Impact of Hydrogel-to-Oleogel Ratio and Presence of Carob Fruit Extracts on Formulated Bigels: Rheological, Thermal, Physicochemical and Microstructural Properties

Abstract

This study explores the development of bigels (BGs) combining a hydrophilic hydrogel (HG) and a lipophilic oleogel (OG) for co-delivery of two carob fruit extracts (CFEs): I-CFE (inositols) and P-CFE (phenolics). The BGs were formulated in HG:OG ratios of 70:30 and 30:70, using a sodium alginate-based HG and an OG composed of olive pomace oil (OPO) and microcrystalline wax (MW). CFEs were loaded in three modes: I-CFE in HG, P-CFE in OG, and both in their respective phases. Rheological, thermal, physicochemical, and microstructural properties were assessed. All the BGs exhibited solid-like viscoelastic behavior, with greater rigidity in 30:70 formulations. The OG phase enhanced the structural BG network, especially when loaded with P-CFE. At 70:30, I-CFE conferred pseudoplasticity and conformational flexibility, particularly in the absence of P-CFE. At 30:70, both extracts acted synergistically, increasing mechanical strength and network organization. Thermal analysis confirmed MW’s role in structuration, with the BGs showing melting peaks between 40–50 °C. The effects studied affected color and stability. Polarized light microscopy confirmed organized microstructures. This is the first work demonstrating the structuring potential and interactive effects of dual carob extracts (I-CFE and P-CFE) within BGs. All the BGs showed suitable fat-replacer properties, remaining self-standing for 21 days, except the 70:30 I-CFE-free formulation. The findings highlight the potential of CFE-loaded BGs as multifunctional fat replacers in healthier meat products.