Fabrication of Plant Sterol Ester–Gelatin Bigels as Cocoa Butter Substitutes: A Strategy for Low-Calorie Chocolate Development

Cocoa butter (CB) substitution remains challenging for low-calorie chocolates due to texture and stability compromises in conventional alternatives. This study developed bigels (oleogel/hydrogel ratios = 3:7, 5:5, 7:3 w/w) from phytosterol ester oleogel and gelatin hydrogel as CB substitutes. The optimal CB substitution was screened by characterizing the bigels’ physicochemical properties. Subsequently, compound chocolates were fabricated using the selected bigel system, with the optimal substitution ratio determined through the comprehensive evaluation of their micromorphology, thermal behavior, and sensory profiles. X-ray diffraction revealed peaks at 4.151 and 3.741 nm. At 70 wt % oleogel, the bigel exhibited the highest hardness (307.34 ± 30.66 g). Subsequently, compound chocolates were produced with bigels at substitution levels of 20–100 wt %, showing melting temperatures (42.66–75.30 °C) significantly higher than CB (41.51 °C). The L * (17.43 ± 0.64) and a * (2.13 ± 0.25) values of the CB group, along with its sensory evaluation score (83.50 ± 2.31), showed no statistically significant difference ( p < 0.05) when compared to 20% (16.62 ± 0.41, 2.57 ± 0.12, 83.50 ± 1.97) and 40% samples (16.19 ± 0.58, 2.66 ± 0.14, 81.14 ± 2.35). Phytosterol ester–gelatin bigels successfully replicated CB’s functional properties, demonstrating feasibility as calorie-reduced alternatives. This work provides a novel strategy for designing structured lipid systems in confectionery applications, addressing both nutritional and sustainability demands in the food industry.