Combined effects of process optimization and agri-food by-product inclusion on the structural and oxidative stability of oleogels

In recent years, the growing interest in structured lipids as an alternative to trans and saturated fats has led to extensive research on oleogels (OGs). However, there are still some challenges to be faced for their use in the food industry, such as texture, oil release over time and oxidation. This preliminary study explores the development of OGs using high-oleic sunflower oil (HOSO), rice bran wax (RBW), glycerol monostearate (GMS), dietary fibers (bamboo, BF; citrus, CF), and brewer's spent grain (BSG). The aim of this work was to assess the combined impact of processing and formulation parameters on the physico-chemical and oxidative stability (OS) of OGs, while valorizing agri-food by-products and evaluating their effects on oil loss (OL%) and structural properties. Different time-temperature conditions, such as low/high temperature with short/long time (LS, LL, HS, HL), were tested. OG-LS (low temperature-short time) showed the lowest reduction in oxidative stability index (-25%) and the lowest increase in peroxide value (+6.6%) compared to the non-structured starting oil. Volatile compound analysis revealed carboxylic acids (51.10-62.43%) as the most abundant class in OGs, followed by aldehydes, alcohols, ketones, and hydrocarbons. Fiber addition influenced OL% depending on concentration and particle size. Specifically, BSG and BF were the most effective at 1%, while BF and CF performed better at higher concentrations (3-6%). To investigate fiber interactions with the OG network, rheological and microscopic analysis were performed on OGs formulated with the best granulometry for each fiber, using RBW and GMS individually and combined. The effects of fiber addition depended on type and concentration of structuring agent, enhancing G' in RBW-based systems, while negatively affecting GMS-based ones. BSG and BF addition was beneficial up to a 6% structurant concentration. Microscopy also confirmed a denser, more homogeneous network, correlated with improved mechanical properties and reduced OL%. Vegetable fibers appear promising for enhancing OG structure, but further studies are needed to elucidate interaction mechanisms and explore alternative approaches.