Abstract:

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.
Key words：blend purple sweet potato-apple beverage；quality indicators；free amino acid composition；sugar
composition；antioxidant activity

Key words: blend purple sweet potato-apple beverage, quality indicators, free amino acid composition, sugar composition, antioxidant activity