visinhthucpham

7/31/2019 ViSinhThucPham

1/87

BO CONG NGHIEP

TRNG CAO ANG CONG NGHIEP 4

KHOA CONG NGHE THC PHAM SINH HOC MOITRNG

Giao trnh:

VI SINH THCPHAM

(Lu hanh noi bo)

Thang 9 nam 2004


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Phan 2: Vi sinh thc pham.........................................................................................................

LI M AU

Vi sinh thc pham la mot trong cac mon hocthuoc ve c s nganh trong chng trnh khung aotao nganh Cong nghe Thc pham. Tat ca cac sinhvien hoc chuyen nganh Cong nghe Thc pham eubat buoc phai hoc mon nay trc khi hoc cac monchuyen nganh.

Vi sinh thc pham cung cap cho sinh vien nhngkien thc c ban ve cac vi sinh vat thng gaptrong thc pham: cac vi sinh vat gay benh thnggap trong thc pham, cac vi sinh vat gay h hongthc pham va cac vi sinh vat lam tang them hngvi cua thc pham.

Bao gom cac chng sau:

- Chng 0 : Mot so phng phap nh lng vi sinhvat

- Chng mot : Mot so loai vi sinh vat gay benhthng gap

- Chng hai : Vi sinh vat trong che bien va baoquan tht

- Chng ba : Vi sinh vat trong che bien va bao

quan ca- Chng bon : Vi sinh vat trong tom, mc va cac

ong vat nhuyen the

- Chng nam: Vi sinh vat trong che bien va baoquan sa

- Chng sau: Vi sinh vat trong bot va tinh bot.

- Chng bay: Vi sinh vat trong cac san phamng, banh, keo

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- Chng tam: Vi sinh vat trong rau qua va cac sanpham t rau qua

Sau khi hoc xong mon hoc, sinh vien phai nam

vng cac kien thc c ban ve he vi sinh vat vi sinhvat thng gap trong thc pham.

Trong mon hoc nay, ieu kho khan nhat oivi sinh vien la nh c ten cac vi sinh vat. Cole n gian nhat la hay coi nh ay la t mi trongmot ngon ng mi. Vay hay hoc moi ni, moiluc co the, hay thng xuyen ghi lai e co the ghichnh xac ten cua vi sinh vat, hay dan danh muc

ten vi sinh vat au ging e toi toi co thenham ten vi sinh vat. Hay ghi tng ten vi sinh vatvao tng manh giay nho va em ra o ban be. Nhvay co le se lam cho viec hoc tr nen thu v hn.Con cac phan khac trong giao trnh, ngoai tr cacnh ngha, con lai khong yeu cau sinh vien phaithuoc long tng cau, tng ch ma ch can hieuva tom lc lai van e mnh hieu la u. Mong cac

ban sinh vien se at c ket qua tot trong quatrnh hoc.

Mac dau a rat co gang trong qua trnh biensoan, tuy nhien giao trnh van cha thc s hoanhao. Chung toi mong nhan c nhieu gop y chanthanh e lan tai ban sau hoan chnh hn.

e hoan thanh giao trnh nay chung toi aphai tham khao rat nhieu sach, giao trnh, tap ch,thong tin t cac thay co, cac giao s, ong nghiep moi ni. Xin chan thanh cam n tat ca moi sgiup nay.

Ngoai ra Xin chan thanh cam n s giup cua Ban giam hieu trng Cao ang Cong nghiep 4a tao ieu kien ve thi gian cung nh kinh ph chochung toi thc hien giao trnh.

Ban bien tap

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CHNG 0:CAC PHNG PHAP

NH LNG VI SINH VAT

0.1.PHNG PHAP EM TRC TIEP

Cac loai vi sinh vat n bao co kch thc lnnh nam men tao Co the nh lng trc tieptrong buong em hong cau qua knh hien vi. Quy trnhem trc tiep cho phep xac nh nhanh chong solng vi sinh vat trong mau. Tuy vay phng phap nay

co cac nhc iem sau:- Khong phan biet c te bao song va te bao

chet

- Khong phan biet dc te bao vi sinh vat vacac hat vat the khac lan trong mau

- Khong thch hp cho huyen phu vi sinh vat comat o thap.

Co ba phng phap em trc tiep:

0.1.1. em trc tiep bang buong emhong cau

Buong em hong cau la mot dung cu bangthuy tinh. Dien tch buong em la 1mm2, chieu caola 0,1mm. Dien tch 1mm2 c chia lam 400 o nhova the tch cua 400 o nho se bang hoac 25 ovuong ln, tng ng the tch cua o vuong ln la1/250mm3.

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Trc khi quan sat cho them vai giot formalinvao trong mau. Pha loang mau sao cho trong moi ovuong nho co khoang 5 10 vi sinh vat. Muon atc yeu cau tren can phai c lng so vi sinh

vat trong mau, hay phai lam th mot vai lan exac nh c cong thc pha loang toi u.

Mau c pha loang bang dung dch co thanhphan:

Thanh phan dung dch pha loang.

- Pepton 0,1%

- Laurylsulphate 0,1%- Methyl blue 0,01%

Cac dung dch pha loang sau khi chuan b phailoc qua trc khi s dung.

ieu chnh knh o phong ai 400 lan roitien hanh em. em so lng te bao trong 5 o lnnam tren ng cheo cua buong em.

Cach tnh so vi sinh vat. Goi x1, x2, x3, x4, x5 la solng vi sinh vat trong tng o ln ta co :

X =5

54321 xxxxx ++++

Ta biet the tch cua 1 o ln bang 1/250 mm3

Do o so lng te bao vi sinh vat co trong 1 ml

mau se la:

So vi sinh vat (trong 1 ml mau) = X .250.1000 = X.250000

0.1.2. em trc tiep bang ng emBreed

Buong em Breed co dien tch 1cm2 c anh

dau. Dung bm tiem cho chnh xac 0,01ml dung dchmau dan tren mat buong em. Say kho bangcach h nhe tren en con bang methyl blue.

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Khi em phet mot lp dau tren be mat canem. So lng vi sinh vat /ml c tnh theo congthc:

N/ml=4a.104

/d2

a: so lng te bao vi sinh vat trong vung em

d: ng knh cua vung em

0.1.3. em trc tiep bang knh hien vihuynh quang:

Khi nhuom vi sinh vat bang mot so thuocnhuom phat huynh quang nh:

- Acridin Cam (AODC)

- 4, 6 dianidino 2 phenyl indol (DAPT)

- Fluoresecin isothio cyanate (FITC)

Mat o vi sinh vat co the xac nh trc tiepdi knh hien vi huynh quang

So em nhan c bang phng phap nay cothe cao gap 2 lan phng phap em khuan lac. Ssai khac nay do cac te bao chet hoac ton thngkhong co kha nang phat trien thanh khuan lac.

Ket qua so em vi sinh vat bang knh huynhquang phan anh so vi sinh vat co that trong mau.

0.2. PHNG PHAP EM KHUAN LAC:

Phng phap nay cho phep xac nh so lngte bao vi sinh vat song trong mau. Nhng te baosong mi co kha nang phat trien thanh khuan lactren moi trng thch hp.

Phng phap nay cho phep nh lng chon loc visinh vat tuy thuoc vao moi trng nuoi cay.

Phng phap nay thc hien nh sau:pha loang

mau sao cho so lng khuan lac xuat hien tren motda petri khoang 25 250. Di mc 25 se kho chnhxac tren mc 250 rat kho phan biet cac khuan lac

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khi em. a mau vao mat thach, dung bau trangxoa eu len toan bo dien tch cua a thach trongieu kien vo trung tuyet oi e tranh lan tap.

Vi moi loai vi khuan oi hoi phai co thi giannuoi cay toi u. Sao cho cac te bao song u thigian phat trien thanh khuan lac.

Ket qua thu c la so trung bnh cua 2 3 apetri vi cung ieu kien nuoi cay.

Ket qua cung thng c trnh bay di dangCFU (colony torming unit) thay v so te bao/ml, v rangco nhieu te bao hnh thanh chung mot khuan lac.

Mac du co mot so nhc iem song ay vanla phng phap tot nhat e xac nh so lng tebao vi sinh vat. Phng phap nay co o nhay cao,nen thng c dung trong kiem nghiem vi sinh vattrong nc, thc pham, benh pham.

Quy trnh chi tiet cua phng phap em khuanlac: mau c pha loang theo day nong o nh sau:

10-1, 10-2, 10-3, 10-4, 10-5V du: lay 1ml mau, pha vao 9ml dung dch, pha

loang tron eu, roi tiep tuc lay 1ml cua dung dch 1cho vao 9ml dung dch pha loang ta c dung dch 2vi o pha loang la 10-2.

1ml mau

opha

loang 10-1

10-2

10-3

10-4

10-5

1ml 1ml 1ml 1ml 1ml

9

ml

9

ml

9

ml

9

ml

9

ml

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C tiep tuc, se co cac dung dch vi o phaloang tang them 10 lan cho en khi tm c o phaloang thch hp, cho phng phap em khuan lac.

Nguyen tac chung la1 phan mau +9 phan dungdch pha loang cho nen neu la 0,1ml can bo sung0,9ml dung dch pha loang

Chuan b moi trng thch hp tren a petri

Cach tnh ket qua :

V du: ket qua so khuan lac trung bnh t 2 apetri thu c la 35, o pha loang 10-4, so lng mau

a vao a petri la 0,1ml ta co: 35.10.10000 =3500000 te bao/ml

0.3. PHNG PHAP MANG LOC:

Phng phap nay cdung e nh lng vi sinhvat trong cac mau ncvi mat o vi khuan

thap. V vay phng phapnay gom bc loc etap trung vi sinh vat cotrong mau nc trenmang loc. Viec xac nhso lng te bao vi sinhvat da vao so khuan lac

em c. Sau khi at mang loc len tren moitrng that co thanh phan dinh dng thch hp.

Theo nguyen ly mot khuan lac la mot te bao visinh vat.

Mang loc co kch thc 0,2 0,45 m c chetao t cac si thuy tinh hay si polypropylene.

Ngoai mang loc thong thng, ngay nay condung mang loc k nc. Cac vach chia o lam bangvat lieu ngan can s moc lan cua cac khuan lac.

So vi sinh vat c tnh theo so khuan lac moc trongcac o.

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0.4. PHNG PHAP MPN (MOST PROBABLE NUMBER)

(So co kha nang cao nhat SCKNCN)

Quy trnh nh lng theo phng phap nay nh

sau:Cho cac ong nghiem cha moi trng dang

long thch hp vi vi sinh vat can xac nh vi 3mc nong o 1/10, 1/100, 1/1000 moi mc 3 ongnghiem. U nhiet o vi thi gian thch hp. Davao ket qua nhn thay chng minh s tang trngcua vi sinh vat can kiem nh (thng la nhnghien tng nh:sinh hi, oi mau, uc) ghi nhan solng cac ong nghiem dng tnh tng o phaloang. S dung cac so lieu nay va da vao bangMac Crady suy ra mat o vi sinh vat c trnh baydi dang MPN/100ml hay so MPN/gam.

o chnh xac cua tr so MPN phu thuoc vao solng ong nghiem lap lai trong moi o pha loang.

