Development and characterization of a novel soy lecithin-stearic acid and whey protein concentrate bigel system for potential edible applications

Bigels are a new technology with great potential in the food industry. Their success with drug delivery suggests they may be able to deliver sensitive compounds in foods, such as probiotics and bioactives. The purpose of this study was to develop and characterize a novel, edible bigel system. The bigel was prepared by homogenizing, at high shear, an oleogel emulsion composed of soy lecithin, stearic acid, soybean oil, and water, and a hydrogel composed of whey protein concentrate and water. Characterization was conducted through small angle x-ray scattering, rheology, and fluorescence microscopy. With addition of the hydrogel component, the oleogel emulsion retained its basic structural characteristics, but lost higher order structuring. The bigels were found to have temperature-dependent G′ values. Despite temperature sensitivity, the bigels showed G’>G″ at all temperatures from 8 to 98 °C. Fluorescence microscopy revealed that a bi-continuous bigel was formed at equal proportions of oleogel emulsion and hydrogel; nevertheless, when either of those phases increased one of them became the dominant continuous phase. Some interaction between the phases may have occurred at 10 wt% water and 15 wt% protein usage in the oleogel emulsion and hydrogel, respectively, and this synergy improved the bigel's mechanical properties. On the contrary, at protein and water contents outside those listed above, the relationship between phases became antagonistic towards the bigel's mechanical properties.