Sodium Caseinate/Sunflower Oil Emulsion-Based Gels for Structuring Food

Abstract

Protein gels have attired attention since they allow structuring foods with no trans or saturated fats. The effects of protein concentration and sucrose addition on gelation kinetics and on physical properties of sodium caseinate (NaCas)/sunflower oil emulsion-based gels were studied by two methods: a new application of backscattering of light (BS) using a Turbiscan equipment and by dynamic oscillatory rheology. Structure of gels was also described by confocal laser scanning microscopy (CLSM) and small angle X-ray scattering (SAXS). Tgel values decreased with increasing sucrose or NaCas concentration. BS method sensed early changes in structure, while rheological measurements were less sensitive to those changes. However, tendencies found by rheological measurements were the same as the ones found by BS experiments. CLSM images of gels formed from emulsions containing high sucrose and protein concentrations had big oil droplets that were not present in initial emulsions. Gels with sucrose concentrations between 15 and 30 wt/wt% released oil. SAXS patterns showed that NaCas nanoaggregate sizes in the aqueous phase were smaller with increasing sucrose concentration. Polar groups of protein interacted with sucrose, and therefore, interactions among protein molecules diminished. As a result of weaker protein molecule interactions, nanoaggregates were smaller. However, this effect was beneficial. In the macroscale, rheological properties and visual appearance of gels were improved. The gel formulated with 5 wt/wt% NaCas and 10 wt/wt% sucrose had a smooth surface and was stable to syneresis and oil release. This formulation was a good alternative to trans fat.