SOUTH AFRICAN NATIONAL STANDARD

Transcription

1 ISBN Any reference to SABS SM 1257 is deemed to be a reference to this standard (Government Notice No of 8 November 2002) SOUTH AFRICAN NATIONAL STANDARD Microbiological examination of canned meat and fish products Published by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001 Tel: Fax: SABS

2 Table of changes Change No. Date Scope Amdt To change the designation of SABS standards to SANS standards and to change the temperature required for autoclaving Foreword This South African Standard was approved by National Committee SABS/TC 034/SC 09, Food products Microbiological evaluation of foods, feeds and beverages, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This document was published in June This document supersedes SABS SM 1257:2000 (edition 2). A vertical line in the margin shows where the text has been technically modified by amendment No. 1. This document is referenced in the Compulsory specification for the manufacture, production, processing and treatment of canned fish, canned marine molluscs and canned crustaceans, as published by Government Notice No. R. 790 (Government Gazette No ) of 9 July 2004 and the Compulsory specification for the manufacture, production, processing and treatment of canned meat products, as published by Government Notice No. R. 791 (Government Gazette No ) of 9 July Reaffirmed and reprinted in September This document will be reviewed every five years and be reaffirmed, amended, revised or withdrawn.

3 Microbiological examination of canned meat and fish products 1 Scope This standard specifies the procedure for the microbiological examination of canned meat and fish products. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this standard. All standards are subject to revision and, since any reference to a standard is deemed to be a reference to the latest edition of that standard, parties to agreements based on this standard are encouraged to take steps to ensure the use of the most recent edition of the standard indicated below. Information on currently valid national and international standards can be obtained from the SABS Standards Division. SANS 5553, Media and reagents for microbiological tests. 3 Laboratory ware and equipment 3.1 Laboratory ware Glassware that is resistant to repeated heat sterilization, and free from inhibitory substances such as heavy metals and free alkali. Borosilicate glass with an expansion coefficient of less than K -1 is recommended. All glassware, disposable plastics pipettes and Petri dishes (if used) shall be sterile Universal bottles Bottles of the McCartney type, that are fitted with standard metal screw caps and that have a nominal capacity of 30 ml Culture tubes Rimless cylindrical tubes that have hemispherical ends, a nominal wall thickness of 1,5 mm and a measuring capacity of 200 mm 40 mm Reagent bottles Reagent bottles of capacity 50 ml and 100 ml and that are fitted with polypropylene or other plastics stoppers of such design that they can be used to deliver drops of reagent. 1

4 3.1.4 Pipettes Ungraduated glass pipettes, or suitable disposable plastics pipettes, of length approximately 30 cm, of external diameter approximately 9 mm and of internal diameter approximately 6 mm, and that have an indentation about 50 mm from one end, to receive a cotton plug Petri dishes Petri dishes of diameter 100 mm and of height 20 mm and made of glass or of wettable polystyrene Inoculating loop A loop of internal diameter approximately 4 mm made at the free end of a length of platinum or platinumiridium alloy wire of diameter approximately 0,4 mm, and mounted in a holder that consists of a thin metal rod or tube. The length of the wire, from the loop to the holder, shall be approximately 38 mm. The loop should be bent at an angle to the length of the wire, which will facilitate the removal of the loop vertically from the liquid while the plane of the loop is kept horizontal. 3.2 Equipment Autoclave A pressure vessel that is capable of producing steam or is connected to a central steam source and is capable of withstanding a pressure of 300 kpa. The autoclave shall be capable of attaining a 3 temperature of ( ) C within 10 min from the beginning of the sterilization cycle. Amdt Incubators and water-baths Incubators and water-baths that have thermostatically controlled heating or cooling devices (or both), and that are so fitted with a means of circulation that the temperature of the total enclosed space is maintained to within 2 C of the thermostat setting Hot air oven (for sterilization by means of dry heat) A thermostatically controlled oven that is heated by electricity or gas and is so fitted with a means of circulation that the temperature of the enclosed space is maintained at 170 C ± 5 C. The heat supply shall be so controlled that the working temperature is regained within 10 min of a momentary opening and closing of the oven door Punches Stainless steel punches that can be sterilized and that are able to make a hole of approximately 15 mm in the lid of a can. 4 Media and reagents NOTE See also the procedure notes in SANS General Personnel The tests shall be undertaken by persons experienced in microbiological aseptic techniques. 2

5 4.1.2 Water Use only glass-distilled water, or demineralized water of equivalent purity, that is, clear, colourless and free from visible suspended matter and of which the ph value, measured at 25 C, is in the range 6,5 to 7, Quality of ingredients In the preparation of the media and reagents, use only ingredients of quality acceptable for microbiological purposes. Use anhydrous salts, unless otherwise specified Accuracy Except where otherwise specified, allow the following tolerances: a) on temperatures... ± 2 C; b) on masses... ± 1,0 %; c) on volumes... ± 1,0 %; and d) on ph value... ± 0,1 ph unit Dehydrated media Many of the media required are obtainable in dehydrated form and, for uniformity of results, the use of such media is recommended. If these media are used, follow the manufacturers instructions strictly regarding reconstitution and sterilization Filtration of media Whenever it is necessary to filter a medium in the course of its preparation, proceed as follows: a) if the medium does not contain a solidifying agent, i.e. it is a liquid medium or broth, filter it through a medium-speed filter paper; or b) if the medium contains a solidifying agent (e.g. agar), filter it through a 10 mm to 15 mm thick layer of pre-wetted absorbent cotton wool. To prevent solidification of the medium during filtration, use a steam-jacketed funnel. Alternatively, carry out the filtration in a steam chamber Adjustment of the ph value of media Where the final ph value of a medium or reagent is specified, so adjust the ph value (if necessary) during preparation and, in the case of media, before sterilization, that, after preparation, the required ph value measured at 25 C is obtained. Unless otherwise specified, adjust the ph values using a solution of hydrochloric acid (c(hcl) = 1 mol/l), as appropriate Dispensing Where specified quantities of media are to be dispensed into bottles, use 30 ml universal bottles (see 3.1.1). Where bulk sterilizing is required, use any suitable glass container of the required quality, or use suitably stoppered culture tubes (see 3.1.2). Dispense reagents into reagent bottles (see 3.1.3). Stir media constantly while dispensing. Whenever the preparation of slopes for surface cultivation is required, dispense the medium in 15 ml volumes and sterilize as specified. Immediately after sterilization, place the bottles or, when relevant, the culture tubes, on a 1-in-4 sloped surface and allow the agar to solidify. 3