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In the present work, an experimental investigation and mathematical modeling of tomato waste hot air drying (HAD) were conducted for drying temperatures of 50 and 60°C, and air velocities of 1 and 2 m s−1. Kinetics, mathematical modeling, and optimization of biological properties using response surface methodology (RSM) were investigated. Increasing the drying temperature from 50 to 60°C shortened the drying time by 5 and 20 min, respectively, for 1 and 2 m s−1 air velocities. The proposed mathematical model with the highest correlation coefficient of 0.9997 well described the moisture variation of tomato waste. Significantly high diffusivity was observed with values of 1.24 × 10−6 and 1.67 × 10−6 m2 s−1. Obtained analysis showed an increase in polyphenol (PPT) and flavonoids (TFC) and a decrease in lycopene content (LYC) and ascorbic acid (AA). Phenomenological modeling and RSM methodology indicated that both drying temperature and air velocity affected the content of TFC, LYC, and AA, whereas, for PPT, the temperature has a positive effect in contrast with negative of air velocity. Optimum drying time, PPT, TFC, LYC, and AA are 44.6 min, 227 mg GAE/g, 32.2 mg GAE/g, 517.92 mg/100 g, and 1.91 mg AAE/100 g, respectively. Optimal drying temperature and velocity were, respectively, 56.7°C and 1 m s−1. [ABSTRACT FROM AUTHOR]

This paper aims to promote the artificial ripening of Algeria's dry Deglet-Nour dates commonly named Frezza, by successive treatments using hot water soaking and hot vapor steaming. The main objective of the study was to optimize the gain in mass during the proposed hydrothermal process using an experimental design method. Water uptake during rehydration has been optimized according to two complete factorial designs; the first 23 based on eight experiments and the second 22 of four experiments. The conducted experimental investigations showed a maximum of water gain by water soaking and a little part by steaming operation. Obtained and analyzed results led to optimal conditions defined by soaking in water at 30 °C during 8 h followed by hot vapor treatment in a confined chamber at 60 °C under 90% RH. Practical Applications Artificial ripening of Deglet-Nour dates, with different hydration techniques, is an industry practice known in Algeria since the 1950s, but under nonoptimized operating conditions. This paper presents a contribution to the optimization of the rehydration process of dates by water soaking and hot vapor steaming. The results of the study will be useful in the sense of ensuring an added value by enhancing the product quality. The obtained results also permit to minimize the necessary energetic consumption for steam production. [ABSTRACT FROM AUTHOR]