AS 5013.11.4:2018 pdf free.Food microbiology Method 11.4: Microbiology of the food chain—Preparation of test samples, initial suspension and decimal dilutions for microbiological examination—Specific rules for the preparation of miscellaneous products (ISO 6887-4:2017/ MOD).
9.1.2 Apparatus
Plastic bags with filter inserts (6.1.2) are recommended to assist in the pipetting of products with substantial insoluble matter in suspension.
9.1.3 Preparation of samples
Mix powdered products thoroughly in their container using a sterile implement (6.6) and then weigh out using aseptic techniques. Weigh accurately into a pre-dispensed volume of diluent (5.2.2) to minimize osmotic shock to the microflora.
Other products may require breaking or cutting up with sterile tools into small pieces before taking the test portion.
9.1.4 Preparation of initial suspension
9.1.4.1 Powdered products, completely soluble
It is not necessary to homogenize fully soluble products mechanically as mixing by hand is adequate. Prepare the initial suspension in accordance with ISO 6887-1.
9.1.4.2 Other less soluble or non-powdered products
Prepare the initial suspension using a rotary blender (6.1.1) or peristaltic homogenizer (6.1.2).
9.1.4.3 Products which swell in water
For all products that swell in water (e.g. polysaccharides and gum gefling agents, dehydrated parsley or chives), make further dilutions (1 in 20, 1 in 50 or 1 in 100, as appropriate) until a suitable suspension is obtained.
Record the use of additional diluent to ensure the correct calculation of enumeration test results.
Where greater dilutions are made, the number of inoculated plates for enumeration tests shall be increased to ensure a minimum of 0,1 g of the test portion is distributed between all plates when low counts are expected.
The solubility of some substances is improved by the addition of a specific enzyme solution to the initial suspension in buffered peptone water (5.2.2). Some examples of suitable enzymes are the following:
— 1 % (volume fraction) alpha-amylase (5.6.1) for swelling starch products, cereals and cereal- contain ing products;
— 1 % (volume fraction) cellulase (5.6.2) for carboxymethyl cellulose, locust beans, carob, guar and cassia gums;
— 2 % (volume fraction) papain (5.6.3) for gelatine.AS 5013.11.4 pdf download.