Production of water-water emulsion gels by yerba mate extract

Yerba mate extract is a powerful antioxidant compound, but it can also be used as a gel network-forming agent. In this context, this study aimed to investigate the induction of gelation by yerba mate extract in protein-polysaccharide mixtures. W/W emulsions produced with sodium caseinate (SC) and gellan gum were characterized in terms of their physicochemical composition and rheological properties. The mechanical properties of the gels produced from the W/W emulsions in the presence of yerba mate extract were evaluated by uniaxial compression, oscillatory rheology and scanning electron microscopy. Different concentrations of SC-gellan promote distinct protein and carbohydrate compositions of the separated phase, with gellan concentration varying between 0.69 and 1.26 % w/w in the top phase. The top phase of these emulsions was used for gel formation by adding varying concentrations of yerba mate extract. The highest firmness (22.41 kPa) was identified with 2 % (w/w) extract and the highest gellan concentration, while gels with extreme extract concentrations (0.5 % and 8 % w/w) and the lowest gellan concentration presented lower hardness (0.6 and 0.92 kPa). Water-holding capacity was related to the quantity and size of the pores formed by the gel network in the different compositions, showing that the protein structures within the pores alter the firmness of the gels formed predominantly of polysaccharides. Our results indicate that W/W emulsions should be more intensively explored for the formation of structures that have different potential applications.