Cultivation of Yeast under Carbon Dioxide Pressure for use in Continuous Sparkling Wine Production

Abstract

Batch fermentations of Montrachet wine yeast under carbon dioxide pressure in a wine medium containing 5% added glucose indicated the feasibility of cultivation of yeast in this manner as the initial tank in a continuous fermentation production of sparkling wine ("champagne"). At 0.6 atm (gauge) carbon dioxide pressure, there was a fourfold inhibition of growth rate, and the final maximum cell concentration was about half of the control. The onset of fermentation was delayed by carbon dioxide pressure; however, the maximum fermentation rate was not greatly affected.

Continuous fermentation, with dilution rates in the range of 0.015 hr^-1 (with a constant volume of four liters and with flow rates in the range of 1 mL/min) showed the typical relationship between steady state cell concentration and dilution rate. The yeast were able to maintain steady state growth at each of the carbon dioxide pressures tested [up to 0.6 atm (gauge)], in spite of the inhibitory effect. From these results it was suggested that a dual-tank system, maintained at 0.3 and 5 atm (gauge) carbon dioxide pressures, with the second tank having six times the capacity of the first, could be used for continuous production of sparkling wine.

In the steady state condition, higher utilizations of glucose were found at the higher carbon dioxide pressures, even though a lower steady state cell concentration was maintained. The extra requirement for substrate at the increased carbon dioxide pressure was explained as an increased maintenance energy requirement at the higher carbon dioxide pressure.

The yeast cultivated in continuous fermentation at increased carbon dioxide pressures were used as inocula for bottle fermentations. Although no adaptation or mutation of the yeast to carbon dioxide pressure was evidenced in the continuous fermentations, the bottle fermentations with the yeast precultivated at the medium carbon dioxide pressure [0.3 atm (gauge)] showed a definite increased fermentation rate (as evidenced by rate of pressure development). The wines from the bottle fermentations were subjected to sensory evaluation and were found to be indistinguishable.