Analysis of volume expansion and dehydration rate of berry slab under microwave-vacuum puffing conditions

The objective of the present study was to characterize the puffing properties of blackcurrant slabs with respect to expansion ratio and dehydration rate under microwave-vacuum condition. Microwave power, vacuum degree, initial moisture content and puffing time were selected as influencing parameters. The results showed that the microwave power had the most significant effect and the vacuum pressure had less effect on the dehydration rate of microwave-vacuum puffing blackcurrant slabs. During the microwave-vacuum puffing berry slabs first underwent stage of volume expansion to form a porous structure, followed by dehydration stage to improve the crispy texture of blackcurrant slab. The observed phenomena provided the essential information for the allocation of microwave energy to produce high quality snack products.

► Microwave power has higher effect than that of vacuum pressure on dehydration speed.
► Microwave-vacuum puffing berry leathers undergo orderly expansion and dehydration.
► Optimal parameter is 4.02 kW microwave power, 70% vacuum degree, 40% moisture content.