| Pears are widely planted in China, and because of their rich nutrient and the special healthcare functions. They are the favorite of people. Pears have the function of moistening lung and relieving cough, discharging fire and expelling of toxin, and oxidation resistance. The fresh pears are the main raw material of this study accompanied by the homology of medicine and food, that is, lily and pericarpium critri reticulatae to make pear tea. This paper studied the choice of the variety of raw materials, browning, and the quality of condensed juice, gave sensory evaluation and analysis of the oxidation resistance of the products. The main findings of this study were illustrated in the following.1. This study chose the five kinds of representative pears:Yuluxiang, Hebei snowflake, Laiyang pear, Su pear and Gaoping yellow pear. The chapter analyzed the quality and characteristics of different kinds of pears from the aspect of juice yield, soluble solids, browning, total titratable acidity, reducing sugar and polyphenols and selected the raw material of pulp and concentrated pear juice. The findings showed that the taste of Hebei snowflake was the best among the five kinds of pears and they can be the raw materials of pulp. The taste of Gaoping yellow pear was not as good as that of Hebei snowflake, but the number of their soluble solids was 13.0° Brix, the degree of browning 0.575, total titratable acidity 2.96g/L, reducing sugar 92.87g/L, polyphenols 275.7μg/mL. All the figures showed that the quality and characteristics of Gaoping yellow pear was best and therefore it was the raw material of making concentrated pear juice.2. The paper used Gaoping yellow pears as the raw materials to make juice, degree of browning as the index, to analyze the influence of ascorbic acid, citric acid and sodium bisulfite under different concentration on the colour of juice, and decided the optimum color-protecting parameters based on the orthogonal test of three factors and three levels. The results showed that used 0.09 percent of ascorbic acid,0.5 percent of citric acid and 0.02 percent of sodium bisulfite before sequeezing juice to protect the color of pears can produce the best result.3. This study did vacuum evaporated to juice of the Gaoping yellow pears, using degree of browning, total titratable acidity, reducing sugar and polyphenols as the index, to explore the influence of different temperature and sugar content on the quality of condensed juice. The findings showed that the quality of the juice changed gradually with different temperature and sugar content. With the gradual increase of the concentration temperature, the color of condensed juice was gradually deeper and the content of polyphenols and titratable acidity was increased, but the content of reducing sugar decreases gradually. However, with the increase of the sugar content, the color of juice became deeper and the content of polyphenols was decreased, other indexes tended to increase.4. Based on the single factor experiment, the chapter made orthogonal process optimization to illustrate the processing conditions of pear tea, and measured the reductive ability, DPPH free radical scavenging activity and hydroxyl free radical scavenging activity of the products. The results of experiment indicated that in the process of making pear tea,400g pulp (360g pears, lily and pericarpium citri reticulatae,20g) soaked in the middle of 100g pears pureed; 24g siraitia grosvenorii and chrysanthemum were contained pear pureed, sugar 25g, and citric acid 0.2g, honey 6g, the rest of 70° Brix of pear pureed. The fruit tea not only had beautiful color, but also good taste. The tea had stronger reduction, DPPH free radical scavenging and hydroxyl free radical (·OH) scavenging activity. |
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