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.