CHARACTERIZATION OF ALOE-VERA GEL BEFORE AND AFTER AUTODEGRADATION, AND STABILIZATION OF THE NATURAL FRESH GEL

The polysaccharides present in Aloe vera gel are presumed to play a key role in the clinical activity of the gel. While clinical studies generally confirm the contribution of the gel to a reduction in inflammation and an acceleration of healing, in some cases the expected therapeutic activity is not observed. This variability could perhaps be attributed to differences in the source of the gel, horticultural conditions and/or post-harvest treatments. Accordingly, polysaccharide content and composition and gel consistency were studied as a function of growth conditions in gels obtained from shrubs of Aloe barbadensis Miller grown in the Negev region of Israel. Autodegradation of the polysaccharides in the freshly produced gel was also characterized, and a method was developed for retarding this process. The polysaccharides were found to consist of glucomannans. Polysaccharides constituted 0.2-0.3% of the fresh gel and 0.8-1.2% of the dry matter content. Irrigation had a greater influence on gel composition than leaf age or season. The fresh gel showed pseudoplastic behaviour, which became Newtonian as a result of post-production autodegradation. The polysaccharides remaining after degradation were mainly mannans. Addition of a natural polysaccharide extracted from a species of red microalgae produced a soft pseudoplastic gel with synergistic rheological properties. The addition of the algal polysaccharide preserved the physical properties of the natural aloe polysaccharides. Chemical means were used to retard microbial degradation.