Worldwide the wine production is increasing in order to satisfy the expanding consumers demand. The improvement of post harvest and processing technologies for wine grape is considered essential to obtain high quality standards wines. In particular, the cooling soon after harvest represents one of the possible way to preserve the berries original quality especially for white wines rich of taste and flavour while withering is a natural process operation to increase the must soluble solid content for red wine if required. In this paper, the effect of different freezing/withering treatments on chemical-physical parameters of Sangiovese and Cabernet grapes must were investigated, in order to define the relation between the processing conditions of the freezing/withering plant and the final quality of must produced.
The freezing system reduced the average product temperature of about 35°C in 220 min, and the energy requirement of the system resulted strictly related to the grape variety and lower to -18°C due to the faster process. Overall, experimental data could be used to design the process protocol and the industrial scale plant for the post harvest wine grapes processing.
The withering process after 9 days produces an average grapes weight loss of 9.98% and 7.5% for the must of Sangiovese and Cabernet cv. respectively. No significant pH reduction has been detected, demonstrating the maintained quality of the original grape. Furthermore, the higher the fan power used, the higher soluble solid content, suggest that the implementation of a computerized controlled system could be useful to optimize the process parameters during the withering of grapes for producing must with higher sugar content i.e. wine with higher alcohol content.