| The shaddock peel is rich in polysaccharide such as pectin. It was used as the main raw material in this research to study the extraction process, structure, physical and chemical properties of its water-soluble polysaccharide. This research was not only of theoretical value, but also provided a new way to produce safe and green new additives which had high antioxidant activity as well as high processing properties by using the shaddock peel which was abandoned massively nowadays.Physical and chemical analysis showed that the main components of the shaddock peel is dietary fiber, in which insoluble dietary fiber accounted for 44.37% and water-soluble dietary fiber 40.24%, followed by water accounted for 8.61%. Other ingredients were: crude protein 3.69%, lipid 0.11%, ash 2.52%. According to the results of single factor experiment, an orthogonal experiment with four factors and three levels was designed to sift out the optimized extraction conditions. The results showed that the subsequence of the four factors on the influence of extraction was: extraction temperature>pH>liquid-solid ratio>extraction time. The optimized extraction conditions were as follows: pH 4, liquid-solid ratio 20:1, temperature 121℃, time 90min. The yield of water-soluble polysaccharide was 21.4% under the optimum condition.The water-soluble polysaccharides extracting from the shaddock peel were purified by passing through the DEAE fiber ion-exchange column, two components A and B were got. The gel chromatography method was used to determine the molecular weight of the components A and B, results were as follows: component A has a relatively small molecular weight at 19097 Da, and two peaks appeared in the HPGPC map of component B, the molecular weight of the corresponding two peaks varied a lot, which were 98438 Da and 12609 Da , respectively. FI-TR results of these two components showed that they both had the characteristic peak of mannose at 890-810 cm-1, which indicated that the polysaccharides extracted from the shaddock peel were a kind of acidic polysaccharide, similar to pectin polysaccharide.Methods like ORAC, DPPH, PAPG auto-oxidation and reduction power assays were used to determine the antioxidant capability and reducing power of water-soluble polysaccharides extracted from the shaddock peel and their components. Results showed that the water-soluble polysaccharide and component A had certain antioxidant capability and reductive capability, which both increased with increasing concentration. When the concentration of the water-soluble polysaccharide and component A were 0.6mg/ml, the value of ORAC were 156.98μmol TE/L and 183.54μmol TE/L separately, the DPPH scavenging activity were 43.67% and 57.15% separately. However, component B had relatively lower antioxidant activity and reducing power. When the concentration of the component B was 7mg/ml, the value of ORAC was only 81.9μmol TE/L. When the concentration of the component B was 0.6mg/ml, the DPPH scavenging activity was only 1.1%.Physical and chemical analysis of water-soluble polysaccharides extracted from the shaddock peel showed that they had good emulsification activity and emulsion stability. In the testing range, their best emulsification activity was achieved in the pH of 7, and the emulsion stability lowered with the increase of pH, emulsion stability stood at 85.24% in the pH of 7. The viscosities of water-soluble polysaccharides solutions increased with the increasing concentration of the solutions. And solutions whose concentration ranging from 2-10% showed typical Newton fluid characteristics, with the rise of pH, their viscosities rise slowly, and tend to become stable when the pH reached 7. The viscosities of water-soluble polysaccharides solutions were not sensitive to the electrolyte, and different additive amount of NaCl had little influence on the viscosity of the water-soluble polysaccharides solutions. |
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