Abstract:

Anthocyanins were extracted from purple sweet potato (Ipomoea batatas) using an environmentally friendly
process. The anthocyanins exhibited characteristic absorption peak at 530 nm, having a molecular weight in the range of
850?1 020 u. The content of vitamin C in Valencia orange and tomato was determined by a new titration method using the
anthocyanins extracted from purple sweet potato in place of 2,6-dichloroindophenol as described in the Chinese national
standard GB/T 6195－1986. The results showed that vitamin C was (25.33 ± 0.34) mg/100 g in Valencia orange and (20.41 ±
0.32) mg/100 g in tomato. The spiked recoveries of VC with purple sweet potato anthocyanins ranged from 95.4% to 98.6%,
with relative standard deviation (RSD) of 1.18%?1.22%, while those with 2,6-dichloroindophenol titration were between
96.5% and 98.7% with RSD of 0.86%?0.88%. The anthocyanin titration method was safe and low-cost with an accuracy
equivalent to that of 2,6-dichloro-indophenol titration.

Key words: Ipomoea batatas, anthocyanins, GB/T 6195－1986, 2,6-dichloroindophenol, vitamin C