Effect of cold plasma pre-treatment 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 non-thermal 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 use and nutrient loss, the process advances sustainable food processing by improving efficiency and reducing environmental impact. Among the drying models tested, the logarithmic model best fit the experimental data, with high accuracy (R² > 0.990, χ² < 0.009, RMSE < 0.033). However, the artificial neural network (ANN) model outperformed the traditional approach, achieving superior predictive performance for the moisture ratio. The optimal network configuration was a three-layered topology with 17 hidden-layer neurons, yielding the lowest MSE, RMSE, and χ² values. Microstructural analysis revealed that CP exposure led to surface etching and the formation of microchannels by reactive plasma species, thereby enhancing moisture diffusion and improving bioactive retention. CP-treated samples showed marked improvement in rehydration ratio (2.96–3.37), total phenolic content (18.74–26.53 mg GAE per g), total flavonoid content (15.23–26.73 mg QE per 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 the drying performance and nutritional quality of fruit by-products.