Improvement of casein / κ-carrageenan composite gel properties: Role of locust bean gum concentration

Processed cheese analogues (PCA) are popular among consumers worldwide for their diverse flavors and forms. Casein/kappa-carrageenan (CA/KC), as the main structural basis of common PCA, suffers from syneresis and thermal instability, which could be well ameliorated by locust bean gum (LBG) as a thickening, non-gelatinizing polysaccharide. However, the mechanism by which LBG improves the gel properties of CA/KC composites has not yet been clarified. In this study, the CA/KC/LBG ternary composite gels were constructed and the effect of LBG concentrations (0-0.5%) on the CA/KC binary gel properties were investigated. Compared with the control CA/KC gel, the addition of low LBG concentrations (0.1-0.3%) significantly increased the water-holding capacity, strength and thermal stability of gels (P < 0.05), while the addition of high LBG concentrations (0.4%-0.5%) weakened the gel properties. To reveal the influence mechanism of LBG, the water migration, molecular interactions and microstructure of gels were compared. The results confirmed that the addition of LBG induced the migration of water molecules from free state to bound state and enhanced the hydrogen bonding interactions between CA/KC gel molecules. In addition, scanning electron microscopy results showed that the addition of low concentrations of LBG induced the unfolding of KC macromolecules into chains, which optimized the gel network structure of KC. The formed CA/KC/LBG ternary composite gels showed more homogeneous and denser gel network structure than the control. In conclusion, the addition of an appropriate amount of LBG could well improve the thermal stability of CA/KC binary gel and the sense of storage stability of PCA products.