Inactivation of an indigenous transglutaminase inhibitor in milk serum by means of UHT-treatment and membrane separation techniques |
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| Affiliation: | 1. Department of Food and Nutritional Sciences, University College Cork, Ireland;1. Food & Bio-Based Products, AgResearch Lincoln, Private Bag 4749, Christchurch, 8140, New Zealand;2. Food & Bio-Based Products, AgResearch Ruakura, Private Bag 3123, Hamilton, 3214, New Zealand;3. Riddet Institute at Massey University, Palmerston North, New Zealand;4. Biomolecular Interaction Centre, University of Canterbury, Christchurch, New Zealand;1. TUM School of Management, Technical University of Munich, Arcisstr. 21, 80333, Munich, Germany;2. Animal Production Systems Group, Department of Animal Sciences, Wageningen University, Wageningen, The Netherlands;3. Chair for Food and Bioprocess Engineering, Technical University of Munich, Weihenstephaner Berg 1, Freising, Germany;1. Midwest Dairy Foods Research Center, Dairy and Food Science Department, South Dakota State University, Brookings 57007;2. Idaho Milk Products, Jerome, ID 83338;3. Dairy Management Inc., Rosemont, IL 60018;1. Key Laboratory of Food Nutrition and Safety, Ministry of Education, College of Food Engineering and Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, China;2. Tianjin Food Safety & Low Carbon Manufacturing Collaborative Innovation Center, 300457, Tianjin China |
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| Abstract: | An indigenous inhibitor in raw milk inhibits cross-linking by transglutaminase (TG). The enzymatic cross-linking of micellar casein, compared with sodium caseinate, taking thermal inactivation of the TG inhibitor in the milk serum into consideration, was investigated. Inhibitor-free micellar casein was prepared by membrane separation combined with heat treatment of the UF permeate. The inhibitor permeated through MF (nominal pore size 0.1 μm) and UF (cutoff 25 kDa) membranes. TG-catalyzed cross-linking of casein micelles was clearly enhanced by UHT-treatment of UF permeate. Variation of the enzyme concentration showed that the inhibitory effect could not be compensated by higher enzyme concentrations when the casein micelles were suspended in unheated milk serum. Sodium caseinate, however, underwent high degrees of cross-linking even in unheated milk serum. By mixing an unheated milk serum and a UHT-treated milk serum at different ratios, the relative TG inhibitor activity was analysed. High inactivation (>80%) of the TG inhibitor is necessary to achieve high degrees of protein cross-linking. |
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