Enzymatic Modification Through Microbial Transglutaminase Enhances the Viscosity of Stirred Yogurt

Abstract

Among others, dairy proteins and, especially, the caseins are well‐suited substrates for enzymatic modification by microbial transglutaminase. Apart from studies on chemically acidified dairy gels, some research has been performed on the impact of cross‐linking on rheology and texture of set yogurt. In this study, stirred yogurt was produced from skim milk that was incubated with transglutaminase. Dry matter of the base milk and starter cultures were varied at two levels, and the products were analyzed after 2 and 9 d of storage. The rheological measurements revealed a significant but shear rate‐dependent impact of enzymatic cross‐linking on the properties of stirred yogurt. Under steady‐shear conditions, the viscosity‐enhancing effect was more pronounced at low shear rates or shear stresses, pointing on enhanced interactions among the aggregated proteins in the products made from cross‐linked milk. The cross‐link‐induced viscosity‐enhancing effect diminished with increasing shear rates. PRACTICAL APPLICATIONS Microbial transglutaminase represents an interesting tool for texture modification of protein‐containing foods. The formation of new covalent cross‐links among and within protein molecules generates considerable changes in the technofunctional properties of the final products. Acid gels, such as yogurt, made from enzyme‐treated milk are characterized by reduced syneresis and improved viscosity. A better understanding of the enzyme‐catalyzed impact on the rheological behavior of stirred yogurt may help create new products with interesting properties.

Effects of varying time/temperature-conditions of pre-heating and enzymatic cross-linking on techno-functional properties of reconstituted dairy ingredients

“…Own studies on the techno-functional properties of transglutaminase-treated milk proteins (Lorenzen, 2000) have shown that the degree of cross-linking decreased in the order of sodium caseinate > UF-skim milk protein > skim milk powder > whey protein isolate. Polymerization of milk proteins by transglutaminase results in increased water holding capacity, gelation and gel strength, rheological and emulsifying properties as well as heat stability of milk proteins (Jaros, Heidig, & Rohm, 2006).…”

Fermented milk products: effects of lactose hydrolysis and fermentation conditions on the rheological properties

“…Maximum shear stress τ max at 100 s −1 was 42 Pa for the reference and 28 and 20 Pa for yoghurt made from hydrolysed milk and by co-hydrolysis, respectively. Consequently, hysteresis area related to τ max , which has been proposed as a measure for the "degree of structural breakdown" (Jaros et al 2007), is lower for the reference, indicating higher shear stability.…”

Transglutaminases: recent achievements and new sources

“…In the processing of prepared foods, especially meat products, salt and/or some phosphates are usually added to improve or increase the waterholding capacity, binding, consistency, and overall texture (Kuraishi et al 2001). Among dairy proteins, casein can be easily cross-linked by TGase, mainly owing to its highly accessible and flexible open chain (Jaros et al 2007). Furthermore, the use of this enzyme was shown to increase the shelf life of certain products and reduce the allergen potential for others (Macedo and Sato 2005).…”