Assay of proteinases of psychrotrophic bacteria in milk using hide powder azure and a simple procedure for clarification of milk.
The clarification of milk by addition of solutions of Triton X-100 and EDTA after digestion of added Hide Powder Azure (HPA) was found to provide a simple method of determining the extracellular proteinase activity of Gram-negative psychrotrophic bacteria in pasteurized whole milk. The light absorbance of the clarified HPA digestion product was measured directly, after a brief incubation period, and was stable to storage of samples in diffuse daylight for at least 2 d. Proteinase produced by growth in refrigerated whole milk of as few as 2.5 X 10(6) cfu ml-1 of Pseudomonas fluorescens AR11 was detected.
D000818:Animals; D002417:Cattle; D010450:Endopeptidases / Q000032:analysis*; D066298:In Vitro Techniques; D008892:Milk / Q000201:enzymology*; D011551:Pseudomonas fluorescens / Q000201:enzymology*
D010450:Endopeptidases