The Wine Grape 🍇

Knowing wine grapes is a crucial first step to making wine. It’s the first visible sign of the quality of a wine. Grapes have been revered as a winemaking fruit since centuries and the reasons are its perfect balance of sugar, acidity, tannins and phenolic compounds that produce this fine alcoholic beverage.

Let us have a look at the physical components of the grape,

The Skin

The first important component is the skin. This membrane of a dozen cells thick is highly important in red wines as it contains a high concentration of tannins (explained later), colouring matter and compounds which determine the eventual flavours in wine. Less so for white wines as the juice spends little time in contact with the skins.

• Cuticle – the wax-like covering over the outer surface of the skin is called a cuticle. It acts like a waterproofing elements and protects the berries from outside influences
• Phenolic compounds - these refer to a group of compounds. Two noteworthy ones are,
• Anthocyanins - pigment compounds that give the grape its colour and in turn gives red wine its colour. 
• Tannins – these are present in skin and seeds and give the wine an astringent and bitter taste. Tannins over time contribute to alter the taste and mouth feel of a wine.

The Pulp

Most of the grape is made of the pulp under the skin. Pulp leads to the grape juice. Sugar, water, aroma, tartaric and malic acid and potassium are few compounds found in the pulp. In flavour and acidity of the white wine comes dominantly from the pulp on the other hand red wines get it from skin and pulp both.

Pips

Pips are also the hoarders of tannins. The number, size and shape of the pips differ for different grape varieties. Winemakers are very careful not to overdo tannins as pips release bitter tannins when crushed.

Stalk

As grapes reach physiological ripeness stalks turn from green to woody and contribute astringency and tartness to the wine

Chemical Structure of a Grape

We looked at the physiological structure but chemical structure of a grape is as important and it is complex. Let’s look at the important ones,

Sugars

The sugars in the grape are what the yeast consume to produce the alcohol in the wine. There are different kind of sugars, primarily there is fructose(sweetest) and glucose. Then there is sucrose (lesser sweet) followed by several others in lesser quantities. Not all sugars are fermentable by yeast, so some wines fermented to be dry can have a slightly sweet taste to them due to these sugars (sometimes even alcohol gives the perception of sweetness)

Acids

The important acids are tartaric and malic acid. The concentration of these acids vary with the varietal, climate, and the ripeness of the grape. Tartaric acid in cooler storage conditions separate from a wine in small crystals that we sometimes witness in a bottle. Malic acids are significant, If there is not enough, the wine will taste “flat,” and will be more susceptible to spoilage. If there is too much, the wine will taste “green,” or “sour.”

Sometimes winemakers go for Malolactic Conversion where with the proper bacteria present malic acid can be converted to lactic acid. It gives wine a smoother- creamier taste. Lactic acid is the same acid found in milk and other dairy products. 

Aromatic Compounds

They are largely contained in the skin of the grapes however, they are also produced during fermentation and maturation. Yeast help produce different aromas and flavours and oak ageing also develop certain aromas in a wine. Aromatic compounds can also combine over time and alter the wine’s taste.

Wine is a complex beverage and many elements influence the final product, but the major structure is defined by the grape. Isn’t it fascinating what a bunch of berries could do!