The effect of fermentation conditions on polyphenol content of raspberry wine

Abstract

In the two past decades, there has been a great deal of research on polyphenol compounds and their antioxidant properties. Raspberry as a fruit species is widely grown in Serbia and is well known in the world for its quality. Being very rich in polyphenol compounds, raspberry is a great source of components of excessive biological value. The objective of this study was to investigate influence of temperature, sulfur-dioxide and selected yeast on fermentation of raspberry pulp and the total polyphenol content of raspberry wine. The pulp of Meeker, one of the most abundant varieties of raspberry (Rubus idaeus) in Serbia, was fermented at 15°C and 22°C with and without selected yeast cells, and with and without addition of sulfurdioxide. The total polyphenol content was determined every 24 hours, according to the Folin Ciocalteau method and results were expressed in mg/L gallic acid equivalents (mg GAE/L). The obtained results indicate that fermentation temperature and addition of sulfur-dioxide significantly influence the extraction of phenolic compounds from raspberry pulp, while the addition of selected yeast cells has no influence. Immediately before fermentation, total polyphenol content in the sample was 1415,7 mg GAE/L. After 72 hours of fermentation, the sample fermented at 15°C with addition of sulfur-dioxide and without selected yeast cells reached its maximum value of 2191 mg GAE/L, whereas the same sample fermented at 22°C reached the value of 2820 mg GAE/L. Other samples had lower values then these two. After 96 and 120 hours of fermentation, in all samples total polyphenol content was slightly lower then after 72 hours.