Effect of pretreatments on refractance window drying, color kinetics and bioactive properties of white sweet cherries ( Prunus avium L. stark gold)

Abstract

The aim of this study was to investigate the effects of different pretreatments (citric acid, sucrose and freezing) on the refractance window (RW) drying, color kinetics and bioactive properties of white sweet cherries. The shortest drying time (180 min) was obtained with freezing pretreatment (FP). The highest Deff was 2.38346 × 10–9 m2/s in FP. Cubic and Sigmoid equations were the best drying models for the control and FP, respectively. Furthermore, quadratic equation was the most appropriate color model for all sweet cherries. FP increased the total phenolic content (4.18 ± 0.86 mg gallic acid eq/g dry matter, DM) and antioxidant capacity (ferric reducing antioxidant power, FRAP) (13.17 ± 1.05 µmol trolox eq/g DM) of dried cherry, as compared to control and other pretreatments. Results indicated that citric acid and sucrose pretreatments (CAP and SP) were not much effective as freezing in cherry drying. This study showed that the combination of FP and RW drying can be an alternative drying for white sweet cherry. Practical applications White sweet cherry is a perishable seasonal fruit whose long term use is not possible during the off-season. Fresh sweet cherries are processed into various food products such as juice, vinegar, alcoholic drink or jam right after the collection from the field. However, other food sectors like bakery & pastry, chocolate, and dairy demand to reach to ingredients any time of the year, and this would be only possible to use the off-seasonal ingredients in dried form. White sweet cherry is one of the preferred ingredients because of its sweet taste, nutritious and bioactive contents. In order to meet the demand of those food sectors, the sweet cherry has been mostly dried using hot air technique; however, this research showed that the refractance window drying can be a good alternative to improve the product quality with the reduction in drying time and energy.