Total polyphenolics and anti-oxidant properties of selected dried fruits and relationships to drying conditions

The total polyphenolic (TPP) and antioxidant (AOX) levels of 41 Australian and imported dried fruits including sultanas (n = 22), Carina and Zante currants (n = 13), apricots (n = 3) and prunes (n = 3) were determined. Significant differences were observed among the sultanas, possibly due to local drying conditions, but not for other fruit types. TPP and AOX levels were positively correlated with lowest and highest levels measured for apricots and Zante currants, respectively. Specific effects of drying conditions on sultanas and Sunmuscat grapes were studied by comparing rack-drying plus emulsion (E) coating with ground-drying (±E). Products dried by the rack (+E) method contained 1.5- to 2-fold higher TPP and AOX levels than ground-dried fruit (±E). Furthermore, TPP and AOX levels remained stable for up to 5 months supporting that drying and not storage conditions, were determinant in TPP and AOX levels of dried grapes. Thus, drying conditions can affect both sensory and health-related quality attributes of grapes.

► Dried fruits represent good dietary sources of polyphenols with concomitant antioxidant activity and represent convenient, shelf-stable and relatively inexpensive sources of dietary polyphenolics and anti-oxidants.
► For grapes but not other dried fruits, drying methodology influences total polyphenol and anti-oxidant levels, with possible implications for health.
► Controlled studies of effects of drying conditions on sultana and Sunmuscat grapes showed that initial drying conditions were determinant in final total polyphenol and anti-oxidant levels, which remained stable after 5 months storage at room temperature.