This study applied Adaptive Neuro-Fuzzy Inference System (ANFIS) to predict the moisture ratio (MR) during the drying process of yam slices (Dioscorea rotundata) in a hot air convective dryer. Also the effective diffusivity, activation energy, and rehydration ratio were calculated. The experiments were carried out at three (3) drying air temperatures (50, 60, and 70 °C), air velocities (0.5, 1, and 1.5 m/s), and slice thickness (3, 6, and 9 mm), and the obtained experimental data were used to check the usefulness of ANFIS in the yam drying process. The result showed efficient applicability of ANFIS in predicting the MR at any time of the drying process with a correlation value (R2) of 0.98226 and root mean square error value (RMSE) of 0.01702 for the testing stage. The effective diffusivity increased with an increase in air velocity, air temperature, and thickness and the values (6.382E -09 to 1.641E -07 m2/s). The activation energy increased with an increase in air velocity, but fluctuate within the air temperatures and thickness used (10.59-54.93 KJ/mol). Rehydration ratio was highest at air velocity×air temperature×thickness (1.5 m/s×70 °C × 3 mm), and lowest at air velocity × air temperature×thickness (0.5 m/s×70 °C × 3 mm). The result showed that the drying kinetics of Dioscorea rotundata existed in the falling rate period. The drying time decreased with increased temperature, air velocity, and decreased slice thickness. These established results are applicable in process and equipment design, analysis and prediction of hot air convective drying of yam (Dioscorea rotundata) slices.

Traditional food processing techniques can no longer meet the ever increasing demand for high quality food across the globe due to its low process efficiency, high energy consumption and low product yield. This review article is focused on the mechanism and application of Infrared (IR) and ultrasound (US) technologies in physical processing of food. We herein present the individual use of IR and US (both mono-frequency and multi-frequency levels) as well as IR and US supported with other thermal and non-thermal technologies to improve their food processing performance. IR and US are recent thermal and non-thermal technologies which have now been successfully used in food industries to solve the demerits of conventional processing technologies. These environmentally-friendly technologies are characterized by low energy consumption, reduced processing time, high mass-transfer rates, better nutrient retention, better product quality, less mechanical damage and improved shelf life. This work could be, with no doubt, useful to the scientific world and food industries by providing insights on recent advances in the use of US and IR technology, which can be applied to improve food processing technologies for better quality and safer products.

This aim of this study was to evaluate the effects of pretreatments and temperature on the hot air drying characteristics of hog plum fruits. Hog plum fruits were pretreated with olive oil/K₂CO₃ or sunflower oil/K₂CO₃ at 28 °C and olive oil/NaOH cum blanching at 96 °C for 15s, hot water at 96 °C for 15s, and dried in a hot air drier at 50, 60, and 70 °C. Mathematical models were used to fit the data of drying and rehydration kinetics. Results showed that increase in temperature reduced drying time, increased effective diffusivity and shrinkage. Sunflower oil aided chemical pretreated sample had the shortest drying time (780 min) and highest effective diffusivity (6.3 × 10⁻⁸ m²/s) at 60 °C, faster rehydration ability at 60 °C, highest retention rate for ascorbic acid (15 %), phenolic content (29 %), and antioxidant activity (12.3 %), while olive oil aided chemical (K₂CO₃) pretreated sample had the shortest drying time at 50 °C (990 min) and 70 °C (600 min), lowest shrinkage (48.5 %), slower rehydration capacity at 40 °C, and lowest colour change (ΔE = 11.5). Modified Henderson and Pabis and Vega-Gálvez were superior to other fitting models in predicting the drying and rehydration kinetics. Sunflower oil/K₂CO₃ pretreatment could help improve the drying and quality characteristics of hog plum.