Effect of Cold Plasma Pretreatment on Drying Kinetics and Nutritional Compounds of Sweet Lime Peel

Abstract

Sweet lime fruits are cherished for their characteristic aroma, refreshing taste, and abundance of bioactive compounds. Cold plasma (CP) is an emerging nonthermal technology that offers a promising approach to enhance drying efficiency while preserving the nutritional and functional quality of food products. The study evaluated the effect of CP pre-treatment at different exposure times (5, 10 and 15 minutes) on the hot-air drying behavior and quality attributes of sweet lime peel (SLP). The CP pre-treatment significantly accelerated the drying rate, reducing the drying time by about 45 minutes. By accelerating drying while minimizing energy input and nutrient loss, the process advances sustainable food processing through improved efficiency and reduced environmental impact. Among the drying models tested, the logarithmic model best represented the experimental data, showing strong agreement with high accuracy (R 2 > 0.990, χ² < 0.009, RMSE < 0.033). However, the artificial neural network (ANN) model outperformed the traditional approach by demonstrating superior predictive capability in moisture ratio, with the optimal network configuration identified as a three-layered topology containing 17 neurons in the hidden layer, which yielded the lowest MSE, RMSE, and χ² values. Microstructural analysis revealed that CP exposure led to surface etching and microchannel formation due to reactive plasma species, which enhanced moisture diffusion and improved bioactive retention. CP-treated samples showed marked improvement in rehydration ratio (2.96-3.37), total phenolic content (18.74-26.53 mg GAE/g), total flavonoid content (15.23-26.73 mg QE/g), antioxidant activity (32.38-44.88%), and ascorbic acid content (60.12-82.28 mg/100 g). These results indicate that CP pretreatment is an effective and sustainable technique for improving drying performance and nutritional quality in fruit by-products.