Microwave/Vacuum Drying of Cranberries (Vacccinium macrocarpon)
Mechanically pretreated (cut) and osmotically dehydrated cranberries (Vaccinium macrocarpon) were dried using microwaves (MW) under subatmospheric pressure. Two MW modes were tested (continuous and pulsed), two combinations of pulsed MW mode (30 sec on/30 sec off, 30 sec on/45 sec off) and three MW power levels (1.00, 1.25 and 1.50 W g-1 of initial sample mass). Three vacuum levels were compared one to another (3.4, 18.6 and 33.8 kPa of absolute pressure). Several process and quality parameters such as time of drying, colour, toughness and rehydration ratio were measured and calculated in order to evaluate different drying conditions. Methods with higher overall MW input (1.25 and 1.5 W g-1) and longer power-off time (45 sec) combined with high vacuum (3.4 kPa) offered high quality dried berries (colour parameters similar to those of fresh fruit, soft and chewable texture, juiciness and good rehydration properties).