S dung moi trng BGBL 37oC co the nh

lng nhom Coliform, cung moi trng nay 45oCcho phep nh lng Coliform trong phan.

0.5. PHNG PHAP O O UC:

Te bao vi sinh vat la mot thc the khi co trongmoi trng se lam cho moi trng tr nen uc. ouc cua huyen phu ty le thuan vi so lng tebao vi sinh vat co trong moi trng. Trong mot gii

han nhat nh, moi quan he gia so lng vi sinh vattrong moi trng ty le tuyen tnh vi o uc cuamoi trng. Do o co the nh lng vi sinh vat trongmoi trng bang may o o uc hay may so mau bc song 550 610nm. Trong trng hp nay canxay dng bieu o tng quan tuyen tnh gia o ucva so lng vi sinh vat co trong moi trng bangphng phap em khuan lac trc tiep. Phng phap

tien hanh theo hai bc:

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1. Pha loang huyen phu cha vi sinh vat cankiem nghiem sao cho cac dung dch thu ckhi o tren may so mau bc song 610nmc cac tr so OD gan 0,1; 0,2; 0,3; 0,4; 0,5.

Dung phng phap em trc tiep xac nh lngte bao vi sinh vat co trong 1ml ky hieu N/ml.

Tnh gia tr log (N/ml) cho tng mc nong o phaloang. Ve o th bieu dien log (N/ml) (truc tung) theocac gia tr OD at tren truc hoanh. Xac nhkhoang tuyen tnh gia log (N/ml) vi OD.

2. Xac nh lng te bao theo o uc:

- o o uc cua huyen phu cua te bao visinh vat can xac nh.

- T tr so OD o c oi chieu tren oth tng quan gia mat o te bao va ODe xac nh lng te bao co trong maunghien cu. Lu y N/ml = 10a vi a=log(N/ml).

Phng phap xac nh mat o te bao theo ouc co the c dung e so sanh mc o tangtrng cua hai hay nhieu chung vi sinh vat trong moitrng long. Trong trng hp khong can thiet giatr tuyet oi cua te bao vi sinh vat th khong canphai xay dng bieu o tuyen tnh gia mat o visinh vat va gia tr OD.

Phng hpap nay cho ket qua nhanh, thngc dung e theo doi hoac nghien cu ac trngtang trng cua cac chung vi sinh vat trong phongth nghiem hoac trong san xuat, tuy nhien khongthch hp cho ng dung trong kiem nghiem vi sinh vat

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CHNG 1:

MOT SO LOAI VI SINH VAT

GAY BENH THNG GAP

Cac qua trnh h hong cua thc pham thngdo vi sinh vat gay nen. Trong o rat nhieu trnghp cac vi sinh vat nay con tao ra cac oc to gayanh hng en sc khoe con ngi. Chnh v vayviec tm hieu ve cac vi sinh vat gay benh e to tm ra cac bien phap khong che chung la vieclam can thiet.

Co 2 dang gay benh co nguon goc t vi sinhvat:

- Vi sinh vat tiet ra oc to va s hien dien cuacac oc to nay trong thc pham la nguyennhan gay benh. V du: Clostridium botulinum tietra oc to gay nen benh botulism (chng ngooc tht); Staphylococcus aureus gay nen benhtu cau khuan

- Vi sinh vat hien dien trong thc pham, t oxam nhap vao c the con ngi. S hien diencua chung hoac cua cac san pham hnhthanh t qua trnh phan giai cac chat trong cthe la nguyen nhan gay benh. V du:Salmonella spp., Vibrio parahaemolyticus, Escherichiacoli,

Tuy nhien co nhieu vi sinh vat mang ac tnhcua ca 2 dang gay benh nay. V du Clostridiumperfringens va Bacillus cereus.

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Trong chng nay, chung ta se cung tm hieumot so loai vi sinh vat gay benh thng gap.

1.1. COLIFORM VA COLIFORM PHAN (FECAL

COLIFORM)ay la nhng vi sinh vat hnh que, G -, khong tao

bao t, co kha nang len men latose va sinh kh trongqua trnh len men nay. Phat trien trong khoangnhiet o (t 2 en 50oC), pH t 4,0 en 8.5, co thesong hieu kh hoac k kh tuy y. Sau 12 16 gi trenmoi trng thach tao ra nhng khuan lac co thenhn thay c.

Coliform i vao thc pham t nc hoac nguyenlieu thc pham co nhiem phan.

Cac loai tieu bieu cho Coliform: Escherichia coli vaEnterobacter aerogenes. Tuy nhien, nngoai ra con cokhoang 20 loai mang nhng tnh chat ac trng choColiform, trong o bao gom ca cac Enterobacteriaceaekhac va cac loai thuocAeromonas.

Nhom Coliform phan la nhng Coliform co khanang phat trien trong moi trng co nhiet o t44.5 450C (cac Coliform khac co t0opt=370C). ay cungla ac iem nhan biet va phan biet Colifom phan.

Tuy nhien viec xac nh nay ch la gia tr dunge tham khao cho viec xac nh ieu kien songcua Coliform.

e xac nh chnh xac Coliform, Coliform phan vangay ca E.coli trong thc pham bat buoc phai dungcac chat ch th.

Dui ay la mot vai tnh chat ac trng choviec lam h hong thc pham cua Coliform:

- Chung co kha nang phan giai nhieu loai cchat khac nhau: carbohydrate, cac chat hu csinh nang lng, cac hp chat cha nit n

gian,..

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- Co kha nang tong hp hau het cac vitamincan thiet.

- Co kha nang phat trien tot trong moi trng

co nhiet o t 10 460

C.- Co kha nang tao ra acid va sinh gas t ng

- Sinh ra mui v h hong, kho chu

Escherichia coli:

c phat hien la vi sinh vat gay benh tnam 1700.

E. coli thuoc ho Enterobacteriaceae, catalose (+),oxidase (-), gram(-) , trc khuan ngan, khong tao baot. Kch thc phu thuoc vao ieu kien nuoi cay.

ay la nhng vi sinh vat co kha nang phattrien nhiet o t 7 50oC. Trong o toopt=37oC,pHopt.= 7.0 7.5, aw opt.=0.95. Phat trien manh trong moitrng Mac Conkey, EMB

Thng song trong ruot gia cua ngi va ongvat, theo phan i ra ngoai

Co kha nang len men nhieu loai ng, sinh hi,kh nitrat thanh nitrit. Gay nhay nht, h hong thcpham.

Kha nang gay benh rat a dang: gay nhiemkhuan ng tieu; vi c the yeu gay nhiemkhuan mau; gay viem mang nao tre s sinh; gaytieu chay.

Cac chat c che s phat trien cua E.coli:chlorin, muoi mat, brilliant green, tetrathionat natri

1.2. STAPHYLOCOCCUS:

Hien nay tm thay 31 loai. Staphylococcus conhng ac tnh c ban sau:

- La cau khuan , G+, cac te bao thng lienket thanh hnh chum nho. Khong di ong,khong tao bao t. Nhiet o toi u la 37oC.

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Chu c kho han, hi nong ( 50oC van songc trong 30 phut). Co kha nang song ctrong nong o NaCl la 9 10%. pHopt= 6 7 ; aw opt= 0,83 0,90

- Co kha nang phat trien tren nhieu loai moitrng khac nhau nhat la tren cac moitrng cha chat hu c. Tuy nhien phai conit trong moi trng. Nguon nit s dung laacidamin.

- Trong ieu kien yem kh: can uracin; trong ieukien hieu kh can: glutamatnatri.

- Trong qua trnh phat trien tao sac to t mautrang en vang sam.

- Thng song da ngi, ng ho hap,ng tieu hoa

Staphylococcus thng tao oc to gay oc chongi: Tao mun nhot, lam ong huyet tng, t ogay nen cac benh nh viem phoi, viem mang nao,

viem c tim, viem than, viem tuy xngCac chat c che s phat trien cua

Staphylococcus: hexaclorophen, tm gential

Cac chat tieu diet Staphylococcus: clorit,neomycine, polymycine.

Staphylococcus aureus:

ac trng nhat cua loai nay la gay viem ruotdan en benh chay mau ruot.

Mang tnh chat ac trng cua loai Staphylococcus,ket lai vi nhau thanh dang chum nho hoac thanhtng chuoi ngan. Phat trien tren moi trng ranthng tao thanh cac khuan lac co mau vang hoacchuyen dan sang mau cam, mac dau vay, trong motvai trng hp cung ton tai dang mau trang.

Phan ln cac Staphylococcus aureus gay ongmau. Song trong ieu kien yem kh tuy tien, tuy

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nhien co kha nang phat trien tot hn trong moitrng hieu kh.

Co mot vai loai Staphylococcus aureus co kha

nang chu mac rat tot (10 20% NaCl) va cung chuc tac ong cua nitrit. Chnh v vay phai rat kiemtra s hien dien cua Staphylococcus aureus oi vicac san pham tht nh: xuc xch, dam bong, lapxng,..

Staphylococcus aureus cung phat trien tot trongmoi trng co nong o ng cao (50 60% ng).Chung len men va phan giai ng nhng lai khong

tao mui v kho chu cho san pham.ieu kien toi u e Staphylococcus aureus phat

trien cung tng t nh vi cac loai Staphylococcikhac.

Nguon gay nhiem Staphylococci vao c thengi thng t nhng ngi b viem mui gay nenviem xoang, t cac ung nhot, hoac cac vet thng b

nhiem trung, t da ngi tiep xuc vi ngi benh.Staphylococci con gay nen chng viem vu bo danen lam nhiem sa va cac san pham t sa.Rieng khong kh khong phai la nguon gay nhiemac trng tr phi trong moi trng co qua nhieuStaphylococci.

Cac san pham thc pham thng coStaphylococci : tht va cac san pham t tht, ca va

cac san pham t ca, sa va cac san pham tsa, salad, pudding, cream. Neu khong c tr lanhung mc th Staphylococci se phat trien manh lietva gay benh.

Lng oc to c tiet ra u e gay benhtrong ieu kien moi trng thch hp la 12h 370C, 3ngay 180C, 7 ngay tai 90C, 4 tuan tai 4 6.70C.

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1.3. SHIGELLA:

Shigella thuoc ho Enterobacteriaceae, la vi khuangay benh l. Di ay la mot so ac tnh chung

tieu bieu cua Shigella:- La trc khuan gram(-), khong di ong, khong

sinh bao t, k kh tuy tien.

