Characteristics of cooked chickpeas and soybeans during combined microwave-convective hot air drying

Moisture content, shrinkage, water activity (Aw), color and texture of cooked chickpeas and soybeans during convective, microwave and combined microwave-convective drying were studied. Combined drying was significantly (P < 0.05) faster than either convective or microwave drying, and resulted in less shrinkage of the dehydrated product. Rapid burning occurred when samples were dried below a Aw of 0.27 ± 0.07 for chickpeas (P < 0.05), and 0.13 ± 0.04 for soybeans (P < 0.05). Both chickpeas and soybeans displayed a transitional behavior in texture when dried to a Aw below 0.40 ± 0.10 (P < 0.05) for chickpeas, and below 0.63 ± 0.15 (P < 0.05) for soybeans, when samples became brittle. Shelf stable dehydrated chickpea and soybean products with low water activity (Aw = 0.35) and good visual quality could be obtained within 14 min of combination drying.