MODULATION OF YEAST-DERIVED AROMA COMPOUNDS IN CHARDONNAY WINES USING ENCAPSULATED DIAMMONIUM PHOSPHATE TO CONTROL NUTRIENT RELEASE

Abstract

Yeast-derived aroma compounds are the result of different and complex biochemical pathways that mainly occur during alcoholic fermentation. Many of them are related -but not limited- to the availability of nutrients in the fermentation medium and linked to nitrogen metabolism and biomass produced. Besides, the metabolic phase of yeast also regulates the expression of many enzymes involved in the formation of aroma active compounds. The work investigates the overall effect of continuous supplementation of nutrients during alcoholic fermentation of a grape must on the volatile composition of wines. To this aim, diammonium phosphate was encapsulated mixed with a hydrophobic lipid matrix in two different supports designed to continuously release the salt for a final addition of 400 mg/L: a tablet-shaped support (Tb) of ~ 4 cm diameter and spherical microcapsules of ~0.2-1 mm diameter (Mc) obtained through spray cooling. The alcoholic fermentation was performed in triplicate at semi-industrial scale standardised conditions of turbidity (~100 NTU), yeast inoculum (200 mg/L) and fermentation temperature (19°C). Results were compared to those of wines fermented in absence of ammonium addition or supplemented with the same dose at the beginning of the alcoholic fermentation.

Among the metabolic compounds studied by GC-MS/MS, the production of acetate esters of higher alcohols was favoured by the Mc continuous ammonium release. This protocol almost doubled the total acetates formed in the untreated wines and increased ~33% and ~40% of those obtained with the one-shot supplementation and the Tb protocol respectively. Among alcohols, 2-phenylethanol and 2-methylbu-tanol were higher in the untreated wines and 1-propanol in the Mc protocol compared to others, even if the total amount of alcohols was not differentiated. Neither total fatty acids nor the corresponding ethyl esters were influenced by the nutrition protocol, even if some compounds were affected: ethyl hexanoate and ethyl octanoate were higher in the Mc protocol, differentiated from the Tb and one-shot protocols. Overall, nitrogen supplementation increased the total amount of esters in wines, being the Mc protocol the most performing, differentiated from the one-shot and Tb protocols that were statistically indistinguishable between them.