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EFFECTS OF THERMAL AND ELECTROTHERMAL PRETREATMENTS ON HOT AIR DRYING RATE OF VEGETABLE TISSUE
Author(s) -
WANG WEICHI,
SASTRY SUDHIR K.
Publication year - 2000
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2000.tb00517.x
Subject(s) - microwave , chemistry , desorption , microwave heating , ohmic contact , joule heating , thermal desorption , thermal , atmospheric temperature range , analytical chemistry (journal) , chromatography , materials science , composite material , adsorption , thermodynamics , electrode , organic chemistry , physics , quantum mechanics
Cylindrical samples of carrot, potato and yam were dried in a hot‐air dehydrator after preheating to 50C or 80C by three different heating methods (conventional, microwave and ohmic). The results showed that enhancement of drying rate increased with pretreatment temperature. Ohmic pretreatment increased the drying rate more than conventional and microwave heating. Desorption isotherms showed that in the low a w range, desorption data of preheated and raw materials were similar. However, the isotherms of preheated samples shifted when a w was high, which indicated that thermal pretreatments altered the structure, and apparently, the water distribution within these materials. For all samples, ohmic pretreatment showed stronger influences on isotherms than microwave heating, while the pretreatment effect of conventional heating was only observed for potato tissue.