Effects of the drying technique on the retention of phytochemicals in conventional and organic plums (Prunus domestica L.)

- The phytochemical content of dried plums was significantly affected by drying methods.
- The variation of hydroxycinnamics and anthocyanins was dependent on drying methods.
- Hydroxymethylfurfural was present only in oven dried products.
- Organic farming may influence the phytochemical content of dried plums.

Plums contain high levels of hydroxycinnamates (neo-chlorogenic acid, Neo-CGA), anthocyanins (ATH) and ascorbic acid. The drying process influences their phytochemical content and plum cultivars are known to have different phytochemical retention after drying, but little data exists regarding to possible differences between conventional (CONV) and organic (ORG) plums. The aim of this study was to evaluate the phytochemical content in three different CONV and ORG plum cultivars (Jubileum, Reeves and Victoria) after freeze drying (FD), conventional oven drying (OD) and solar drying (SD).The three cultivars responded differently to the methods of drying. Notably, Jubileum decreased its ATH mostly when subjected to OD while its Neo-CGA content was mostly reduced after SD. Additionally, ORG Victoria and Reeves stood out for the low decrease of Neo-CGA after drying compared to the same cultivars cultivated with conventional system. The Folin-Ciocalteu index, which was significantly different in OD (6942 mg GAE/kg dw) and SD (5420 mg GAE/kg dw) samples, was positively related with both Neo-CGA and hydroxymethylfurfural. The present findings suggest that for some cultivars, the organic system influences the nutraceutical quality of dried product, thus representing an important factor that regulates the phytochemical content of dried plums.