The chemical composition and water sorption isotherms of two Omani date 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 had 3.95±0.04% and Fard had 4.44±0.03%. Moisture sorption isotherms conducted at three temperatures displayed a crossing effect due to the dissolution of crystalline sugars at higher temperatures and moisture contents. Modeling with the GAB equation predicted monolayer moisture contents (Xm) 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 as the moisture content changed from 5.0 to 40.0%. Differences in moisture sorption behavior of the two varieties were attributed to compositional differences. Compositional data alone, could not act as a universal moisture sorption model since other complicating factors, such as crystalline sugar dissolution, were involved.
ASJC Scopus subject areas
- Food Science