- Shigella ch tao acid t ng.

- Khong phat trien tren citrat, KCN thach, khongtao H2S.

- Phat trien trong khoang nhiet o t 10 40oC,t0opt = 370C, pH = 6 8, nong o muoi 5 6%.Nhay cam vi nhiet.

- Thng nhiem vao ca, qua, rau, tht, cac loaisalad t nc hoac phan ngi.

Shigella tao oc to gay kch thch len thanhruot, len he than kinh trung ng, gay tieu chay, cche hap thu ng va acid amin ruot non. Neu

tac ong len he than kinh th co the gay t vong.Khi b nhiem Shigella, chung se tan cong lp bieumo niem mac ruot gia, gay hoai t, lam loet,xuat huyet. Khi ruot gia b ton thng gay au bungd doi, tieu chay nhieu lan, phan nhay nht, comau.

1.4. SALMONELLA

Neu phan loai theo mc o gay benh cuaSalmonella ta co cac loai sau:

- Loai ch gay benh cho ngi (vd: S. typhi gaysot thng han tai ngi)

- Loai ch gay benh cho ong vat (vd: S.typhimurium gay sot thng han tai chuot)

- Loai gay benh cho ca ngi va ong vat

(chiem a so)Mot so tnh chat cua Salmonella:

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- La trc khuan gram (-), khong tao bao t, cotien mao (tr S. gallinarum), co kch thc tebao vao khoang 0,5 3 m.

- Len men glucose, sinh kh. Khong len men lactoseva saccharose.

- Phat trien manh trong moi trng Mac Conkey,thach Brilliant green. Sau 24h 37oC co the thaykhuan lac

- Giong nh nhieu loai vi khuan khac Salmonellaco kha nang phat trien trong khoang nhieto tng oi rong t 6 en 45.60C, tuy nhiennhiet o phat trien toi u la 370C.

- Salmonella phat trien trong khoang pH t 4.1 9.0. Trong cac mon salad co o pH khoang 5.5 5.7 khong nhan dang c s thay oi mui vkhi Salmonella phat trien.

- o am toi u cho s phat trien cua Salmonellala 0.93 0.95.

Salmonella xam nhap vao c the bang hai conng: t phan ngi hoac ong vat; t ngibenh. Trong o phai ke en tac ong cua ongvat long vu, trng cua chung va nhat la phancua chung a lam cho viec lan truyen Salmonella dedang hn. Ngoai ra chuot, meo, ruoi cung la nhngtac nhan gian tiep dan en viec Salmonella lanrong hn khi chung truyen phan vao cac thc phamkhong c bao quan ky. Trong qua trnh giet mocung can phai e phong s nhiem Salmonella neukhong thc hien ung quy trnh an toan thc pham.

1.5. YERSINIA:

Hien nay tm thay 11 loai

Mot so ac tnh chung cua Yersinia:

+ La trc khuan gram(-). Trong mot sotrng hp co kha nang chuyen ong. Thuoc

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loai k kh tuy tien, khong tao bao t, khongsinh nha bao

+ Khoang nhiet o phat trien toi u t 25

32o

C+ B tieu diet 60oC trong vong 1 3 phut

ai dien tieu bieu la Yersinia enterocolitica.Yersinia enterocolitica phat trien tren nhieu loai thcpham khac nhau: bo, heo, dch trng, pho mat mem,sa, ca, tom, cua, ga, au phu, Y. enterocoliticathng gay benh ng ruot, gay viem da day taingi. Sau 24 36 h sau khi s dung thc pham comam benh th trieu chng cua benh bat au xuathien nh au bung, sot, tieu chay, cac vet loet daday hnh thanh. Neu e lau se dan en chay mauda day.

1.6. VIBRIO:

Co khoang 28 loai. Trong o co 4 loai thnggap nhieu trong hai san:

- V. vulnificus -V. alginolyticus

- V. cholerae -V. parahaemolyticus

Mot so ac iem chung:

- La phay khuan. Phan ln thuoc gram (-). Diong nhanh nh n mao au. Khong sinh nhabao, phan ng oxydase dng tnh. Thuoc loai

hieu kh tuy tien.- Vibrio la loai vi khuan a man, trong moi

trng song yeu cau co khoang 1 3% NaCl.Co the phat trien trong moi trng co nongo muoi en 7.0%. Nhiet o phat trien toi ula 35 370C, tuy nhien van phat trien c khoang nhiet o t 10 440C. Khoang pH maVibrio co the phat trien t 5.0 11.0.

- Thng co mat hai san, cac san phamhai san, nc bien. Tuy nhien b tieu diet

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di tac ong cua nhiet o. Noi mot cachkhac, khi nau chn thc pham th khong phai los s tac ong cua Vibrio.

-

Co kha nang gay benh dch ta, nhiem trungmau.

1.7. CLOSTRIDIUM:

Hien nay phat hien ra hai chung gay ngo octhc pham:

- Clostridium botulinum: tao oc to gay hai enhe than kinh

- Clostridium perfringens: gay au bung, tieu chayva giai phong nhieu kh. Khi vi khuan hnhthanh bao t tao ra oc to ruot, gay ngooc cho ngi.

Mot so ac tnh chung:

- Trc khuan gram (+), khong di ong, yem kh,tao bao t. Bao t rat chu nhiet.

- Nhiet o phat trien toi u la : 43 47oC, pH t5 9

- B c che bi NaCl 5%, hoac NaNO3 2,5%

C.botulinum la vi khuan sinh oc to. Te baoC.botulinum b tieu nhiet o 800C (chung A) va 900C (chung B). Trong a so trng hp C.botulinum sinhgas va tao mui kho chu. T ac iem nay ta cothe loai bo thc pham nhiem C.botulinum mot cachde dang. Tuy nhien can e phong mot so trnghp ngoai le, luc nay ta khong nhan biet cbang cam quan ve s nhiem vi khuan C.botulinumcua thc pham, do o ngi s dung se b nhiemoc to gay hoi chng botulism (ngo oc tht).

Trong qua trnh x ly nhiet, cac bao t cua

C.botulinum rat kho b tieu diet. e tieu diet baot can co s tac ong cua nhiet o theo thi gianthch hp (Esty and Meyer 1992):

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21/87


tim ngng ap. Ket qua la ngi b b t vong do

te liet he thong ho hap. S t vong nay thng

dien ra sau 3 6 ngay s dung thc pham nhiem oc

to.

Phng thc duy nhat e cha tr la s dung

cac chat khang oc to. Tuy nhien no ch hieu

nghiem neu s dung khi phat hien ra cac trieu

chng au tien cua benh. Con e khi cac trieu

chng ac trng xuat hien th a muon roi. Chnh v

vay viec xac nh benh la rat kho khan. Kem theo

viec s dung chat khang oc to la phai gi cho

ngi benh trang thai yen tnh, s dung phng

phap th nhan tao, tao s can bang cac chat long

trong c the,..e ngan chan s nhiem C.botulinum vao c the

can chu y thc thi cac viec sau:

- Nen x ly nhiet cac o hop trc khi

s dung.

- Loai bo cac o hop co trieu chng

phong, meo mo.

- Khong nem cac thc pham co mui kho

chu.

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- Khong s dung cac thc pham a c

nau chn nhng khong c bao quan tot va

khong c ham nong.

- Can un nong lai thc pham nghi ng

trong khoang 15 phut.

oi vi cac san pham xong khoi th can chu y

mot so iem sau:

- San pham c gi sach, tay trc khi camsan pham c ra sach.

- Ttrong qua trnh xong khoi can gi t nhat

820C trong 30 phut.

- Lam lanh nhanh sau khi ong goi va bao quan

lanh.

- Tat ca cac bao b s dung phai la loai c

bo Y te cho phep va chu lanh tot.

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CHNG 2:

VI SINH VAT TRONG

CHE BIEN VA BAO QUAN

THT

2.1. QUA TRNH NHIEM VI SINH:

Tht la mot san pham co rat nhieu chat dinhdng, ong thi co o pH t 6 6,5 rat thch hpcho s sinh trng va phat trien cua vi sinh vat.ong vat co the b nhiem vi sinh vat bang conng noi sinh hoac ngoai sinh. Nhng du b nhiemkhuan bang con ng nao i na th cung lamgiam chat lng cua tht nhieu khi dan en khongthe s dung c. So lng vi sinh vat co thtphan anh chat lng cua tht. Tht b coi la kemchat lng khi tren 1 cm2 be mat cua tht hoac trong1g tht co t 107 vi khuan tr len.

Cac gia suc khoe manh thng t b nhiem visinh vat theo con ng noi sinh. Mac dau vay tavan tm thay mot so loai vi sinh vat tai mau cuamot so tht o nh: staphylococci, streptococci,Clostridium, Salmonella.

Nguon gay nhiem vi sinh vat cho cac ongvat thng la: qua trnh choc tiet, cao long,mo. Luc nay vi sinh vat t cac thanh phan nh

long, long, phan hoac dung cu giet mo i vaotht. Trong cong nghe giet mo hien ai gietmo treo, s lay nhiem vi sinh vat giam xuong

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rat nhieu. Chnh v vay, e giam s lay nhiemvi sinh vat cho tht ta can phai chu y en khauve sinh cua qua trnh giet mo; nhat la oi vidung cu, phong giet mo, ong vat giet mo,

ngi lao ong.Do nguon lay nhiem vi sinh vat vao tht rat

rong, nen co rat nhieu loai vi sinh vat b nhiemvao tht. Cac vi sinh vat thng gap la cac visinh vat hoai sinh, bao t cua nam moc(Penicilium, Mucor, Cladosporium,..), cac te baonam men (Candida, Torulopsis, Debaryomyces,..) vaoi khi la cac vi sinh vat gay benh (Micrococcus,Pseudomonas, Moraxella, Bacillus, Clostridium,Escherichia, Salmonella,...)

2.2. CAC QUA TRNH BAO QUAN:

2.2.1. S vo khuan:

e am bao ve sinh an toan thc phamcho cac qua trnh san xuat cac san pham t

tht, nha san xuat phai chu y en s vokhuan cua phong, khong kh, dung cu, thiet b,nc s dung trong giet mo va che bien; nhancong lam viec tong phong giet mo va chebien.

Ngoai ra, oi vi cac san pham ti songhoac a che bien th phng phap bao quantrong cac bao b c hut chan khong se giup

cho cac san pham nay e c lau hn mavan gi c hng v ac trng. Phng phapbao quan nay giup cho san pham khong tiepxuc trc tiep vi oxy, khong kh, nc do otranh c cac h hong do moi trng va vi sinhvat t moi trng tac ong len san pham.Vi cac vi sinh vat co san trong tht va sanpham t tht th tuy vao moi loai vi sinh vat ma

phng phap hut chan khong se co tac ongkhac nhau. oi vi cac vi sinh vat nhstaphylococci, vi khuan lactic, nam moc th s phat

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trien cua chung se b ngan chan lai trong ieukien chan khong. Tuy nhien, oi vi Clostridiumbotulinum va cac vi khuan song k kh th khongco tac ong.

