Formation and physical properties of casein–gellan gum/Ca2+ gels with interpenetrating polymer network

Low-acyl gellan gum (LA) is widely used to enhance casein-based gel properties in yogurt manufacture. The addition of Ca 2+ triggers sol–gel transition of LA. Hence, LA/Ca 2+ gel might cooperate with casein (CN) gels to generate interpenetrating polymer network during the acidification process and improve gelation properties of CN-based gel products. However, there is limited information about the effect of LA/Ca 2+ on gelation properties of CN. In this study, the effect of LA/Ca 2+ on the formation and physical properties of CN was investigated. 0.5% CN-LA/Ca 2+ exhibited higher water holding capacity and hardness (97.53%, 1999.8 g) compared with CN gel (29.26%, 268.4 g) or 0.5% CN–LA gel (59.30%, 696.8 g). The hardness of 0.5% CN–LA is between with 0.05% CN–LA/Ca 2+ and 0.2% CN–LA/Ca 2+ , indicting Ca 2+ cooperated with lower LA displayed a similar gel strengthening effect compared with individual LA. Moreover, LA/Ca 2+ gel, as continuous phase, formed prior to CN gel during acidification, and then CN gel was interpenetrated in LA/Ca 2+ gel. Overall, the addition of Ca 2+ to CN-LA mixture system can significantly enhance the gelation properties by forming CN–LA/Ca 2+ gels with interpenetrating polymer network, which can be used to reduce the addition of LA and effectively improve the quality of CN-based gel products. • Acid and Ca 2+ induced casein–low-acyl gellan gum/Ca 2+ gel were successfully prepared. • The addition of low-acyl gellan gum/Ca 2+ significantly enhanced the physical properties of casein-based gels. • The structure of casein–low-acyl gellan gum/Ca 2+ gels composed of two polymers was an interpenetrating network. • Low-acyl gellan gum/Ca 2+ was gelled prior to the formation of casein gel network.