Candied Orange Peel Produced in Solutions with Various Sugar Compositions: Sugar Composition and Sorption Properties of the Product

摘要

This study investigated the relationships between equilibrium water content and water activity for candied orange peel produced by saturation in sucrose-based and glucose-fructose syrups, and for native orange peel. Dry matter loss due to candying was found to be the highest for glucose-fructose syrup dehydrated products. The greatest amount of sugars was absorbed by products candied in sucrose syrup. The sorption isotherms of candied orange peel corresponded with type III isotherms, according to Brunauer's et al. classification, whereas the sorption isotherm of native orange peel displayed a sigmoidal shape characteristic for type II isotherm. For products owing the highest sucrose content (above 40%), the sorption isotherms showed a discontinuity in the water activity range of 0.3-0.4. The results demonstrated that the sorption properties of the studied products depend on the levels of individual sugars they contain. Principal component analysis revealed marked differences between candied and native peel and between products candied in sucrose syrup and those prepared in glucose-fructose syrup. Seven most popular models used for describing the sorption process of foods were examined. Among those, the Lewicki model appeared to best describe the experimental data. The Peleg model was well fitted into the data for candied orange peel in the limited range of water activity (up to 0.86).