Development and characterization of plant-based bigels for fat replacement using Hibiscus rosa-sinensis petals and Syzygium cumini (jamun) seed waste

Bigels are biphasic formulations composed of two distinct structured phases with differing polarities, namely an oleogel phase and a hydrogel phase. Recently, increased demands for saturated fat substitutes and consumers' health consciousness have drawn attention to new bioactive rich bigels. This study aimed to develop and characterize anthocyanin-enriched plant-based bigels from Hibiscus rosa-sinensis petals and Syzygium cumini (jamun) seed waste as sustainable substitutes for saturated fats. Bigels were prepared by integrating aqueous jamun seed waste and hibiscus petal extracts separately into a rice bran oil–aloe vera bigel matrix by homogenization at 600 rpm to prepare synthetic emulsifier-free bigels, which were evaluated for their physicochemical and biofunctional properties. Microscopic analysis revealed that hibiscus bigels exhibited smooth, round, well-defined globules, achieving a spreadability of 373.3 g·cm·s⁻¹ and a swelling ratio of 185%, whereas jamun seed bigels showed coarse, irregular spheroids with a spreadability of 320 g·cm·s⁻¹ and a 130% swelling ratio. Antioxidant activity, determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, was significantly higher in hibiscus bigels (84.6% ± 2.1% and 78.8% ± 1.9% radical-scavenging, respectively) than in jamun seed bigels (62.3% ± 1.7% and 55.4% ± 2.0%). Antimicrobial testing using the agar diffusion method demonstrated broader inhibition zones for hibiscus bigels against Escherichia coli (9 mm) and Staphylococcus aureus (13 mm) compared with jamun seed bigels (10 ± 0.4 mm and 12 ± 0.5 mm). These findings indicate that hibiscus-based bigels offer superior structural integrity, antioxidant capacity, and antimicrobial efficacy, highlighting their promise as health-promoting, plant-derived fat replacements for functional food and nutraceutical applications.