2.2.2. Nhiet o cao:

Hau het cac san pham t tht co o acid thcpham thap va la moi trng dinh dng rat totcho vi sinh vat phat trien. Do o bao quan nh thenao e san pham co the e lau va van on nhchat lng la ieu ma cac nha san xuat luon suyngh.

Cong nghe o hop la mot trong nhng congnghe s dung ky thuat ac biet e bao quan thcpham khong b h hong di tac ong cua vi sinhva moi trng trong mot thi gian dai. Co hai loai:

1. Tht c cho vao hop thiec, tiet trung 1210C, va bao quan nhiet o thng

2. San pham t tht c thanh trung va c

bao quan lanh.Ngoai ra con nhng phng phap s dung nhiet

o cao khac nh:

- Luoc s tht co the e tht c lauhn mc d kien. Tuy nhien se lam bien mauva lam mat mot so dng chat trong tht.

- Xong khoi xuc xch: s dung nhiet ova cac chat co trong khoi e bao quan sanpham.

- Tht c che bien thanh cac dangthanh pham va ban thanh pham se e c lauhn.

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2.2.3. Nhiet o thap:

2.2.3.1. ong lanh:

Sau khi giet mo tht c lam lanh nhanh va

c tr lanh nhiet o (-)1.4 (+)2.2 0C. Thigian tr lanh oi vi tht bo co the ti 30ngay, vi tht heo bao quan c 1 2 tuan.

Thi gian bao quan phu thuoc vao lng vi sinhvat co tren tht, nhiet o lam lanh va trlanh, o am cua phong tr lanh.

Thi gian bao quan se lau hn neu phong baoquan c bm CO2 hoac ozon. Tuy viec thay thekhong kh trong phong bao quan bang CO2 khiencho vi sinh vat khong phat trien c dan enviec tht bao quan c lau (gap oi thi gian),nhng no cung lam thay oi mau cua tht, lammat i sac hong cua tht. Chnh v vay, theo kinhnghiem, ngi ta khuyen cao rang lng CO2 avao tot nhat nam trong khoang 10 30 % so vilng khong kh trong cac ohong bao quan tht

va 100% trong phong bao quan jambon.Thi gian bao quan tht cung se tang khi

co khoang 2.5 3ppm ozon trong phong baoquan. Tht co the e c ti 60 ngay 2.20C,o am 92%. Ozon la chat co hoat tnh oxy hoacao chnh v vay no co kha nang diet vi sinh vatcao, tuy nhien ozon cung khien cho tht b nhatmau.

Vi sinh vat gap trong cac san pham thtong lanh thng la cac vi khuan a lanh thuocchung Pseudomonas, mac dau vay cac vi khuannhAcinetobacter, Moraxella,Alcaligenes, Micrococcus,Lactobacillus, Sterptococcus, Leuconostoc, Pedicoccus,Flavobacterium, Proteus va cac nam men, nammoc van co the phat trien tren tht nhiet

o thap.

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2.2.3.2. Cap ong:

Tht va cac san pham t tht c onglanh ot ngot xuong ()400C roi c tr lanh t

()12.2 en ()28.90

C.Qua trnh cap ong tieu diet khoang lng visinh vat co trong tht, lng con lai b giam dantrong qua trnh tr ong. Ch con mot so t visinh vat ton tai nhng khong phat trien nh:Pseudomonas, Acinetobacter, Moraxella, Alcaligenes,Micrococcus, Lactobacillus, Flavobacterium, Proteus.Cac vi sinh vat nay ch phat trien tr lai khi

tht c ra ong.2.2.4. Tia chieu xa:

Neu s dung tia t ngoai trong qua trnh onglanh se keo dai thi gian bao quan. Thng cs dung khi can bao quan cac tang tht co kchthc ln. Cac tia chieu xa tieu diet hoac c chemot lng ln vi sinh vat co trong khong kh va tren

be mat tht ngay lap tc, tieu diet cac vi sinh vatco tren be mat cua cac thiet b dung cu trongphong (vi ieu kien cac thiet b, dung cu naynam lo thien tiep xuc trc tiep vi cac tia chieuxa).

Mot so qua trnh oxy hoa va hydro hoa chatbeo co the xay ra trong qua trnh chieu xa.

Trong qua trnh chieu xa ngi ta dung tia Gammaco gii han. Neu can tiet trung ta s dung mc20 70KiloGray. mc nay se khong lam thayoi mui v va mau sac cua san pham.

2.2.5. Say kho:

Say kho la phng phap bao quan truyenthong oi vi tht va cac san pham t tht. Cocac dang nh tht va cac san pham cua tht c

phi kho hoac say kho. oi khi s dung ca cac phu

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gia nh nitrat, nitrit va s dung phng phap xongkhoi e x ly cac san pham t tht.

Nh vao o am thap ma lng vi sinh vat

giam thieu i rat nhieu. Them vao o la cac chatho tr qua trnh diet khuan giup cho viec bao quanc tot hn.

Cac san pham say kho khong can bao quanlanh.

2.2.5. Chat bao quan:

Trong rat nhieu san pham tht s dung hon

hp: NaCl, ng, nitrit. Tac dung cua chung nh sau:- NaCl: con goi la muoi an, la chat bao

quan va chat tao v. Neu tron lan san phamthng cha khoang 15% NaCl. Neu dung dungdch NaCl tiem vao san pham hoac ngam, sdung khoang 24%. Muc ch lam giam ham lngnc trong san pham.

-

ng: la chat tao v. Ngoai ra conc s dung lam nguon nang lng cho cac vikhuan phan giai nitrat s dung (cho cac sanpham len men).

- Natri nitrit: c dung e tao thanh NO,chat nay tac ong len tht tao thanh mau actrng cho tht. Ngoai ra con co tac dung dietmot so loai vi khuan bi tnh acid.

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MYOGLOBIN(hi ota) Fe2+

OXYMYOGLOBIN(oti) Fe2+

METMYOGLOBIN(nau) Fe3+

NITRIC OXIDMYOGLOBIN*

(o) Fe2+

NITROSYLHEMOCHROME(hong) Fe5+

DENATURED

METMYOGLOBIN(nau) Fe3+

Soxy hoa

SkhQuatrn

hoxyhoaQuatrnhkh

Soxy hoa

NO +Skh

Soxy hoa

NO +Skh

Soxy hoa

+Skh

Soxy hoa(nitrit)

Bien tnhprotein(nhiet)

Bien tnhprotein(nhiet)

NO

* : mau yeu cau oi vi san pham

Phan ln cac san pham sau khi cho chat baoquan eu c em i xong khoi. Cac thanh

phan co trong khoi co kha nang tieu diet vangan chan khong cho vi sinh vat phat trien,giup cho san pham e c lau hn.

Ngoai ra, oi vi cac san pham len men conc tron them acid lactic hoac vi khuan lactic etao hng v ac trng cho san pham. Tai VietNam cac san pham len men thng c e cholen men t nhien di tac ong cua vi khuanlactic.

Ngoai ra cung co mot so san pham cngam dam. Cac san pham nay thng c chovao lo. Acid ngoai tao hng v con giup cho sanpham e c lau hn.

Cac vi sinh vat thng gap:

-

Xuc xch: Leuconostoc mesenteroides, vikhuan lactic, Streptococci, Pedicocci, Micrococci, nammen.

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- Jambon: Lactobacilli, Micrococci, Enterococci,Stereptococci, Leuconostoc, Pedicocci.

2.3. CAC DANG H HONG CUA THT:2.3.1. Hoa nhay:

Hien tng nay thng thay be mat thtp lanh khi bao quan o am tng oi cuakhong kh (cao hn 90%). Qua trnh tao thanh mangnhay nay con phu thuoc vao nhiet o bao quan.

Trong ieu kien 0oC, o am khoang 85 90% tht

co the bao quan c khoang 2 tuan. Hien tnghoa nhay c coi la giai oan au cua qua trnh hhong tht.

Cac vi khuan thng thay lp nhay:Micrococcus albus, M. liquefaciens, M. aureus, M. candidus,Streptococcus liquefaciens, E. coli, Bact. aerogenes, Bact.alcaligenes, Bac. mycoides, Bac. mesentericus,Pseudomonas, Leuconostoc, Lactobacillus, . va mot so

loai nam men.2.3.2. Len men chua:

Tht b len men chua la do vi khuan lactic vanam men; sau o vi khuan gay thoi va nammoc tiep tuc phat trien tren moi trng o.

Thong thng cac loai tht cha nhieu glycogenthng len men chua, tao thanh nhieu acid hu

c. moi trng acid vi khuan gay thoi b cche, tuy nhien nam moc lai phat trien. Nammoc hoat ong va tao thanh NH3 va kiem nitruaco tac dung trung hoa acid tao ieu kien cho cacvi khuan gay thoi phat trien.

2.3.3.S thoi ra:

Tht b thoi ra thng do hai qua trnh phan

huy cua vi khuan k kh va hieu kh gay nen. Vikhuan gay thoi hieu kh la: Proteus vulgaris,Bacillus subtilis, Bacillus mesentericus, Bacillus

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megatherium, Vi khuan gay thoi k kh la:Clostridium perfringens, Clost. putrificum, Clost.sporogens,.. Cac vi khuan nay cha nhieuprotease phan giai protein thanh NH3, H2S, scatola,

acid butiric va cac chat co mui kho chuQua trnh thoi ra hieu kh thng bat au

t be mat cua tht, lam cho tht b thay oidan dan. Trong giai oan au be mat cua thtb mem dan, tht b thay oi ve mau sac vamui, phan ng cua tht nga sang kiem, tuynhien ben trong van con tot. Sau o vi khuanphat trien manh trong tht se lam cac mo lienket b t va protein b phan huy.

Qua trnh thoi ra k kh do cac vi khuan kkh gay nen. Cac vi khuan nay nhiem vao trongtht t ng ruot. San pham tao thanh tqua trnh nay la NH3, cac acid beo, cac chat comui thoi.

2.3.4. S bien oi sac to cua tht:

Tht b bien oi t mau o sang mau xam,nau, hoac xanh luc di tac dung cua vi khuan.Neu mui cua tht van bnh thng va khong tmthay oc tnh, th ch can loai bo cac vet mau latht van s dung bnh thng. Vi khuan thng lamcho xuc xch, lap xng co mau xam la mot soloai vi khuan lactic nh: Lactobacillus, Leuconostoc.

