Smal l berries, antioxidants and human healt

Edgardo Giordani, Cristina Romani [Dipartimento di Scienze delle Produzioni Agro-alimentari e dell'Ambiente, Università di Firenze];
Stefania Nin [CREA, Unità di Ricerca per il Vivaismo e la Gestione del Verde Ambientale ed Ornamentale di Pescia];
Massimo del Bubba, Claudia Ancillotti [Dipartimento di Chimica Ugo Schiff, Università di Firenze]

Small berry fruits, primarily strawberry, currants, gooseberry, blackberry, raspberry, blueberry and cranberry, are very rich sources of bioactive compounds, namely phenolics and organic acids. Natural berry antioxidants, their characterization and utilization in functional foods and clinical assessment of their protective role against oxidative damage for human health are among the major targets of contemporary research. Composition and concentration of antioxidants are dependent on the genotype, environmental conditions, cultural practices, stage of maturation, storage conditions and post-harvest handling. An overview of small fruit production, their bioactive compounds and factors affecting the accumulation of antioxidants in berries is presented. Particular attention is given to genetic factors, field management, post-harvest management, and processing operations that may affect the fruit phytochemical content. Blueberry, bilberry, blackberry and black currants are particularly rich in antioxidants. Most common antioxidants in berry fruits are ascorbate, carotenoids, vitamin E, and phenolic compounds. Ascorbate is abundant in berries of currants. Carotenoids are present in small concentrations in berry fruits. Phenolic compounds include phenolic acids and flavonoids. Flavonoids are further divided into anthocyanins, flavonols, flavanols, flavons, and flavanones. Small berries are particularly rich in anthocyanins, which confer showy colours from dark red to blue. Anthocyanins contribute 73 and 84% of the total antioxidant potential in black currant and bilberry, respectively, but only 21% in raspberry and red currant. Flavanols contribute less than 14% to total potential in small berries. Hydrolizable tannins are present especially in strawberry, raspberry, and black currant; condensed tannin concentrations are variable in small berries. Low concentrations of resveratrol, pterostilbene, and piceatannol are present in blueberry, bilberry, and strawberry. Fruit maturation affects phenolic compounds and anthocyanins. Periods of water deficit during fruit development usually increase phenolic concentration in small berries. High temperatures during storage decrease berry shelf-life and phenolic concentrations. Freezing only slightly modifies phenolic compounds, whereas drying tends to degrade anthocyanins more easily than other phenolic compounds. Exposure to UV-C radiation can increase phenolic concentrations. Fumigation with SO2 followed by storage under controlled atmosphere conditions prolongs the berry life of blueberry cultivars and contributes to maintain high antioxidant potential. Cooking conditions can also affect phenolic concentrations. Ascorbate losses range from 15 to 55% with traditional cooking, whereas fewer antioxidants are lost when foods are heated in microwave ovens rather than in traditional ones. Recent results on the beneficial effects of dietary antioxidants in humans and some analytical aspects are also reported.

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