Impact of Drying Process on Grindability and Physicochemical Properties of Celery

Abstract

The objective of this study was to evaluate the impact of various drying methods: freeze drying, vacuum drying, convection drying, and convection-microwave drying at microwave powers of 50 W and 100 W, along with process temperatures (40 °C, 60 °C, and 80 °C), on the drying kinetics, selected physicochemical properties of dried celery stems, and their grindability. The page model was employed to mathematically describe the drying kinetics across the entire measurement range. Convection-microwave drying significantly reduced the drying time compared to the other methods. The longest drying duration was observed with freeze drying at 40 °C. The product obtained through freeze drying at 40 °C exhibited the least alteration in color coordinates, the highest antioxidant capacity, and the greatest retention of chlorophylls and total carotenoids. At a specific temperature, the quality of the product obtained from vacuum drying was slightly lower compared to that from freeze drying. The most substantial changes in the physicochemical properties of the dried product were observed with convection-microwave drying at a microwave power of 100 W. The drying method selected had a significant impact on the energy consumption of grinding, average particle size, and the grinding energy index of the dried celery stems; these parameters worsened as the drying temperature increased. The product with the best quality characteristics and disintegration parameters was achieved using freeze drying at 40 °C.