Webinars

Aromatic potential of the grape and its expression in wine
Dr. Miquel Puxeu Vaqué, VITEC - Centre Tecnològic del Vi

The aroma of wine is a mixture of thousands of volatile compounds with different origins. Some of them are from grapes, commonly called varietal aromas and intrinsic to the grape variety. Others originate during alcoholic or malolactic fermentation. These are secondary products formed during the fermentation and called fermentative or secondary aromas. The third group of aromas are tertiary and have their origin in wine evolution and ageing. In main grape varieties, the aroma complexity dramatically increases during alcoholic fermentation as a result of the synthesis of important volatile compounds by the wine yeast Saccharomyces cerevisiae and the release of varietal aroma precursors. Depending on the specie or species of yeasts involved in the alcoholic fermentation, the resultant aroma profile can be very diverse, due to the important role that the yeast play in the synthesis of volatile compounds.

Grape-derived aroma precursors are a potent pool of potential aroma compounds that can actively contribute to the final wine sensory profile and play a major role. Two main groups of potential aroma molecules include volatile thiol pre-cursors and terpene and C13-norisoprenoid, as well as glycosides. 
Volatile thiols are virtually non-existent in grape juice but can be released during fermentation from their conjugated cysteinylated or glutathionylated precursors due to the β-lyase activity of certain Saccharomyces cerevisiae strains, keeping in mind that these aptitudes are also present in other yeast species. At certain concentrations, volatile thiols including 4-MMP, 3-MH and 3-MHA, can impart passionfruit, grapefruit, box tree and guava aromas in various varieties, including Sauvignon blanc and Verdejo. The thiols 4-MMP and 3-MH are formed from the non-volatile grape-derived pre-cursors (‘released’), whilst 3-MH can be converted to the more aroma-active 3-MHA by the yeast (‘converted’).

In the grape, monoterpenes, sesquiterpenes and C13-norisoprenoids can be present in a free, volatile form, adding to the fruity, floral and spicy notes in wine. A large concentration of these compounds, however, are bound to a sugar molecule and thus odourless. These glycosylated pre-cursors can be released via acid hydrolysis (usually taking place during wine ageing and storage), or enzymatic hydrolysis. The selection of the appropriate yeast for the alcoholic fermentation will directly impact the degree of release of primary aromas from the grape. Once released, these compounds can considerably alter the wine aroma profile. 
Focus all the attention in wine alcoholic and malolactic fermentations is a good strategy to elaborate expressive and singular wines enhancing the entire quality of grapes.


The synergy between innovative yeast and bacteria blends for wine quality
Elda Binneman, Anchor Oenology

Innovation is a key concept for Anchor and as a result, we have developed many innovative and unique commercial yeast and bacteria cultures, all based on sound, scientific research validated at pilot, as well as industrial scale. Three key innovations, the first of their kind in the world, include inter-species yeast hybrids and scientifically formulated yeast and bacteria blends. These are specifically developed to enhance the sensory profile of the wine by accessing the grape-derived potential pool of aromatics.

The crossing of different yeast to produce hybrids involve three main steps: sporulation, isolation of the spores and fusion of the spores to create a new hybrid wine yeast strain. Based on this natural technique, we have created the world’s first interspecies wine yeast hybrids, which allows us to combine the most advantageous characteristics of the two parent strains, in one unique, new strain. 
The first scientifically formulated yeast blends were created to release and convert volatile thiols, as well as form stable esters (via the esterification of yeast-formed higher alcohols and grape-derived fatty or organic acids) during fermentation. The yeast does not produce these precursors, but rather play a role in releasing them from their non-volatile forms that are part of the global aromatic potential derived from the grape.

Concerning malolactic fermentation, Oenococcus oeni has long been regarded as the reference bacteria for the completion of this fermentation. This genus of bacteria is robust and able to withstand the more challenging conditions of malolactic fermentation, including pH and sulphur tolerance. It is for this reason that most commercial bacteria cultures for wine have consisted of O. oeni. In recent years however, interest in Lactobacillus species have grown. Research has shown that Lactobacillus species, L. plantarum in particular, display a more complex enzymatic profile, specifically concerning the release of grape-derived aroma compounds (β-glucosidase activity) and using grape-derived molecules (via iminopeptidase and esterase activity) to enhance the organoleptic properties of the wine. This has allowed us to view malolactic fermentation as a potential aroma and quality enhancing process, rather than just the conversion of malic to lactic acid. 
Anchor is the first company to launch a blended bacteria culture, to harness the fermentation capabilities of O. oeni, whilst focusing on the sensorial contribution of the L. plantarum strain. Co-inoculation, adding the bacteria together with the yeast, allows the L. plantarum strain to release and produce compound to enhance the sensory profile of the wine, together with the O. oeni presence to complete the fermentation. The use of these blended cultures can enhance freshness, fruitiness and softness, as well as reduce astringency, bitterness and greenness.

Miquel Puxeu Vaqué, VITEC - Centre Tecnològic del Vi
Químico e doutorado em Enologia. Miquel Puxeu Vaqué é responsável pelo laboratório de investigação de Enologia do VITEC, Centro Tecnológico do Vinho em Calalonia, Espanha, há mais de dez. Possui uma vasta experiência em análise de vinhos, vinificação, consultoria em adegas e gestão de projetos de investigação e inovação nacionais e internacionais.

Elda Binneman, Anchor Oenology
Enóloga com mestrado em enologia. Elda realizou um extenso trabalho no campo do desenvolvimento de produtos enológicos, com especial foco nas bactérias do ácido lático e na fermentação malolática. Atualmente, Elda é gerente internacional de produtos da gama de produtos enológicos Anchor.