Study On Sweet Potato Pectin’s Preparation By Extracts Of Enzyme And Its Quality Analysis

Sweet potato residues can be used as fine raw materials for extracting pectin since it contains rich pectin, which accounts for about20%～30%of the weight of it. In this paper, the main factors affecting extraction, purification of sweet potato pectin by enzyme method were discussed and verified, and the optimum conditions for extraction, purification were confirmed. Then combined with the optimum extraction parameters of acid method reported in the literature, two kinds of sweet potato pectin were prepared by the enzyme method and the acid method, respectively. Also, a comparison was made to evaluate their qualities. The results are as follows.Sweet potato residues was used as raw material.1:1mix of compound enzymes from hemicellulase and cellulase were used in the experiment; the important factors including temperature, pH value, solid-liquid ratio, enzyme quantity and extraction time, which affecter pectin-yield were conducted. On this basis, the effects of temperature, pH value, solid-liquid ratio and extraction time on pectin yield were investigated by central composite design experiment, the acquired and verified optimal extraction conditions were:temperature50℃, pH value5.2, solid-liquid ratio11:1, enzyme quantity0.6%and extraction time5.2h. Based on the results of orthogonal design test on pectin yield, the selected optimal purification conditions were:cycles of concentration1/4, the concentration of ethanol80%, washing times1. Under this optimal condition, the yield of pectin was17.3%and the galacturonic acid content was80.0%.According to the optimum preparation conditions of sweet potato pectin by enzyme method and combined with the optimum extraction parameters of acid method reported in the literature, two kinds of sweet potato pectin were prepared by enzyme method and acid method, respectively. The pectin yield extracted by enzyme method (17.4%) was higher than that of acid extraction (10.0%). And it’s molecular weight and gel strength were171.6kDa and202.6g/cm2, were lower than the pectin prepared by acid method (293.5kDa and288.1g/cm, respectively). What’s more, the pectin etherification degree (55.2%) extracted by enzyme was lower than that of acid extraction (60.0%). The enzyme extraction showed a higher galacturonic acid content (80.1%) and the neutral sugar content (26.7%) than acid method (73.1%and23.5%, respectively).