Drying characteristics of blackcurrant pulp by microwave-assisted foam mat drying

In order to study the feasibility of microwave-assisted foam mat drying method for the dehydration blackcurrant pulp, a reasonable foaming additive formula was determined and the microwave-assisted foam mat drying characteristics of blackcurrant pulp were analyzed. The concentration of glyceryl monostearate (GMS) and soy protein isolated (SPI) with food grade, selected as the foaming additive, had obvious effects on the foaming properties of blackcurrant pulp. A reasonable foaming additive formula for the blackcurrant pulp with optimum expansion and high stability was developed that the 6% GMS and 3% g SPI as foam inducers and the 10 mL carboxylic methyl cellulose (CMC) with concentration of 0.5% as foam stabilizer, accompanying with the stirring time of 6 min. The experimental results of microwave assisted foam mat drying method showed that the drying intensity of foamed blackcurrant pulp increase with the increase of initial microwave intensity and the decrease of thickness of material layer. Contrasting the microwave with conventional hot air as the heat source for the foam mat drying of blackcurrant pulp, the qualities of dried blackcurrant product in terms of drying rate, color and appearance dried by microwave method are superior to that dried by the hot air. The parameters including the initial microwave intensity of 14.0 W/g and thickness of material layer of 5 mm are recommended for the continuous microwave belt dryer to dry the foamed blackcurrant pulp. Therefore, microwave assisted foam mat drying is suitable for the dehydration processing of blackcurrant pulp.