The Impact of Carbonic Maceration Pretreatment on the Convective Drying of Seedless Grapes: RSM Optimization, Drying Characteristics and Microstructure

In the last 2 decades, Turkey and the United States have produced half of the world's dried grape production. Sultani seedless grape, used as a material in the study, is the most important grape variety since being economically growing in Turkiye for dried grape production and its exportation. The aim of the present study was to investigate the drying of seedless grapes by carbonic maceration (CM) pretreatment and following hot air drying. By the way statistical analysis was carried to determine how the process parameters affected the drying behavior of grape samples. Finally, the studied parameters of both process steps, pretreatment and following drying, were simultaneously optimized according to the investigated responses. The results showed that drying temperature and CM process parameters significantly affected the drying efficiency. Notably, when compared to the control, the CM treatment accelerated the drying process by more than 24%. Furthermore, antioxidant potential, surface color, and texture were found to be better preserved in the dried grapes treated with CM. While pH, hue, TPC, and TEAC values of optimum dried grapes were significantly higher, TA and HMF values were remarkably lower than control samples (without CM pretreatment) (p ≤ 0.05). Throughout CM pretreatment and following the drying process, the dependent variables, being elasticity, antioxidant capacity, drying time, and hue value, were optimized by the response surface methodology (RSM). The optimal drying temperature (DryT), CM pressure (CMP), CM temperature (CMT), and CM time (CMt) parameters were as 77°C, 0.30 MPa, 4°C, and 8 h, respectively. For drying operations, CM's significant advantages should be considered in terms of enhancing the process and the product. As a result, this study offers significant findings in this context. The CM has been found to be an effective technique utilized before drying grapes based on the results that were achieved.