Application of Antioxidants from Agro-Industrial By-Products in Dairy Fat Systems: Oxidation Kinetics of Ghee and Active Packaging for Butter

Apple, pear and grape pomaces are underexploited sources of phenolic compounds, potential natural alternatives to synthetic antioxidants. This study evaluated their cold-macerated (4 °C) extracts in ghee and in butter packaged in active chitosan films. Extracts were obtained under a 22 factorial design (water or absolute ethanol; 24 or 48 h). Ethanol yielded higher total phenolic content (TPC) and antioxidant capacity than water, particularly in grape pomace. The 48 h ethanolic extracts of apple (AP-E), pear (PP-E) and grape (GP-E) pomaces were selected for their higher TPC and antioxidant capacity; GP-E showed an IC50 at least 94% lower than AP-E and PP-E in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. In ghee under accelerated storage (30, 45 and 60 °C, 35 days), extracts were compared to a synthetic Butylated Hydroxyanisole/Butylated hydroxytoluene (BHA/BHT) blend using oxidation kinetics and Arrhenius modeling. GP-E exhibited the lowest oxidation rate constants at all temperatures, significantly below BHA/BHT. PP-E did not differ significantly from the synthetic blend at 45 and 60 °C, and AP-E presented no significant effect at 60 °C. In butter wrapped in functionalized chitosan films (15 days storage at 21 and 30 °C), GP-E films produced the lowest oxidation values. PP-E films did not differ significantly from polyethylene control. These results suggest GP-E, and to a lesser extent PP-E, as a potential natural antioxidant for high-fat dairy matrices.