Tài liệu Practical Food Microbiology 3rd Edition - Part 4 pptx

Preparation of samples

4.1 Receipt and storage

4.2 Preparation of sample suspension

4.3 Preparation of decimal dilutions

4.4 Preliminary examination of cans and flexible long-life packs

4.5 pH measurement

4.6 Direct microscopic examination

4.7 Water activity

4.8 Good laboratory practice

4.9 Laboratory accreditation

Receipt and storage

Food samples collected under the Food Safety Act 1990 that may be the subject

of legal proceedings need to be handled according to Code of Practice No. 7,

‘Sampling for Analysis or Examination’ (revised October 2000) [1] and the asso￾ciated ‘Guidance on Food Sampling for Microbiological Examination’ [2]. The

guidelines laid down in these documents are applicable also to all samples of

food taken for microbiological examination. In the context of the code ‘exami￾nation’ means microbiological examination by a food examiner (microbiolo￾gist). A copy of this code should be available in every laboratory. The provisions

of Part III, ‘Samples for Examination’, of the Code of Practice and the Guidance

are summarized below.

Size and nature of sample for examination

The quantity of sample submitted should normally be at least 100g. The sample

may consist of a single unit or a number of units. This will depend on the pur￾pose of the examination, for example whether a particular pathogen is being

sought. Existing national sampling protocols should be taken into considera￾tion. In any case of doubt the food examiner should be consulted.

Handling for examination

Officers should ensure that, as far as possible, samples for examination reach the

laboratory in a condition microbiologically unchanged from that existing at the

time of sampling. Contamination of the sample and microbial growth or death

during sampling, transport and storage should be avoided. Aseptic handling

techniques should be used throughout the sampling process.

4.1

4

Preparation of samples 91