Development of Selective Enrichment Broth for Coliforms using Response Surface Methodology

Abstract

Background: Food Safety and Standard Authority of India has adopted conventional IS-5887 (Part-I) 1976 and IS-5401 Part-1 (2012) protocol for monitoring of E. coli and coliforms in dairy products respectively. These methods are time consuming, relying on bacteriological media and sometimes require further isolation and confirmation to finalize the true contaminant. The current investigation was carried out to develop such a broth media which will support growth of coliforms and inhibit other organisms associated within the micro-environment of coliforms and get entry in dairy products due to wrong processing practices and post production contaminant. Methods: The present investigation involved formulation of selective broth for coliforms by optimizing the rate of addition of Sodium lauryl sulphate salt, Gentamicin sulphate+Amoxycillin (in 1:1 ratio) and Cefsulodin by Response Surface Methodology (RSM). Result: Formulation of selective broth for coliforms and E.coli consisting of Sodium lauryl sulphate salt, Gentamicin sulphate+ Amoxycillin and Cefsulodin which was added at the rate of 0.25 g, 10 µl and 312.5 µl respectively per 100 ml of broth. This combination of ingredients along with base composition of broth were able to increase the growth of coliforms as well as able to inhibit population of Salmonella typhi ATCC 14028, Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 25923.