Use Violet Red Bile Glucose (VRBG) Agar for examination of food, animal feed, and environmental samples, for the presence of indicator groups such as coliforms. As well as providing evidence of food hygiene and safety, indicator groups provide a measure of food quality and spoilage potential. One of the most common groups of bacteria employed as indicator organisms by the food industry are the coliforms, which can be regarded as a subgroup within the Enterobacteriaceae
. However, in an attempt to improve assessment of food safety and quality by the food industry, there has been a move towards testing for total Enterobacteriaceae
rather than limiting testing to coliforms.
In processed foods, particularly foods subjected to heat treatment, these organisms can provide a reliable indication of process failure, under-processing, or post-processing contamination.
- Easy-to-read results: due to inclusion of neutral red indicator and crystal violet in the medium Enterobacteriaceae form purple pink colored colonies.
- Adheres to ISO 21528 and ISO 11133:2014 standards.
modified Violet Red Bile Lactose Agar by adding glucose to improve recovery of all Enterobacteriaceae
. Later work by Mossel and Cowell;2,3
demonstrated that lactose could be omitted, resulting in the formulation known as VRBGA. Enterobacteriaceae
rapidly ferment glucose and so reduce the pH of the medium, which produces purple/pink coloured colonies due to the inclusion of the neutral red indicator and crystal violet in the medium. These colonies are usually surrounded by purple halos of precipitated bile salts. Crystal violet and bile salts inhibit the growth of Gram-positive flora.
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