Gelation of Cross-Linked Casein under Small and Large Shear Strain
Article first published online: 29 NOV 2013
© 2013 Wiley Periodicals, Inc.
Journal of Texture Studies
Volume 45, Issue 2, pages 130–137, April 2014
How to Cite
Rohm, H., Ullrich, F., Schmidt, C., Löbner, J. and Jaros, D. (2014), Gelation of Cross-Linked Casein under Small and Large Shear Strain. Journal of Texture Studies, 45: 130–137. doi: 10.1111/jtxs.12056
- Issue published online: 3 APR 2014
- Article first published online: 29 NOV 2013
- Accepted manuscript online: 13 NOV 2013 05:39AM EST
- Manuscript Accepted: 7 NOV 2013
- Manuscript Received: 28 JUL 2013
- microbial transglutaminase;
The extent of cross-linking by microbial transglutaminase of acid casein in phosphate buffer was varied, and its consequences on the rheology of chemically acidified gels were studied. Gel formation upon acidification was measured by dynamic rheometry and in rotational experiments at a shear rate of 0.002/s. Torque development during gelation under shear, and stiffness and fracture strain of the final gels was significantly affected by the amount of cross-linked caseins. Moderately cross-linked casein exhibited peculiar gelation behavior under shear as monitored with a perspex cylinder device and a video system. Macroscopically visible “threads” with a regular pattern were formed, which appeared to depend on amount and size of cross-linked casein aggregates. From experiments with varying gelation temperature and acidulant concentration, it was observed that larger aggregates result in weaker gels when acidification rate is increased; in native systems, gelation rate did not show any effect.
Texture and rheology are important quality parameters of acid milk gels that can be modified, among others, by cross-linking milk proteins using microbial transglutaminase. The present results demonstrate that it is crucial to control both the intensity of cross-linking and acidification conditions to obtain products with the desired texture.