AS 1766.2.3-1992

1 - AS 1766.2.3-1992 FOOD MICROBIOLOGY - EXAMINATION FOR SPECIFIC ORGANISMS - COLIFORMS AND ESCHERICHIA COLI
1 - PREFACE
1 - METHOD
1 - 1 SCOPE
1 - 2 REFERENCED DOCUMENTS
2 - 3 DEFINITIONS
2 - 4 REFERENCE CULTURES
2 - 4.1 Enterobacter aerogenes
2 - 4.2 Escherichia coli
2 - 4.3 Use of reference cultures
2 - 5 POUR PLATE METHOD
2 - 5.1 General
2 - 5.2 Culture media
2 - 5.3 Presumptive test for coliforms
2 - 5.4 Confirmatory test for coliforms
3 - 5.5 Calculation
3 - 6 TRIPLICATE TUBE METHOD
3 - 6.1 Culture media and reagent
3 - 6.2 Presumptive test for coliforms
3 - 6.3 Confirmatory test for coliforms
3 - 6.4 Tests for E. coli
4 - 6.5 Optional confirmatory tests
4 - 6.6 Interpretation of results
4 - 7 MOST PROBABLE NUMBER (MPN) METHOD
4 - 7.1 Culture media and reagent
4 - 7.2 Presumptive test for coliforms
4 - 7.3 Confirmatory test for coliforms
4 - 7.4 Tests for E. coli
4 - 7.5 Estimation of the most probabl e number (MPN) of organisms
4 - 8 REPORT
5 - 9 REFERENCES
6 - APPENDIX A - FLOW DIAGRAM OF TESTS FOR COLIFORMS AND ESCHERICHIA COLI
7 - APPENDIX B - CULTURE MEDIA
7 - B1 SCOPE
7 - B2 EC BROTH
7 - B3 VIOLET RED BILE AGAR

This Standard sets out procedures for the examination of foods for coliforms and Escherichia coli, as follows: (a) Pour plate method-this is a quantitative test and is used for estimating the number of viable coliforms per specified unit of material under test.(b) Triplicate tube method-this is a qualitative test and is suitable for determining the presence or absence of coliforms and E. coli in a stated quantity of material under test.(c) Most probable number (MPN) method-this is a quantitative test and is used for estimating the most probable number (MPN) of coliforms or E. coli per specified unit of material under test.NOTES:1 A flow diagram of the procedures is shown in Appendix A.2 The methods described are general methods and modifications may be required according to the material under test. Such modifications, if required, are prescribed in the relevant methods dealing with particular products.3 The MPN method is better as a quantitative test than the pour plate method when the material under test contains debilitated organisms.4 Where the test is to estimate the level of coliforms only as an index of potential spoilage of the product and of hygiene, an incubation temperature of 30°C is specified. However, where the test is to be extended to include the estimation or detection of E. coli, incubation at 37°C is specified. Cultures which have been incubated initially at 30°C cannot be used for further tests for E. coli.5 Methods for the examination of rinse fluids and filterable liquid products for coliforms and E. coli by membrane filtration are given in AS 1095.4.1.5 and AS 1095.4.1.6 respectively.

First published in part as AS 1095.3.1-1973.
AS 1766.2 first published 1976.
Revised and redesignated in part as AS 1766.2.3-1987.
Second edition AS 1095.3.1-1987.
AS 1766.2.3-1987 and AS 1095.3.1-1987 revised, amalgamated and designated AS 1766.2.3-1992.