Fermentation in winemaking
The process of fermentation in winemaking turns
History
The natural occurrence of fermentation means it was probably first observed long ago by humans.
Process
In winemaking, there are distinctions made between ambient yeasts which are naturally present in wine cellars, vineyards and on the grapes themselves (sometimes known as a grape's "bloom" or "blush") and cultured yeast which are specifically isolated and inoculated for use in winemaking. The most common
The addition of cultured yeast normally occurs with the yeast first in a dried or "inactive" state and is reactivated in warm water or diluted grape juice prior to being added to the
Upon the introduction of active yeasts to the grape must,
Other compounds involved
The
Some strains of yeasts can generate volatile thiols which contribute to the fruity aromas in many wines such as the gooseberry scent commonly associated with Sauvignon blanc.
Brettanomyces yeasts are responsible for the "barnyard aroma" characteristic in some red wines like Burgundy and Pinot noir.[13]
Methanol is not a major constituent of wine. The usual concentration range is between 0.1 g/liter and 0.2 g/liter. These small traces have no adverse effect on people and no direct effect on the senses.[14]
Winemaking considerations
During fermentation, there are several factors that winemakers take into consideration, with the most influential to ethanol production being sugar content in the must, the yeast strain used, and the fermentation temperature.[15] The biochemical process of fermentation itself creates a lot of residual heat which can take the must out of the ideal temperature range for the wine. Typically, white wine is fermented between 18–20 °C (64–68 °F) though a wine maker may choose to use a higher temperature to bring out some of the complexity of the wine. Red wine is typically fermented at higher temperatures 20–30°C (68–86°F). Fermentation at higher temperatures may have adverse effect on the wine in stunning the yeast to inactivity and even "boiling off" some of the flavors of the wines. Some winemakers may ferment their red wines at cooler temperatures, more typical of white wines, in order to bring out more fruit flavors.[11]
To control the heat generated during fermentation, the winemaker must choose a suitable vessel size or else use a cooling device. Various kinds of cooling devices are available, ranging from the ancient Bordeaux practice of placing the fermentation vat atop blocks of ice to sophisticated fermentation tanks that have built-in cooling rings.[16]
A risk factor involved with fermentation is the development of chemical residue and spoilage which can be corrected with the addition of
The ethanol produced through fermentation acts as an important co-solvent to the non-polar compound that water cannot dissolve, such as pigments from grape skins, giving wine varieties their distinct color, and other aromatics. Ethanol and the acidity of wine act as an inhibitor to bacterial growth, allowing wine to be safely kept for years in the absence of air.[17]
Other types of fermentation
In winemaking, there are different processes that fall under the title of "Fermentation" but might not follow the same procedure commonly associated with wine fermentation.
Bottle fermentation
Bottle fermentation is a method of
Carbonic maceration
The process of carbonic maceration is also known as whole grape fermentation where instead of yeast being added, the grapes fermentation is encouraged to take place inside the individual grape berries. This method is common in the creation of Beaujolais wine and involves whole clusters of grapes being stored in a closed container with the oxygen in the container being replaced with carbon dioxide.[19] Unlike normal fermentation where yeast converts sugar into alcohol, carbonic maceration works by enzymes within the grape breaking down the cellular matter to form ethanol and other chemical properties. The resulting wines are typically soft and fruity.[20]
Malolactic fermentation
Instead of yeast, bacteria play a fundamental role in malolactic fermentation which is essentially the conversion of malic acid into lactic acid. This has the benefit of reducing some of the tartness and making the resulting wine taste softer. Depending on the style of wine that the winemaker is trying to produce, malolactic fermentation may take place at the very same time as the yeast fermentation.[21] Alternatively, some strains of yeast may be developed that can convert L-malate to L-lactate during alcohol fermentation.[22] For example, Saccharomyces cerevisiae strain ML01 (S. cerevisiae strain ML01), which carries a gene encoding malolactic enzyme from Oenococcus oeni and a gene encoding malate permease from Schizosaccharomyces pombe. S. cerevisiae strain ML01 has received regulatory approval in both Canada and the United States.[23]
See also
References
- ISBN 0198609906.
- ISBN 0789208830.
- ISBN 0671687026.
- ISBN 0198609906.
- ^ Nigro, Dana. "Taking the Water out of Winemaking". Wine Spectator, 2 October 2015.
- ^ Cockcroft, Marlaina. "It's in the Bag". New Jersey Monthly, 15 March 2017.
- ^ Gemma Beltran, Maria Jesus Torija, Maite Novo, Noemi Ferrer, Montserrat Poblet, Jose M. Guillamon, Nicholas Rozes, and Albert Mas. “Analysis of Yeast Populations During Alcohol Fermentation: A Six Year Follow-up Study”. pp. 3–4 Systematic and Applied Microbiology 25.2 (2002): 287–93.
- ISBN 0198609906.
- ^ Gemma Beltran, Maria Jesus Torija, Maite Novo, Noemi Ferrer, Montserrat Poblet, Jose M. Guillamon, Nicholas Rozes, and Albert Mas. “Analysis of Yeast Populations During Alcohol Fermentation: A Six Year Follow-up Study”. Systematic and Applied Microbiology 25. February 2002: 287–93.
- ISBN 0198609906.
- ^ ISBN 0198609906.
- ^ "fermentation." Oddbins Dictionary of Wine. London: Bloomsbury Publishing Ltd, 2004. Credo Reference.
- ISBN 0198609906.
- ^ Jackson, Ronald S. Wine Science Principles and Applications, p. 277. San Diego, California: Academic Press, 2008.
- ^ Jackson, Ronald S.; Wine Science Principles and Applications, p. 276. San Diego, California: Academic Press, 2008. [ISBN missing].
- ISBN 0789208830.
- ^ Jackson, Ronald S.: Wine Science Principles and Applications, p. 276. San Diego, California: Academic Press, 2008 [ISBN missing].
- ISBN 1563054345.
- ISBN 1563054345.
- ISBN 1891267914.
- ISBN 1563054345.
- ^ "Wine Research Centre at UBC - Malolactic yeast ML01 – the Facts". Archived from the original on 2012-03-16. Retrieved 2012-03-05.
- ^ "New substances: risk assessment summary EAU-224". Ec.gc.ca. October 2018. Retrieved 17 November 2018.