A rapid method for quantitative determination of beta-carotene, including cis-isomers, in dried mango has been developed. Applicability of available methods to dried products was limited because of formation of artifacts caused by extraction and preparation. The analytical procedure was based on the extraction of carotenoids from dried mango mesocarp using a mixture of methanol and acetone/hexane, allowing the separation of disturbing fibers. No saponification was required. Furthermore, carotenoid determination by HPLC on a C30 stationary phase was achieved. This method was applied to determine beta-carotene and its stereoisomers in fresh, dried, and solar-dried mango slices of four cultivars. Drying resulted in a complete and partial degradation of xanthophylls and all-trans-beta-carotene, respectively. Isomerization was shown to depend on the drying process. Whereas conventionally dried mangoes were characterized by elevated amounts of 13-cis-beta-carotene, solar-dried mango slices contained additional amounts of the 9-cis-isomer. Calculation of vitamin A values was based on the real amount of the beta-carotene stereoisomers and ranged from 113 to 420 and from 425 to 1010 RE/100 g for fresh and dried mango slices, respectively.

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The equilibrium moisture contents of longan were determined experimentally using the dynamic method at temperatures ranging from 30 to 50 C and water activity ranging from 11 to 97%. The sorption isotherm curves of longan were sigmoidal in shape and decreased with increased temperature at constant relative humidity.Five selected isotherm models were tested to fit the experimental isotherm data of longan. The GAB model fitted the best to the experimental data of longan and the modified Oswin model was the next to the GAB model. The agreement between the best-fitted models and experimental data was excellent. The isosteric heats of sorption, determined from equilibrium data using the ClausiusClapeyron equation, were found to be a function of moisture content.

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