One can do a much deeper dive into what makes up wine, however for the first write-up on the subject, we will not go too crazy. Just want to start with a sufficient foundation that when we talk about other topics like how to navigate a wine list, you will have some of the basics covered.
Firstly, wine is simply fermented grape juice. The sugars that are in the grapes get converted to alcohol by the yeast called Saccharomyces Cerevisiae, (S. Cervisiae). So that is where the alcohol comes from. Fortunately there is a whole lot more going on otherwise it would be similar to diluted vodka.
The majority of wine is water, roughly making up ~85%, and the alcohol by volume (abv) typically can range for a normal wine from roughly 7.5% to 16% these days. Then the remainder of components are the acids, sugars, glycerol, the multitude of various flavour/aroma compounds and some complex chemicals like anthocyannins and polyphenols. So let us break that all down further and go over how these components impact your sensory experience when you enjoy some wine.
Water will not bring much to the party other than being the universal solvent (things easily dissolve in it). Alcohol will also act as a solvent but it can give wine a warming sensation that can be subtle or be quite “hot” on the back of your throat if the alcohol sticks out. So really boozy wines are sometimes perceivable on the palate which is typically a negative note for a wine. Glycerol is a small molecule that you can also find in a lot of different things, it is just a viscous liquid that has a slightly sweet flavour to it. You do not really taste glycerol however it impacts the mouthfeel of the wine. It is most notably evident in biologically aged Sherry like a Fino or Manzanilla. These lack glycerol and are very light-bodied, and taste even more “dry” or not sweet because of the absence of glycerol. Moving along onto the more exciting components.
There are a few different acids in wine. The main one is tartaric acid. It makes the wine have a low pH, and on the palate this is why wine is refreshing, mouthwatering and “crisp.” Malic acid is the next most abundant and it is the same acid in apples. With more malic acid present, the wine will have a stronger tart green apple sensation the wine will have. Tartaric acid will maintain its concentration over time in the development of the grape, malic acid will decrease as the grape ripens. This is why early harvested grapes (less ripe) are more tart, and when later harvested grapes (more ripe) can lack acidity. Therefore both of these acids are present in the grape and will end up in the resulting wine. There is some citric acid present in grapes as well in small quantities.
Next we have lactic acid (milk and yogurt acid) which is not naturally present in the grapes / wine but can be produced during the winemaking. If lactic acid is formed, it is made by Lactic Acid Bacteria converting malic acid into lactic acid. This chemical process is called Malolactic Fermentation or Malolactic Conversion. The abbreviation wine people will use for this process is “Malo.” So if the wine undergoes Malo, the malic acid, which is quite tart, with a low pH (more acidic) is converted to lactic acid, which is less acidic. Therefore wines that have gone through Malo are less tart and softer on the palate. Just think tart green apple vs Greek yogurt. Lastly, but very importantly, during Malo, the bacteria can convert citric acid into diacetyl. This is important for all the Chardonnay lovers out there because diacetyl is the one of the main flavour compounds of butter. Hence, you can have a buttery chardonnay and they are usually less tart, more creamy and sometimes can taste pretty much like a stick of butter.
Now let us cover sugar and my BBQ sauce analogy. As grapes ripen, they accumulate sugars and this is so birds eat the grapes (also why malic acid decreases as the grapes ripen so the birds know when to eat the grapes).
Depending on the style of wine, a winemaker has different options to control the final level of sweetness in the wine. This will be explained in an odd way, however I will explain it so that the wine terms for describing sweetness in wine make more sense. So, if there is sugar in the final wine, it is known as residual sugar (RS) because it is leftover (a residue) after fermentation. If the wine was fermented to completion, as all the sugar is gone, then the wine was fermented “dry,” as in no residual sugar was leftover.
So this is why people describe a wine that has no perceivable level of sweetness as “dry” because it was fermented dry, as there is no RS left. “Off-dry” is then describing the next level of sweetness up because it is “not quite dry,” or has some RS left.
If you are making a higher quality wine to be “off-dry” or with some sweetness, then you can interrupt fermentation by stopping the yeast from eating all the sugar. Thus leaving residual sugar leftover in the wine. When winemakers do this, you then also have less alcohol as a result. This is seen in high quality and sweeter styles of German Riesling. When done well, they are some of the best wines. Another option, and viewed as a cheaper option and typically results in lower quality wines, is to add in grape sugar to the wine. This is done by a liquid called RCGM, or rectified concentrated grape must. Basically grape syrup. It does not integrate as well and can be more noticeable.
