Effect of the Novel Radiant Zone Drying Method on Anthocyanins and Phenolics of Three Blueberry Liquids

Abstract

The Radiant Zone dryer (RZD) is a novel drying method designed to dry liquid food products into powders. The impact of RZD on the phytochemical content of three blueberry liquid products (extract, juice, and puree) was examined. Comparative analysis between liquid and dried products revealed no statistically significant changes in the total anthocyanins (extract liquid/powder, 11.7/11.2 mg/g of dry weight; juice liquid/powder, 2.7/2.5 mg/g of dry weight; puree liquid/powder, 1.7/1.6 mg/g of dry weight, quantified as cyanidin 3-glucoside equivalents) and total phenolics (extract liquid/powder, 97.1/113.1 mg/g of dry weight; juice liquid/powder, 16.6/17.4 mg/g of dry weight; puree liquid/powder, 8.3/6.2 mg/g of dry weight, quantified as gallic acid equivalents). Total antioxidant activity also showed no significant variation between wet and dried products. The high-performance liquid chromatography-diode array detector (HPLC-DAD) analysis of the products exhibited a similar profile of 13 glycosylated anthocyanins. This study demonstrates that the novel RZD produces high-quality products because the retention of anthocyanins and phenolics during dehydration using RZD is the same as that for freeze drying. The RZD method of operation and its advantages over other dryers is also discussed.