Evaluation of pump-over thermal effect during red grapes fermentation: preliminary results

In oenology, pump-over is a mechanical technique used to enhance the fermentative maceration. Pump-overs are conducted, with or without air contact, by taking the must from the bottom of the fermentation tank, and using it to spray the cap. The aim of this practice is the enhancing the phenolic and volatile compounds extraction from grape skins. Consequently, wine quality is improved in this way. During some temperature monitoring tests a “secondary” effect of pump-over has been highlighted. Temperature affects volatile and phenolic compounds concentration too. Particularly, low temperatures may be used to improve volatile production by yeasts during fermentation, and regulate the extraction of polyphenols compounds from the solid to the liquid phase. The aim of the work is to describe the thermal effect of pump-overs with and without air contact during a red fermentation. Tests have been performed during the September 2014 Tenuta Argentiera (Bolgheri (LI), Italy) in a tank of 20 m3 capacity. Six probes were placed into the fermentation tank, for temperature monitoring in different zones during pump-overs. Both kinds of pump-overs produce two main effects during fermentation: a temperature homogenization, reducing the differences among the zones of the tank, and a cooling effect, reducing the average temperature of the must. Hence, in addition to their effect on compounds extraction, pump-overs could be useful to reduce and control the temperature during red fermentation