Journal
FOOD HYDROCOLLOIDS
Volume 44, Issue -, Pages 372-379Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.foodhyd.2014.10.007
Keywords
Water holding; Hydrogels; Caseins; Swelling; Kinetics
Categories
Funding
- Fonterra
- New Zealand Ministry for Primary Industries through the Primary Growth Program (PGP) 'Innovation to Transform the Dairy Value Chain'
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The water holding capacity of casein gels was investigated by measuring the swelling and de-swelling under a variety of conditions of temperature and salt concentration. Transglutaminase cross-linked sodium caseinate (15% w/w) gels will swell in good solvents or shrink in poor solvents until an equilibrium casein volume fraction is reached, and this is determined by the cross-link density. The results are interpreted using extended Flory-Rehner theory for weak polyelectrolytes. NaCl and CaCl2 solutions tend to shrink the gels through the decreased Donnan pressure. In contrast, high volume fraction renneted casein (48% w/w) gels tend to swell in NaCl and CaCl2. These results are consistent with theory since the equilibrium volume fractions appear to be at an intermediate value (estimated about 20%). Experiments on casein micelles, which can be considered nano-gels, show the same behavior and trends. Physically cross-linked gels such as a highly concentrated renneted casein gel and casein micelles show the same (de-) swelling behavior. Cross-linked caseinate gels (15% w/w) have a lesser tendency to swell due to the lower casein volume fraction. Physically cross-linked gels will eventually completely dissolve in a good solvent. The results presented give a clear picture of the parameters that determine the equilibrium water content of a food polymer gel. (C) 2014 Elsevier Ltd. All rights reserved.
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