AS 5013.28:2009 pdf free
AS 5013.28:2009 pdf free.Food microbiology
Completely immerse a screw-capped glass test tube or glass McCartney bottle holding 10 mL of sample, in water maintained at 63.5±5°C in a thermostatically controlled water bath fitted with a suitable agitator. The temperature of the sample shall reach 63°C within 5 min. After a further 30 min, remove the tube or bottle from the water bath and immediately 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 level of the water is above the level of the milk or cream. Upon removal from the iced water, wipe the tube or bottle with a tissue.
This Appendix sets out a method for counting the number of microbial cells and clumps in liquid milks and cultured milk products by microscopic examination of a stained film, viz.by a procedure not having a separate defatting step and which may be used on raw milk and similar products with low fat content in order to obtain results more rapidly.
NOTE: The degree of accuracy in estimating microbial numbers by this method depends on the number of microorganisms present in the milk. It is generally recognized that the degree of reproducibility by one operator decreases with counts of less than 500 000 per millilitre of milk,even when the technique is followed exactly.
Factors contributing to this poor reproducibility within and between operators are inaccuracies in measuring volumes, area of smear, inadequate fixing and staining, poor microscopy, irregular distribution of microorganisms, small number of fields actually counted in proportion to fields present in the smear, and eye fatigue.
Microbial count based on groups of microorganisms which appear to be the same type: cell of like kind within 5 um of a group are deemed to belong to that group, regardless of closeness to each other, cells of different types are deemed to be separate clumps.AS 5013.28 pdf free download.
