Monoglyceride-structured rubber seed oil oleogels as a partial cocoa butter replacement in chocolate: physical properties, oxidative stability and applications.

In this study, rubber seed oil (RSO) was structured into oleogels (RSOOs) using monoglycerides (MG) as a food-grade gelator. The RSO fatty-acid profile was determined by GC/Q-MS. The profile was dominated by C16-C18 species, principally linoleic acid (C18:2n-6, 40.39%), oleic acid (C18:1n-9, 22.86%) and alpha-linolenic acid (C18:3n-3, 21.72%), together with palmitic (8.23%) and stearic (6.07%) acids; this gave class totals of 14.65% saturated, 23.15% monounsaturated and 62.20% polyunsaturated fatty acids and n-6/n-3 = 1.863. The critical gelation concentration was 5.0 wt% MG at 25 °C. Across the 1-12 wt% MG series, RSOO hardness increased from 20.045 to 1127.846 g and oil-binding capacity (OBC) from 24.92% to 99.87%. FTIR showed no new or lost absorption bands on gelation; small C-H band shifts and an intensified O-H envelope were consistent with van der Waals and hydrogen-bonding interactions supporting a physical network. XRD showed β/β' short spacings whose intensity increased with MG content while polymorph identity remained unchanged. RSOOs were solid-like and thermoreversible. Under accelerated storage (40 °C, dark, 21 days), the 12% MG-RSO accumulated secondary oxidation products (TBARS) less than pure RSO and DPPH radical-scavenging capacity higher than pure RSO, an effect attributed to physical immobilization of the oil and compositional dilution rather than demonstrated intrinsic antioxidant activity. A 7 wt% MG RSOO, selected on the hardness-OBC plateau and on economic grounds, was used to replace 0-100% cocoa butter (CB) in chocolate. The chocolate melt peak shifted from 21.93 °C to 17.84 °C. A practical replacement window of 20-60% retained acceptable thermal stability and sensory quality, with the 20% formulation receiving the highest flavor-balance score. Above 60%, chocolates failed structurally at 30 °C, and 100% replacement collapsed at 25 °C. The results support RSOO as a partial CB replacement within a defined, conservative window.