Phase separation phenomena in gelatin-glucose syrup mixtures: Microstructures and gel characterization

Abstract

This study delves into phase separation phenomena occurring within gelatin-glucose syrup (GS) mixtures, focusing on compositions ranging from 6 to 10% gelatin and 40–60% GS. The investigation employed 250 Bloom gelatins with distinct properties and GS with varying dextrose equivalence (DE). Microstructural analyses of mixtures were conducted using inverted fluorescent microscopy both immediately after blending at 80 °C and following a 24-h incubation at different temperatures. Visual observation as well as rheological, thermal and textural analyses were employed to monitor bulk phase separation occurring at 45 and 60 °C and gel properties upon cooling. Upon mixing, a diverse range of morphologies emerged, ranging from single-phase configurations to bicontinuous, protein-in-polysaccharide, and polysaccharide-in-protein arrangements, which was attributed to the immiscibility between gelatin and the DP10+ polysaccharides in the GS beyond a concentration threshold and potentially driven by the molecular ordering of gelatin and the shear forces during mixing. The miscibility of polymers and the nature of continuous phase were markedly influenced by the dosage and properties of gelatin (MW and pI) and GS (DE). During incubation at 60 or 45 °C, structural rearrangement occurred, with certain compositions undergoing substantial bulk separation. Rapid cooling effectively arrested the initial microstructures, giving rise to the formation of turbid gel networks. Comparative analysis of the gel properties indicated that GS generally promoted the formation of gelatin gels, but excessive addition of low DE GS proved counterproductive to proper gel development, resulting in the formation of soft, weakly structured gels prone to syneresis or even outright nongelation.