Technological Studies On Jujube Juice Extracting From Chinese Jujube With Enzyme Treatments

In this paper, the measures for extracting jujube juice with enzymes were studied, and the comparisons between the enzyme methods and hot water method have been made. Some factors influencing the extraction efficiency and the clarification results were analyzed systematically. The extraction and clarification conditions were optimized.The experiments results showed that the optimal extraction conditions with hot water were that the rate added water to jujube pulp was 5 to 1, the incubation temperature and time was 75* and 8h separately, the jujube sugar extraction efficiency was35.16% account for jujube pulp weight, the vitamin C content in extracted juice was 13.12mg/100ml, the solid material was 7%. The optimal extraction conditions with pectinase were that the added pectinase should be 0.25% account for jujube pulp, and the water used in extraction should be 5 times of jujube pulp, the extraction should be performed at 50* of incubation temperature for 4h, the extraction efficiency of jujube sugar was 43.62% account for the weight of jujube pulp.The effects of incubation temperature, time and pH value on the extraction efficiency of mixed enzyme methods were studied by means of the methods of orthogonal experiments, after that, a current, rotational and combination design of quadratic regression method was used and the results showed that the optimized conditions should be performed at 50℃ of incubation temperature for 4h at pH 4, the sugar extraction efficiency was 47.12% account for the weight of jujube pulp, vitamin C content was 19.34 mg/100ml, solid materials was 11%. The extracts was bright and possessed strong jujube smell and good taste. The extraction efficiency under the enzyme treatments was higher than that under the hot water treatment.The experiment results also showed that clarified juice had the maximal transmittance at 620nm , and the low temperature method for clarification was better for nutrients preservation, the total sugar remains was 97.35%, Vc remains was 94.51%, and its transmittance was 91.1%. Adding 4% of gelatin and treated for 4h, the nutrients in jujube juice were destroyed at large extent, and the transmittance of the jujube juicereached 93.8%, the total sugar lost 9.02%, the solid materials lost 11.96%, Vc lost 3.82mg/100ml and the total acids lost 2.22%. Although the transmittance of the clarified jujube juice with honey can only reach 90.4%, the preservation of juice nutrients were very good. When the clarification was done with 0.1% of pectinase at 50℃ and pH 3.5, the transmittance of the jujube juice was higher. The results indicated that the effect of chitosan for clarification was the best, the transmittance of the jujube juice reached 98.8%, the total sugar content was similar to that of untreated juice , the solid materials and Vc lost little more than that of untreated juice, the optimal conditions for chitosan clarification were adding 3% chitosan at 45℃ and pH 3.5 .The transmittance of the clarified juice keeped the same after storing for 7 months at low temperature, but a remarkable decreasing trend was appeared after 3 months' storage at ambient temperature. The destructing degree of Vc was much smaller at low temperature than at ambient temperature. The clarified juice treated with chitosan has little sediment at low temperature during the storage period.