The composition of two varieties of Omani dates, fard and khalas, was determined as maturity progressed. Free sugars and dietary fibre content were examined in detail. High‐performance liquid chromatography (HPLC) of the extracts showed that at the early green stage (Arabic kimri), dates contained small amounts of glucose and fructose. At the intermediate yellow (khalal) and red (rutab) stages, large amounts (500–565 g kg−1 dry weight) of sucrose had accumulated, but no additional glucose or fructose was detected. At the final mature (tamar) stage, all sucrose was converted to glucose and fructose (>800 g kg−1 dry weight). Dietary fibre, determined as non‐starch polysaccharides (NSPs) by gas chromatography (GC), decreased from 250 g kg−1 (kimri) to 50 g kg−1 (tamar) on a dry weight basis. The principal monomers of NSPs were glucose, galactose, xylose, mannose, arabinose and rhamnose. On a dry weight basis, pectin, protein and ash contents decreased as the dates matured. On a fresh weight basis, changes in NSPs, pectin, protein and ash could be attributed to loss of moisture and the accumulation of sucrose initially, or of invert sugar later as maturation progressed. © 1999 Society of Chemical Industry

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The chemical composition, water activity, temperature and equilibrium moisture content (EMC) for 10 selected fruits were determined. Two methods of water sorption modeling, the GAB equation and the artificial neural network (ANN) method, were compared for their ability to predict water sorption behavior. Unlike the GAB equation, which uses only physical data for modeling, the ANN method uses both physical and chemical compositional data to make predictions. The ANN was superior, in most cases, to that of the GAB equation, in predicting EMC. This superiority was due to the availability of the additional chemical compositional 1543 ORDER REPRINTS 1544MYHARA AND SABLANI information. The ANN method could predict EMC with a mean relative error of 9.85% and a standard error (S x ) of 1.59% EMC. The correlation coefficient (r 2 ) of the relationship between the actual and predicted values of equilibrium moisture content obtained by the ANN was 0.9938. The ANN model was able to show a temperature dependent crossing of water sorption isotherms, due to the dissolution of sugar crystals in the fruit. The ANN was also able to predict the extent of crossing, depending upon differences in the individual fruit chemical composition.