Textural Properties of Beta-lactoglobulin - Sodium Alginate Mixed Gels at Large Scale Deformation

The denaturation and gelling properties of mixed systems of β-lactoglobulin and sodium-alginate have been investigated as a function of alginate molecular weight, chemical composition, concentration, pH and ionic strength. Differential scanning calorimetry and small strain oscillatory measurements showed that denaturation temperature were lower than the gelling temperatures under the conditions examined. The denaturation temperatures were dependent on both pH and ionic strength, but unaffected by alginate concentration and type. The mechanical and textural properties of mixed gels of β-lactoglobulin and sodium alginate were dependent on several factors; the gel strength increased as a function of alginate concentration under ambient conditions, and decreased as the pH and/or the ionic strength were changed. High molecular weight alginate gave the most pronounced effects, probably due to the accessibility of the alginate for protein binding. The chemical composition of the alginate had negligible effect on the mechanical properties of the gels. PRACTICAL APPLICATIONS: As both proteins and polysaccharides are widely used in the food industry, it is important to understand the interactions between these two biopolymers in order to envisage final product properties. The present article gives an overview of several important parameters when mixing β-lactoglobulin and sodium alginate. β-Lactoglobulin is the main protein in whey and one of the major food protein ingredients. Alginate is a polysaccharide that is often used in the food industry because of its functional properties. This study shows that if the conditions and the alginate type are adequately chosen, the textural properties of food products can be controlled and tailored.