The Composition and Utilization of Shoot Tips of Sweet Potatoes for Starch Purpose

The optimal conditions for extracting protein from the shoot tips of sweet potatoes are systematically screened and the nutrient compositions in the shoot tips of sweet potatoes for starch purpose and those for vegetable purpose are compared. As the results show, when the shoot tips of fresh sweet potatoes were stirred in 0.1% NaHSO₃ solution of 2 times volume at 30 ℃ for 30 min, the extraction rate for water-soluble protein was 52%; under these conditions, when papain was added and the mixture was hydrolyzed at 50 ℃ for 4 h, the extraction rate for water-soluble protein was increased to 75% and the proteolysis degree of shoot tips was 24.8%. With this method, the content of protein, free amino acid and flavonoids in the shoot tip powder were 24.19%, 5.41% and 3.31%, respectively. There was no significant difference in these aspects between the products prepared from the shoot tips of sweet potatoes for vegetable purpose and those for starch purpose. This study has opened up a feasible way for using the sweet potato shoot tips abandoned in the field.