Effect of hybrid drying method on physical, textural and antioxidant properties of pumpkin chips

In order to obtain pumpkin chips, hot air drying (HAD), freeze-drying (FD), combinations of hot air drying + explosive puffing drying (HAD + EPD) and freeze-drying + explosive puffing drying (FD + EPD) were studied and, the impacts of various methods and conditions (temperature, vacuum pressure and decreased the moisture content level after pre-drying) on the physical, antioxidant and textural properties of pumpkin slices have been examined.The best texture attributes, the highest rehydration ratio (RR), the highest volumetric expansion (VE), and the lowest bulk density were obtained from FD + EPD products. Otherwise, when FD samples were compared with FD + EPD ones, it was clearly seen that higher retention of total phenolic content, antioxidant capacity, total carotenoids and a better color quality were obtained. However, the combination of FD + EPD allows drying at a slightly shorter processing time that is compared to a single FD. FD + EPD products provided the highest crispness when it is compared with HAD + EPD. This fact indicated that the pre-drying method (FD) and the reduction of moisture level had a major impact on textural properties. Consequently, the FD + EPD combination proved that it is a more promising process when it was compared to other drying techniques in order to produce nutritious pumpkin chips.