FERMENTATION CHAOS: THE ORIGIN OF COMPLEXITY (PART I)
During the fermentation process the yeasts, microorganisms directly involved in the process, come into contact with the sugars of the fermentable raw material and develop together with alcohol and carbon dioxide a real chaos of molecules, some of great organoleptic value, others less especially appreciated if present in large quantities.
The distiller's work will be fundamental to bring order to the chaos by separating what is pleasant and compliant from what is not. Hence all the expressive richness of the spirits where the quality formula always involves starting from selected raw materials that do not show any rotting.
The fermentative boiling (from 'fervere' which means to boil), if left free to occur in its spontaneity, leads to results that are not at all predictable and not always interesting. Many companies thus prefer to select the yeasts that will trigger the fermentation and strictly control the production parameters in order to guarantee a certain reproducibility. This is the logic of the large ones, but the small producers, working on other quantities and with different timing, have the possibility, through spontaneous fermentations (the yeasts transported by the air, are already present in the cellar environment and on the external part of the materials to be fermented), to ensure a certain degree of variability while keeping the process variables under control.
Science has now identified the fundamental mechanism of the conversion of sugar into alcohol which takes place in the cytoplasm of yeasts. From a molecule of glucose (C6H12EITHER6), two molecules of pyruvate are obtained (C3H4EITHER3). Through the action of the enzyme pyruvate decarboxylase, pyruvate is transformed into acetaldehyde, and carbon dioxide is released. Thanks to the action of a further enzyme, alcohol dehydrogenase, acetaldehyde is finally transformed into ethanol.
Knowledge of the reaction mechanism allows us to predict the alcoholic potential in distillation of any sugary material with a simple calculation. For example, if they have 1 kg of sugar in 10 liters of water, the mixture will have a sugar concentration equal to 10 brix and the potential alcohol content will be equal to: 10 brix * 0 .6 = 6% alcohol which is a theoretical value because fermentation is not always able to take place completely and then there are drops in yield.
Technical development has certainly made it possible to bring clarity to the dynamics that guide the fermentation process, but to date not all the secondary reaction mechanisms are yet known, so that aura of mystery that has always been linked to fermentation remains, giving space to various interpretations.
Felipe Fernandez-Armesto, historian of the second half of the 20th century, well expressed the suggestive power of fermentation:
“Fermentation is pure magic, because it can transform a simple bunch of grapes (and let's add any sugary matter) into a potion capable of changing behavior, suppressing inhibitions, clouding vision and opening the doors to entire imaginary kingdoms.”