A comparative study of drying methods on tomato peel residues: physicochemical and antioxidant properties

This study aimed to systematically evaluate the effects of vacuum freeze drying (VFD), vacuum drying (VD), natural drying (ND), vacuum microwave drying (VMD), hot air drying (HAD) and microwave drying (MD) on the physicochemical properties, microstructure, and antioxidant capacity of tomato peel residues (TPs). Focusing on identifying the optimal approach that strikes a balance between product quality and industrial feasibility. The results indicated that VFD effectively retained the appearance color, microstructure, lycopene content (12.35 mg/100 g), reducing sugar content (4,024 mg/100 g), hydration capacity, and antioxidant capacity of TPs. VMD exhibited the highest vitamin C content (20.45 mg/100 g) and quality comparable to VFD, along with short drying time and low energy consumption. HAD resulted in the highest levels of total phenolic content (48.66 mg/100 g) and total flavonoid content (72.85 mg/100 g). VMD proved to be the most promising technology for achieving large-scale, high-value industrial drying of TPs due to its exceptional drying efficiency and excellent overall quality retention capabilities. This study provides key theoretical foundations and technical pathways for the value-added utilization of tomatoes processing by-products, holding significant importance for advancing the green, circular, and sustainable development of the food industry.