Impacts of timing of nitrogen addition on Chardonnay fermentations sequentially inoculated with <i>Metschnikowia pulcherrima</i> and <i>Saccharomyces cerevisiae</i>

Sequential inoculation of Metschnikowia pulcherrima and Saccharomyces cerevisiae has been shown to produce wines containing less alcohol. However, the inoculation creates competition between these yeasts for scarce nutrients such as amino acids and ammonia. This study examined impacts of the timing of nitrogen addition (1, 3, or 5 days after M. pulcherrima inoculation) on fermentation kinetics, yeast assimilable nitrogen (YAN) consumption, and formation of by-products, including ethanol. After adjusting 28 ˚Brix, M. pulcherrima P01A016 on day 0 and S. cerevisiae Lalvin NBCTM on day 4 were inoculated into Chardonnay must with or without YAN supplementation. Most wines reached dryness by day 31, except for those without the supplementation. YAN addition on day 5 significantly reduced fermentation duration by 20 % while producing higher concentrations of glycerol (10.5 g/L). Wines that reached dryness with sequential inoculation had similar alcohol content to those inoculated with only S. cerevisiae (15.5–16.1 % versus 16.3 % v/v). Regardless of timing, YAN supplementation supported sequential inoculation for fermenting Chardonnay wines to dryness. Furthermore, the timing of nitrogen addition had a significant impact on fermentation duration and glycerol synthesis, but it did not significantly affect alcohol reduction. The timing of nitrogen addition may be used to shorten fermentation time and enhance glycerol production in the wine industry.