Enzymatically Cross-Linked Sodium Caseinate as Techno-Functional Ingredient in Acid-Induced Milk Gels

Sodium caseinate is widely used as techno-functional ingredient in food processing. However, no studies are currently available on applications of enzymatically cross-linked sodium caseinate although such a modification might have a potential to improve its techno-functional properties and thus reduce the amount of protein necessary to achieve the desired product properties. In the present study, aqueous sodium caseinate solutions were cross-linked by microbial transglutaminase to different extents and subsequently spray-dried. These powders were either redissolved in water or added to reconstituted skim milk to compare acid-induced gels from sodium caseinate solutions to gels from milk with added sodium caseinate. Gelation induced by glucono-δ-lactone was studied using time-based oscillation rheology. The maximum storage modulus (G′_MAX) of sodium caseinate gels increased with increasing cross-linking extent, whereas enriched milk gels showed a peak in G′_MAX at moderate cross-linking extents. Heat treatment of the enriched milk shifted the highest G′_MAX to an even lower cross-linking extent. The results show that constituents of complex food matrices as well as processing routes affect the techno-functional properties of modified food proteins such as cross-linked caseins. It was possible to reduce the amount of added protein from 10 to 7.5 g/kg when cross-linked sodium caseinate was used while obtaining milk gels with similar G′_MAX and forced syneresis. Future studies should elaborate ways to further improve the properties of cross-linked sodium caseinate to allow for an even greater reduction in protein enrichment.