This is a favourite claim of the so-called “natural” or “non-interventionist” winemaking movement. One of the reasons why they claim it is better to do natural fermentation instead of using commercial yeasts is that commercial yeasts with their “predictable aromatic profiles” can make, say Sauvignon blancs from Europe, taste like New Zealand Sauvignon blancs. Or worse even, it can make Chenin blanc and Ugni blanc taste like Sauvignon blanc. I have personally been in a tasting with a group of oenologists representing most of the wine countries in the world where the Germans presented a Muller-Thurgau. Everyone, including the French (much to their despair) thought it was a Sauvignon blanc. I have also once given a South African Colombard to a group of French winemakers to taste and they also believed it to be a Sauvignon blanc.
So how does this happen and is it “wrong?” The “naturalists” feel it is wrong. Winery sales figures show it is “right.” Consumers like these aromas. Wines around the world can taste similar because we make wine mostly from one specie – Vitis vinifera. Then we also use yeast which originates from mainly one specie – Saccharomyces cerevisiae. Each grape variety is not equipped with a unique set of flavour active compounds. Only the combination is unique. This combination will differ between grape varieties as well as within the same grape variety in different vineyard blocks and vintages. The main aromatic compounds found in grapes are monoterpenes, C13 – norisoprenoid derivatives, pyrazines, thiols and certain amino acids that can be converted to aromatic higher alcohols and esters. The latter two groups are non-aromatic in grapes and converted by the fermenting yeast to a flavour active form. In some cases pyrazines found in Sauvignon blanc are seen as a positive. When present in reds such as Cabernet and Merlot it is seen as a negative.
Thiols smell like guava, passion fruit, grapefruit, black currant and gooseberry. Sauvignon blanc happens to have the highest thiol precursor concentration in the grapes. Wine yeasts convert these precursors to their flavour active forms and differ in their efficacy to do so. Many other white grape varieties contain these thiols but in lower concentrations. So unless you use yeasts that are very good in expressing these aromas and combine it with certain winemaking practices, these aromas will go unnoticed – as they did for many years. However, winemakers around the world are upping their game – competition is tough. They are using modern technologies and as a result they are tapping into these flavour profiles of their grapes that they did not know exist. As a result they can sell their wine in a bottle and not a box. Is this wrong?
Yes yes stone me, I work for a wine ingredients company and I have a commercial interested in winemakers using yeast. However, my clients who’s Chenins, Colombards, Ugni blancs, Muller-Thurgaus and Verdelhos that have “Sauvignon-like” aromas are certainly not complaining about their sales. If you have very good quality grapes then you have many other flavour active compounds that can “sell” your wine for you and you don’t necessarily have to make such an effort to express the thiols. When you have less than top quality grapes, then optimising what you have is a good idea and if that means optimising thiol expression then so be it.
Just for the record – contrary to popular belief I do support natural / un-inoculated fermentations when conditions are right for it. See my earlier blogpost: Natural vs. inoculated fermentations.