Apple pomace, a major by-product of juice processing, requires effective drying for valorization and preservation. This study investigated the thin-layer drying kinetics of apple pomace from three varieties (Starkrimson, Idared, and Jonagold) under forced convection at 57 °C, 63 °C, and 68 °C. Seven mathematical models were used to fit the experimental moisture ratio data and evaluated using statistical indicators (R², RMSE, χ², and MBE). In addition, the proximate composition, titratable acidity, water activity, color parameters, rehydration capacity, total phenolic content, antioxidant activity, and phenolic and organic acid profiles of the resulting apple pomace powders were assessed. Of the models tested, the Midilli–Kucuk model demonstrated superior performance with the highest R² (>0.99) and lowest RMSE and χ² values across all varieties and temperatures. The Page and Logarithmic models also showed good predictive capability. Significant differences in phenolic content and antioxidant activity were observed between powders from different apple varieties, with Starkrimson showing the highest values, followed by Jonagold and Idared. These findings provide essential kinetic parameters for optimizing apple pomace drying processes and support the development of value-added products from this abundant agro-industrial by-product.

Pear pomace, a major by-product of the juice processing, represents a valuable yet underexploited source of bioactive compounds. In this study, ultrasound-assisted extraction (UAE) was optimized using response surface methodology to enhance the recovery of phenolic compounds from pear pomace powder with aqueous ethanol as the extraction solvent. A Box–Behnken design was employed to evaluate the effects of ethanol concentration (40–80%), extraction time (30–90 min), and ultrasonic power (48–144 W) on total phenolic content and DPPH radical scavenging activity. The results demonstrated that the negative quadratic effect of ultrasonic power on phenolic extraction yield exhibited the highest level of statistical significance. Extraction using 40% ethanol for 64.45 min at a power intensity of 117.6 W enabled the optimal recovery of phenolic constituents, yielding 280.1 mg GAE/L in the extracts. Using HPLC, the study explored how variations in ethanol concentration and extraction time affect the phenolic composition of the extracts. Chlorogenic acid, rutin and epicatechin were found to be the major polyphenolic compounds. Overall, pear pomace demonstrated strong potential as a low-cost source of phenolic compounds, and the optimized UAE process proved to be an efficient and robust approach for maximizing phenolic recovery.

Pear pomace, a major by-product of industrial juice processing, represents a valuable resource for the development of functional ingredients. This study aimed to investigate the drying kinetics and quality attributes of pear pomace from two cultivars (Santa Maria and Abate) subjected to thin-layer convective drying at 57, 63, and 68 °C and an air velocity of 1.5 m/s. Experimental moisture ratio data were fitted using twelve empirical and semi-empirical models, and model performance was evaluated based on statistical criteria. The Midilli–Kucuk, logarithmic, and two-term models provided the best fit to the experimental data. Effective moisture diffusivity ranged from 1.44 to 1.90 × 10⁻⁸ m²/s and increased with temperature. The resulting powders were characterized in terms of physicochemical properties, proximate composition, and bioactive compounds. Significant differences (p < 0.05) between cultivars were observed for most quality parameters. Total phenolic content (200.64–301.09 mg gallic acid equivalents (GAEs)/100 g dry sample) and antioxidant activity (0.56–0.97 mmol Trolox/100 g dry sample) were approximately 1.5-fold higher in Abate than in Santa Maria pomace powder. Drying temperature had no significant effect (p > 0.05) on these parameters; however, individual phenolic compounds, such as rutin and epicatechin, showed a decreasing trend with increasing temperature. These findings support the potential of pear pomace as a functional ingredient and provide useful information for optimizing drying processes.