Determination of color stability of red beet juice concentrate stored at different temperatures

In this study, the changes in bioactive compounds (betalain content, total phenolics), antioxidant activities and visual colour parametrers of red beet juice concentrate stored at different temperatures and times has been investigated. For this purpose, red beet juice concentrates were stored at glass jars with and without aluminium foil. The initial betacyanin,betaxanthin, total phenolics contents and antioxidant capacity were found as 1179 mg/L, 883 mg/L, 4332 mg/100 mL and 151 µM/100 mL, respectively. It was determined that betacyanin and betaxanthin contents of red beet juice concentrate degraded with increasing storage temperature and time and this degradation followed a first-order reaction model. Activation energies for betacyanin degradation in samples stored at glass jars with and without aluminium foils were calculated as 65 J mol-1 and 90 J mol-1, respectively. The activation energy for betaxanthin degradation in both samples was found as 91 J mol-1. Total phenolics of red beet juice concentrate stored at different storage temperatures and times increased a compared to a zero-order reaction kinetics. Activation energies for the increase in total phenolics content of samples with and without alüminium foil were detected as 72 J mol-1 and 78 J mol-1, respectively.The increase in L*, C* and b* color parameters and antioxidant activites of red beet juice concentrate and the decrease in +a* parameter obeyed a zero-order reaction kinetics. On the other hand, any significant change was observed in Hue (h value).