The Influence of Sugar Addition on Stability of Phenolics, Flavonoids, Anthocyanins and Antioxidant Activity in Red Grape Juice

Stability of phenolics, flavonoids, anthocyanins, and antioxidant activity in red grape juice and red grape juice with addition of sucrose, trehalose, glucose and fructose (5, 10 and 15 %) during storage of 3 weeks at 4 degrees C was investigated. Antioxidant activity was determined by FRAP and DPPH methods. Results showed that type of sugar and its concentration had, in juice samples more or less, influence on all investigated parameters. The highest retention of total phenolics was in grape juice with an addition of 15 % sucrose (89.3 %) and 15 % fructose (88.7 %). The highest amount (15 %) of all added sugars caused the highest retention of total flavonoids (23.5-24.7 %). The highest retention of anthocyanins were in grape juice with an addition of 15 %,of trehalose (57.6 %) and 15 % glucose (51.51 %). Antioxidant activity, regardless of used method for determination (FRAP and DPPH), after one week of storage increased in all investigated samples. Antioxidant activity started to decrease after two weeks. After storage of 3 weeks the highest retention (80 %) was detected in the juice sample with an addition of 15 % of glucose measured by FRAP method, than in the sample with an addition of 15 % of trehalose measured by DPPH (24.3 %).