Abstract
Enzymatic cross-linking by microbial transglutaminase is a prominent approach to modify the structure and techno-functional properties of food proteins such as casein. However, some of the factors that influence structure-function-interrelations are still unknown. In this study, the size of cross-linked sodium caseinate nanoparticles was modulated by varying the ionic milieu during incubation with the enzyme. As was revealed by size exclusion chromatography, cross-linking at higher ionic strength resulted in larger casein particles. These formed acid-induced gels with higher stiffness and lower susceptibility to forced syneresis compared to those where the same number of ions was added after the cross-linking process. The results show that variations of the ionic milieu during enzymatic cross-linking of casein can be helpful to obtain specific modifications of its molecular structure and certain techno-functional properties. Such knowledge is crucial for the design of protein ingredients with targeted structure and techno-functionality.
Highlights
Casein, the main protein fraction in milk from ruminants (e.g., ~80% in bovine milk), is the main contributor to structure formation in fermented dairy products such as cheese or yoghurt, and the origin of casein-based ingredients with targeted functionality [1].For instance, sodium caseinate (NaCn) is produced by acid precipitation of casein, washing, neutralisation of the precipitate with NaOH, and subsequent spray-drying [2]
For more than two decades, enzymatic cross-linking by microbial transglutaminase has been investigated as a possibility to modify techno-functional properties of casein in milk and to improve, e.g., texture and water holding capacity of
NaCn and calcium caseinate (CaCn) solutions were prepared by dispersing acid casein powder in demineralised water and neutralising it with 1 M NaOH or 0.02 M Ca(OH)2, respectively
Summary
The main protein fraction in milk from ruminants (e.g., ~80% in bovine milk), is the main contributor to structure formation in fermented dairy products such as cheese or yoghurt, and the origin of casein-based ingredients with targeted functionality [1].For instance, sodium caseinate (NaCn) is produced by acid precipitation of casein, washing, neutralisation of the precipitate with NaOH, and subsequent spray-drying [2]. The main protein fraction in milk from ruminants (e.g., ~80% in bovine milk), is the main contributor to structure formation in fermented dairy products such as cheese or yoghurt, and the origin of casein-based ingredients with targeted functionality [1]. NaCn possesses a wide range of techno-functional properties that are relevant for the food industry, such as gel formation, emulsification, foaming, as well as water and oil binding capacity, and exhibits a good stability against heating and ethanol, making it suitable as ingredient for a number of foods [1]. NaCn in food products are yoghurt [4,5], cream liqueurs and other emulsions [6,7], as well as plant-based, fermented drinks [8].
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