Excessive cross-linking of caseins by microbial transglutaminase and its impact on physical properties of acidified milk gels |
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Authors: | Doris Jaros Mandy Jacob Clemens Otto Harald Rohm |
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Affiliation: | 1. Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany;2. Technische Universität Dresden, School of Science, 01062 Dresden, Germany;3. Technische Universität Dresden, Chair of Food Engineering, 01062 Dresden, Germany;1. Department of Analytical Chemistry, Faculty of Science, University of Santiago de Compostela, 27002, Lugo, Spain;2. Modestya Research Group, Department of Statistics, Mathematical Analysis and Optimization, University of Santiago de Compostela, 27002, Lugo, Spain |
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Abstract: | By varying cross-linking intensity, the effect of microbial transglutaminase on acid gels made from casein solution and raw milk was studied. To avoid any impact of heating, N-ethylmaleimide was used for enzyme inactivation after appropriately checking its efficiency. Up to a specific degree of oligomerisation gel stiffness and firmness increased and tan δ, time at gelation onset and syneresis decreased. Above approximately 70% and 25% of cross-linked protein in casein solution and raw milk, respectively, these parameters showed an opposite behaviour, and weak gels with high syneresis were obtained. Substrate differences, such as preferred cross-linking of adjoining κ-caseins on the surface of the micelle enhanced the effect of steric hindrance in raw milk and impaired proper rearrangements upon acidification at a much lower level of oligomerised protein. It is mainly dimeric and trimeric casein that successfully contributed to the enhanced properties of milk protein gels. |
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