Alternatives to SO2 at Crush: Chitosan and non-Saccaromyces Yeast

Joy Ting

March 2020

Microbial Diversity on Grapes Chitosan at Crush Bioprotective non-Saccharomyces yeast WRE Experimental Results

Since we are not able to meet in person to taste and discuss our experimental wines, I have chosen a series of experiments to present in a video format. These experiments explore the use of chitosan and non-Saccharomyces yeast at crush to reduce microbial load and volatile acidity in the finished wine. The following videos include some background information on the microbes found on grapes, how SO2 does (and does not) affect them, and how both chitosan and non-Saccharomyces yeast might be used to combat spoilage in addition to or instead of SO2. Though a video is not the same as tasting and discussing the wines together, hopefully the information presented is useful in sharing the results of these experiments and giving context to their interpretation. Many references are cited in the videos. Full citation for these references are listed below.

 

Progression of micrbial life during and after fermentation, Combina et al. 2005

Microbial Diversity of Grapes

Joy Ting

March 2020

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.

Watch the presentation here

Using Chitosan at Crush to Control Microbial Spoilage

Joy Ting

March 2020

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

Non-Saccharomyces Yeast for Bioprotection

Joy Ting

March 2020

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

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