The effect of tannin addition and storage temperature on phenolic compounds and color stability of shalgam juice

In this study, color stabilization of shalgam beverage during storage by preventing phenolic component losses was aimed. For this purpose, shalgam juices were produced using traditional production method. Tannin was added at three different concentrations (300 mg/L, 600 mg/L and 900 mg/L) at the beginning of the second fermentation (black carrot fermentation). Shalgam juices produced were stored at two different temperatures (4 °C and 20 °C) for six months and the effect of storage duration and temperature on colour properties of shalgam was investigated. The total acidity values (expressed as lactic acid) of shalgam juices produced with the addition of different amounts of tannins varied between 7.09-7.87 g/L. At the end of the six-month storage period, a positive correlation was determined between the amount of added tannin and the total amount of monomeric anthocyanin. It means that copigmentation occured between tannins and anthocyanin compounds. In comparison to the initial value, losses of total phenolic substances were higher in control group than the all tannin added shalgams at the end of the six month storage. The shalgam produced by the addition of 600 mg/L tannin has the closest color to its original color and its polymeric color ratio was determined as % 28.13. When the different storage temperatures were compared, it was determined that the loss ratio of phenolic compounds and anthocyanins of shalgam beverage increased with the increment of storage temperature. The redness value (+a*), which is the distinctive color of shalgam beverage, was found to be lower in control sample than tannin added samples at both storage temperatures. According to the sensory results, the shalgam produced with the addition of 600 mg/L tannin has the highest scores in all properties tested. In addition, this shalgam sample was preferred in the first rank by 8 out of 11 panelists through preference test.