NH HNG CA THNH PHN SA N YAOURT

ng Hunh NhMSSV: B1205195

, yaourt c hng v thm ngon, b dng v quan trng hn c m n mang li rt nhiu li ch cho sc khe con ngi: Yaourt c tiu ha cao v cc cht c chuyn ha ti dng c th hp th c c bit i vi ngi gi v tr em, l thc n n king c tc dng cha bnh v c tc dng kch thch s tit dch v, kch thch s trao i cht, h vi khun lactic (c trong cc sn phm ny) c tc dng khng ch s pht trin ca vi khun gy thi ra rutNgoi cc thnh phn dinh dng nh protein, lipid, glucid, yaourt cn cha nhiu vitamin, cc cht khng th rt c ngha trong iu tr mt s bnh.T dng yaourt truyn thng ban u nhm to thm nhiu sn phm a dng phong ph c gi tr dinh dng cao, hp dn ngi tiu dng, bng cch nghin cu su v cc thnh phn nh hng n cht lng sn phm sa chua. Do vn t ra l nng cao gi tr yaourt thng qua thay i cc thnh phn, to ra s mi l cho sn phm, m thnh phn quan trng nht l sa nn ti thc hin nghin cu kho st nh hng ca thnh phn sa n cht lng sn phm yaourt gp phn a dng ha sn phm yaourt th trng trong nc.

. Gii thiu sa ln men (yaourt)2.1Ngun gc-Yaourt c sn xut ch yu Trung ng v cc nc a Trung Hi. Trc c nhiu tn gi cho sn phm ny nh Mast (Iran), Leben, Laban (Iraq, Egypt), Zabade (Sudan). Mt s sn phm kh ging yaourt nh Dahi (n ). -Yaourt chnh l sa chua do b nhim trong khi vt sa v s dng.-Yaourt c th c sn xut t nhiu loi sa khc nhau hoc t hn hp cc loi sa, c bit khi lm yaourt t s cu yaourt s c mi v v c c chc chn v c bit cng c th lm sn phm trung gian gia sn phm ln menvaf phomat ti.2.2Phn loi yaourtNgi ta chia yaourt thnh 3 loi ph thuc vo thi im tin hnh qu trnh ln men:-Yaourt dng truyn thng (set yoghurt): ngay sau khi b sung chng, ngi ta rt vo hp ngay v ln men trong hp.-Yaourt dng khuy (stirred yoghurt): b sung chngr v ln men trong xitec ln, sau lm lnh rt vo hp.-yaourt dng ung (drinking yoghurt): sn xut tng t nh dng stirred. Sau khi ng t pha ch thnh dch c th qua hoc khng qua x l nhit trc khi rt hp. 2.3Vi sinh vt trong ln men sa chua (yaourt) sn xut cc loi sn phm sa ln men, ngi ta cy cc chng vi sinnh vt khc nhau vo sa kt qu l chuyn lactose thnh acid lactic, CO2, acid acetic, diacetyl, acetaldehyde v kt hp cht bay hi khc to cho sn phm c mi v c trng. Mt s sn phm nh: kefir, kumis, cn cha mt lng nh ru etylic.H vi sinh vt dng ln men saChng vi sinh vt c th bao gm mt hoc hn hp ca nhiu loi. Mt s loi nh: Streptococcus lactic, Streptococcus cremoric, Streptococcus thermophillus ch c tc dng ln men lactose v to acid lactic. Mt s loi khc nh: Streptoco-ccus diacetylactic, Leuconostoc citrovorum li c kh nng to ra cc cht thm.3. Cc qu trnh sinh ha xy ra trong ln men sa chua (yaourt)Qu trnh sinh ha ch yu xy ra trong ln men sa chua l ng lactose u tin chuyn ha thnh glucose v galactose, sau cc ng n ny chuyn thnh acid pyruvic v cui cng to thnh acid lactic Lactose

Glucose Galactose

Sn phm trung gian Acetaldehyde Ethanol CH3CHO Acid pyruvic+CO2, CH3CHO CH3COCOH Acetoin CH3COCHOHC+ 2H + H2O +O2 - 2H Diacetyl Acid lactic Acid lactic CO2+ CH3COOH CH3COOH CH3COCOC3 Ln men Ln men d th ng th Hnh 1.1 Qu trnh sinh ha xy ra trong qu trnh ln men sa chuaAcid lactic sinh ra lm gim gi tr pH ca sa n im ng in ca protein sa gy nn hin tng ng t ca chng. Ngoi ra do casein hin din trong sa ti di dng calcium caseinat, cht ny tc dng ca acid lactic c sinh ra to thnh acid caseinic v lactate calcium. Acid caseinic t do khng h tan do to thnh khi ng.Chuyn ha sinh hc c ngha nht trong sa do nhm vo khun lactic gy nn. Ngoi sn phm chnh l acid lactic, qu trnh lnmen ng lactose cn cho nhiu sn phm ph khc l cc acid d bay hi, ru, ete, aceton v dyacetyl.

Bng 1.6 Cc bin i sinh ha ch yu trong qu trnh ln men yaourtCht tham giaCc bin i

1.Trao i cht cacbon hydratLactose b thy phn bn trong t bo vi khun bng enzyme -D Galactose sidase to thnh glucose v galactose. Glucose c s dng ch yu chuyn ha thnh acid lactic.Phc h calcium-casenat-phosphat b mt n nh do s hnh thnh acid lactic dn n s to thnh khi ng yaourt.S to thnh nhng thnh phn mi trong yaourt o bi qu trnh ln men ca ng sa nh: acetaldehyde (2,2 4,1 ppm), aceton (1,0 4,0 ppm), dyacetyl (0,4 13,0 ppm)

2. Thy phn proteinGing vi khun trong sn xut yaourt c kh nng thy phn protein mc thp to thnh cc peptide v cc acid amin cht ny tham gia vo phn ng ha hc v phn ng enzyme to thnh nhng hp cht mi.C Streptococcus thermophillus v Lactobacillus bulgaricus u c enzyme peptidase phn gii protein, protid to thnh cc peptid gy ng.Kt qu ca qu trnh thy phn protein l to thnh nhiu acid amin t do (23,6 70 mg/100mL)

3. Thy phn cht boGing vi khun ln men yaourt cng c th phn gii lipit mc no (c bit i vi triglyceride mch ngn) v sn phm phn gii ny gp phn vo mi ca sn phm cui cng.

4. Cc cht khcTnh trn trung bnh, c s gia tang v thnh phn niacin, acid folic trong qu trnh ln men, nhng cc vitamin khc nhau nh: B1, B12, B6, B5 b phn hy tng i nhiu.

(Dng Th Phng Lin, 2000)