Sustainable processing approach: influence of microwave power and foam thickness on drying kinetics and quality of foam-mat dried mandarin powder

Foam mat drying is a new and very effective process for converting liquid into stable fruit powders. The purpose of this study was to investigate the effects of microwave drying parameters on the foam-mat drying behavior and quality of mandarin juice powder. The research findings are based on the production of a high-quality, color-retentive, and energy-efficient fruit powder. Mandarin juice was foamed with guar gum as an emulsifier (0.45 g 100 g −1 ), soy protein isolate (3.30 g 100 g −1 ), and sugar (10 g 100 g −1 ) and whipped for 6 min. The prepared foam was dried under different microwave power levels (from 180 to 900 W) with varied foam thicknesses of 2, 4, and 6 mm. The combination of raised power from microwaves with reduced foam thickness in layers leads to a faster rate of moisture evacuation. The eleven drying models were fitted, and among all models investigated, the Midilli model best represented the drying curves under all conditions studied. The moisture diffusion varied between 0.041 × 10 −9 and 3.29 × 10 −9 m 2 s −1 , and the corresponding energies of activation were found to be 19.68, 19.29, and 18.94 Wg −1 for 2, 4, and 6 mm thicknesses, respectively. The light-yellow hue (L value) of the mandarin powder was found to be between 51.57 and 38.61 at microwave power levels ranging from 180 to 900 W. Ascorbic acid retention rose as microwave power climbed from 180 to 540 W (24.45 mg/100 g to 29.02 mg/100 g), but declined when microwave power increased from 540 to 900 W. Water activity ranged from 0.40 to 0.57. The findings of this study will be valuable to the food processing industry, particularly in the creation of an efficient foam-mat drying process for citrus products. Under these optimum conditions, large-scale productions of good-quality mandarin powder may be achieved, retaining more nutrients, with improved color and increased shelf stability, appropriate for usage in beverages, confectionery, nutraceuticals, and instant food premixes.