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Synergistic Effect of Sugars and Phenolics on Antioxidant Activity of Pomegranate Juice

Addition of phenolics for fortification is common way to increase nutritional value and antioxidant activity of fruit products. Sugars are common additives in production of those products. Consequently, influence of phenolics and sugars on anthocyanins and antioxidant activity was investigated. Pomegranate juice samples were prepared with addition of only phenolics (gallic acid, catechin and quercetin ; individually and in combinations), only sugars (sucrose and trehalose) or combination of phenolics and sugars. Control was pomegranate juice without addition of phenolics and sugars. Spectrophotometric methods were used for determination of antioxidative activity and anthocyanins. Sample with addition of trehalose had the same anthocyanin content (172.78 µg/mL) as control sample (172.81 µg/mL) while sample with sucrose addition had lower content (168.08 µg/mL). All samples with addition of phenolics had higher content than control sample. Considering only samples with addition of phenolics, the highest anthocyanin content had samples with addition of gallic acid, catechin+gallic acid and catechin+quercetin+gallic acid. In samples with addition of sugars, the highest anthocyanin content had samples with catechin+quercetin+gallic acid. DPPH, ABTS and FRAP methods were used for determination of antioxidative activity, and on the bases of this results synergistic effect of phenolics addition was determined. Antioxidative activity determined by ABTS was higher in all samples in comparison to control. Synergistic effect was determine in juice with addition of catehin+quercetin and juice with addition of trehalose and catechin+quercetin+gallic acid. Antioxidative activity determined by FRAP was higher or the same as control. Synergistic effect was determine only in juice with trehalose addition with all phenolics combinations. Using DPPH radical for determination of antioxidative activity different results were observed. In comparison to control, lower antioxidant activity was determined in juice with gallic acid, juice with sucrose and catehin + gallic acid and quercetin + gallic acid, juice with trehalose and catechin + quercetin. Synergistic effect was observed only in juice without sugars addition. Results of this study showed importance of interactions between matrix constituents during product formulation thus in some cases there is no positive effect of addition of phenolics.

phenolics; sugars; synergistic effect; pomegranate juice

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