Effect of drying technologies on bioactive compounds maintenance in pumpkin by-products
Latvia University of Life Sciences and Technologies, Faculty of Food Technology, Riga street 22, LV-3004 Jelgava, Latvia
During the pumpkin processing large amounts of waste material as a combination of pumpkin peel, seeds and the flesh between seeds has produced. Therefore it is important to investigate the possibilities for using the pumpkin residues. The aim of this research was to investigate the effect of different drying technologies on maintenance of bioactive compounds in pumpkin by-products. Two pumpkin residue products of Hubard group pumpkins were used to obtain pumpkin powder: residue products formed in the process of extracting industrial pumpkin purée by heating it in a heat exchanger and treating through a sieve of pulpier; residues resulting from pumpkin juice extraction process mechanically pressed from fresh, chopped pumpkins. In order to be able to choose the most suitable drying technology pumpkin by-products were dried in the microwave-vacuum, convective (at 40, 50, 70 and 80 °C) and freeze-drying type dryers. For all samples total carotenes, the ascorbic acid, total phenols content (TPC) and antiradical activity (DPPH˙, ABTS˙+) were determined by using standard methods. The highest total carotenes content was retained in freeze-dried pumpkin powders. The most suitable drying method for obtaining pumpkin powder with the highest ascorbic acid, total phenolic content and antiradical activity is drying in convective type drying at 80 °C temperature.