What is Wine?

Wine is grape juice that has undergone fermentation. Only one species of the genus Vitis is grown for human consumption: V. vinifera (otherwise known as the European grape). Despite the name, wines are not limited to those produced from the American native grape species V. labrusca. Different kinds of fruit can be fermented to create wine. For instance, peach and blackberry wine are both names for wines that are fermented using the juice of peaches and blackberries.

what is wine

Winemaker Collecting Grapes

Enology: Scientific Winemaking

Little was understood about fermentation or what caused spoilage until the 19th century. The ancient Greeks used clay amphorae to store their wine, whereas the ancient Romans used oaken cooperage to extend the shelf life of their wines[1]. On the other hand, they likely drank through most of their wines within a year after the harvest, adding extra tastes to mask any degradation. It was customary to use oak barrels for maturing prior to the mass production of glass bottles and the widespread use of the cork stopper in the 17th century[2]. This shifted when it was learned that wine stored in bottles could be consumed at a later date without becoming bad.

Most of the benefits of mechanical progress in the twentieth century may be attributed to improvements in quality assurance. Stainless steel is an excellent material for storage and fermentation containers since it is durable, resistant to corrosion, easily cleaned, and can be refrigerated to precise temperatures[3]. Reducing the potential for infection from airborne microorganisms is the goal of automated, hermetically sealed racks and filtration equipment. Mechanized grape harvesters and field crushers were first used in the 1960s, speeding up the harvest and allowing the grapes to go straight into the fermentation tanks[1].

The Wine Grape

Cultivation

Grapes thrive in excellent to warm climates but may even be cultivated in semitropical zones. They are not adapted to the cooler regions of the temperate zone if the growing season is too short for the fruit to ripen or if the low winter temperatures kill the vine or its producing buds. The fruit may not mature to full ripeness in any of these cases. V. vinifera is more vulnerable to frost damage than V. labrusca[4]. The weather profoundly affects the flavor and aroma of perfectly ripe grapes. The variable degrees of heat the plants receive throughout the growing season contribute significantly to the unique flavors of grapes grown in different regions. Factors like soil temperature, solar exposure, and diurnal temperature variation are essential.

what is wine

Wine Grapes Ready to be Harvested

Places with a low heat summation, like certain sections of France and Germany, may also be particularly vulnerable to the effects of seasonal weather. This is particularly true in places where it is colder. Fruit from these regions, where the growing season is often warmer than usual, is typically more completely grown and harmonic than fruit from cooler regions. If it is too hot during the growing season, the fruit will not be as brightly colored or acidic, and the berries will not make raisins as much (since they will not lose as much water) —the warmer the climate, the sweeter the dessert wine.

Weeding and pruning are examples of agricultural activities that may affect the end product’s chemical composition. How soil composition impacts wine quality is unclear and may vary significantly from place to region. Grape nutrition, soil temperature, root penetration, water retention, and soil permeability may all be affected by soil composition.

The Wine-Making Process

Harvesting

When creating wine, it is best to use grapes at the peak of ripeness without becoming mushy. In cooler regions, such as northern Europe and the east coast of the United States, the lack of sufficient heat to initiate ripening may require picking before the grapes have reached full maturity. You might use additional sugar or switch to grape juice concentrate to compensate for the resulting lack of sweetness. Grapes with these qualities have a high sugar content because of the natural moisture loss during ripening on the vine or drying in the sun after harvest[5].

The famous Málaga wines of Spain are produced using a process called partial raisining. Utilizing the beneficial mold Botrytis cinerea may hasten the drying. These grapes are often used to produce dessert wines. For these wines, fermentation must be halted before all of the sugar is converted to alcohol. Methods like injecting sulfur dioxide, using small fermenting vessels, or processing at low temperatures are utilized[6].

The content of the grapes may be significantly affected by when they are harvested, making it crucial that this occurs at the ideal period. Wines harvested too early tend to be weak and watery, whereas harvests that occur too late might produce powerful wines that lack acidity[3]. It is possible that harvesting will need more than one attempt.

Following their harvest, grape clusters are first placed in smaller containers such as buckets or cartons before being transferred to larger ones for transport to the winery. Using a machine to harvest the berries involves breaking the stems or shaking the clusters to release the fruit. The grapes may either be dropped directly into the crusher at the winery or dumped into a sump and transported there by a continuous conveyor system[4].

