Influence of convective and microwave drying on Algerian blood orange slices: Drying kinetics and characteristics, modeling, and drying energetics

Abstract

This research work aims to explore for the first time the effect of two drying processes on Algerian blood oranges (Citrus sinensis [L.] Osbeck): microwave(200, 400, 600, and 800 W) and convective(40 C, 60 C, 80 C, 100 C, and 120 C), on drying characteristics. The drying time was reduced from 90 min at 120 C (rate of 2.00 10 2 kgH2O/ kg dm.min) to 13 min at 800 W microwave output (rate of 28.86 10 2 kgH2O/ kg dm.min). The drying data were fitted to 38 models. Sledz et al. and Midilli and Kucuk models were found to be the best fit to describe drying kinetics for microwave and convective, respectively. The effective diffusivity ranged from 2.07 10 9 to 15.67 10 9 m2 /s for microwave and from 0.07 10 9 to 1.97 10 9 m2 /s for convective drying. The activation energy was estimated to be 8.871 W/g and 33.7 kJ/mol for microwave and convective respectively. The highest energy consumption was obtained by convective drying (0.49 107 MJ/kgH2O) whereas the highest energy yield was obtained by microwave drying (36.93 10–2 %). Practical Applications Due to the great variability of drying techniques, it is difficult to design the best process for a given product. When choosing a process, several parameters must be considered including precise process control, short drying time, low energy consumption, and high energy efficiency. Blood orange is a seasonal variety, to make it available, drying is one of the most used techniques. Thus, the objective of this study was to compare two drying processes of blood orange slices (microwave, convective). The results of this research allowed to select an alternative technique (microwave) to manufacture dehydrated orange slices that could be useful to facilitate their use out off-season in the formulation of different food products, food fortification, and pharmaceutical industry. Novelty Impact Statement: Two conventional and innovative drying methods were applied to dry blood orange slices, and in terms of kinetic results and modeling. The models of Midilli and Kucuk and Sledz were best suited for convective and microwave drying, respectively. Microwaves provide faster drying, low energy consumption, and high energy efficiency.