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Plasmin activity as a possible cause for age gelation in UHT milk produced by direct steam infusion

På svenska

Author

  • Valentin M. Rauh
  • Anja Sundgren
  • Mette Bakman
  • Richard Ipsen
  • Marie Paulsson
  • Lotte B. Larsen
  • Marianne Hammershoj

Summary, in English

The effect of enzymatic activity in direct steam infusion heat treated milk with ultra-short holding times (>150 degrees C for <0.2 s) on age gelation during storage was investigated. Preheating at either 72 or 95 degrees C for 180 s was performed. Milk pre-heated at 72 degrees C showed extensive proteolysis and exhibited bitter off flavour and contained <40% intact alpha(s)- and beta-caseins after 6 weeks storage at 20 degrees C. No proteolysis of kappa-casein was detected. Plasmin was identified as active protease and activation of plasminogen was observed as an increase in the rate of casein hydrolysis. Proteolysis in the stored samples correlated with a decrease in pH and with changes in colour. Gelation occurred after 10 weeks along with an increase in viscosity and extensive proteolysis of alpha(s)- and beta-caseins. In conclusion, plasmin activity was involved in age gelation and bitterness caused by proteolysis was the shelf-life limiting factor. (C) 2014 Elsevier Ltd. All rights reserved.

Department/s

  • Department of Food Technology, Engineering and Nutrition

Publishing year

2014

Language

English

Pages

199-207

Publication/Series

International Dairy Journal

Volume

38

Issue

2

Document type

Journal article

Publisher

Elsevier

Topic

  • Food Engineering

Status

Published

ISBN/ISSN/Other

  • ISSN: 0958-6946