Comparison of the effect of four drying methods on polyphenols in saskatoon berry

The aim of the study was to evaluate the influence of different drying methods on physicochemical parameters of 3 saskatoon berry cultivars: 'Honeywood', 'Smoky' and 'Martin'. Convective drying (CD), microwave-vacuum drying (MVD) and combined drying (CD/MVD) significantly affected moisture content, water activity and colour. Among polyphenolic compounds, 10 flavan-3-ols, 7 anthocyanins, 8 phenolic acids and 11 flavonols were identified by the UPLC-PDA-Q/TOF-MS system in dried saskatoon berries. The total content of identified polyphenolic compounds present in dried saskatoon berries ranged from 21.4 to 66.3 g/kg dry matter, for respectively 'Martin' and 'Smoky'. The strongest ability of extracts to scavenge ABTS radical cations was noted for 'Honeywood', followed by both 'Smoky' and 'Martin'. Antioxidant capacity of products was connected with the content of polyphenolic compounds. 'Honeywood' and 'Smoky' can be best recommended for the production of dried merchandise. The microwave vacuum drying at 480 W with reduction to 120 W give product with the quality similar to this obtained by freeze drying, especially when it comes to the retention of polymeric procyanidins and flavonols present in the fruit. In conclusion, quality of dried saskatoon berry can be successfully moderated by appropriate selection of drying techniques and parameters.