Effect of different drying procedures on the bioactive polysaccharide acemannan from Aloe vera (Aloe barbadensis Miller)

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. All the drying procedures caused a considerable decrease in the acemannan yield (∼40%). 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. In addition, methylation analysis suggested the deacetylation of mannose units (>60%), which was confirmed by 1H NMR analysis. Interestingly, all these changes were reflected in the functional properties which were severely affected. 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. 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.