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Effect of Jam Processing on Phenolics and Antioxidant Capacity in Strawberry Fruit (Fragaria ananassa × Duch.)

Strawberry (Fragaria x ananassa Duch.), as one of the most commonly consumed berry is an important dietary source of fiber and bioactive compounds ; in particular, the phenolic composition seems to strongly influence the quality of the strawberries and the potential health benefits. Since the strawberries are seasonal fruit and there are not available at the market throughout the year it will be useful to know whether the strawberry jams could also represent a good source of bioactive compounds in the diet. Therefore, the aim of present study was to evaluate changes and stability of individual anthocyanins, phenolic acids and flavanols, as well as antioxidant capacity and colour parameters in three strawberry cultivars before and after jam production. Low-sugar jams were prepared under atmospheric pressure with addition of sucrose or fructose. Phenolic compounds were determined by HPLC-UV/VIS PDA analysis. Antioxidant capacities were measured by DPPH, ABTS, FRAP and ORAC assays. Colour parameters were measured by CIELab system. In all strawberry purees and jams, five anthocyanins were identified and quantified with pelargonidin-3-glucoside being the predominant. Regarding to phenolic acids in all investigated samples hydroxybenzoic acids were predominant, followed by hydroxycinnamic acids and flavanols. Among all samples, ellagic acid was found in the highest concentrations. Most important losses due to thermal processing were observed for anthocyanins (34-76 %). The most stable were hydroxybenzoic acids with losses of 10-19 % with even increase of ellagic acid content in jams compared to fresh fruit. Type of added sugar as well as strawberry cultivar significantly affects anthocyanins, phenolic acids and flavanols stability (p≤0.05). Furthermore, sugar type in comparison to strawberry cultivar, showed stronger influence on antioxidant capacity stability during jam processing. Determined colour parameters L, a, b and C decreased during jam processing, while H values increased, with significant influence of strawberry cultivar.

antioxidant capacity; jam processing; phenolic compounds; strawberry (Fragaria x ananassa Duch.)

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