The influence of pretreatments on the convective drying of pumpkin pieces (Cucurbita maxima) at different air temperatures

Abstract

In this paper the effects of pretreatment on convective drying of pumpkin (Cucurbita maxima) at air temperature of 55°C and 65°C was presended. Three series of blanching in hot water were performed, with the addition of vitamin C, 1% (pretreatment I), potassiummetabisulfite, 0.3% (II) and without additions (control sample). The moisture content in raw pumpkin was 89.13%, while in dried material, moisture content ranged from 10.46% to 18.25%. Better preservation of pumpkin pieces was achieved by conduction drying at air temperature of 55°C, which was proved by the rehydration degree, which achieved values of 93.08% (pretreatment I), 79.95 % (II) and 96.23% (control). The rehydration degree reached the following values at air temperature of 65°C: 65.16%, 62.92% and 70.82%, for pretreatment I, II and control sample, respectively. The process of convective drying of pumpkin pieces can be described by the exponential model in the form y=y0+A1exp[-(x/t1)].

Keywords

• pumpkin
• drying
• blanching pretreatment
• rehydration