Oxidative stability of beeswax oleogels: effects of lipid matrix composition and artichoke leaf extract incorporation

Abstract

This study investigated the oxidative stability of beeswax-based oleogels (4%, w/w) formulated with refined high-linoleic (HL) and high-oleic (HO) sunflower oils and enriched with fractions obtained from a commercial artichoke leaf powder (AP). Each oil system was evaluated independently by comparing its oxidative stability with the respective antioxidant-free control. From a macroscopic perspective, both oils formed self-standing oleogels under the adopted conditions, although structural, rheological, textural, thermal, microstructural and oil-binding properties were not investigated. AP was characterized by caffeoylquinic derivatives, and its aqueous (AQ) and ethyl acetate (EA) fractions differed in their phenolic profiles. In preliminary Rancimat tests on bulk oils, carried out at 120 °C and 130 °C for the HL and HO series, respectively, EA was more effective than AQ, increasing induction time (ITI%) by approximately 33% in HL and 19% in HO. Consequently, only EA was incorporated into oleogels at a nominal dose of 300 ppm CAE. Under the adopted extraction conditions, apparent phenolic recovery from oleogels was about 50% of the nominally added amount, corresponding to approximately 160 ppm CAE, whereas recovery from the corresponding bulk oils was only 3.3%, corresponding to about 10 ppm CAE. EA showed positive but moderate antioxidant activity in oleogels in both Rancimat and oven storage tests, likely due to the limited actual phenolic concentration available in the system. Overall, these findings suggest that beeswax-based oleogels may improve the apparent retention of artichoke phenolics compared with bulk oils. However, incomplete dispersion, possible phenolic transformations during processing and the lack of validated extraction-recovery protocols highlight the need to carefully verify the effective phenolic dose in structured lipid matrices.