2.3.5. S phat sang:khi tht b bao quan chung vi ca th se xuat

hien tren be mat cua tht vi khuan Photobacterium,vi khuan nay gay nen s phat sang tht. Quatrnh nay khong kem theo s thoi ra.

2.3.6. S oi :

mot so loai vi khuan co kha nang oxy hoa m

cha trong tht nh: Pseudomonas, Achromobacter,..

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2.3.7. S moc:

Qua trnh nay thng xay ra do Mucor, Penicillium,Aspergillus, phat trien tren be mat cua tht. Trc

tien moc moc tren be mat, sau an sau dan vaotrong ti 2 5 mm.

2.3.8. S hnh thanh vet mau:

Tuy vao loai vi khuan hieu kh khac nhau matren be mat tht se xuat hien cac vet mau khacnhau:

- Bacterium prodigiosum hoac Serratia marcerans :

tht co cac vet o- Pseudomonas pyocyanes : tao vet xanh

- Pseudomonas fluorescens : tao vet xanh luc

- Chromobacterium : tao vet xamnhat, nau en

- Micrococcus : tao vet mau

vangNeu tht van co mui bnh thng va khong tmthay cac oc to th sau khi tay sach cac vetmau th van co the s dung c bnh thng.

2.4. VI SINH VAT TRONG MOT SO SANPHAM T THT:

2.4.1. Tht muoi:

tht muoi thng cha NaCl, KNO2, KNO3, ng,gia v. Trong tht muoi khong phai ch co cac visinh vat a chet hoac khong phat trien, mavan ton tai mot so loai vi sinh vat co khanang song trong moi trng co nong o muoicao. V nh: Salmonella ch b chet trong nong omuoi 19% sau 75 80 ngay. Cac loai cau khuanth chet nong o muoi 15%, tu cau vang

chet nong o muoi 20 25%. e lam tangkha nang c che hoat ong cua vi sinh vatcung nh keo dai thi gian bao quan, ngi ta

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thng gi tht muoi ieu kien nhiet olanh xuong khoang 2 50C hoac em xong khoi.

2.4.2. Tht bao quan lanh:

Tht bao quan lanh thng hai dang : planh va lanh ong.

- oi vi tht p lanh, tht c bao quan nhiet o t 1 ( 3)0C vi o am tng oi la90 92%; cac loai vi sinh vat a lanh thng gapla: Pseudomonas, Achromobacter, Flavobacterium,

Alcaligenes, Aerobacterium, Micrococcus, Lactobacillus,Streptococcus, Leuconostoc, Proteus; thi gian baoquan t 15 30 ngay tuy loai tht va phamchat cua tht.

- oi vi tht ong lanh th tht c bao quantrong thi gian dai, hien nay thng ngi ta lamcap ong xuong di ( 18)0C luc nay ch conmot so rat t vi sinh vat con co kha nang tontai.

2.4.3. Tht hop:thong thng tht c cha trong cac hop kn

va c tiet trung nhiet o cao. Trong quatrnh tiet trung hau het vi sinh vat b tieu diet,tuy nhien can phai e phong mot so loai

bao t cua vi khuan van co kha nang ton tai, nh:Bacillus subtilis, Bacillus mesentericus, Clostridium

botulinum. Chnh v vay sau khi tiet trung can kiem tralai.

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Hnh 1: Trc khuan k khClostridium perfringens.

2.4.4. Xuc xch, gio, lap xng:ay la cac san pham s dung trc tiep, chnh v

vay yeu cau ve sinh cung cao. Tht dung cho cac

san pham loai nay phai la tht loai tot, ong thi

chat lng cua cac gia v cung nh phu gia them

vao cung can c lu y en. Cac vi khuan sinh

bao t co the uc tm thay cac san pham

dang nay nh: B. subtilis, B. mesentericus, B. mycoides, E.

coli, Proteus vulgaris,..

2.4.5.Cac san pham che bien khong quanhiet o cao:

Cac san pham nh nem, tai neu s dungnguyen lieu khong c kiem tra ky. Ngi tieudung co the nhiem mot so ky sinh trung nh:

-San dai heo ( Taenia solium)

-San dai bo(Taenia saginata).

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Hnh 2: Vong i cua san dai bo.

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Hnh 3 : Vong i cua san dai heo.

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CHNG 3:

VI SINH VAT TRONGCHE BIEN VA BAO QUAN

CA


Ca la mot san pham co rat nhieu chat dinhdng, ong thi la loai ong vat mau lanh tren

da ca co mot lp nht giau protein, trong mang cacha nhieu dng chat nen ca la mot moi trngdinh dng rat thch hp cho cac loai vi sinh vat phattrien

Ca co thanh phan dinh dng tng t nhthanh phan dinh dng cua tht. Tuy nhien, do cautruc khong chat che bang tht, va do moi trngsong cua ca la nc nen de dang b o nhiem vi

sinh vat hn tht. V the cac qua trnh bien oi vanguyen nhan gay bien oi tht ca cung xay ragiong nh tht. Vi sinh vat co the xam nhap vaoca bang nhng con ng sau:

- Xam nhap qua ng ruot: Khi ca chet cacmen phan huy protein thanh ruot tao ieu kienxam nhap cho vi sinh vat t he thong tieuhoa vao ca.

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- Xam nhap t niem dch bieu b: Tuyen da catiet ra chat dch, ay la moi trng tot cho visinh vat phat trien va xam nhap vao tht ca.

- Xam nhap t mang ca: Do thong b maukhi chet, ay la moi trng thch hp cho vi sinhvat phat trien va xam nhap vao tht ca.

- Xam nhap qua vet thng c tao ra trong quatrnh anh bat.

Ngoai ra, trong qua trnh che bien neu nguonnc b o nhiem cung la nguyen nhan nhiem visinh vat vao tht ca.

Trong ruot va tren da ca thng co nhng vi sinhvat thuoc giong Pseudomonas, Moraxella,

Achromobacter, Flavobacterrium, Vibrio con cac vi khuannh Micrococcus,Bacillus, Clostridium vi so lng t. Stang trng cua nhng vi sinh vat nay gay nen sh hong cua san pham.

Colifroms co the khong co hoac rat t, khong

co mat Salmonella, Shigella va nhng vi khuan ngruot khac. S co mat nhng vi khuan nay chngto co s nhiem khuan t moi trng anh bat vache bien b o nhiem. Trong qua trnh che bien conco the nhiem Clostridiun botulinum (ca hop).

Ngoai ra, ca con b nhiem mot so loai kysinh trung nh san bao gom cac loai sau:

-San liet au (Diphyllobothrium latum).-San hat hong (Clonorchis sinesis).

-San hat meo (Opithorchis felineus).

-San d hnh (Heterophyes heterophyes)

-San Yokogawai (Metagonimus yokogawai).

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Hnh 4: Vong i cua san liet au (Diphyllobothriumlatum).

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Hnh 5: Mot so loai san thng b nhiem bi cac loaithuy sinh.

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Hnh 6: Vong i cua san hat hong(Clonorchis sinesis)


Ca thng c s dung dang ca song, ca ti(mi chet), ca p a, ca kho, p muoi va cacdang che bien vi muc ch bao quan bang congnghe phc tap (ong hop, xong khoi, cha bong)

Cac qua trnh bao quan ca cung nh bao quantht. e bao am tnh an toan cua san pham canlu y en cac yeu to dan en o nhiemvi sinh vatvao san pham. Mot trong nhng nguyen nhan gaynhiem vi sinh vat vao san pham la nc dung trongcac qua trnh. V vay, nguon nc can phai c

x ly tot. Va nguyen lieu ca can phai ctuyen chon ky lng.

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3.3. CAC DANG H HONG CUA CA:

Cac dang h hong cua ca thng do s phattrien cua vi sinh vat gay nen. Cac san pham a

qua che bien cung co nhng dang h hong giongnh cac h hong cua tht. Tuy nhien, do ban chatcau truc cua ca nen chung ta xem xet nhng dangh hong cua tht ca da tren nguyen lieu ca chache bien e quyet nh cac bc che bien khacnhau tuy vao trang thai cua nguyen lieu. Mc oti cua ca c chia thanh ba dang: ti (dung eche bien hoac e an); kem ti (ch dung e anch khong dung cho cac qua trnh che bien); Can (khong dung lam thc pham c).

Bo phan Ca ti Ca kemti

Ca n

Than ca Co cng Co dauhieu phan

giai, thanoan dedang

Len menthoi, than

ca oan dedang

Mat Loi, trong,giac macan hoi

Khong loi,nhan nheova hi uc

Lom, kho,nhan hoacrach

Mieng Ngam cng Hi m M han

Mang Bam chathoa khe,khong nhtva hoi

Dankhongchat, mauxam, conht vamui hoi

H khoihoa khe,nau enxam, nhtban, muithoi

Vay Ong anh,dnh chatthan, khonghoac t nien

Khongong anh,con dnh,niem dch

M, longleo, coniem dchban va co

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Bo phan Ca ti Ca kemti

Ca n

dch trong,

khong mui

uc mui n

hoiBung va

hau mon

Khong phnh,hau monthut vao,trang nhat

Hi phnh,hau monloi va hihong

Bung phnh,hau monloi va obam

Tht ca Ran chac,an hoi,

dnh chatvao xng

Mem, anhoi cham,

con dnhvao xng

Mem nhun,khong dai

hoi, tachkhoi xngde dang

Th giayquy

Axit Axit Kiem

Thnghiem

H2S

Am tnh Am hoacdng tnh

Dng tnh

Hamlng

NH3 / 100 g


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Tng t nh oi vi tht muoi, van con nhng visinh vat ton tai c di dang tiem sinh trongnong o muoi cao. Chnh v vay can chu y tive sinh thc pham trong qua trnh x ly ca. Neu

thay xuat hien cac nam mau nau, th coi nh camuoi a b hong.

Cac vi khuan nh Clostridium botulinum, Salmonellab ngng phat trien trong moi trng co nongo muoi tng oi thap, tuy nhien khong chetma van con co kha nang ton tai trong motthi gian dai. Vi Clostridium botulinum, khi asinh oc to th du nong o muoi cao cungkhong pha huy c oc to nay.

Trong ca con ton tai nhng vi khuan co khanang thch ng dan vi moi trng muoi hoacnhng vi sinh vat a muoi nh: Serracia salinaria,Torula wemeri, Micrococcus rocus, Khi cac vi sinhvat nay phat trien se lam cho ca co motlp mau hoac b vet o, dan dan ca se b

mem, b nht. Cac protein cua ca b phanhuy thanh NH3, indola, scatola,.. e giam bthien tng nay can ra sach cac vet mauhnh thanh, sau o ngam ca vao dung dch conong o muoi cao co pha 3 5% acid acetic. Honhp nay co tac dung lam cng ca, lam chethoac lam vi sinh vat ngng phat trien

Trong qua trnh muoi ca mot so bien oi hoa

sinh xay ra di s hoat ong cua vi sinh vatco trong ca cung lam cho san pham ca muoitr nen mem, thm du. Cac san pham camuoi loai nay co the an trc tiep ma khongcan nau.