Crushing

Modern winemaking equipment often includes a crusher-stemmer, crushing the grapes, and removing the stems. Typically, it is in the shape of a perforated cylinder with paddles that spin at 600 to 1,200 revolutions per minute. Grapes are crushed and dropped through the cylinder’s openings, where the bulk of the stalks are ejected. Roller crushers are another viable alternative. Crushing with one’s feet or stomping on something with one’s shoes is an archaic activity that is seldom seen nowadays[4].

what is wine

Grapes Entering a Manual Grape Crusher

In the Champagne region of France, where white juice is created from white grapes using red grapes as a foundation ingredient, pressing is the preferred technique for crushing grapes. The containers are often filled with whole bunches of red grapes and then sealed. The fruit’s respiration, which consumes oxygen and releases carbon dioxide, ultimately kills the skin cells, leaving the fruit’s outer layer entirely permeable for dye extraction. There is also some malic acid respiration happening inside the cell. When cultivated in hotter locations, this respiration process takes longer, which may lead to wines that are light in color and acidity and have a distinctive aroma[3].

Juice Separation

When white grapes are harvested, the juice is usually extracted from the fruit immediately, while the skins and seeds are discarded. This is done so that the wine may be fermented without oxidation. As the method is the same for white and non-white grapes, it does not matter which ones are used. Allowing the white skins to soak in the juice for 12-24 hours may improve the flavor extraction, but it may have the opposite effect on the color extraction[3].

There are two main strategies used to separate sediments from the juice. Crushing grapes and storing them in a container with a plastic bottom and, in most cases, plastic sides may lead to a significant loss of grape juice. Must refer to the solid residue left after grapes have been crushed, whereas free flow juice refers to the liquid that flows away without being pressed. Most often refers to unfermented grape juice, with or without the skins[3].

Because red wine production requires concurrent fermentation of the grape skins, seeds, and juice, continuous presses are ideal for this process stage. The grape skins become considerably less slippery during fermentation, making it much easier to squeeze the juice out. Therefore, more juice may be recovered from the grapes using free-flowing techniques than would be possible with unfermented musts[7]. If the particles are not excessively slippery, pressing may be an effective way to separate liquid from solids.

Wine spirits may be distilled using the pomace, or crushed grape remnants, that are left over after wine has been extracted. Both the white and red wine fermentation processes have this characteristic. In order to get a lower alcohol content in the finished wine, water is often added prior to stopping the fermentation process and draining the liquid. The pomace may be further cleaned and pressed, or it can be swiftly distilled in specialized stills[2].

Must Treatment

White musts are murky and need settling to remove the suspended particles. Avoiding fermentation and ensuring that the suspended material settles correctly may be aided by preventative measures, such as injecting sulfur dioxide in advance and reducing the temperature during the settling process. Centrifugation is used to filter out unwanted solids from the white must in wineries all over the world.

By moving in a circle, a powerful pulling force is generated. Musts that have become an unattractive brown color are often subjected to pasteurization, which destroys the browning enzymes responsible for the discoloration. It is not typical practice to add pectin-breaking enzymes to the must before pressing[7]. Bentonite is a clay that may be added to musts to help remove some of the nitrogen and speed up the clarifying process.

Heating has recently seen a popularity resurgence to eliminate color and inactivate enzymes in red musts before fermentation. The purpose of this is to facilitate pre-fermentation. This method might help make sweet red wines if executed rapidly, at moderate temperatures, and without subjecting the wine to excessive oxidation[3]. Use with red grapes that have been infected with the parasite fungus Botrytis cinerea, and benefit from brief durations of fermentation on the skins. Wine is produced using this process. Highly concentrated polyphenol oxidase enzymes, which cause browning, are found there[8].

Fermentation

Careful monitoring and controlling of the fermentation process are essential for producing high-quality wines. The existence of sufficient quantities of suitable yeasts is one of the prerequisites since they will prevent the growth of undesirable microbes. By ensuring the yeast has all the resources they need to grow, oxidation may be prevented by keeping the temperature under control. Finally, it is essential to handle the red cap of floating skins properly[9].

Grapes often develop a surface colony of bacteria, molds, and yeasts. Therefore, this will be the outcome. While Saccharomyces is the winemaker’s preferred yeast, wild yeasts like Pichia, Kloeckera, and Torulopsis might outnumber it throughout fermentation[6]. Despite the widespread belief that only Saccharomyces yeasts can ensure a quick and thorough alcoholic fermentation, other yeast genera may contribute significantly to the final product’s flavor, particularly in the early going.

