Introduction to Wine Components.

Wine is quite a unique product, in that there is no typical “ingredients” list on the label. In my opinion, the only actual ingredient is fresh grapes. A major Hollywood celebrity produces her own wine brand and uses a marketing style which fixes a problem that you didn’t know existed in the first place. Her site tells you about all of the potential additives to wine and prides herself on a very minimalistic approach. This is fine, but it is nothing new. It’s just low intervention winemaking.

Most additives used in modern, quality winemaking are pure forms of a naturally occurring component of grapes, wine and oak. The same yeasts we add are found naturally on the grapes in the vineyard. Any acid we add has been extracted from the spent grape skins and seeds. Same with the grape tannins. Oak tannin additives can be used that have been extracted from oak.

All these additives are natural, and we cannot differentiate between natural and added in the resulting wine. One important thing to note is there are absolutely no flavour additives used, or even available for use in winemaking. The flavour in wine is 100% grape derived. The use of additives such as acid and tannin allow us to re-balance the wine to best enhance the flavour and provide good product shelf life.

Let’s investigate what wine is made of.

First, the basics.

The largest component of wine is water, comprising approximately 80 – 90%. The water comes from the grapes, with very small amounts added in the winemaking process to aid in the addition of wine additives, which we will cover later.

The next largest component by volume is alcohol (ethanol). Ethanol, a byproduct produced during fermentation by yeast converting sugar, is the main alcohol in wine. It typically ranges from 8-15% by volume, contributing to the wine’s flavour, body, and warming sensation.

Then there are acids, crucial for the wine’s structure, balance and preservation. The primary acid is tartaric, with smaller proportions of malic, citric and lactic. Acids provide freshness and complexity and adds length to the palate.

Sugars play a large role prior to alcoholic fermentation, however the remaining, or “residual sugar” is significantly less. A wine is called “dry” when the yeast has exhausted all of the fermentable sugars it can, and the “residual sugar” is below about 3gms per litre.

Phenolic compounds make up most of the wine’s body, texture and colour. They include tannin (producing a drying, grippy mouth sensation), flavonoids (part of the flavour component) and anthocyanin (responsible for colour)

Esters, aldehydes, ketones and thiols are a few of the enormous range of volatile aroma and flavour compounds which contribute to the distinct smell and taste of a particular wine.

Sulphites are added (and produced by yeast) to prevent oxidation and spoilage, preserving the freshness and contributing to the longevity of the wine.

Grapes: The Raw Ingredient

Quite simply, grapes are the absolute key ingredient in making wine. Everything required to make wine exists within the grape berry itself or resides on the surface of the berry. Different grape varieties (or cultivars) refer to different types of the grapevine species Vitis vinifera. For example, Shiraz and Chardonnay are both Vitis Vinifera species, but each have their own unique genetic differences that alters certain characteristics.

Some of these characteristics are berry size and skin thickness, colour, flavour profiles, ripening times, acid and tannin content, climatic preferences and disease resistance. These traits are very important when selecting grape varieties to grow in a certain region. McLaren Vale for example is an excellent region for grape varieties such as Shiraz and Grenache, but less so for Pinot Noir and Riesling.

All of the components listed above come from the grape or are produced in the fermentation process by yeast. The waxy bloom on the outside of a grape berry attracts native yeasts and sticks them to the berry surface. Simply harvesting ripe grapes, crushing them into a container and leaving it for a week is enough to produce an alcoholic wine. However, unless there is some monitoring and intervention, undesirable characteristics may develop and spoil the wine.

Yeast: The most important single-celled fungus we know

The most common yeast used in winemaking is Saccharomyces cerevisiae, which efficiently ferments sugars in grape juice, turning them into ethanol (alcohol) and carbon dioxide (CO2). This fermentation process is essential for creating alcoholic beverages like wine. Incidentally, the goal of the yeast is to grow and divide, using all the energy the sugar molecule can provide, producing CO2 and water at the end. However, the anaerobic conditions in winemaking do not allow the full completion of the fermentation process. CO2 is still produced, but the alcohol cannot be broken down any further by the yeast. It is toxic to the yeast, so it is excreted from the cell.

Wild yeasts are naturally occurring yeasts that are present on grape skins and in the winery environment. These yeasts can start fermentation on their own, leading to “wild fermentation” or spontaneous fermentation. Often, these yeasts cannot complete the fermentation to “dryness” (full use of the sugars) so a cultured yeast may be added to complete the fermentation.

A “Wild Ferment” is a fermentation allowed to proceed without the addition of yeast by the winemaker. A wild ferment will consist of many different strains of wild yeast. There may be quite a few Saccharomyces cerevisiae strains present, but also many other species which can produce some undesirable characters in the wine. Conversely, a ‘good’ wild ferment may have very complex characteristics, and improved texture and other qualities not found with single strain ferments. Wild yeast fermentations are not consistent or generally very repeatable, and rarely fully ferment to dryness.

Cultured yeasts are selected for desirable traits and then commercially produced, providing more predictable fermentation results. Different yeast strains can influence the wine’s flavour, aroma, and overall style. Most cultured yeasts were selected from fermentations in European wineries. These fermentations were “wild” ferments, but some tanks displayed greatly improved fermentations, aromas and flavours. Samples were taken and the predominant yeast in that fermentation was isolated. We can now purchase these desirable yeasts and choose a yeast strain that can enhance specific grape aromas and flavours.

New developments by yeast companies now allow for a simplified mixture of both ‘wild’ and ‘cultured’ yeast fermentations. Selected positive ‘wild’ strains can be added at the start of the fermentation to improve texture and complexity, then a selected Saccharomyces yeast can cleanly finish the ferment.

Sugar: Natural and Added

The two main types of sugars found in grapes are glucose and fructose. These are simple sugars (monosaccharides) and are essential for the fermentation process in winemaking.

Glucose is a simple sugar that is usually more abundant in the early stages of grape development. It is easily fermented by yeast, making it one of the first sugars to be consumed during the winemaking process.

Fructose is another simple sugar found in grapes and tends to increase as grapes ripen. It is sweeter than glucose, so wines with higher fructose content may taste sweeter, especially if fermentation stops before all the fructose is converted into alcohol.

Some countries allow the addition of sugar into the juice to produce a higher alcohol content if the natural grape sugars are low. Typically, this is due to climatic and varietal conditions. In McLaren Vale, we rely on the natural grape sugars alone. In fact, the opposite situation is true. The warm climate of McLaren Vale allows full ripening of the grapes, and if we are not careful, the sugar content can go higher than is desired.

Part 2 to come…

In part 2 I’ll cover acid, alcohol, tannin and Sulphur Dioxide.

While you’re waiting, order a bottle or two of Rusty Mutt Shiraz and investigate the ingredients yourself…