Roger Boulton, an emeritus professor from the University of California Davis and a leading figure in wine chemistry, delivered an insightful presentation at the Australian Wine Industry Technical Conference, focusing on precision fermentation management. He highlighted two major challenges faced during fermentation: sluggish or incomplete fermentations and the production of hydrogen sulfide due to elemental sulfur present in the must.
Boulton proposed innovative strategies to address these issues. One is the incorporation of real-time monitoring and prediction models of fermentation behavior. However, the more significant breakthrough involves managing redox potential during fermentation. Along with his PhD student, James Nelson, Boulton has successfully controlled the redox potential in commercial-scale fermentations for the first time.
Redox potential, or oxidation-reduction potential, influences the behavior of yeast and bacteria during fermentation and can be measured in wine. Boulton and Nelson developed a method to track these redox reactions in real-time using sensors attached to fermentation tanks. They discovered that when redox levels dip below -100 mV, hydrogen sulfide levels begin to increase, which can develop into problematic concentrations. By carefully managing redox levels—maintaining them at around -50 mV through controlled oxygen introduction—they reduce the risk of off-flavors in the wine.
Their work has been applied to large-scale fermentations, including a notable 140,000-liter Sauvignon Blanc fermentation in New Zealand. Boulton asserts that this method profoundly impacts fermentation performance, leading to more consistent results.
In conjunction with redox control, they monitor additional fermentation parameters, such as density and temperature. High juice temperatures, for instance, have been found to contribute to sluggish fermentations.
While this research is promising and groundbreaking, it may incite some debate within the wine industry regarding traditional fermentation practices. For those interested in diving deeper into the specifics of Boulton and Nelson’s work, more information is available in their publication here: Link to Research.