Study on sorption equilibrium moisture and isosteric heat of sesame

Equilibrium moisture content ( EMC) data for sesame seeds of four Chinese varieties were collected by gravimetric method at 11% to 96% relative humidity ( ERH) and 10, 15, 20, 25, 30, and 35℃ above nine saturated salt solutions.Seven models, named CAE, Modified- Chung- Pfost ( MCPE) , Modified- Halsey ( MHAE) , Modified-Henderson ( MHE) , Modified-Guggenheim- Anderson- deBoer ( MGAB) , Modified- Oswin ( MOE) and StrohmanYoerger ( STYE) were fitted to the sorption data, and the best fitted equation was determined to be MOE. The isosteric heats for both sesame adsorption and desorption decreased rapidly with increasing seed moisture initially, however, after the moisture was more than 7.5% wet basis ( wb) , they decreased tardily with increasing moisture content ( mc) .The isosteric heats of sesame desorption were considerably higher than those of adsorption below 7.5% mc.The heat of vaporization of sesame approached the latent heat of pure water at a moisture content of about 10% wb, which was about 2450kJ /kg.The isosteric heats of black sesame sorption were similar to those of white sesame sorption. The absolutely safe storage moisture content of sesame at 25℃ was 6.46% wb, and the relatively safe mc at 25℃ was 6.94% wb.