Formulated to ISO 6579, Buffered Peptone Water (BPW) is a pre-enrichment medium designed to help sub-lethally damaged Salmonella spp. recover before introducing them into a selective enrichment medium. Enzymatic digest of casein is the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance in the medium. Di-sodium hydrogen phosphate and potassium di-hydrogen phosphate act as buffers in the medium. This nutritious medium is free from inhibitors and is well buffered to maintain pH 7.0 for the incubation period. Sub-lethal injury to Salmonella spp. occurs in many food processes and this pre-enrichment step greatly increases the chance of their recovery, especially if a low number of cells are present in a sample.