Ca ngam chat bao quan: co the s dung acidacetic 4 6% e ngam ca (trong tht ca se atc vao khoang 0,8 1,2%). Ngoai ra con cans dung them natribenzoat (1g/kg ca) hoac motso loai chat khang khuan khac nh: acid salixilic

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(0,03 0,05%), acid benzoic (0,25%), acid boric(0,15%), hydroperoxyt (0,1 0,2%), acid formic (0,1 0,2%). Ben canh o co the s dung cac chatkhang sinh nh: oreomixin, biomixin, vi ham

lng thap e bao quan ca. Ca kho: ca trc khi c lam kho co the

c ngam muoi 5 7%. o am cang thap thcang han che s phat trien cua vi sinh vat;vi vi khuan, o am can di 30%, vi nammoc o am can di 15%.

3.4.2.Cac san pham che bien co qua

qua trnh nhiet:Nhng san pham che bien co qua qua trnh nhiet

neu khong bao am ngiem ngat co the nhiemmot so loai vi sinh vat nh: Bacillus, Pseudomonas,Staphylococus, Vibrio parahaemolyticus. Nhng vi sinhvat nay co trong nguyen lieu cha b tieu diet hetva tai phat trien khi gap ieu kien thuan li.

Ca p lanh: ca c bao quan nhiet ot ( 2) ( 5)0C vi o am tng oi la 90 92%. Cac loai vi sinh vat a lanh thng gap la:Pseudomonas fluorescens, Bact. putrifaciens, Mucorstolonifer, Mucor mucedo, Aspergilus niger, Peniciliumglacum, Rhizopus. Cac dung cu thiet b s dungtrong qua trnh chuyen ch, cha ng va xly ca nhat thiet phai c lam ve sinh sach

se va c sat trung trc khi s dung. Ca ong lanh: thng c bao quan ( 18)

( 20)0C. Trong giai oan au phan ln vi sinh vatb chet, tuy nhien van con ton tai nhieu loai dang tiem sinh, nh: Sarcina, Micrococcusaurantiacus, M. flavus, M.roseus, Bac. subtilis, Bac.mesentericus, Pseudomonas, E.coli, Aspergillus,Penicillium, Mucor,..

Ca hop: thong thng ca c che bien vac cha trong cac hop kn va c tiet trung

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nhiet o cao. Trong qua trnh tiet trung hauhet vi sinh vat b tieu diet, tuy nhien can phaie phong mot so loai bao t cua vi khuanvan co kha nang ton tai, nh: Bacillus subtilis,

Bacillus mesentericus, Clostridium botulinum. Chnh vvay sau khi tiet trung can kiem tra lai.

Cac san pham o hop ca thng la: cangam dau, ca co muoi, ca ngam nc sot,ca sot ca chua, Ngi ta nhan thay rang, moi trng acid bao t cua vi khuan se kemben, trong moi trng co dau m th o ben

vi nhiet lai tang. Do o trong dang o hopco nc sot at pH 4,5 th vi khuan Clostridiumbotulinum khong phat trien c. Con trong cacsan pham o hop co chat beo va protein thse lam tang o chu nhiet cua vi sinh vat. Doo nhieu o hop sau khi gia nhiet van co khanang con ton tai cac vi sinh vat nh : Bacillussubtilis, Bacillus mesentericus, Bacillus thermophylus, cac dang bao t cua Clostridium sporongenes,Clostridium botulinum,. ay thng la cac visinh vat k kh do o neu trong san pham conton tai loai vi sinh vat nay th mot thi gian sautrong o hop se xuat hien cac kh H2S, CO2 lamcho o hop phong len.

3.4.3. Cac san pham xong khoi:

Tren cac san pham xong khoi thng co

cac vi sinh vat nh Gram (+) nh Micrococcus, Bacillus ,nam men va mot so vi khuan Gram am. Bao tnam moc thay nhieu tren ca hun khoi.Salmonella va Staphyloccos cung thay co trong sanpham ca xong khoi. Ngoai ra trong sam pham caxong khoi con phat hien b nhiem Clostrdiumbotulinum

3.4.4. Bot ca:

Trong san pham bot ca ac iem cua congnghe nen trong chung co the cha E.coli gay

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benh va Salmonella la nhng vi sinh vat co tachai cho ngi s dung.

3.4.5. Cac san pham ca an ti, song:

Nhng ngi co thoi quen an ca song (goica) co the b nhiem mot so benh do nguyenlieu b nhiem nh: Thng han, ta, san. Trongnhng trng hp co giai oan che bien nhietnhng khong ky. Ngi s dung cung co thenhiem mot so vi sinh vat do ban than nguyenlieu mang hoac do o nhiem trong qua trnh chebien.

CHNG 4:

VI SINH VAT TRONG

TOM, MC VA CAC ONG

VAT NHUYEN THE

4.1. QUA TRNH NHIEM VI SINH:Tom, mc va cac loai nhuyen the do song

trong moi trng nc v the qua trnh nhiem vi sinhvat chu yeu t moi trng song. Cac vi sinh vatthng thay trong moi trng nc eu co thenhiem vao nhng loai ong vat tren. Ngoai ra dothoi quen an tao co cha chat oc cua mot soloai nhuyen the dan en cac loai nhuyen the naycung cha chat oc anh hng en ngi s

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dung. Mot so loai con la vat trung gian truyen motso ky sinh trung cho ngi.

Do cau truc c the khong chat che nen khi

nhiem vi sinh vat cac loai ong vat nay co toc ophan huy rat nhanh.

Cac vi sinh vat thng thay trong tom, mc vanhuyen the nh: Salmonella, Vibrio, ca vi khuan ngruot gay benh va mot so virut gay benh cho tomdo nguon nc b o nhiem hoac do ban than congiong trong nuoi trong mang benh lay truyen chonhau. Ngoai ra trong mot so loai so con cha chat

oc cua tao c tiet ra khi chung an loai tao nay.


Tom, Mc, va nhuyen the thng c s dung dang ti. Ngay nay do nhu cau xuat khau vacuoc song cong nghiep nen xuat hien them motso qua trnh che bien nh sau:

4.2.1. Dung nhiet o thap:Nham muc ch bao quan san pham dang nguyen

lieu cho cac qua trnh che bien tiep theo. Co thedung a e p trong thi gian ngan (Van chuyent ni anh bat vao b, chuyen en ni tieu thutren th trng trong nc). ong lanh vi muc chbao quan thi gian lau (van chuyen en th trngxa hoac tr hang cho thi gian ti).

4.2.2. Say kho:

S dung cac nguon nhiet lay i phan ln lngam trong nguyen lieu vi muc ch bao quan sanpham. Tuy nhien cac bao quan nay thng dungcho tom va mc, con nguyen lieu t nhng loainhuyen the t dung cach nay.

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4.2.3. Bao quan bang muoi ham lngcao:

Mot so tom nho (tep) c dung lam mam

ay la mot qua trnh che bien nhng co muc chbao quan. Tuy nhien, san pham nay co th trngkhong ln (chu yeu th trng trong nc) nenlng s dung khong nhieu.

4.3. CAC DANG H HONG CUA TOM, MC VACAC LOAI NHUYEN THE:

Cac san pham tom, mc, nhuyen the thngs dung chu yeu dang ti nen van e baoquan san pham luon ti la mot yeu to rat quantrong. Hien tng h hong cua tom, mc, va cacloai nhuyen the chu yeu do vi sinh vat phat triengay nen:

- Khi tom mi chet tht tom mem sau o doqua trnh phat trien cua vi sinh vat mang tomtach ra va de dang rung au, tiet dch co

mui hoi vo tom sam mau. Mat tom co mauxam uc do nhng vi sinh vat len men thoi sinhra. ay la dau hieu tom a b h hong quamc. Vay khi tht tom co mau toi sam, muiv n thoi, tht b la tom n khong nendung.

+ S bien o cua tom:

Qua trnh bien o cua tom xay ra khi tomti gia nhiet, tom c bao quan trong moitrng acid hoac khi ngam tom trong ru.

C che cua s bien oi xay ra nh sau:trong vo va tht cua tom ti co chaastaxanthin co mau xanh tm, chat nay tao phcvi protein. Trong ieu kien nhat nh astaxanthinb tach ra va b oxy hoa thanh astanxin mau

o gach.

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Vi tom e lau khoang 8 12h sau khianh bat nhiet o 30 400C, di tac dungcua cac vi sinh vat nh: Pseudomonas,Lactobacillus, Coryneformes astaxanthin se b tach

ra khoi tom va b oxy hoa lam cho tom bbien o. i kem qua trnh nay la s phan giaicua protein gay nen qua trnh thoi ra.

+ S bien en cua tom bien:

Hien nay van con nhieu y kien khac nhau vehien tng nay.

Co tac gia cho rang hien tng bien en tom do cac vi khuan lay nhiem vao gay nen.

Co tac gia lai cho rang hien tng nay xay rala do tyrozin co trong tom b oxy hoa di tacdung cua tyrozinase, cac chat mau toi nhmelanin hnh thanh tch lai dan roi tao thanhom en tren tom.

Co ngi lai cho rang ay la do phenylalanin

tham gia vao qua trnh oxy hoa tao thanh cacsi, cac si nay tap hp lai thanh cac chatmau toi.

Hien tng bien en lam giam gia tr camquan tom, tuy nhien van co the s dungtom loai nay bnh thng.

- Mc do co cau truc c the chac hn tom va

nhuyen the nen thi gian h hong lau hn. Tuynhien, cac qua trnh h hong do ly do sinh hocva do tac ong cua vi sinh vat xay ra cunggay nen hien tng n thoi san pham.

- Cac loai nhuyen the do chung luon gi motlng nc ngoai moi trng song trong cthe, nen khi chet chung rat de dang b phanhuy do s phat trien cua vi sinh vat. Chnh v

the, cac loai nhien the neu khong co bien

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phap bao quan b chet khong c dung eche bien.

4.4. VI SINH VAT TRONG MOT SO SAN PHAM

T TOM, MC VA CAC LOAI NHUYENTHE:

4.4.1.Cac san pham s dung khong quache bien nhiet:

Trong nhng san pham nh goi, tai co themang cac loai vi sinh vat nh Salmonella, Vibrio, mot sovi khuan ng ruot va mot vai loai ky sinh trungco vat trung gian truyen benh la so, oc.

4.4.2.Cac san pham ong hop:

Do qua trnh x ly khong at trong san phamong hop co the cha Clostridium gay ngo oc chongi s dung.

