MOISTURE SORPTION ISOTHERMS AND CHEMICAL-COMPOSITION OF OMANI DATES

The chemical composition and water sorption isotherms of two Omani dat e varieties, Fard and Khalas, were determined. Compositional analysis showed that Khalas contained more glucose (44.69 +/- 0.04%) than Fard (43.55 +/- 0.70%), but less non-starch polysaccharide (NSP). Khalas ha d 3.95 +/- 0.04% and Fard had 4.44 +/- 0.03%. Moisture sorption isothe rms conducted at three temperatures displayed a crossing effect due to the dissolution of crystalline sugars at higher temperatures and mois ture contents. Modeling with the GAB equation predicted monolayer mois ture contents (X-m) of 13.9% for Fard and 14.4% for Khalas. Isosteric heat of sorption, for both varieties, varied from 9.4 to -1.6 kJ/mol a s the moisture content changed from 5.0 to 40.0%. Differences in. mois ture sorption behavior of the two varieties were attributed to composi tional differences. Compositional data alone, could not act as a unive rsal moisture sorption model since other complicating factors, such as crystalline sugar dissolution, were involved. (C) 1998 Elsevier Scien ce Limited. All rights reserved.