Department of Agriculture Food and Environment
University of Pisa
Angela Zinnai completed his 1st Ph.D at the age of 25 years from the Scuola Superiore Sant'Anna, Pisa. She is an associate professor of Food technology of Pisa University. In 2008, she received a “Special Mention” at “Montana Premium” for Food Science Research (with her colleague Venturi F.). She published more than 80 papers in journals or volumes and serving as a referee for research projects and papers. She was a scientific responsibles for an Original Patent (PT2008A000006) that received a “Special mention of the Jury” at 24° SIMEI. She was a Chair at Bioprocess 2013 (Kansas City, USA).
Alcoholic fermentation is a complex biochemical process mainly conducted by yeasts belonging to the species Saccharomyces cerevisiae. As largely reported in literature, the lack of some nutrients, unsuitable reaction temperatures, too low pH values, the presence of significant concentrations of inhibitors in the reaction medium, the development of dangerous microorganisms, the alteration of ionic equilibrium, can induce a deep modification of the alcoholic fermentation kinetics. Over the last twenty years, the winemakers have been processing grapes characterized by great concentrations of phenols and aromatic compounds but also by very high sugar contents which lead to an higher ethanol level in the wine. In many cases, such ethanol levels have a negative impact on wine quality and increase the risks of stuck of fermentations ending up with wines with high residual sugar concentrations (> 5 g/l). The basis for the decline in sugar conversion is not fully understood and the increase in fermentation rate by the addition of selected yeasts strains to the must could often result ineffective. On these basis, the kinetic aspects related to hexoses conversion were investigated in order to calculate the specific substrate consumption rates. The experimental data have been fitted a kinetic model, based on mathematical equations involving a reduced number of functional parameters characterised by a defined biological meaning. The availability of this model could greatly help the enologists to solve technical problems related to slowing fermentations not only during wine making but even for the all other industries which extensively use Saccharomyces species.