乳品技能题（Dairy skills）.docVIP

乳品技能题（Dairy skills） Dairy review questions I. determination of antibiotics in raw milk Method for the determination of GB4789 (TTC: three determination method of nitride phenyl tetrazole) 1.1 equipment and materials Water bath: (79 + 1) 0C, (36 + 1) 0C incubator: (36 + 1) 0C Marker pen, test tube, sterilizing straw: 10ml, 1ml, sterilized tube Electronic balance: accuracy to 0.01g, refrigerator: 4 ~ -200C 1.2 culture medium and reagent 1.2.1 bacteria: Streptococcus thermophilus (strictly according to the product instructions, storage conditions, storage) 1.2.2 sterilization skim milk preparation: weigh 10g anti skimmed milk powder in 90ml distilled water, fully dissolved after sterilization by 1130C 20min. C1.2.340g/L 2, 3, 5 and three chlorinated benzene tetrazolium (TTC) solution: weigh 1.000gTTC, dissolved in 5ml distilled water, with brown bottle in 70C refrigerator before use with sterile distilled water and diluted to 5 times. If the solution becomes green or pale brown, it cannot be reused. Preparation of 1.4 bacterial fluid 1.4.1 vaccination should be performed under sterile conditions. 1.4.2 if it is dry powder, should be in aseptic conditions, according to the packing instructions, take a certain amount of dry powder, soluble in a certain amount of sterilized skim milk, (36 + 1) 0C culture 15h; before use, with sterile skim milk 1:1 dilution. 1.5 operation steps Take the sample 9ml with the Straw tube sterilization, sterilization, cooling water bath heating 80 0C 5min, 370C, 1ml and aseptic bacterial liquid, 36 + 1 0C water bath culture 2h, plus TTC indicator 0.3ml, 36 + 10C water bath culture 30min, as observed for positive, then cultured in water bath for second 30min observe, each sample for two copies, in addition to a positive and negative control, positive control tubes without antibiotics and antibiotic 1ml (reconstituted milk 8ml concentration to the minimum detectable amount exceeds the list below), the negative control for antibiotic free recovery