Effects Of Storage Temperature And High Temperature Setrilization On The Physiological Metabolism And Nutritional Quality Of Sweet Potato

As the nutritional value of sweet potato gradually got the attention of experts and consumers, astraditional agricultural products, the sweet potato storage and processing research has importantsignificance on its nutritional value and utilization. In order to discuss the appropriate storage conditionsof sweet potato, this paper studied the the mechanism of physical and chemical composition changeduring the storage temperature and the effect of high temperature sterilization processing on nutritionalquality of sweet potato. The contents are following:At first, we selected four varieties of sweet potato from Zhejiang Province which are commonplanted. These varieties are Bai pi with white flesh, Xin xiang with orange flesh, Zhe B with yellowflesh and Yu zi with purple flesh. According to determine their starch content, reducing sugar, totalphenol content, total flavornoids and antioxidant ability,the results were showed that the total phenoland flavor of Xin xiang and Yu zi are much more than others. There are significant differences amongthe antioxidant abilities in four varieties (P≥0.05). Bai pi has the most percentage of starch and Xinxiang has the least.We choose Xin xiang as test sample because of its good quality in order to discuss the appropriatestorage temperature for sweet potato. The sweet potato were stored in5℃,15℃,25℃, and therespiration rate, conductivity, Pectin metabolism, starch were measured every5days. The resultsindicates that the respiratory intensity and conductivity of sweet potato storage in5℃was restrainedand began rising after5thday. As the result of chilling injury, the pectin metabolism strengthened during10thand25thdays. The condition of25℃sped up the respiratory metabolism of sweet potato and thestarch content decreased dramatically. The15℃is a suitable temperature for sweet potato since theindexes are not fluctuant. By determination of total phenols, flavonoids and DPPH and ABTS radicalclearance and FRAP reducing power found antioxidant indexes such as low temperature storage ofsweet potato after10d, ABTS radical scavenging ability increased, the phenol content.15℃storageof sweet potato at the early stage of the antioxidant capacity is higher than5℃, but after the fall.25℃storage under the total phenol content change "S" shaped. The effect of steam sterilization at100℃,110℃,121℃for appropriate time on the microbialsafety, antioxidant compounds and antioxidant activity of two selected sweet potato varieties wereinvestigated in this study. Antioxidant abilities were tested by2,2-diphenyl-1-picrylhydrazyl (DPPH),2,2’-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid)(ABTS). The ascorbic and β-carotene weremeasured by HPLC. Total phenols content, flavornoids, ascorbic and anthocyanin, β-carotene wereanalyzed for correlation with antioxidant activity. Total phenols were highly corrected with DPPH freeradical scavenging ability, the anthocyanin and β-carotene values poorly corrected with ABTS andFRAP. There are significant differences (P≤0.05) between121℃and other treatments of total phenolsand flavornoids content. Therefore, processing at121℃for20min has positive effects on dietary safety,nutrient value in sweet potato.