For the development of a new process which minimize the degradation of bioactive components from Aloe vera gel, the optimization of DIS (dewatering & impregnation soaking) process were investigated using Taguchi’s approach. The physicochemical and in vitro physiological characterization of DIS products and their active constituents were also carried out.
Each level of three variables of soaking temperature, concentration of trehalose and immersion time was 3 levels, and L9(33) orthogonal array was designed by Taguchi method. Water loss(WL) and solid gains(SG) were measured as the objective functions.
The optimal setting for maximum WL/SG was obtained at temperature of 45℃, time of 2 hr and concentration of 30%. Kinetics constants of mass transfer (kw, ks1, ks2) of WL and SG were 0.25 hr-1/2, 1.482 hr-1/2 and -0.073 hr-1/2, respectively. This means that mass transfer mechanisms of WL and SG are different and that solvent passes through the permeable membrane to the trehalose solution.
Under optimum condition, the maximum water loss and minimum solid gain was 42.8 and 7.8%, respectively.
Glucomannan and o-acetyl levels of DIS aloe obtained by optimized DIS process were higher than those of fresh aloe. Results of rehydration of DIS aloe samples at 25, 60 and 90℃ also showed that the bioactive polysaccharide level and surface structure from native Aloe vera gel were maintained. These results indicated that DIS process was relatively suitable for minimally processed product from Aloe vera.
Results of 1H-NMR, FT-IR spectra and TGA analysis for DIS aloes showed the characteristic patterns of typical polysaccharide. Surface structure of DIS aloe by SEM were similar to gel-like structure, while surface structure of standard aloe polysaccharide showed fiber-like structure.
For physiological function of DIS aloe, glucose/bile acid entrapment activity were investigated and compared with fresh aloe. Glucose dialysis retardation index (GDRI) percentage of DIS aloe showed 59-38% after 2 hr of the dialysis, indicating excellent effect comparing with fresh aloe (36-19%). Similarly, bile acid retardation index (BDRI) percentage of DIS aloes shoed 66-84%, which were relatively high comparing with fresh aloe (76-92%)..
FT-IR spectra, polysaccharide content and %APS/insolubility of deacetylated aloe were investigated because importance of acetylation in aloe polysaccharide. Swelling, water absorption and solubility index of deaceylated aloe were lower than native aloe. In addition, deacetylated aloe showed the different characteristic patterns of typical polysaccharide. This means that deacetylated aloe loose the characteristic of native aloe polysaccharide.