4.4.3.Cac san pham kho:

Cac san pham kho co the nhiem vi khuan do

qua trnh say khong at hoac do nguyen lieu avao che bien a b nhiem. Ngoai ra nhng sanpham mac du a c say tot nhng trong thi gianbao quan vi ieu kien khong tot se b tai nhiemvi sinh vat va cac loai nam moc.

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CHNG 5:

VI SINH VAT TRONGCHE BIEN VA BAO QUAN

SA


Sa la mot san pham thu nhan t mot soong vat co vu nh bo, nga, de. ay la motchat dch c the co thanh phan dinh dng cao.Chnh v the ay cung la moi trng thch hp e visinh vat phat trien. Qua trnh nhiem vi sinh vat cothe t moi trng hoac t ban than ong vat bnhiem benh.

Cac vi khuan gay ang:

- Streptococcus liquefaciens: co nhieu tnh chat gangiong Streptococcus lactis, phat trien tot 300C,

co kha nang tao enzym lam ong tu sa. S.liquefaciens gay nen qua trnh pepton hoa tao rasan pham co v ang kho chu.

Trc khuan ng ruot: Cac vi khuan thuocnhom nay nhiem vao sa t phan chuongti, a so khong lam ong sa, ch mot so tloai lam ong sa cham. ai dien cho nhom

nay la E.coli, co kha nang lan men glucid vaanbumin, sinh kh tao cac sa ong co ranh.

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Vi khuan buttiric: thuoc nhom Clostridium. Xamnhap vao sa t thc an ong vat, t rm,ra, phan,, do vat sa khong ung ve sinh.Neu sa b nhiem vi khuan loai nay th rat

kho loai bo, do thanh trung Pasteur khong dietc bao t cua chung. Trong moi trng sacac vi khuan nay bien oi acid lactic thanh cacacid bay hi, acid butiric, hydro, va cacbonic. Acidbutiric gay mui kho chu cho sa. Khi phat hienra s co mat Clostridium th sa a hong.

Vi khuan gay thoi: khong gay len men ng

sa, a so thuoc nhom vi khuan sinh bao t,co kha nang tao enzym phan giai protein thanhpepton, acid amin t do va NH3. Pepton gay viang cho sa. Gom cac loai:

- Cac vi khuan hieu kh: nh Bacterium fluorescen,Proteus vulgaris, Bacillus subtilis, Bacilus mesentericus.

- Cac vi khuan k kh nh: Bacillus putrificus, Bacillusbotulinus.

Vi khuan hoai sinh: a so la nhng loai sinh baot chu nhiet cao, co hai trong viec bao quansa. Mot so loai thng gap: Staphylococus,Tetracoccus, Bacillus megatherium, Bacillus mycoides,Bacillus sporogenes

Nam men: mot so nam men thuoc hoMycoderma co kha nang tao enzym phan huyprotein va lipid, tao nen cac san pham gay vang kho chu cho sa.

Nam moc: nhieu loai nam moc co kha nangtao enzym phan huy protein va lipid, tao nencac san pham gay v ang kho chu cho sa.Nam moc thng phat trien sau nam men nenta thng tm thay chung trong sa b h hong

nang hoac tren phomat mem. Cac loai thnggap: Endomyces lactis, Mucor, Aspergillus,Penicillium, Oidium.

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Ngoai ra trong thien nhien con co nhieu dang vi sinhvat khac nhau co the gay h hong sa neu bnhiem vao sa. Co nhng vi sinh vat lam cho satr nen nht, lay nhay nh: Bacterium lactia viscosum,

Bacillus lactorubefaciens,.. Hoac tao mau khac thng sa nh: Pseudomonas cyanogeces, Bacillus cyanogenestao nhng cham xanh sam tren be mat sa;Pseudomonas synatha, Bacterium synxanthum sinh mauvang kim loai khi khong co mat vi khuan lactic;Sarcina tao mau vang; Serratia marcescens tao mauo,

Cac loai vi sinh vat thng nhiem vao sa nh sau:

4.1.1. Brucella

La cau trc trung Gram (-), co ba loai Brucella ccho la gay benh cho ngi la B. abortus; B. suis;B.melitenis co trong sa ong vat nhai lai, de vacu. Khi b nhiem vi khuan nay trieu chng sot, ueoai, au nhc c the se xuat hien sau 1 3 tuan benh.

4.1.2. Mycobacteria:

La vi khuan Gr(+), va la vi khuan khang conkhang axit. Co ba loai Mycobacteria gay benh la M.tuberculosis; M.avium va M. bovis. Loai Mycobacteria ccho la b nhiem vao sa bo t nhng con bo bnhiem vi khuan nay.

4.1.3. Vi khuan Streptococcus huyet giai

La loai cau trung Gr(+) xap xep dang chuoi. LoaiStreptococcus thng nhiem vao sa la S. pyogenes.S xam nhap vi khuan nay vao sa do cac vatcha sa.

4.1.4. Corynebacter

La trc khuan Gr(+) khong di ong, khong sinh

bao t. Loai C. diphtheriae c thay nhiem vao sa.S xam nhap vi khuan vao sa dot moi trng

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hoac t nhng nhng vet loet cua ngi lam viectrong trang trai mang vi khuan nay tren.

Ngoai ra sa con la moi trng tot cho cac vi

sinh vat khac phat trien neu khong bao am ieukien ve sinh tot hoac khong c thanh trung tot.


4.2.1.Thanh trung:

Hnh 7: S o he thong tiet trung UHT gian tiep bangcach un nong trong thiet b trao oi nhiet dang khung

ban

1- thung can bang; 2- bm ay; 3- thiet b trao oi nhietdang khung ban; 4- thiet b ong hoa; 5- injector; 6- thiet b

lu nhiet;7- thung tam cha (vo trung); 8- thiet b rot vo trung

Sa c dung phan ln dang ti ch quaqua trnh thanh trung. Do tnh chat va thanh phancua sa, ong thi do yeu cau s dung nen sati ch co the bao quan bang phng phap thanhtrung. Qua trnh thanh trung ch dung nhiet okhong cao (630C/30 phut; 770C/15 giay), hoac bangphng phap UHT (ultra high temperature) nham tranh

bien tnh sa.Thong so ky thuat:

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* Tiet trung UHT:

San pham danglong

Cac thong so cua quatrnh UHT

San pham acide cao pH4.5

135-149oC / 30-1 giay

Sa ( My) 138oC / 2 giay

Sa ( Anh) T> 135oC / >1 giay

Sa co hng lieu( Anh) T> 140oC / >2 giay

* thanh trung pasteur:

San pham Nhiet o ( oC)/ Thigian

Sa ( My) 630C/30 phut ; 770C/15giay

Sa ( Anh) 630C/30 phut ; 720C/ 15giay

Dch chiet trai cay 850C/15 giay

Trng dang long(My)

600C/3,5 phut

Trng dang long(Anh)

64,40C/2,5 phut

Bia 65

0

C/20 phut

4.2.2. Sa ac co ng:

Da vao nguyen tac trong nong o ng cao(60%) tat ca cac vi sinh vat eu khong the phattrien c. Sa ac co ng la mot san phamche bien cua sa ngoai ra con mang muc ch bao

quan.

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4.2.3. Sa bot:

Vi cong nghe say phun ngi ta tao ra sanpham sa bot ay la san pham co thi gian bao

quan lau nhat cua sa.4.2.4. Bao quan bang nhiet o thap:

Dung nhiet o thap e lam giam hoat ongcua vi sinh vat. Tuy nhien, phng phap nay giathanh cao va thi gian bao quan khong lau. Chnen ap dung phng phap nay khi ket hp vi thanhtrung hoac dung trong qua trnh van chuyen en cs che bien.

4.3. CAC DANG H HONG SA:

Sa ch co mot dang h hong ang ke nhatla len men lac tic chuyen glucose thanh axit lactic lamsa b chua. Chnh v the chung ta can co bien phapbao quan sa ngay sau khi thu hoach xong nham duytr trang thai nguyen lieu tot cho nhng qua trnhche bien tiep theo.

Ngoai ra vi thanh phan dinh dng cao, khi bnhiem vi sinh vat khac vao sa va s phat triencua chung gay nen mot so bien oi ca chat valng sa. Co nhng vi sinh vat trong qua trnh phattrien sinh ra san pham phu la nhng oc to gayanh hng en ngi s dung.

4.4. VI SINH VAT TRONG MOT SO SAN PHAM

SA:Vi khuan len men chua:

- Streptococcus lactis: la vi khuan hieu kh tuy tien,hnh que co nhanh. Co kha nang len men glucose,lactose, galactose, mantose, dextrin thanh acid lactic.Khong len men saccharose. Phat trien tot 30 35oC. Sau khoang 5 7 ngay vi khuan tao c o

acid khoang 90 1200

T (o Tecne: la so ml dungdch NaOH hoac KOH 0,1N can thiet e trung hoa100ml sa). Sau khi at o acid cc ai, o acid se

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c gi nguyen theo thi gian. Thng c dungtrong san xuat sa chua, b chua

- Streptococcus cremoris: la lien cau khuan cung co

khi di dang song cau khuan, phat trien nhiet o 20 250C. Cac ieu kien nuoi caygiong nh S.lactis. Thng lam ong sa, nhngcung co the lam nht sa. Co kha nang lenmen lactose thanh acid lactic, nhng khong len mensaccharose, mantose, dextrin. Thng c dungtrong san xuat b chua.

- Lactobacterium bulgaricum: la trc khuan len men

lactic. Phat trien tot nhiet o 22 530

C, co khanang lam cho sa b chua en 200 3000T .

- Lactobacterium lactis: la trc khuan len men lactic.Phat trien tot nhiet o 22 500C, co khanang lam cho sa b chua en 110 1800T. Gayong sa sau 12h.

- Lactobacterium casei: la trc khuan len men lactic.

Phat trien tot nhiet o 300

C, co kha nanglam cho sa b chua en 180 2000T. Lam ongsa sau 2 3 ngay. Gi vai tro quan trong trongqua trnh lam chn phomai. Co the phat trien nong o muoi cao en 5,3%.

- Lactobacterium plantarun: la trc khuan len menlactic. Phat trien tot nhiet o 300C, co khanang lam cho sa b chua en 180 2000T. Lam

ong sa sau 2 3 ngay. Gi vai tro quan trongtrong qua trnh lam chn phomai. Tuy nhien mot sochung thuoc loai nay co kha nang gay nhngvet r tren mat phomai.

- Lactobacterium helveticum: con c goi la trckhuan phomat. Phat trien tot 22 510C, tao aciden o 200 300oT.

- Propionibacterium: la cac trc khuan khong baot, khong chuyen ong, co khi dang tron.Phat trien tot ieu kien k kh hn hieu kh.

