Therefore, these important modifications should be taken into consideration, since not only the functionality but also the physiological effects attributed to many Aloe vera-based products could also be affected.Ī B S T R A C T The aim of this study was to evaluate the effect of water deficit on the composition of the main polysaccharides and rheological behaviour from Aloe vera (Aloe barbadensis Miller) mucilage. Thus, water retention capacity values from processed samples decreased ∼50%, and a reduction greater than 80% was determined in swelling and fat adsorption capacity values. Interestingly, all these changes were reflected in the functional properties which were severely affected. In addition, methylation analysis suggested the deacetyla-tion of mannose units (>60%), which was confirmed by 1 H NMR analysis. Degradation affected not only the backbone, as indicated by the important losses of (1 → 4)-linked mannose units, but also the side-chains formed by galactose. All the drying procedures caused a considerable decrease in the acemannan yield (∼40%). The main effects of different drying procedures: spray-, industrial freeze-, refractance window-and radiant zone-drying, on acemannan, the main bioactive polysaccharide from Aloe vera gel, were investigated. These important changes in the physico-chemical properties and, also, in the flow behavior of the dehydrated Aloe vera samples could be related to structural modifications observed for the acemannan polymer, the main bioactive polymer present in Aloe vera gel and in particular, to the modification of its degree of acetylation. Interestingly, the viscosity of all the processed samples exhibited a higher temperature dependence (E a > 28 kJ/mol) than the reference sample (E a ¼ 21 kJ/mol).
Moreover, a shear-thinning behavior, exhibited by the fresh Aloe vera gel, was modified to a Newtonian behavior in all the processed samples. All processed samples exhibited lower water activity (90%) and higher hygroscopy (>80%) than the reference sample. In addition, fresh Aloe vera gel was lyophilized and used as a reference.
Further, the flow behavior of all dehydrated Aloe vera samples was investigated at different temperatures (10, 20, 30, 40, and 50 C). The drying methods applied were: spray-drying, industrial freeze-drying, refractance-window-drying and radiant-zone-drying.
The main aim of this study was to evaluate the effect of different drying procedures, used at industrial scale, on physicochemical properties, such as water activity, solubility, hygroscopy and, also, on the flow behavior of Aloe vera (Aloe barbadensis Miller) gel.
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