BBQ Sauce analogy time. Stay with me on this. If you make homemade BBQ Sauce, and you want it to taste good, you want to have a balance between all the different components in the sauce. Wine is no different. You will have a fruit base in there, like pineapple, and some sugar for sweetness, maybe some chilli for heat, lemon juice for acidity, salt and for kicks you can char-grill the pineapple for some umami and slight bitterness. You are trying to achieve a balance of sweetness, saltiness, fruit flavour intensity, acidity and umami. If you add too much sugar, or not enough pineapple, or too much chilli, the sauce will be unbalanced, and potentially not enjoyable because of it.
In wine, if you have a wine with an elevated amount of sugar, you will want to have an elevated amount of acidity to balance out the sweetness. Then if you want better balance, more fruit intensity would help (described as more fruit “weight” than saying “fruity”) to go with the elevated sweetness and acidity. So if you have a very mono-dimensional BBQ Sauce that is just very sweet, or a wine that is just very sweet, it is kind of disgusting.
Speaking of flavours, let us move onto aroma / flavour compounds. These compounds can give both aromas and flavours. So the compound for the aroma of apple, for example, is also the compound for the flavour of apple. That’s why it is written aroma / flavour. To simplify, I will use them interchangeably rather than both.
These compounds can give you the notes of apple, pear, peach, cherry etc. These compounds are mostly made as byproducts of the grape juice being eaten by yeasts however there are a small amount of flavours that are from the grape itself. Each wine can have specific flavour compounds while others can have a range. Pinot Grigio will be pretty much the same group of flavours (lemons, apples, pears) each time whereas Chardonnay can range from apples and pears, to stone fruits (peach, apricot) to tropical notes like passion fruit or pineapple.
You can then have some compounds that are from the winemaking itself like flavours that come from using new oak (cedar, vanilla, baking spices, smoke). Tasting diacetyl, or butter in wine is from the winemaking. It is a choice typically to let the wine go through Malo or not. Some flavours can come from ageing a wine. If it gracefully ages beyond the 5 year mark or so. This can give notes of honey, nuts, ginger, leather, caramel or meat as examples.
So depending on the grape variety (or blend of varieties) in the wine, you can have different aromas, then another layer of aromas from the winemaking, and then if the wine is aged, you can get a whole other layer of flavours coming out to play. This is why some people really invest a substantial amount of money in ageing wine, buying aged wines or both.
The last group of compounds I’ll go into here are some of the larger more complex organic compounds like anthocyannins and polyphenols. Anthocyannins are the colour pigments you get in black grapes (what people call grapes that make red wine) or the golden hue of some white wines like Gerwürztraminer. Anthocyannins are important for obviously the colour of the wine. They also interact with tannins.
Speaking of tannins, they belong to the group of compounds called polyphenols. These are large compounds and are the antioxidants in wine. Tannins are also a very important group of compounds in red wines. They give the perception of drying out your gums out and depending on their character will be softly “gripping” your gums or can be more coarse, textural or “chewy”(depending roughly how ripe the grapes were and/or how old the wine is). As grapes ripen, tannins get more ripe and less obtrusive with their texture (softer) and less apparent on the palate. Unripe tannins are harsher, more textural or "chewy" in feeling and bitter in nature. As a wine ages, tannins bind to themselves and slowly fall out of solution (creating the sediment in the bottom of the bottle of an aged red wine). So if a wine has harsh or very high tannins, these will soften and decrease over time. Tannins additionally are an important preservative for wines and help a red wine age.
Oak, being a plant material, can also add tannins into wine. The impact is seen most when the barrels are new. As oak gets used each year it has less and less of an impact on the wine in terms of the addition of oak tannins and flavours. This means that a white wine that is matured or made in new oak barrels can get some oak tannins infused into it. These can be more obtrusive in youth but help a white wine age since these tannins also help preserve the wine. Tannins are important in red wines and also some white wines if they spend time in new oak barrels. However, along with everything else in wine, the perception of tannins are impacted by their balance with the other components of the wine just like residual sugar.
We’ll finish the post here now that we have covered a good foundation in a lot of what is in wine. As we cover more topics here this information will be helpful to know as we go. If you have any questions about any of this, toss your question(s) below and we would be happy to help answer them.
Hope that helps with your wine journey, until next time!