Microwave-assisted stabilization of lipid-rich melon seed powder: enzyme inactivation, oxidative stability, and quality changes during storage

This study investigated the effectiveness of microwave-assisted stabilization in reducing endogenous enzyme activities, delaying lipid deterioration, and preserving the quality of lipid-rich melon seed powder (MSP). A 3 × 3 factorial design comprising three microwave power levels (100, 200, and 300 W) and three treatment durations (30, 60, and 90 s) was employed. Nine microwave treatments and an untreated control were evaluated for lipase and lipoxygenase (LOX) activities, physicochemical characteristics, antioxidant activity, and functional properties. Storage stability was assessed over 60 days by monitoring free fatty acid (FFA) content, peroxide value (PV), and thiobarbituric acid reactive substances (TBARS). Among the tested conditions, MW8 (300 W × 60 s; nominal specific energy input of 360 J/g) achieved the greatest enzyme inactivation, reducing lipase and LOX activities by 78.2% and 69.0%, respectively. After 60 days of storage, MW8 exhibited substantially lower FFA content (2.45% versus 5.65%), PV (5.97 versus 12.80 meq O 2 /kg sample), and TBARS (1.02 versus 2.18 µM MDA/g sample) than the untreated control. MW8 also increased total phenolic content and DPPH radical-scavenging activity while improving water and oil absorption capacities. Extending the treatment duration to 90 s at 300 W did not provide additional enzyme inactivation or storage protection, demonstrating a non-linear response to microwave treatment severity. Overall, microwave treatment at 300 W for 60 s provided the most favorable balance between enzyme inactivation, delayed lipid deterioration, and preservation of the evaluated quality characteristics under the investigated experimental conditions.