In the last decade, a variety of process analysis devices have been introduced which allow winemakers to monitor alcoholic fermentations. These systems visualize the fermentation rates and progress, but are too inaccurate to estimate actual sugar concentrations during fermentations.
We present an innovative FT-NIR spectroscopy based system that provides accurate real-time information about key-fermentation parameters including glucose, fructose, and ethanol concentrations throughout fermentations. Integrating this in-line sugar analysis with process control enables fully automatic fermentations and new ground-breaking strategies.
Specifically, the system allows to process high sugar containing musts (e.g. for the production of hot climate, late harvest or icewines) without causing the yeast hyperosmotic stress response, which leads to increased formation of undesirable byproducts such as acetic acid and acetaldehyde, and, possibly, fermentation problems.
This can be achieved with a continuous fed-batch fermentation where must is slowly and automatically added to the fermentation tank at such rates as to keep sugar concentrations constant at low levels (e.g. 50 g/l) during the fermentation.
We will present data that shows that such an approach leads to a 80-90% reduction in acetic acid values and also decreases acetaldehyde levels by 50%. In addition, cooling costs can be reduced by 1/3 since the cold settled must partially cools the fermentation during additions, and smaller yeast inocula can be used. Some examples of white and red wine fermentations will be presented and the effect of this innovative fermentation management strategy on sugar, acid and ester composition, yeast viability, and sensory aspects will be discussed, as well as its application to malolactic fermentation.
Winner of the 2013 International SIVE Awards “Research for Development”. Scientific work presented at the 8th edition of Enoforum (7-9 maggio 2013, Arezzo, Italy)
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