Thermo Scientific™ Raka-Ray Agar Base Oxoid™

Members of the family Lactobacillaceae occurring in the brewing process are important spoilage organisms because products arising from their growth and metabolism are often seriously detrimental to flavor. Detection is complicated by the diverse nutritional and environmental requirements of the family.

Raka-Ray Agar¹ enables brewers to monitor in-process beer quickly and accurately for a wide range of organisms including pediococci.

Investigations in which various combinations of growth stimulating agents were added to Universal Beer Agar led to the recognition of a number of agents including sorbitan mono-oleate, liver extract, yeast extract and N-acetyl glucosamine which gave superior results in respect of colony size, colony numbers and incubation time when compared with unmodified Universal Beer Agar.

These investigations provided the basis for the formula of Raka-Ray³ Medium in which sorbitan mono-oleate is included as a stimulant for lactic acid bacteria in general⁴. Fructose is present as the essential carbohydrate source for Lactobacillus fructivorans⁵ while maltose is present to detect lactobacilli which cannot utilize glucose⁶.