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Winemaking (vinification) has been around for millennia, and winemakers continue to study to improve the wine. Oenology – the science of wine and winemaking – has been reviewed by vintners (winemakers) to continually improve their products. Their studies have supported the health effects of wines. To understand the impacts on our health, you must first understand the winemaking process.
I’m sure most of us know wine is made from grapes; however, it is not simple stomping on some grapes and drinking the result. The first step to vinification is agriculture (obviously); you need grapes before wine-harvesting can be done mechanical or hand-harvested.
What is harvested depends on the vintner; there are hundreds of different grapes (cultivars). They will look at the sugar levels, acidity, ripeness, and volatile organic compounds (VOC) to determine which grapes to use in the winemaking process. Once picked, the grapes are destemmed, and any leaves, sticks or unwanted additions are removed – at least for red wine – white wine typically keeps the stems and leaves in to create a more ‘earthy’ aroma. The tannins are the significant compounds involved with the wine’s colour, smell and taste.
After harvesting, the grapes need to be crushed and then pressed. Crushing can be done in a few ways; The first image that comes to mind is the stomping on the grapes bare-foot in a barrel – the most used method for centuries – thankfully, we can now drink our wine untouched by toes thanks to machinery. The result of crushing produces must – the pulp of the grapes. The degree of crushing varies depending on the wine and the winemaker. For example, Pinot noir or Syrah intentionally leave some whole grapes (berries) to allow for more fruity aromas (due to the retention of certain organic compounds and a particular fermentation method).
The purpose of crushing is to release the contents of the grapes – particularly the sugars – to get the juice. There is no significant difference between red and white at this point. However, the vintner is likely to make its own unique adjustments to crushing methods and techniques.
The juice that comes from the must will make the wine; it is also the key difference between red and white. The must (juice and crushed grapes with the skins) are fermented and pressed for red wine. The liquid is extracted (pressed) for white wine and then fermented, so there is no contact with the skins, hence the characteristic clear white colour. For Rose, the must is allowed to sit in the juice for a short period (3-24 hours) before pressing and fermentation.
Without fermentation, wine would just be grape juice. The primary fermentation method adds yeast (a fungus) to the must (or juice for white). The yeast consumes the sugar to produce ethanol and carbon dioxide.
Arguably, the most essential step of vinification fermentation needs the most control. Then, the vintner decides how to approach it, but oxygen, temperature, sugar, and fermentation rate are the most important. Oxygen is essential to control as fermentation only occurs in oxygen-free environments. Next, however, the temperature is vital. Red wines are fermented at around 22 to 25 °C while whites are fermented at approximately 15 to 18 °C; this explains why red wine has higher alcohol content because yeast likes warm environments.
To avoid the production of acetate (vinegar) and to control the alcohol content, sulfites (SO2) can be added at the wine-makers discretion. Usually, the yeast can’t survive in more than 12% ethanol, but specific yeasts have a higher alcohol tolerance and can produce up to 18% ethanol. Once satisfied with the primary fermentation, most wines will head into secondary fermentation (malolactic fermentation).
Malolactic fermentation uses bacteria intending to remove any ‘tart’ tastes and reduce acidity. For example, lactobacillales are the bacteria used in malolactic fermentation. This process takes about three-six months (again, depending on the vintner), where most of the testing of wines occurs. The purpose of this is to convert malic acid to lactic acid, ultimately making the wine ‘softer’ by reducing the acidity of the wine. Certain wines (particularly Riesling) limit this fermentation to create a more acidic wine; white wines generally aim to be more acidic, while red wines typically complete the secondary fermentation process.
Pressing is an essential step in vinification. First, the must is pressed to separate the juice from the pomace (the pulp leftover). This occurs after fermentation for red wines and before for white wines. The original method of pressing was using wooden baskets to press down on the must; nowadays, industrial pressers are most commonly used. After pressing, the juice must be placed in a container to continue the process. Oak barrels are used, as well as steel containers (most common) or glass containers (popular with amateur vintners). These all affect the final result, especially barrel storage, as the tannins in the barrel’s wood affect the liquid. Steel containers are the most sterile and easiest to control; glass is cheaper and cleaner.
Once pressed and placed in the container, cold stabilisation is performed. It is the process of dropping the temperature of the wine close to freezing for about two weeks to reduce tartrate crystals (cream of tartar) known as wine crystals which precipitate out and are filtered out. During this time, while the wine is being aged, most of the testing is done to check the acidity, alcohol content, VOC, and other compounds.
Blending is done at the vintners’ discretion. They can choose to blend various cultivars and adjust acidity and tannin concentrations. For sweet or dry wines, fermentation is usually stopped prematurely – using sulfites, generally – to increase the sugar content. To make up for the loss of alcohol, high-proof grape brandies can be added (such as in port).
As for fining or clarifying –removing any unwanted tannins, harsh sourness or particles that might cloud the wine – using various agents is the step before adding preservatives.
One commonly used fining agent is gelatine, which binds or reacts with these unwanted compounds and forms sediment filtered out. Of course, the wine has no gelatine, but it makes it non-kosher. Other fining agents are animal products such as casein (a cow milk protein), egg whites or albumin, bone char and even egg shells! To create kosher wines, non-animal products can be used, such as cellulose pads or bentonite.
The last step before bottling is the addition of preservatives and filtration. Although there are other preservatives, SO4 is the most common. It functions as an antioxidant and antimicrobial. In addition, it prevents bacterial growth and inhibits any fermentation. After this, the wine is filtered through some machines to produce a clear product. Then it is bottled and sold.
Vinification is a complex process that requires a lot of time and attention to detail, but this is why wine is arguably the healthiest alcoholic drink. This is because it has the highest concentration of VOC, which each have its own significant impact on health. Read more to find out about how wine affects our health.
Winemaking is an age-old profession. Wine is arguably the healthiest liquor – find out how it’s made and affects us.
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