This is especially true if fermentation was started with a yeast strain other than Saccharomyces. This is particularly the case if the yeast employed to initiate fermentation was already present in the substrate. Because it transforms sugar into alcohol more effectively and is less vulnerable to the growth-inhibiting effects of alcohol, Saccharomyces yeast is preferred over other yeast species[8]. For that reason, it is the superior yeast for fermenting any beer. However, there have been situations when strains of Saccharomyces cerevisiae have produced alcohol at levels as high as 18%, although the usual top limit for alcohol concentration is about 16%[6].

Clarification

The suspended material (yeast cells, skin particles, etc.) in certain wines settles out quickly, and the wine’s supernatant retains almost all of its brightness even after the sediment settles. Since 50-gallon wooden barrels have a greater surface area-to-volume ratio than larger containers, they are ideal for this purpose[2]. The uneven interior of a wooden coffer aids the settling of suspended particles. This is particularly true of wines made in warmer areas or stored in large tanks, where the cloudiness may persist for years.

When something is clarified, the particles that have settled to the bottom due to age are dissolved. The critical actions carried out throughout this procedure include fining, filtration, centrifugation, cooling, ion exchange, and heating[6].

Aging and Bottling

Aging

The quality of many wines improves with time in barrels or bottles. The wines will peak at some point and then decline as they age. A wine’s acidity decreases as it ages, becoming clearer and more stable as sediment settles to the bottom, and its myriad ingredients mix to generate complex compounds that affect the taste and aroma[6].

Wines are aged for some time in oak barrels, which are wooden containers that allow air to enter while allowing water and alcohol to evaporate. Wood essences have a role in imparting flavor. Alcohol in wine is concentrated when it is stored in low humidity settings, whereas it is diluted when the wine is stored in high humidity environments[8]. What kinds of substances evaporate depends on the relative humidity. As the wine’s water and alcohol evaporate, a space called headspace or ullage is left behind. To compensate for the volume loss, you may transfer some of the exact wine from another bottle.

what is wine

Wine Aging in Barrels

Bottling

To prevent microbial development before bottling, wine may need to be blended, filtered, and treated with antiseptics. Since different barrels of the exact same wine may age differently, blending is required to create uniformity in the final product. Wines that are somewhat weak in color or acidity may be improved by mixing with wines that are more remarkable for these traits. Blending may enhance a wine’s quality by making it more nuanced and exciting to drink[3].

Conclusion

As we have established, wine is an alcoholic beverage made from the fermentation of grapes. Fruit wine, sometimes called country wine, is made from fermented fruit juices rather than grapes. However, traditional wines are made from grapes cultivated for that reason. In addition, good grapes are essential for making a drinkable wine. Despite the continued use of native species, vines have been sent worldwide, and new grape types are being developed every day to ensure success in the ideal growing conditions. More than that, making wine is a labor-intensive process that takes a long time and requires many hands, no matter what wine is being made.

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References

[1] “Wine – Flavoured Wines | Britannica,” in Encyclopædia Britannica, 2022

[2] Jancis Robinson, The Oxford Companion to Wine (Oxford: Oxford University Press, 2015).

[3] Elisa GuerraDoce, “The Origins of Inebriation: Archaeological Evidence of the Consumption of Fermented Beverages and Drugs in Prehistoric Eurasia,” Journal of Archaeological Method and Theory 22, no. 3 (2015): 751–82.

[4] Helder Fraga et al., “Integrated Analysis of Climate, Soil, Topography and Vegetative Growth in Iberian Viticultural Regions,” ed. Inés Álvarez, PLoS ONE 9, no. 9 (September 24, 2014): e108078.

[5] Jancis Robinson, The Oxford Companion to Wine (Oxford: Oxford University Press, 2015).

[6] Michael Spilling and Winnie Wong, Georgia (New York: Marshall Cavendish Benchmark, 2009).

[7] BBC News, “‘World’s Oldest Wine Found in 8,000-Year-Old Jars in Georgia,” BBC News (BBC News, November 13, 2017).

[8] “Now That’s What You Call a Real Vintage: Professor Unearths 8,000-Year-Old Wine,” The Independent, December 28, 2003.

[9] Wine Folly Research, “What Is Wine? A Beautiful Explanation | Wine Folly,” Wine Folly, 2022.

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