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FREE RADICAL SCAVENGING ACTIVITY AND PHENOLIC CONTENT IN STRAWBERRY FRUIT AND JAMS

Fresh fruit of three strawberry cultivars Fragaria ananassa × Duch. (cvs. Clery, Honeoye and NF 421 (Asia)) were investigated and used to produce jams. Produced jams were analyzed before and after dark storage at 20 °C, for 6 months. The aim of this investigation was to characterize all the samples in relation to the total phenolics, flavonoids, nonflavonoids, total anthocyanins and antioxidant activity. The content of total phenolics, flavonoids and nonflavonoids were determined according to the Folin-Ciocalteu assay. Anthocyanins were determined by spectral method based on the bisulfite bleaching of monomeric anthocyanins. The antioxidant activity was evaluated by 2, 2-diphenyl-1-picrylhydrazil radical (DPPH۰ ). Among investigated strawberry fruit cv. Clery showed the highest amount of total phenolics, followed by Honeoye and NF 421 (Asia), while regarding to total anthocyanins, cvs. Honeoye and NF 421 (Asia) showed higher and cv. Clery showed the lowest amounts of total anthocyanins. The jam processing under applied conditions had appreciable effects on preserving stability of polyphenolics. Our results showed that total phenolics were more stable during processing in comparison with total anthocyanins. Regarding to flavonoid and nonflavonoid content, obtained results showed that in all investigated samples flavonoids were predominant. Relevant differences among cultivars were observed when total phenolics, total anthocyanins, flavonoid and nonflavonoid contents in jams was compared. After 6 months storage, in all investigated samples total phenolics, flavonoids and nonflavonoids were more stable than anthocyanins, without marked influences of cultivar. Compared to the strawberry fruits, whose antioxidant activities were in the range of 90, 74% to 92, 41%, the jams also represented a significant source of antioxidant compounds, even considering the lower content of phenolic compounds with the antioxidant activities of 83, 76% to 85, 65%. Six month storage had influence on further decreasing of antioxidant activity by 7% to 12%. Among investigated samples, the highest correlation was found in the total anthocyanins contents and the DPPH. Hence, the obtained results showed that besides fresh strawberry fruit, the strawberry jams also possess noticable content of important bioactive compounds with considerable antioxidant activity.

strawberry; jam; phenolics; antioxidant activity; storage

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