Abstract:

The changes in the contents of total polyphenols, total flavonoids and total anthocyanins, and radical scavenging
capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide anion free radicals in red raspberry
vinegar produced by submerged fermentation were analyzed during the fermentation process. The results indicated that the
contents of total polyphenols, total flavonoids and total anthocyanins increased first and then decreased. The scavenging
rates of all three kinds of free radicals increased significantly with acetic acid fermentation. After acetic acid fermentation
for 10 days, 68% of the total polyphenols, 85% of the total flavonoids and 38% of the total anthocyanins were retained, and
the scavenging rates of DPPH, hydroxyl and superoxide anion free radicals were 98.63%, 78.36% and 83.82%, respectively.
Our results also showed there were had extremely significant positive correlations among the contents of total polyphenols,
total flavonoids and total anthocyanins, and each of these was highly negative correlated with principal component 1. The
scavenging rates of DPPH, hydroxyl and superoxide anion free radicals also had extremely significant positive correlation
with each other, and each showed a highly positive correlation with principal component 1. In addition, the brewing process
was divided into three clusters by cluster analysis, which represented the changing trend of antioxidant properties at different
fermentationstages.

Key words: red raspberry vinegar, antioxidant properties, radical scavenging rates, principal component analysis, cluster analysis