High-Molecular-Weight Chitosan as a Sustainable Structuring Agent for Olive Oil Oleogels: Toward Healthier and Greener Food Systems

Abstract

This study investigates, for the first time, the formulation and physicochemical properties of oleogels structured with highmolecular-weight chitosan (HMW-CH, 2439 kDa) through Schiff-base crosslinking. The objective was to evaluate the potential of HMW-CH as an oleogelator while emphasizing its economic and environmental advantages, since avoiding depolymerization reduces reagent use, energy consumption, processing time, and overall production costs, contributing to improved sustainability. Oleogels were prepared via an emulsion-templated method using olive oil and varying both chitosan concentration (0.8 and 1.0%) and oil-to-water (O/W) ratios (60/40 and 50/50). Initially, aldehyde selection was performed based on drying kinetics and oil binding capacity, identifying 4-hydroxybenzaldehyde as the most suitable crosslinker.Microscopy and rheological analyses of emulsions, followed by structural, rheological, textural, thermal, and oxidative characterization of oleogels, were conducted to elucidate structure-property relationships. Significant correlations between emulsion properties, microscopy, and oleogel rheology suggested predictive potential for formulation design. Oleogels exhibited predominant gel-like behavior (G′>G″) across strain and frequency sweeps, confirming a stable three-dimensional network. Higher chitosan concentration (1%) significantly increased viscoelastic moduli, while O/W ratio showed minor effects. A downward shift in chitosan Tmax to ~270°C indicated reduced thermal stability due to polymer-matrix interactions. Oleogels showed high oil binding capacity (86-88%), with no major dependence on chitosan concentration or O/W ratio, although a significant interaction (p = 0.008) suggested synergistic effects on network stabilization. Hardness ranged from 1.22 to 1.54 N, with O/W ratio exerting a moderate but significant influence (p=0.05), aligning with textural requirements for spreadable products. Peroxide values remained low (<21 meq O₂/kg), attributed to the drying process, and chitosan exerted a significant effect (p<0.0001) in reducing primary oxidation. Digestibility tests showed decreased lipid hydrolysis compared with pure olive oil, suggesting that the dense chitosan network restricts enzymatic access to the oil phase. Overall, this study demonstrates that HMW-CH is a promising and sustainable structuring agent capable of producing oleogels with stable networks, desirable textural properties, and enhanced oxidative and digestive resistance, supporting their potential use as functional fat substitutes or controlled-release matrices.