu li ch. C mt s vn tn ti cn gii quyt

- Phi tm ra cc phng php bo qun, chng li s h hng ca tm mtcch hiu qu.

- Kim sot qu trnh ln men lactic cng nh qu trnh thy phn protein to ra sn phm c cht lng ng u, s phi hp gia cc hng v tt nht.

- iu chnh li hng v (nht l phn gia v s dng) sao cho ph hp vi as ngi tiu dng (cn phi tin hnh kho st th trng).

VI. Ph lc v ti liu tham kho

Hnh VI. Sn phm tm chua

Ti liu tham kho[1] Nguyn c Lng Cng ngh vi sinh Tp 3 Thc phm ln men truyn

thng, Nh xut bn i hc Quc gia Tp.HCM, 2006, Trang 83 112[2] Nguyn Xun Thnh Gio trnh Vi sinh vt hc cng nghip Nh xut bn

gio dc, 2004, Trang 203 206.[3] Nguyn Ngc Tun, L Thanh Hin Ch bin bo qun Tht v Sa, Nh xut

bn Nng nghip, 2004, trang 42, 43.[4] Nguyn Th Cm Tuyt Mn n Vit Nam, Nh xut bn ph n, 2001, trang

134.

[5] Lehninger A principles of biochemistry- 4th edition Freeman puslishing,2004, page 480 601.

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