Determination and comparison of the total polyphenol contents of fresh and commercial fruit juices

Purpose – This paper aims to study the importance of polyphenols in human health and, based on recommendations on the replacement of carbonated drinks with nutritious beverages, like fruit juices, seeks to compare the polyphenol contents of natural and commercial juices. Design/methodology/approach – The total polypheol content of 39 fresh and 159 commercial (100 percent and less than 50 percent) fruit juices was analyzed by the terbium sensitized fluorescence method. The ANOVA with Tukey post hoc test, and also an independent t-test, were used for statistical analyses. Findings – The mean polyphenol contents of fresh juices were significantly (p<0.001) higher than those of 100 percent commercials (5.34±2.7 vs 3.28±0.86 mg/l). In fresh juices the concentration ranged from 1.06±0.08 (pineapple) to 10.14±0.07 (sour cherry) mg QE/100 ml, while in 100 percent commercial juices the range was from 2.37±0.05 (orange) to 5.34±0.4 (pomegranate) mg QE/100 ml, and in <50 percent commercial juices they ranged from 1.04±0.7 (red grape) to 2.21±0.07 (white grape) mg QE/100 ml. The polyphenol contents of dark juices, in both fresh and commercial products, were significantly higher than others (p<0.001) and most fresh fruit juices possessed higher amounts of polyphenol than commercial ones. Although various juices differed in the quantity of total polyphenol, they can be considered as a good source of functional beverage. Originality/value – This paper provides information about the polyphenol content of fresh and commercial (100 percent and <50 percent) fruit juices. To the best of the authors' knowledge, there have been no articles which aim to compare the polyphenol content of Iranian fresh and commercial fruit juices. For analysing the polyphenol contents, the newly developed terbium sensitized fluorescence method was used, and also the applicability of this new method was compared with the commonly used Folin-Ciocalteau method.