Effect of Pump-over Conditions on the Extraction of Phenolic Compounds during Cabernet Sauvignon Fermentation

Abstract

The formation of the cap during red wine fermentation necessitates use of some mode of cap management to maintain proper control of fermentation temperatures and promote phenolic extraction during the course of alcoholic fermentation. Pump-overs are among the most common modes of cap management and involve pumping the fermenting juice from below the cap and spraying it over the top. The efficacy of pump-overs at maintaining temperature and promoting phenolic extraction is thought to be affected by the volume and frequency of pump-over, but these effects have not been thoroughly investigated in a highly controlled environment. Research-scale Cabernet Sauvignon fermentations (100 L) were performed in which the volume and frequency of the pump-overs were systematically varied, and phenolic extraction was monitored during fermentation. Pump-over volume and frequency did not have a significant effect on phenolic extraction in research-scale fermentors, although the results obtained may depend on fermentor size or design. Half of the fermentor volume twice per day was the minimum mixing needed to maintain phenolic extraction and temperature control during fermentation. However, analysis of the bottled wines showed no significant differences in phenolic content five months posttreatment.