Chitosan-Based Oleogels: Emulsion Drying Kinetics and Physical, Rheological and Textural Characteristics of Olive Oil Oleogels

Abstract

Oleogels are of high interest as promising substitutes for trans fats in foods. An emulsion-templated method was used to trap olive oil in the chitosan crosslinked with vanillin matrix. Oil in water emulsions (50:50 w/w) with different chitosan content (0.7 and 0.8% w/w) with constant vanillin/chitosan ratio (1.3) were air-dried at different temperatures (50, 60, 70 and 80ºC) and freeze-dried (-26ºC and 0.1 mbar) to produce oleogels. Only falling-rate periods were determined during air-drying kinetics and were successfully modelled with empirical and diffusional models. At drying temperature of 70ºC the drying kinetics were the fastest. Viscoelasticity of oleogels showed that elastic modulus significantly increased after drying at 60 and 70ºC, and those dried at 50ºC and freeze-dried were weaker. All oleogels showed high oil binding capacity (> 91%), but the highest values (> 97%) were obtained in oleogels with a threshold elastic modulus (50,000 Pa). Oleogels color depended on drying temperature and chitosan content (independent of the drying method). Significant differences were observed between air-dried and freeze-dried oleogels with respect to oxidative stability. Oxidation increased with air drying time regardless of chitosan content. Found results indicated that drying conditions must be carefully selected to produce oleogels with specific features.