Hariyani, Sri, Datta, Nivedita, Elliott, Anthony J and Deeth, H. C (2003) Production of proteinases by psychrotrophic bacteria in raw milk stored at low temperature. Australian Journal of Dairy Technology, 58 (1). pp. 15-20. ISSN 0004-9433

Abstract

Raw milk samples from two different sources were stored at 2°C, 4°C and 7°C for 10 days and the growth of psychrotrophic bacteria, production of proteinase and proteolysis in the milks were measured during storage. Peptide analyses by the fluorescamine method and RP-HPLC were used in determination of proteolysis and proteinase activity. The average times taken for the psychrotroph counts to reach 107 cfu/mL at 2°C, 4°C and 7°C were approximately 9, 7 and 4 days, although there was considerable variation in growth rates in the different milks. There was little correlation between psychrotroph counts and either proteolysis or proteinase activity levels. At 2°C, no milk stored showed significant proteolysis by the fluorescamine method after 10 days' storage, but significant proteinase activity could be measured in some of these milks at 8 and 10 days. RP-HPLC analysis was a more sensitive means of detecting peptides than the fluorescamine method.

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