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Investigation of Protease Production by P seudomonas fluorescens BJ ‐10 and Degradation on Milk Proteins
Author(s) -
Zhang Shuwen,
Li Hongjuan,
Uluko Hankie,
Liu Lu,
Pang Xiaoyang,
Lv Jiaping
Publication year - 2015
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/jfpp.12496
Subject(s) - protease , casein , food science , pseudomonas fluorescens , proteolysis , chemistry , protein degradation , pasteurization , food spoilage , whey protein , enzyme , biology , biochemistry , bacteria , genetics
The production of protease by P seudomonas fluorescens BJ ‐10 and degradation on milk proteins were carried out. The results showed that the growth rate and protease activity in nutrient broth were lower than in milk. The maximum viable counts at both 6 and 28 C in milk were approximately 10–11 log colony forming units (cfu)/m L . The highest protease activity in milk reached 227.99 U / mL . The protease preferentially degraded caseins in the following order κ‐casein > β‐casein > α s ‐casein and had low activity on whey proteins. Correlation analyses showed that protease activity was significantly ( P < 0.01) related to viable counts. Regression equation was y = 31416.26–31415.33/(1 + 101.64 × −26.97), R 2 = 0.98. The protease showed a typical heat‐stable behavior. After treatment at 130 C for 3 min, more than 39.36 % activity remained. Crude protease caused coagulation of ultra high temperature milk after 5 days of storage at room temperature. We concluded that protease plays an important role in milk spoilage. Practical Application This work provides an alternative way for dairy processing enterprises to evaluate milk quality based on measured protease activity. Protease from psychrotrophic bacteria in milk plays an important role in milk spoilage after long periods of storage. In addition, dairy processing enterprises could reduce the storage time to avoid proteolysis in milk and consequent degradation of milk quality.