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The relationship between grape juice composition and the progress of alcoholic and malolactic fermentation


Summary

Objective

To better understand monitoring and management options for alcoholic and malolactic fermentation and the management of difficult fermentations.

Background

Difficulties with alcoholic and malolactic fermentation are routinely reported and can be attributed to a diverse range of causes. Sulfur dioxide addition to bins and crushers is used to control pre-fermentation microbial activity. However, even moderate levels can negatively affect the progress of malolactic fermentation. In addition, some yeasts produce large amounts of sulfur dioxide, which is inhibitory to malolactic fermentation. This is a particular concern, as simultaneous alcoholic and malolactic fermentations are increasingly being used to reduce total fermentation time.

Research approach

This project brings together yeast and bacterial fermentation, for an integrated approach to the study of alcoholic and malolactic fermentation performance. The fermentation program will evaluate yeast and environment interactions, to determine strain fitness and implantation efficiency and the impact of harvest variables on juice composition. Bacterial and environment interactions will be studied using model fermentations to identify factors that stimulate or inhibit malolactic fermentation, and the genetic basis for variation between strains of malolactic bacteria will be evaluated. Uniquely Australian regional isolates of malolactic bacteria will be tested for their robustness in co-inoculated fermentations using a range of winemaking interventions.

Sector benefits

The new knowledge generated will inform and improve winemakers’ decisions when managing fermentation performance issues, reduce the likelihood and impact of stuck or sluggish fermentations, improve winery scheduling issues and avoid any product quality downgrades.