Effect of cross-linking with transglutaminase on the heat stability and some functional characteristics of sodium caseinate

The effect of heating (140 degreesC, 0-60 min between pH 6.0 and 7.0) on the turbidity, pH 4.6 soluble amino group content and urea PAGE profiles of sodium caseinate (NaCN) and transglutaminase (TGase)-treated NaCN was determined. pH-dependent heat-induced changes in the turbidity and urea PAGE profiles of NaCN were initially attributed to casein aggregation followed by subsequent degradation on extended heating. Cross-linked NaCN samples (incubated with TGase at 20 degreesC, [E:S] of 1:50 and 1:20 for 185 min) were generally less turbid and had lower pH 4.6 soluble amino group content on heating than unmodified NaCN. The nitrogen solubility of cross-linked NaCN was improved at pH 2.0, 3.0 and 5.0. Some improvements in emulsifying activity index and stability of cross-linked NaCN were observed at pH 5.0 and 10.0. The improved heat stability and nitrogen solubility observed after TGase cross-linking may help extend the range of applications for NaCN. (C) 2002 Elsevier Science Ltd. All rights reserved.