Understanding varietal aromas during alcoholic and malolactic fermentations
ACETALDEHYDE MANAGEMENT DURING WINEMAKING
CO-INOCULATION OF SELECTED WINE BACTERIA
This Winemaking Expert explores the ever increasing practice of co-inoculation. In France and Spain for example, close to 50% of MLF is now done via co-inoculation. The advantages are numerous, such as ensuring a faster more secure process and reducing time for the MLF. Co-inoculation is an important modulator in sensory development, and it helps limit the development of spoilage microorganisms and thus limits off flavor compound productions. For example, a wine bacteria like the Enoferm Beta can produce higher levels of diacetyl during sequential inoculation. Co-inoculation on the other hand, will reduce the production of diacetyl and consequently reinforces the fruity character of white wines. Timing of inoculation, interaction with yeast, the presence of precursors that promote the production of aromatic molecules, pH and temperature conditions are all criteria that modulate aromatic expression in wines. Choosing a wine bacteria has become a parameter to take into consideration for developing a specific wine profile.
Sculpting the aromatic profile of wine through diacetyl management
In addition to carrying out the bio-deacidification of wine, malolactic (ML) bacteria influence aroma and flavour through various mechanisms, including the production of volatile grape- and yeast derived metabolites. In wine, one of those volatile compounds – diacetyl – has important stylistic implications. This diketone, also known as 2,3-butanedione, is associated with the “buttery” character of wine and is formed as an intermediate metabolite in the reductive decarboxylation of pyruvic acid to 2,3-butanediol.The formation and degradation of diacetyl is closely linked to the growth of such ML bacteria as Oenococcus oeni and the metabolism of sugar, malic acid and citric acid. Yeasts are also able to synthesize diacetyl during alcoholic fermentation (AF). However, most of this diacetyl is further metabolized to acetoin and 2,3-butanediol. This issue of Winemaking Update will review winemaking practices and the latest findings to help modulate diacetyl content in wine through malolactic fermentation (MLF).