Beer Science: Flavour Chemistry

Now that I’ve covered the basics of how to rate a beer I do get asked often by young brew-tasting acolytes: “How do you know what flavours you’re tasting and how do you describe them?” well now dear reader let’s look a little bit at the basics of beer science, specifically flavour chemistry or how I learned to stop worrying and love my beer.

I’m going to start with dark beers and work my way towards lighter brews so bear with me.

Malted Barley – This grain is a key ingredient for almost any beer style, light/dark, sweet/bitter. However Stouts and Porters have a key difference to the lighter-coloured beer styles; Roasted barley. This lends to the brew flavours such as: Coffee, dark chocolate and in higher ABV beers; Vegemite roasted and smoky notes. Stouts tend to use more unmalted roasted barley – which gives a drier mouthfeel and a more direct coffee note. Which came first, the Porter or the Stout you ask? Unlike the chicken/egg scenario this one has a simple answer: Porter was first. The Stout came along when brewers started releasing a “Stout” (or heavier version) of their Porters. Then one day they dropped the “Porter” from the name and called it plain old “Stout”. They have now become interchangeable style terms so you know what to expect when you buy one or the other.

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We’re not off Malted Barley yet – This grain has a habit of adding classic flavour characters to many beers, in this example: Pale Ales, Brown Ales, Amber Ales… basically any style with “Ale” in the name. The malts in question are known to brewers as Caramel Malts. There are many types of these malts serving different purposes to different styles, some are used to match bitter hops with sweetness, others are used to drive the profile and give a unique character or body to it, in essence what you will find with beers that use Caramel Malts is first the colour (from light yellow to dark brown) then you should get the following flavours that associate with these malts: Caramel, biscuit, nutty, malty and brown sugar.

Caramel1 Biscuit1 Nut1 Malt1 BrownSugar1

LOL, you thought I was done with Malted Barley? What about Lager Malts?! I also want to add to this section Adjuncts (i.e. the name given to any other unmalted grains such as: Corn, Rice, Rye, Wheat, Oats, and Barley – what!? Barley again, I hate you). So “Adjunct” came about because in the eyes of the harsh German (now personified by me) Reinheitsgebot the only grain ingredient in beer was deemed Malted Barley, anything else was an “Adjunct”. The beer styles that tend to use Lager Malts and Adjuncts are, unsurprisingly, Lagers. The flavours you can expect from Lager Malts and Adjuncts are: Grain, corn (Corn), honey, pepper (Rye), and not a flavour but a character is added by rice; dry/crisp notes.

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Yeast has a HUGE effect on the flavour of beer, however if the right yeast has been pitched in the right conditions most of the time you won’t even notice it’s even in the beer. In fact up until Louis Pasteur wrote his paper “Mémoire sur la fermentation alcoolique” in 1857 the whole process of fermentation was considered to be some sort of Voodoo trickery. Now there are several chemical byproducts of yeast, in the brewing process, that add many different flavours but for now I want to concentrate on what yeast itself brings to the table: Bread, sourdough, biscuit and bread in general.

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Esters are a result of the yeast having a great time fermenting beer. They come in a variety of flavours, but you can generally tell them from all the other flavours because they are almost exclusively fruity. Here’s a big list of the types of essences which can be derived from these miraculous volatile chemical compounds: Apple, cherry, pear, pineapple, strawberry, honey, banana, lemon, grape, raspberry, peach, orange, rum, dark fruits, and flowers… oh yeah, that’s not a conclusive list either.

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Another thing yeast likes to do whilst fermenting is create Phenols – these are also chemical flavour compounds found in many food and beverage sources but in beer they tend to add more specific essences than the Esters, such as: Banana, clove, bubblegum, smoke, plastic, rubber band and medicinal herbs. Phenols are especially popular in? Right you guessed it – Weizens and Belgian Ales.

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Next up is that bad boy Diacetyl – A generally (as I found out in a batch of homebrew gone awry) unwanted chemical compound, from yeast again of course, that provides a buttery or butterscotch note to the beer. In styles such as a traditional English IPA or Bitter a small amount of Diacetyl is considered acceptable, however as I discovered it can really destroy the flavour of any beer if left unchecked.


One last thing about yeast is Lambic Yeasts, aka “the yeasts wine-makers love to hate” because one saccharomyces cerevisiae is their favourite, and another brettanomyces bruxellensis they consider vermin. Lambic yeasts are used in Lambic beers, which are fermented spontaneously by wild yeast spores floating around in the air (yeast is everywhere man!) and adds the following flavours: Barnyard, cider apples, white wine, lactic acid and an overall sourness.

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What about Hops? Well I’ve saved the best for last, because Hops are the beer-all end-all IMHO. Yes, that holy plant of beer, which when added in certain conditions can provide a multitude of much wanted characters: Pine, lemon, orange, grapefruit, white wine, kiwi fruit, stone fruits, pineapple, papaya, mango, melons, lychee, jackfruit, passionfruit, medicinal herb, earth, cut grass, black tea, spice, wood, hemp and floral… anyway those are the main ones I could think of.

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Well that about wraps it up for now, I hope you feel confident enough to describe a thing-or-two in the context of beer flavours. If however you are unsure of how to describe a certain taste sensation you’re experiencing in that latest triple hop-bomb IPA or some new and crazy expensive BrewDog experimental beer and you want my advice please by all means post the bottle to me and I will give you some free advice (after chugging it down).