Grapes are far from sterile when they come into the winery from the vineyard. Rather, they bring in a vast number and diversity of microbes that may be beneficial or detrimental to the quality of the resulting wine. As soon as the grapes are crushed, competition for dominance ensues that will likely have significant impact on aroma and flavor. Recent advances in molecular biology have allowed researchers to characterize this diversity and succession with much more specificity in recent years. In order to understand the effect of winemaking interventions like chitosan or bioprotective yeast on wine quality, we must first understand the microbes we are dealing with. This presentation contains a brief review. It was first recorded in the Spring of 2020 in lieu of having in-person sensory sessions during the COVID-19 pandemic.

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Chitosan has been used at nearly every stage of winemaking.

At crush, chitosan can be used to reduce the population of spoilage microbes. This can be used in addition to SO2 in difficult vintages and in lieu of SO2 in less difficult vintages.

In 2019, two WRE experiments explored the use of chitosan to control volatile acidity and microbial growth at crush. The results were presented as a video recording due to restrictions on in-person gatherings during the COVID-19 pandemic.

Watch the presentation here

Many new non-Saccharyomyces yeast products have become available in recent years. These products have been marketed for their bioprotective qalities as well as their ability to add complexity to the finished wine. In Virginia, wet vintages and high humidity may increase the overall microbial load on our grapes, leading to a greater need for protection against spoilage. Addition of non-Saccharomyces yeast at crush may be a valuable tool to replace SO₂ use or augment its effectiveness.

In 2019, two WRE experiments examined the effectiveness of non-Saccaromyces yeast in reducing microbial populations and volatile acidity. The results of these trials were presented in a recorded video due to restrictions put in place during the COVID-19 pandemic.

Watch the presentation here