Extraction And Properties Study Of Pectin From Jerusalem Artichoke Residues

Jerusalem artichoke, widely cultivated in northern China, is a flower plant of the family helianthus. Compared with other crops, Jerusalem artichoke can grow well in arid soil and salina land and resist many plant pests and diseases. It is productive and nutritious, and tubers contain about 12~20% inulin, a certain amount of protein, pectin and cellulose. Now Jerusalem artichoke tubers are mainly used to produce inulin. Therefore, a large amount of by-products are produced. These by-products are mainly used as feed after simple process or treated directly as litter. Preliminary experiments indicated that Jerusalem artichoke residues contained about 15% pectin on dry weight basis. If these residues can be utilized to produce pectin, the added value of Jerusalem artichoke industry will be larger. Pectin is an natural high molecular weight polysaccharide of the cell walls in all land plants. The dominant structural feature of pectin is a linear 1â†'4-linked chain of poly-α-D-galacturonic acid and neutral sugars, such as L-rhamnose, L-arabinose, and D-galactose. It is widely used as stabilizing, thickening, emulsifying and gelling agents in food industries. What’s more, pectin is also used in medicine industry, and it has several biological and physiological functions, such as reduction of cholesterol levels and cancer incidence. Now most pectin is prepared from citrus peel and apple pomace. Jerusalem artichoke residues was used to extract pectin and the contents of this thesis are as follows: 1 Jerusalem artichoke residues were obtained after pretreatment, and the content of the main components of Jerusalem artichoke residues were analyzed. 2 Different solvents(hydrochloric acid, sulfuric acid, sulphurous acid and phosphoric acid) were compared on the yield of pectin. Results have shown that the effect of phosphoric acid extraction was the best. Based on single factor experiments, Box-Behnken Design was used to study and optimize the effects of processing variables on the yield of pectin. Under the optimal extraction conditions: pH 1.52, 63.62 min, 100 ℃and a liquid-to-solid ratio of 44.4 m L/g, the maximum pectin yield was up to 18.76%. 3 Effects of different drying methods(freeze drying, spray drying and vacuum drying) on the properties of Jerusalem artichoke pectin were evaluated and they were compared with apple pectin. â… .FTIR spectral analysis showed no major structural differences in Jerusalem artichoke pectin samples produced by various drying treatments; â…¡.The antioxidant activity of pectin dried by different methods was investigated in hydroxyl and DPPH radical scavenging systems in vitro. The results revealed that activities of spay dried pectin(SDP) and apple pectin(AP) were stronger than those of vacuum oven dried pectin(ODP) and vacuum freeze dried pectin(FDP); â…¢.The result of the solubility of pectin dried by different methods was: SDP>FDP>AP>ODP; â…£The DE of Jerusalem artichoke pectin was 55.96% and it was HMP. Drying methods had no significant difference on DE and pectin yield, while they had significant effect on the content of galacturonic acid, water and ash. 4 The results of experiments on rheological property of Jerusalem artichoke pectin showed that: â… The viscosity increased with the increasing of concentration and the viscosity of apple pectin solution is bigger than Jerusalem artichoke pectin solution. â…¡These two pectin solutions’ viscosity were both affected by temperature, when processing temperature rise to 90℃ above, the viscosity was very low, and pectin tended to Newton fluid. â…¢ Effects of pH on the viscosities of the two pectin solutions were consistent, the apparent viscosities were bigger under weakly acidic conditions. While pectin viscosity gradually reduced with the increase of acid concentration or alkali concentration. â…£ The adding of sugar could improve the apparent viscosities of pectin solutions, and the apparent viscosities were proportional to the concentration of sugar. â…¤ Effects of Ca2+on the viscosities of the two pectin solutions were slight, and the viscosities increased with the increasing concentration of Ca2+.