Caffeine-loaded whey protein hydrogels reinforced with gellan and enriched with calcium chloride

Gellan gum and CaCl₂ were exploited to modulate the textural and techno-functional properties of heat-set whey protein hydrogels. Enrichment with CaCl₂ increased the amount of released caffeine from the protein hydrogel in conjunction with decreasing cohesiveness index and microstructural features modification. Gellan bundles as visualised by microscopic images conferred a remarkable reinforcing influence to gel samples; enrichment with gellan at 0.5 mg mL^-1 increased the gel hardness value approximately 6.4 fold. Based on Fourier transform infrared (FTIR) spectroscopy it was suggested that gellan and CaCl₂ enrichments decreased the β-sheet content of the protein gel matrix in favour of random coil structures. FTIR spectroscopy also proposed cation-π interactions between Ca²⁺ ions and electron-rich amide bonds of whey proteins, as well as interactions between carboxyl groups of gellan and the ε-amino group of lysine in β-lactoglobulin.