Lipid oxidation is one of the main factors contributing to the deterioration of the quality of bakery products, negatively affecting their flavor, texture, appearance and nutritional value. This reduces their quality and shortens their shelf life, thus reducing consumer acceptance. Lime by-products, rich in phenolic compounds with antioxidant potential, offer a sustainable strategy to both reduce food waste and improve product stability.

This study investigated the effect of increasing concentrations (0%, 1%, 2%, and 3%) of lime by-product extract on lipid oxidation in muffins during storage. Lime by-product consists of lime pomace, the residue remaining after juice extraction. The Thiobarbituric Acid Reactive Substances (TBARS) assay, which quantifies malondialdehyde (MDA) as a marker of lipid oxidation, was used to monitor oxidative stability. Muffins were stored at 4 °C in sealed plastic containers, and TBARS measurements were taken on days 1, 2, 4, 7, 10, and 14.

Results showed that all extract-enriched muffins (M1, M2, and M3) exhibited significantly lower MDA levels than the control (M0) from day 0. M2 initially had the lowest MDA concentration (0.41 mg Eq. MDA/kg on day 0), followed by M1 and M3 (both 0.45 mg Eq. MDA/kg on day 0). However, over time, M1 consistently showed superior oxidative stability and ended with the lowest MDA value on day 14 (0.56 mg Eq. MDA/kg, p < 0.05). Interestingly, the highest extract concentration (M3) showed higher MDA levels, suggesting a pro-oxidant effect, since on day 10, M0 had 0.65 mg Eq. MDA/kg, while M3 showed 0.71 mg Eq. MDA/kg.

These findings demonstrate that moderate enrichment with lime by-product extract (1%) can effectively delay lipid oxidation in muffins, thus extending shelf life up to 14 days, while enhancing sustainability. Furthermore, this approach adds flavor to food while contributing to food waste reduction through upcycling of citrus processing residues. Importantly, higher extract concentrations may not provide added benefits and may accelerate oxidation due to pro-oxidant effects.