Role of Microbes in different wine production
Microbial production of Beverage
Advanced biotechnology plays a significant role in food and beverage production, particularly in the major industry sector. An important area within biotechnology is Food Biotechnology, which focuses on improving food products’ quality, nutritional consistency, color, safety, and preservation.
Alcoholic beverages are produced worldwide, and historical evidence suggests that the fermentation of grains dates back to as early as 4000 B.C. The production of alcoholic beverages has been an integral part of human civilization. The biological and chemical principles underlying alcoholic beverage production were elucidated by Louis Pasteur in the second half of the nineteenth century.
Wines originated in the Middle East and Europe. Both red and white wines typically contain 10–16% alcohol content. The large-scale production of wine primarily uses grapes from the Vitis vinifera species. Grapes are an excellent choice for wine production because the juice is rich in natural sugars and other essential nutrients, possesses natural acidity, and can develop pleasant aromas and flavors — all of which contribute to making exceptional wine.
Louis Pasteur often used to state, “Wine is the most healthy and most hygienic of beverages.”
Production of wines
For the production of wine, the following steps are followed:
- Select high-quality grapes, as they are essential for wine production.
- Next, crush the grapes either mechanically or by foot to extract the juice. This juice, which is ready for the fermentation process, is technically referred to as a “must.”
- Add sulfur dioxide to inhibit the growth of non-wine yeasts and contaminating bacteria. This process is known as partial or complete sterilization.
- Next, inoculate the must-in bioreactors with the desired strains of the yeast Saccharomyces cerevisiae.
- Oxygen is produced in bubbles during the fermentation process, which promotes the healthy growth of yeast cells. Over time, aerobic conditions are gradually established.
- Wine production typically takes between 2 to 5 days. Other fermentation conditions, such as temperature and time, vary depending on the type of wine being produced.
- At the end of fermentation, the wines are transferred to storage tanks or vats, where they are allowed to age. This aging process can take several months or even years. Aging is crucial for the development of the wine’s characteristic flavor and aroma.
Types of wines
There are hundreds of different types of wines produced in various parts of the world.
RED WINE
Red wine is a popular choice for many people in the West, often enjoyed during lunch and dinner. The red color of this wine comes from the pigments extracted from the skins of black grapes during the crushing process. Examples of red wines include Cabernet Sauvignon, Merlot, and Syrah.
Saccharomyces cerevisiae is the primary yeast used in red wine production. It is responsible for producing alcohol dehydrogenase. Additionally, several lactic acid bacteria, including Oenococcus oeni, Lactobacillus plantarum, Lactobacillus brevis, and Pediococcus pentosaceus, play a crucial role in malolactic fermentation (MLF). This process enhances the wine’s aroma, improves microbial stability, reduces acidity, and increases the mouthfeel.
WHITE WINE
White wine can be made from black grapes after the removal of the skins or from white grapes. Examples of white wines include Chardonnay, Riesling, Sauvignon Blanc, and Pinot Grigio.
Saccharomyces cerevisiae yeast is primarily used in the production of white wine, as it converts grape sugars into alcohol. Non-saccharomyces yeasts can also be employed to enhance the color stability, intensity, and tonality of the wine. Various types of lactic acid bacteria, such as Oenococcus oeni, contribute to the release of metabolites during the fermentation process. These lactic acid bacteria help produce lactic and acetic acids from sugars, glycerol, and tartaric acid in the wine.
Additionally, organisms like filamentous fungi and Downy mildew (Plasmopara viticola) may lead to off-flavors in the wine. Both yeasts and lactic acid bacteria can influence the color of the wine.
ROSE WINE
Rosé wine is produced with limited contact between the skins of red grapes and the juice during fermentation, employing the skin contact method. Grape varieties commonly used in the production of rosé wine include Grenache, Mourvèdre, and Pinot Noir, and it is made in many regions around the world.
The fermentation process typically utilizes Saccharomyces cerevisiae yeast, which plays an important role in producing alcohol dehydrogenase, various alcohols, esters, and anthocyanins. These compounds contribute to alcoholic fermentation and the color stability of the wine. Other yeast species, such as Candida, Pichia, and Zygosaccharomyces, also play important roles in the production of rosé wine. Additionally, lactic acid bacteria influence the color of red wines and help convert sugar into lactic acid in a process known as lactic souring.
DRY WINE
Dry wine has a higher alcohol content and contains no residual sugar, making it the opposite of sweet wine. During the production of dry wine, sugars are fully fermented to produce alcohol. Some examples of dry wines include Pinot Grigio, Sauvignon Blanc, and Merlot. Yeast, lactic acid bacteria, and acetic acid bacteria are used during the fermentation process of dry wine.
SWEET WINE
Sweet wine has a sweet taste due to residual sugar remaining after fermentation. It is also referred to as dessert wine. Popular varieties of sweet wines include Moscato, Riesling, Port, Lambrusco, Muscat, and Sauternes.
FORTIFIED WINE
The typical alcohol concentration in wines is below 16%. Wines can be fortified by adding distilled spirits, such as brandy, to achieve the desired alcohol level. Examples of fortified wines include sherry, port, and vermouth.
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