AS 5013.28:2009 – Food microbiology Method 28: Examination of specific products—Liquid milks and creams.
6.4 Preparation of dilutions for liquid milks and liquid milk products onk The procedure shall be as follows:
(a) Prepare dilutions of the sample as described in AS 5013.1 Ii. using peptone salt solution (3.2) or other diluent as specified in the AS 5013 series.
(b) Mi thoroughly and, using peptone salt solution (3.2). prepare tenMd dilutions as described in the AS 5013 series,
6.5 Preparation of dilutions for cream saniples only
6.5.1 liquid cream
The procedure shall he as follows:
(a) Weigh 10.0 ±0.1 g of sample.
(b) Dilute with 90 mL of pcptone salt solution (3.2) prewarmed to about 45°C.
(C) Mi thoroughh and, using pressarmed peptone salt solution (3.2). prepare further
tenfold dilutions as described in the AS 5013 series.
6.5.2 Thickened or caaguialed cream
The procedure shall be as follows:
(a) Mis thoroughly by gently stirring with a spoon or spatula.
(bI Weigh 10.0 ±0.1 gof sample.
(c) Dilute with 90 mL of 2% trisodium citrate solution prewarmed to about 45°C.
(d) Mis thoroughly and, using prcwarmcd peptonc salt solution (3.2), prepare further tenfold dilutions as described in the AS 5013 series.
7 (;I:NI:RAI. TISTS
7.1 Direct microscopic count
Proceed as described in Appendis A. IF necessary. dilute the cream 1:10 with water of approved quality (see AS 5013) before preparing the smear.
7.2 Specific microorganisms
Use the relevant procedures described in AS 5013 to esanhinc for specific groups of 111 icroorgarbisnis.
NOTl: Sec Clause 8 below for thermoduric bacteria.
7.3 Test for penicillin
Use the disc assay method for pcnicillin.
8 COLINT 01’ THIRMOI)LRIC HAC’IFkIA IN RAW tlI.k ANI) (‘RIAM
8.1 1.ahoratory pasteurization
Pasteurize the sample in accordance with the following procedure and at the same time use a pilot tube containing milk or cream in which a thermometer is immersed to monitor the temperature of the sample under test.
Completely immerse a screw-capped glass lest lube or glass McCartney bottle holding 10 ml. of sample, in water maintained at 63.5 0.5°C in a thermostaticall) controlled water bath fitted with a suitable agitator. The temperature of the sample shall reach 63°C within 5 mm. After a further 30 mm. remove the tube or bottle from the water bath and immcdiatel cool to 5°C or below in iced water. In placing the container in the cooling water. avoid wetting the closure but ensure that the lesel of the water is abose the lesel of thc miIl or crcam Liprin removal from the iced water, wipe the tube or bottle with a tissue.
8.2 Colony count
Use the pour plate method described in AS 5013. using plate count agar and incubating at 30 ±1 C for 72 ±2 h.
9 PIIOSPIIATASE TEST FOR PASTEURIZED MILK AND CREAM
Carry out the phosphalase test in aecordaiicc with AS 23001.10. directly on the chilled. undiluted sample.
NOTE: After pasteurization, reactivation of phosphatasc in cream can occur. Care should thcrcforc be esercised in the interpretation of results.
10 TEsT REPORT
The following information shall be reported:
(a) All details ncccssar for the complete identification of the sample.
(b) Reference to this Australian Standard, i.e. AS 5013.28.
(c) Date of testing.
(d) Any aboonnality observed in the phsieal condition of the container or the product.
(e) Results of the tests.
(f) An circumstance or conditions that may base influenced the results.