Xc nh coliforms Nguyn tc : - C5 v coliforms l nhng trc khun ng
rut, gram m, kch thc khong 0,5 3,0 , cu trc thng, khng sinh bo t,
hiu kh hoc k kh ty nghi, c kh nng ln men lactose, sinh hi, sinh
acid t 35- 370C trong 24-48 gi. Vi khun nhm Coliforms bao gm :
Escherichia Coli, Enterobactor, Citro bacter, Klebsiella, Serratia
tn ti trong rut ngi, sc vt v ngoi cnh. N c biu th cho mc khng bo m
ca qu trnh sn xut hay tnh trng vs trong sn xut. - Tng s coliforms c
xc nh theo phng php m s c xc sut ln nht MPN ( most probable number)
khi nui cy trong moi truong tng sinh Lauryl Sulfate Tryptose Broth
v mi trng khng Brilliant Green Bile (2% ) broth. Dng c: a. giai on
tng sinh : - Ly 250 ml, ng ghim 16 co nt bng - ng Durham chuan bi
mi trng : - Lauryl Sulfate Tryptose Broth. Ly 100ml mtrg cho vo ly
250ml, phn phi vo 9 ng nghim, mi ng khong 10ml, dng nt bng khng c
cha bt kh . a v mi trng t 45-500C. Practice: Tng sinh: ly 3 ng mi
trng tng sinh, cho vo mi ng 1ml nguyn mu. Tng t nh vy cho 6 ng mi
trng tng sinh cn li tng ng vi cc mu pha long t 10-1 v 10-2. Trn cn
thn mu v mi trng. Xc nh tng s vsv hiu kh. Nguyn tc: - vsvhk l vs vt
ch sng c trong diu kin c oxy t do. N biu hin tnh trng v sinh ca thc
phm, mc nhim gy nguy him ca nguyn liu hay cc iu kin nhit , thi gian
ch bin, hay bo qun khng ph hp. ngoi ra, s lng vsv hiu kh cn bo trc
kh nng h hng ca sn phm. - Tng s vsvhk c xc nh theo phng php m s
khun lc mc trn mi trng Tryptone Glucose Yeast Agar . Dng c: - a
petri, ly, pipet Chun b mi trng. Xc nh s vi khun vibrio
parahaemolyticus gy ng c v tiu chy. Nguyn tc: Mt lng mu dc tng sinh
trong mi trng chn lc c trng. Cy phn lp sang mi trng phn bit chn lc
c trng. Dng c que cy gt. Chun b mi trng - Mi trng tng sinh
Colistine polymicine broth. - Mi trng phn lp TCBS - Thanh trng mi
trng.
Tin hnh: - ht 1ml mu nguyn vo trong ng nghim cha 9ml mi trng tng
sinh chn lc 370C/ 6-8h. - Cy phn lp sang TCBS, nui 370C trong 20
gi. - m khun lc thu c. - Khun lc mu xanh n xanh dng, ng knh khong
3-4mm Kt qu: - m khun lc mc trn cc a petri c cha 15-150 khun. xc nh
tng s clostridium perfringens nguyn tc: - L trc khun ch im y t v ch
im phm cht do u nhim phn ngi, ng vt, bn t, nc cng rnh. C hnh th trc
khun ln, khi ngn khi di,hai u mng hoc dng ring l, hoc chui, sinh bo
t hnh trng trong cc mi trng ng, khng di ng, gram dng. - pp m s khun
lc mc tren mi trng Tryptose sulfite cycloserine ( TSC) Agar t=37
trong 20h. Chun b mi trng v tin hnh: mt Tryptose sulfite
cycloserine ( TSC). thanh trng mi trng nhit 121 trong 10. un tan
chy mi trng PERFRINGENS AGAR BASE v a v 45-50. Ly 50mlbb
