Effects of conductive drying on drying kinetics and retention of bioactive compounds in mistletoe leaves

Abstract

The aim of this study was to investigate the effect of conductive drying on the quality characteristics of mistletoe leaves. Drying generally took place in both constant and falling rate periods. Page and Modified Page models with the highest R2 and lowest χ2 and RMSE values were found to satisfactorily describe the drying behavior of the mistletoe leaves. Changes in total phenolic content (TPC), total antioxidant activity (TAA), and ascorbic acid content (AAC) of mistletoe leave samples were measured during conductive drying at three different temperatures (50, 60, and 70 °C). Total phenolic content was determined as 686.61±2.96 mg GAE/100 g DM in fresh samples and ranged between 150.97–105.09 mg GAE/100 g DM after drying. The total antioxidant activity values of dried mistletoe leaves decreased significantly compared to fresh ones. The ascorbic acid content of mistletoe leaves was found to be 84.00±2.42 mg/100 g DM before drying. The total antioxidant activity and ascorbic acid content samples were degraded following the second order reaction kinetics. However, the change in the total phenolic content occurred in accordance with the first-order kinetic model. The higher antioxidant activity, phenolic compounds, and ascorbic acid content, and lower half-life values were observed in conditions where the temperature (50 °C) is low.