Water Vapour Desorption of Deglet Noor and Alig Dates
A. Nabili, H. Bouabidn, M. Trifi and M. Marrakchi
Book of Abstract. Information & technology for sustainable fruit & vegetable production, The 7th Fruit, Nut and Vegetable Production Engineering Symposium, 12-16 September 2005, Monpellier, France. Page 36
2005
บทคัดย่อ
Desorption isotherms at 5, 30 and 40°C were determined gravimetrically for Deglet Noor and Alig dates. The products have been hydrated then equilibrated over saturated salt solutions in the range of relative humidity from 11 to 92 %; 21 days were necessary to reach the thermodynamical equilibrium. Deglet Noor and Alig dates exhibited S-shaped isotherms witch departed from each other and the discrepancy got more pronounced with decreasing temperature and increasing relative humidity. The Guggenheim-Anderson-de Boer equation (GAB), regressed using indirect non-linear regression method, described the sorption behaviour satisfactorily. Estimated GABparameters and constants were in good agreement with what the model dictates ad with literature. Critical moisture content was estimated to be 28.3 and 5.5 % dry basis at 5°C for Deglet Noor and Alig dates respectively. These values are smaller than what the FAO/OMS Codex Alimentarus onU-DF-08 imposes for commercial whole dates. Heat of desorption estimated using the Clasius-Clapeyron equation was 68.87 and 62.66 Kjmol-1 for Deglet Noor and Alig dales, respectively.