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Lam ong sa sau 5 7 ngay. o acid tao thanh160 1700T. Tao thanh chu yeu la acid propionic,acid acetic, CO2 ngoai ra con tao thanh mot t acidformic, acid butiric, acid valerianic va vitamin B12 . Phat

trien tot niet o 30 350C. ng dung trong sanxuat phomai dai ngay

- Nam men: cac loai nam men co kha nang lenmen glucid ong vai tro quan trong trong viec trgiup qua trnh len men cua vi khuan lactic, ongthi tao them cac hng v ac trng, lamphong phu them san pham len men. Cac giongthuoc Torulopsis th c ng dung trong che bienb e tang them thi gian bao quan cua b.

Cac vi khuan sinh hng:

La cac vi khuan co kha nang tao ra trong sa vacac san pham t sa cac acid bay hi (acid acetic,acid propionic) va nhieu hng thm (diacetin, eter)

- Streptococcus citrovorus: phat trien kem, khong

gay ong tu. Nhiet o phat trien toi u la 300

C.- Streptococcus paracitrovorus: phat trien khoe hn,

gay ong tu sau 2 3 ngay. Nhiet o phat trientoi u la 300C.

- Streptococcus diacetilactis: phat trien manh, taonhieu acid, tao diacetin co mui de chu. Nhiet ophat trien toi u la 350C. Co mot so chung gayong tu sau 16 18h mot so khac sau 48h. ay laloai co gia tr nhat trong cac loai sinh hng.

- Leuconostoc citrovorum: co te bao hnh cau, trongmoi trng acid tao te bao dai, nhon hai au.

Tao t acid lactic. t khi lam ong sa. Tao ra acetilametylcarbonin hoac acetoin lam cho b co mui thm.c ng dung trong san xuat b.

- Nam moc: mot so loai nam moc c s dung

trong san xuat phomat, tao mui thm ac biet chosan pham nay. V du: Oidium lactis.

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4.4.1.Sa chua:

San pham sa chua che bien t sa ti sau khithanh trung c len men bang vi khuan Lactobacillus,

Streptococcus ket hp vi nam men Saccharomyceskefir. Hoac bang he vi sinh vat Streptococcustherophylus, Lactobacillus bulgaricus. Cac sinh vat naycon song trong san pham cho en luc s dung.

Trong san pham nay khong c co cac loai vi sinhvat khac. Khi sa chua b h hong ngha la no ab nhiem vi sinh vat khac.

4.4.2.Sa ti tiet trung:

Bang cach s dung nhiet o nham tieu dietvi sinh vat co trong nguyen lieu. Tuy nhien, do tnhchat cua sa nen ch c tiet trung bang phngphap Pasteur( s dung nhiet o khong cao). Hien naycong nghe phat trien a tao ra cong nghe tiettrung UHT( nhiet o cao, thi gian tiep xuc thap).Sa tiet trung UHT co thi gian bao quan tot hn.

Tuy nhien, neu dung cu cha khong am bao ve

sinh sa co the b nhiem nhng vi sinh vat do vatcha mang theo.

Hnh 8: Vi khuan Corynebacter diphtheriae nhn di knh hienvi.

4.4.3. Sa ac co ng:

nong o ng cao la moi trng khongthuan li cho vi sinh vat phat trien. Tuy nhien, sa

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ac co ng van la moi trng cho vi khuan lenmen lactic chuyen lactose thanh axit lactic lam chuasa.

4.4.4. Sa bot:Dung phng phap say phun ta co san pham

sa bot nham keo dai thi gian bao quan launhat. Trong sa bot b von cuc do hut am ln hn6% co the b nhiem trung va nam moc.

4.4.5. Phomai:

Pho mai che bien t casein sa cho len men t

nhien hoac bang he vi khuan len men chua va nammoc. Do trong san pham con mot lng nc nenco the b nhiem vi khuan len men thoi (sinh H2S)gay h hong san pham.

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CHNG 6:VI SINH VAT TRONG

BOT VA TINH BOT


Bot va tinh bot la san pham cua cac loai ngucoc (lua, lua m, lua mach), mot so loai cu (khoaim), va mot vai loai au (au xanh). Ban chat botla mot san pham co ham lng am thap. V the,bot va tinh bot neu c bao quan tot se rat t

co kha nang vi sinh vat xam nhap va phat trien.Qua trnh nhiem vi sinh vat cua bot va tinh bot

ch xay ra khi o am cua chung vt qua gii han.Luc nay hoat ong cua enzym co trong san phamthuy phan tinh bot thanh glucose giup cho vi sinh vatphat trien. S phat trien manh me cua he vi sinhvat nhanh chong lam h hong san pham.

Cac loai con trung (sau, mot) cung la oitng thng thay trong san pham bao quan khongtot (e h, khong co bao b kn).

Ngoai ra san pham bot con mang theo nammoc khi nguyen lieu b nhiem trong qua trnh baoquan.


Bot va tinh bot la nhng san pham can duy trmot mc o am toi thieu. Chnh v the, viec bao

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quan chung la nham muc ch khong cho am xamnhap.

Bao b co kha nang chong tham thau am la

vat lieu can thiet trong qua trnh bao quan bot vatinh bot. Ngoai ra kho cha cung can lu y, khong bngap, khong am thap.

6.3. CAC DANG H HONG BOT VA TINH BOT:

6.2.1.Nhiem do vi khuan:

Cac vi khuan co kha nang len men ngglucose va sinh bao t co the phat trien trong bot

neu bot b am. anh lu y trong so cac vi khuano la Bacillus mesentericus (gay benh khoai tay). Neubot b nhiem vi khuan gay benh khoai tay khi emche bien banh se gay hien tng keo si goi labenh si dnh.

Hnh 9: Vi khuan Bacillus mesentericus gay benh khoai

tay trong cac moi trpng nuoi cay va nhn di knhhien vi.

6.2.1.Bot b moc:.........................................................................................................

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Trong qua trnh bao quan neu o am tang caonam moc se phat trien trong khoi bot gay bienchat. Ngoai ra mot so nam( Aspergillus flavur,Penicillium flavur )khi phat trien con tao ra sac to

va oc to lam cho bot b bien mau va nhiemoc. Bot khi a bien mau do nam moc khong cdung e che bien. Nam moc phat trien se sinh ranhieu oc to, trong o Aflatoxin tac ong manh lenhe than kinh gay ngo oc cho ngi s dung. Conhieu loai Aflatoxin nhng loai co oc tnh cao laAflatoxin B1, B2, G1, G2

Hnh 10: Cau truc cua Alflatoxin

6.2.2. Bot von cuc:

San pham khi hap thu am se de b von cuc.Am con la ieu kien tot cho cac loai vi sinh vat dedang xam nhap va phat trien gay h hong bot.

6.2.3. Nhiem sau mot:

Bot va tinh bot thng b con trung xam nhapkhi ieu kien bao quan khong tot. Con trungkhong ch lam hao hut so lng san pham ma con.........................................................................................................

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lam giam mc o cam quan cua bot do phanchung thai ra. Cac loai con trung thng thay trongbot thuoc:

-Bo canh cng (mot)-Bo canh vay (ngai) pha hoai gao

-Bo rang ca (Rep) pha hoai bot m

-Bo bet (nhen) pha hoai gao va bot m.

6.4. VI SINH VAT TRONG MOT SO SAN PHAMBOT VA TINH BOT:

Bot va tinh bot neu c bao quan totthng t b h hong do vi sinh vat v ban than sanpham khong ap ng o am thch hp cho vi sinhvat phat trien. Tuy nhien neu bao quan khong totmot so vi sinh vat co the phat trien.

6.4.1.Bot m:

Neu hap thu am do bao quan khong tot bot m

se b von cuc mot so vi sinh vat sinh bao t cokha nang s dung ng glucose (Bacillusmesentericus) se phat trien. Ngoai ra cac loai contrung co the xam nhap nh mot bot, rep, nhen.

6.4.2. Bot dinh dng:

Do co bo xung mot so chat dinh dng khacco the nhiem vi sinh vat ban than nguyen lieumang vao nh sau mot, nam moc hoac do nhiem

trong qua trnh che bien (san pham bot thngkhong qua qua trnh nhiet).

6.4.3. Banh m:

c lam t bot m hoa vi nc va muoi lenmen bang men banh m va nng nhiet o 220oC -250oC. Mot so vi sinh vat co trong banh m nh nammoc khi b h hong nh: Bacillus mesentericus lam

banh m khi be ra co nht keo thanh ch; nammoc lam cho banh bien mau va v (ang).

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Trong qua trnh san xuat banh m va cac loaibanh lam t bot m, co vai tro quan trong cua nammen. Thng s dung nhat la Saccharomycescerevisiae. Vi cac chung tinh khiet co chon loc, se

giup tao ra loai banh ngon, thm, xop. Ngoai vai trotao CO2, nam men con tao ra cac chat gay hng nhetanol, aceton, diaceton,

Ngoai ra oi khi nhng chung vi khuan len menlactic cung ong mot vai tro rat quan trong trong quatrnh san xuat nhat la oi vi banh m en, chungthng gap nhat la: Lactobacillus plantarum,Lactobacillus brevis, Lactobacillus fermentum.

6.4.4. M si, m ong, m thanh:

Do ieu kien kho khan nen nc ta sanpham m si sau khi san xuat ch qua qua trnh hap(khong qua say) va cung cap ra th trng. V thecac san pham nay thng b nhiem nam moc gayh hong san pham.

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CHNG 7:VI SINH VAT TRONG

CAC SAN PHAM NG,

BANH, KEO


ng c lam t cac loai cay cha ham

lng ng cao nh ma, cu cai ng, hoac bangcong nghe phan huy tinh bot di tac dung cuaenzym. Trong qua trnh che bien eu s dung nhiet.V the, a so vi sinh vat eu b tieu diet. Tuy nhien,mot so vi khuan sinh bao t va chu nhiet co theton tai trong ng, khi gap ieu kien thch hp sephat trien va gay benh cho ngi s dung. Ngoaira trong qua trnh bao quan, neu ieu kien khong

tot ng co the b nhiem mot so vi sinh vat nhnam moc, nam men va cac vi khuan co the phattrien trong moi trng co ham lng ng cao.

Cac san pham banh keo c lam t ng vamot so thanh phan khac nh bot, va cac chat botr (mui ,mau, chat bao quan). Tuy theo congnghe che bien co qua qua trnh nhiet hay khongcac san pham banh keo nhiem vi sinh vat khacnhau.

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Nhng san pham banh keo khong qua qua trnhnhiet ngoai vi sinh vat co trong nguyen lieu con bnhiem vi sinh vat do moi trng, dung cu, va ngiche bien o nhiem vao san pham nh: vi khuan

ng ruot, vi khuan tao bao t khong chu nhiet,nam moc, nam men. Nhng vi sinh vat nay gay hhong san pham va co tac hai en ngi tieudung.

Nhng san pha

visinhthucpham

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