Effects of UV-C irradiation and traditional thermal processing on acemannan contained in Aloe vera gel blends

The effects of pH (3.5, 4.5, and 5.5) and UV-C irradiation dose (12.8, 24.2, 35.8, and 54.6 mJ/cm(2)) on the physicochemical properties changes in 10% Aloe vera gel blends; in addition, the acemannan concentration and structural changes in the precipitated polysaccharides were evaluated. A thermal treatment (TT; 45 s at 90 degrees C) was used for comparison. In contrast to TT, a dose of 24.2 mJ/cm(2) did not induce significant changes of free sugar content. Moreover, TT and UV-C irradiation did not significantly affect the content of mannose but increased those of galactose, fructose, and glucose. H-1 NMR analysis revealed minimal changes in the isolated fractions of acemannan, indicating that compared to the unprocessed control sample, the acemannan deacetylation was more pronounced by TT (27%) than by UV-C irradiation (11% at 54.6 mJ/cm(2)), without any significant difference between the two. UV-C irradiation of Aloe vera gel blends at pH 3.5 and 24.2 mJ/cm(2) was an alternative to TT and efficiently preserve the characteristics of acemannan.