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The Science Behind Tastes and Aromas

One of the funnest (ahem) things about wine is being able to say you can taste burnt rubber, mushrooms and nail varnish in them. No, really. We all start off spotting tastes like jam, blackberries and almonds and end up talking about leather, wet dog and old wood.

The fruit flavors are easy to explain – after all, wine is usually made from fruit… However, once you get further into your wine journey, you’ll start to wonder why you can taste pepper and fungi. These smells and tastes don’t come out of nowhere, and you’re not imagining them – they are a scientific fact. Here’s where they come from.

Volatile acidity

This is down to acetic acid and ethyl acetate and it smells like vinegar, cherry, nail varnish or nail varnish remover; pungent and sharp. It tastes like spice, or sharpness, usually at the finish.

Volatile acidity is referring to the volatility in the wine – its reactivity, which can make it go bad. Acetic acid increases when there’s been too much exposure to oxygen and acetobacter, the bacteria that makes vinegar. At higher concentrations – 1.4g/L in reds and 1.2g/L in whites – it’s a fault and a nail varnish remover smell takes over. At lower levels, it adds a nice fruity punch.

Reduction

Reduction is down to a group of compounds – dimethyl disulfide, dimethyl sulfide, hydrogen sulfide, and ethane thiol. This group smells of truffles, rotten eggs, cooked cabbage, burnt rubber, radishes and mushrooms. Thankfully, at lower levels, it adds a creamy mouthfeel, rather than a taste of rotten egg or scorched tyre!

Some people worry about sulfur in wine because they associate it with sulfites and headaches. Reduction occurs naturally during fermentation and adds complexity and interest to the aromas. It’s caused by a lack of oxygen during fermentation, so a sulfur atom gets roped into bonds, rather than an oxygen one. In small doses, you get the smells listed above, but at higher levels, the smells start to take over – and not in a good way.

These smells should give off after half an hour or so – if they don’t, that’s a problem! Some people say putting a clean coin into the glass or decanter helps – it’s worth a shot.

Brettanomyces

 

This smell is caused by 4-ethyl phenol and 4-ethyl guaiacol and these two compounds add the smell of cloves, leather, cardamom and even Band-Aids to wine.

Brettanomyces, or Brett to its friends, is a wild-type yeast that produces some interesting and pungent smells. It’s often considered a fault, especially if you can taste Band-Aids, but many people love the spiciness and woodiness that come from lower concentrations. Brett was a lot more common before modern sterilizing procedures and some people will mourn its passing if it ever happens.

Acetaldehyde

This is quite a poisonous compound, but it lends the taste of green apples, bruised apples, jackfruit and even wet paint to wines. It’s tangy and sharp from the mid-palate to the finish.

Acetaldehyde is present in all wines – dry wines tend to have between 30ppm and 80ppm. Sherries rely on acetaldehyde for their particular aromas and they have nearer 300ppm. It can be pleasant, with candied apple at lower levels and almonds at higher concentrations.

Now you know the names behind the smells, you’ll be able to “see” them more.

Categorized: Bulk Wine News