Rubén Martínez, a graduate in Biology and Biochemistry at Elhuyar Fundazioa, and colleagues have developed a new methodology that makes it possible to know what physiological state the yeast is in at each point in the wine fermentation process. 

This knowledge is of particular interest for producers, since changes in the grape directly affect the chemical composition of the must.

His thesis, entitled "Estudios avanzados de la fisiología de levadura en condiciones de vinificación. Bases para el desarrollo de un modelo predictivo" (Advanced studies into yeast physiology in vinification conditions. Bases for developing a forecasting model) is part of the Demeter project, which seeks to study and find out the possible effects of climate change on viticultural and oenological activities, and to come up with new strategies to address the problems caused by global climate change on viticulture and wine production.

One of the estimated effects of climate change on vineyards is the fall in their productivity, changes in the distribution of the pests and diseases that affect them, and changes in the chemical composition of the grape.

Ruben Martinez Moreno , Nafarroako Unibertsitate Publikoa

"By drawing an analogy with cinema," Martinez explained, "Wine fermentation would be a full-length film from which, thanks to this methodology, we could extract all the stills that comprise it.

"The main aim of this thesis is to contribute towards the development of a model to forecast the behavior of the Saccharomyces cerevisiae yeast during the vinification process. This would make it possible to know in advance how this yeast responds to the changes (many of which are due to climate change) that are taking place in the chemical composition of grape must." 

Simulating the yeast's metabolism

The main aim of this thesis was to contribute towards the development of a model for forecasting the metabolism of S. cerevisiae during the vinification process. This work has shown that study of the fermenting process allows the process to be divided into various stages or phases and that each one of them can be imitated in continuous cultivation. Another of the achievements has been to develop a model that enables the metabolism of the yeast to be simulated.

This thesis also demonstrates the need and importance of knowing the chemical composition of the must in the winery, in particular the nitrogen content that the yeast can assimilate and the nitrogen requirements of the yeast. "By knowing these two parameters," says the researcher, "it is possible to design different protocols for taking action during the fermenting process in order to improve the organoleptic quality of the wine."