So, now that I’ve briefly introduced bitterness, I suppose I should step back and start with a more basic subject: how you use your 5 senses and the 5 basic tastes to enjoy beer.
The 5 Senses:
We all remember from grade school that the human body’s five senses are sight, sound, touch, smell, and taste. It’s fairly obvious that smell and taste play a part in experiencing beer, but what about the others?
Our eyesight comes from light in the visible range of the spectrum striking our retinas and exciting molecules which transmit a signal for our brain to interpret. In beer, we notice the color, the clarity, the foam thickness, and the lacing in the glass. All of these things are very important in building our impression of the beer. It’s amazing how the color of the beer can bias the drinker before they’ve even tasted it. I’ve seen taste panels ascribe caramel-like flavor descriptors to pale American lagers with caramel food coloring added to mask the true color.
We hear things because pressure waves are transmitted through the air which strike our eardrum which eventually leads to a signal being sent to the brain. Just like with our eyesight, our ears only respond to a small range of possible frequencies. Sound isn’t a big part of beer, but it does play a role in telling us how carbonated the beer is when the crown is removed, and the gurgling from filling the glass is not to be discounted.
Our sense of touch is due to various nerves embedded in our skin which respond to changes in temperature and pressure. The relationship that touch has with beer is an interesting one due to the variety of stimuli: the mild pain associated with carbonation, the cold temperature of the beer, the wetness of the liquid, the burn from the alcohol, and even the dryness of the astringency are all touch-based sensations.
Before I discuss taste, we need to dispense with one misconception. You remember that picture of your tongue with the areas mapped out to each basic taste? Yeah, that one. Forget it. While there can be general areas which respond more to certain taste stimuli, each type of taste bud is found in each place on the tongue. Now, we’d expect taste to play the biggest role in experiencing beer, but that’s debatable. Our sense of taste is only made up of 5 types of stimuli: sweet, salty, sour, bitter, and umami. (some are now debating whether to add “fatty” to this list).
Sweetness is common in beer as residual carbohydrates which went unfermented by the yeast. Sweetness is a receptor-based sensation, meaning there are specific places on your tongue which respond to different molecules with the specificity of a key in a lock. It is closely related to bitterness in this regard.
Sour is usually a bad sign in beer (a sign of bacterial infection), but can be considered normal in some styles. It’s characterized by a tart puckering sensation at the corner of the mouth, and is caused by a change in the ionic gradient across the cell membranes of your tongue cells due to a higher presence of hydrogen atoms (acidity).
Salty is a taste that usually isn’t present in beer (although there are salts in beer), and is similar in its action on the tongue to sour: disrupting membrane gradients which activate nerve cells.
Umami is a recent addition to the basic tastes which is not really found in beer. It’s a brothy, savory flavor commonly associated with monosodium glutamate.
Smell covers all the rest. If what you’re tasting right now in your beer is not sweet, sour, bitter, or salty, then it’s in your nose. Test it out right now: plug your nose while you eat something. You won’t get any flavor other than the basic tastes. Now unplug your nose and BAM. Flavor. Aroma is another receptor-based sensation, but this time the receptors are in the olfactory bulb at the top of your sinus cavity, otherwise known as the base of your brain. Each receptor in your nose responds to only 1 odor molecule. When you consider that we can smell certain compounds at parts-per-trillion levels along with the specificity of receptor/ligand interactions, it’s amazing how sensitive we can actually be with this equipment. Smell enters the nasal cavity in one of two ways: through the front of the nose, as when you life the glass to your nose and inhale though your nostrils. The aromatic compounds are volatilized off the surface of the beer and into your nose where they interact with their receptors. The other way we smell beer is by drinking it. As the beer sloshes and warms in the oral cavity, the aroma compounds are volatilized (even faster) and as you breath out your nose these compounds reach your olfactory bulb. While these two methods of smelling can both provide a similar type of experience, you may be surprised just how different they can be.
We’ll cover some of these basic tastes in more detail later.
So next time you drink a beer, pay attention to just how your body is taking it all in.
beer sensory science 
