Comparison of Grape Pomace Drying Using a Solar Dryer and Under Open Sun Conditions

In this research, the effects of open sun drying and solar drying methods on drying characteristics and some quality criteria of grape pomace were investigated for determining an optimum drying method. Fresh grape pomace was provided by Viticulture Research Institute, Grape Juice Processing Plant in Tekirdag, Türkiye. The longest drying period was determined as 147.05 hours for the method of open sun drying while the shortest drying period was determined as 78.5 hours for the method of solar drying. In the solar drier, solar collectors with flat surfaces were used. The drying period was found faster using the solar dryer compared to the use of the open-air drying method. The final moisture content of the solar dried pomace was found to be 11% while the final moisture content of open-air dried pomace was found to be 13.0%. After the drying process, in addition to determining the quality criteria of pomace, seeds and skins were separated using a separator. The content of the total phenolic and antioxidant activity of extracts obtained from open sun-dried grape seeds were determined as 89.57 (g/kg), and 32.89 (µmol troloks/g), respectively whereas the content of the total phenolic and antioxidant activity of extracts obtained from solar dried grape seeds were 112.24 (g/kg), 34.12 (µmol troloks/g), respectively.