Differences in physicochemical and functional properties of from-concentrate and not-from-concentrate apple pomace: an investigation based on different drying methods.

Apple pomace (AP), a byproduct of apple processing, is nutrient-rich, and its properties are influenced by both the quality of the apples and the juice extraction process. Drying technology can enhance its economic utilization. This study compared the effects of industrial drum drying (ID) and laboratory hot-air drying, heat pump drying and freeze drying (FD) on the physicochemical, functional and structural properties of from-concentrate AP (FC-AP) and not-from-concentrate AP (NFC-AP). The results indicated that FC-AP had higher dietary fiber and pectin content, while NFC-AP exhibited better color, higher total sugar content and stronger antioxidant activity. Among the various drying techniques, the quality of pomace processed with ID was second only to that achieved with FD, which benefited from the short drying time of ID, at only 30 min (specific energy consumption of 4.88 kWh kg-1). The ID-treated FC-AP exhibited a browning index of 57.50, total sugars of 266.49 g kg-1, soluble dietary fiber of 79.11 g kg-1, total phenols of 4.12 g kg-1 and total flavonoids of 5.97 g kg-1, along with the highest antioxidant activity. The choice of apple juicing process significantly affects the physicochemical properties of AP, influencing its high-value utilization. In practical industrial production, ID-treated pomace balances pomace quality and economic costs, offering an advantageous solution for improving pomace utilization efficiency. © 2025 Society of Chemical Industry.