The physical and structural properties of acid-Ca²⁺ induced casein-alginate/Ca²⁺ double network gels

The design of protein or polysaccharide interpenetrating network gels according to their physicochemical properties is required to obtain the desired properties of hydrogels. In this study, a method was proposed to prepare casein-calcium alginate (CN-Alg/Ca²⁺) interpenetrating double-network gels by the release of calcium from a calcium retarder during acidification to form calcium-alginate (Alg/Ca²⁺) gel and casein (CN) acid gel. Compared with the casein-sodium alginate (CN-Alg) composite gel, the CN-Alg/Ca²⁺ dual gel network with an interpenetrating network gel structure has better water-holding capacity (WHC) and hardness. The rheology and microstructure results showed that the dual-network gels of CN and Alg/Ca²⁺ induced by gluconic acid-δ-sodium (GDL) and calcium ions were the network structure of the Alg/Ca²⁺ gel, which was the "first network", and the CN gel, which was the "second network". It was proven that the microstructure, texture characteristics, and WHC of the double-network gels could be regulated by changing the concentration of Alg in the double-network gels and that the 0.3 % CN-Alg/Ca²⁺ double gels showed the highest WHC and firmness values. The aim of this study was to provide useful information for the preparation of polysaccharide-protein mixed gels in the food industry or other fields.