Quality Indicators, Nutritional Composition and Antioxidant Activities of Blended Purple Sweet Potato Beverage

The aim of this study was to investigate the quality indicators,component contents and their antioxidant activities of a blended purple sweet potato-apple beverage which was prepared in our laboratory by hydrolyzing purple sweet potato in the presence of α-amylase and glucoamylase and subsequently mixing with apple juice.The soluble solid content and total acid content were no less than 8% and approximately 0.5%,respectively.The anthocyanin content and light transmission were 6.18 mg/100 mL and 43.9%.All microbiological indicators tested met the GB(the Chinese national standard) requirements.The beverage had nice color,good taste and mouth feeling.Twelve free amino acids including five essential amino acids(EAA) were detected with an automatic amino acid analyzer.The contents of total amino acids(TAA) and EAA were 33.68 mg/100 mL and 9.15 mg/100 mL,respectively.Sugar composition and contents were analyzed by high-performance liquid chromatography.The beverage contained 38.94 mg/mL glucose,7.59 mg/mL fructose and 0.84 mg/mL sucrose.The hydroxyl radical scavenging activity of the beverage was 44.79%.The DPPH radical and superoxide anion scavenging activities were 94.49% and 83.02%,respectively.Therefore,this blended beverage has significant antioxidant activity as shown compared with commercial counterparts.