Oxidative stability of oleogels: Structure and antioxidant function assessment by isothermal calorimetry

Oleogels are promising alternatives to conventional solid fats, combining healthier lipid profiles and favorable functional properties. However, limited oxidative stability remains a major constraint to their broader application, as inconsistent results across different formulations are reported in the current literature. The oxidative stability and textural characteristics of stearin-based oleogels prepared with stripped sunflower oil were systematically evaluated in this study. Using isothermal calorimetry and oximetry, the effects of the concentration of the radical initiator azobisisobutyronitrile (AIBN) (1–25 mM) in accelerating oxidation by generating free radicals, stearin content (5–10%) in enhancing network density for oxygen barrier formation, antioxidant type (2,2,5,7,8-pentamethyl-6-chromanol, tert‑Butylhydroquinone, ascorbic acid, propyl gallate, and Trolox) and concentration (10–90 µM), and nature of the oleogelator (stearin, bees wax, candelilla wax, sunflower wax, stearic acid, and glycerol monostearate) were investigated. The isothermal calorimetry approach allowed non-invasive continuous kinetic measurement at room temperatures giving novel insights in oxidation stability of oleogels. Increasing AIBN levels significantly accelerated lipid oxidation, as evidenced by a reduction in induction periods (τ). In contrast, higher stearin content enhanced gel firmness and oxidative stability through formation of denser crystalline networks that impede oxygen diffusion. Among the tested antioxidants, propyl gallate exhibited the greatest protective effect, followed by 2,2,5,7,8-pentamethyl-6-chromanol, which conferred moderate stability. Ascorbic acid was ineffective under the tested conditions, likely due to poor solubility and reactivity in the non-aqueous oleogel matrix. Oleogels structured with sunflower wax exhibited the highest resistance to oxidation, with a strong positive correlation between gel firmness and oxidative stability. These findings indicate that oxidative stability in oleogels can be modulated through targeted formulation strategies, providing a basis for the design of functional lipid matrices with extended shelf life and enhanced performance in food and related applications.