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Influence of temperature and ultrasound on content of phenolics and antioxidative activity of aronia juice

The aim of this work was to determine influence of temperature and ultrasound on content of phenolics and antioxidative activity in aronia juice. Also influence of sugar (sucrose or trehalose) addition was investigated. Sugars were added in amount of 10%. Phenolics, flavonoids, anthocyanins and antioxidative activity was determined in the samples after treatment of samples at 20, 40 and 80 °C for 30 minutes and after treatment of samples with ultrasound at 20, 40 and 80 °C for 30 minutes. Results were compared to the control sample, the sample without addition of sugars. With increasing temperature and using ultrasound, content of phenolics in the control sample and the sample with sucrose addition was lower in comparison to the sample with trehalose addition. Those results are confirming protective role of the trehalose on the phenolics during treating of the aronia juice with high temperature comparing to the sample with sucrose addition. Regarding flavonoids content lower values were determined with the increase of temperature and using the ultrasound in all samples. It is well known that anthocyanins are very unstable pigments and lots of efforts are made to achieve their stability during processing and storage. They are very sensitive to the high temperature and they easily degrade, what was also proven in our study. The samples with the addition of the trehalose had higher anthocyanin content with increase of temperature treatments than control sample or the sample with the addition of the sucrose. Ultrasound treatment showed positive effect on anthocyanins content at 20 °C in all samples. However, with increase of temperature there was no positive effect of ultrasound treatment or sugar addition on anthocyanin stability in aronia juice. Antioxidative activity was measured with DPPH, ABTS and FRAP methods. Comparing the results which were given with application of those three methods, the highest antioxidative activity was given using ABTS method.

aronia juice; phenolics; anthocyanins; antioxidative activity; ultrasound; temperature

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