What does genetics have to do with IPAs?

by Billy Broas


It was an ironic situation.

Our BJCP study group was holding one of its bi-weekly meetings. Studying for the exam means refining your tasting abilities. Ideally, you and the other judges are in agreement on what you smell and taste in a beer. The first thing you do after a round of scoring is compare your score to that of your cohorts and hope you’re not too far off.

Yet this particular night, we were about to prove that no matter how hard we studied, mother nature has ensured that we’ll never taste things exactly the same.

Your own pair of genes

Possession of TAS2R38, aka the PTC gene, codes for a bitter taste receptor on the tongue. In beer-drinker language, if you have the tasting form of this gene then you can taste the chemical known as PTC, which tastes bitter.

You can determine whether or not you have the gene by using PTC paper. Depending on the person, the paper is revoltingly bitter, slightly bitter, or tasteless.

I remember doing this experiment in high school biology class. I remember it because the paper was so disgusting. Curious to try again (and possibly torture my friends), I picked up some test strips for my BJCP study group.

The results

Four of us chewed on the paper. Here’s how it turned out:

  • Bess:Very bitter
  • Chris: Little to no bitterness
  • Billy: Very bitter
  • Jeremy: Little to no bitterness

PTC party! A bunch of geeks, with the biggest one behind the camera.


Pretty interesting. Bess and I were ready to vomit while Chris and Jeremy had no reaction.

But I wasn’t done with my bag of tricks.

I also picked up some thiourea test strips, which are similar to PTC. The interesting thing about this test was that while it was still bitter for Bess and I, Jeremy and Chris found it bitter as well.

Finally we tried the weirdest one, sodium benzoate, which is commonly used as a food preservative. Reactions were all over the place. I found it mostly tasteless but slightly sweet, Bess found it moderately sweet, Jeremy found it salty, and Chris got the distinct essence of hot tub. Go figure.

Something doesn’t add up

Here’s what I find most puzzling about this whole thing. Scientist claim that this is natural selection at work – that if you can taste PTC, then you will avoid potentially toxic plants that taste bitter. In modern-day, PTC-tasters supposedly avoid bitter foods. Here’s a quote I found:

Supertasters will not consume any bitter foods, like dark-green leafy vegetables, coffee or chocolate..

First of all I don’t consider myself a supertaster, but the PTC paper was fucking gross. Seriously.

So why do I love all of those foods and of course, IPAs? Honestly I don’t know. The one thing I can say is that although they’re all bitter, the paper didn’t have one iota of the pleasure as those other foods. I won’t be packing paper strips as a snack any time soon.

Maybe you can acquire the taste for bitterness after all. Maybe the one thing stronger than evolution is India Pale Ale. I’ll buy that.

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{ 14 comments… read them below or add one }

Timothy Augustin April 4, 2012 at 9:49 am

Very interesting. It looks like you mentioned several people who barely picked up on the paper, what exactly does that mean considering their perception of an IPA’s taste?

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Billy Broas April 5, 2012 at 8:37 am

That’s a good question. We definitely all enjoy IPAs and all find them bitter, even the guys that didn’t taste anything with the PTC. It’s hard to make a connection between what we tasted on the paper and our beer preferences. I will say that I although I do love IPAs, I am picky about them and find many to have a harsh bitterness that others seem to enjoy. So maybe that is the PTC gene at work. I wish someone would do a more in depth study.

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Steve Bloomfield April 4, 2012 at 9:59 am

I’ll have to try this test. I’m supposedly not a bitter taster according to 23andme.com (well, it actually says “Has about an 80% chance of not being able to taste certain bitter flavors.”

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Billy Broas April 5, 2012 at 8:43 am

Hey Steve, how exactly does that website work? It is fairly accurate?

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Steve Bloomfield April 5, 2012 at 9:09 am

They send you a little tube that you spit in and with that they read about a million SNPs of your DNA. Mostly the stuff that varies among humans. They give you reports of any markers you have that show increased or decreased risk of some diseases. As for accuracy, their reading of your DNA is accurate but interpreting it is debatable. Mostly because the research behind it is new. For example, my wife is supposed to be lactose intolerant but she isn’t. So if you have a marker for some trait there is only a likelihood that you’ll have that trait.

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Billy Broas April 6, 2012 at 9:23 am

Sounds fun. I may give it a shot. Thanks for sharing.

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Steve Bloomfield April 6, 2012 at 11:42 am

I’ve ordered the test strips. My wife, my son and me all are not supposed to taste certain bitters. My wife and I love IPA’s but I remember a time when I hated certain beers like Pilsner Urquell because I thought they were too bitter. But I’ve grown to like bitter things.

Billy Broas April 6, 2012 at 5:54 pm

You’ll have to let me know how the strips turn out. The bitterness took a while to grow on me as well, but damn I’m glad it did because I love IPAs.

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Steve Bloomfield April 11, 2012 at 9:23 pm

Well, my wife did taste a tiny bit of bitterness with the PTC strip, but I didn’t taste anything. The sodium benzoate strip tasted like iodine to her, and was a little sweet to me. The others tasted like nothing/paper to both of us. We did a half blinded test but didn’t tell each other the results until the end. I’ll have to bring these to work just to see if I can find someone who tastes these.

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Billy Broas April 12, 2012 at 10:12 am

The benzoate strip is a nutty one. Well I guess that website got your bitterness gene correct. Probably a good idea to find someone who can taste it just to make sure it’s not a dud. I feel bad for them though! Thanks for sharing.

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Jacob Zadnik August 16, 2012 at 7:46 am

I actually had the opportunity to try this test, along with a more scientific genetics test much like the one Steve Bloomfield mentioned in his comment, in an Intro to Bio class my freshman year of college. There’s actually a lot of mendelian genetics behind the stregnth at which you taste the PCR chemical.

We did the test with the paper as an experiment to tell our phenotype (how you appear/what gene is being expressed), I tested as a “weak taster”, meaning it tasted bitter but not so bad that I made faces (you should have seen some of the people in the class!). To see if our taste matched our genetic make up (i.e. check for placebo) we looked at the SNP that causes the difference. We used a polymerase chain reaction (PCR) to amplify the section containing the SNP in question. Then, we ran the amplified sample through gel electrophoresis and stained the result with bromide. The distance between and location of bands in the gel told us what our genetic make up was regarding the TAS2R38 gene. My gel readings indicated that my genotype (how you are genetically) was that of a weak taster. That is, I cary one copy of the gene to taste the PCR and one copy of the gene to not taste the bitterness.

I, like yourself, am a bit of a hop head but according to genetics should be able to taste the PCR chemical, to some degree. I’d really like to see this experiment compairing PCR tasting ability to affinity to IPA’s done on a larger scale. I agree: something doesn’t add up…

It’s alwyas very interesting to look at the science behind things from time to time; great post and great site!

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Jacob Zadnik August 16, 2012 at 7:50 am

Not sure why but in my comment I used, “PCR,” in place of, “PTC” quite a few times. My mistake.

IPA, PTC, PCR, DNA, too many acronyms!

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Steve Bloomfield August 16, 2012 at 9:22 pm

Wow, that sounds like an awesome freshman year class!!

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Billy Broas August 16, 2012 at 9:37 pm

Like Steve said, that is one awesome class. I’m glad I took those biotech courses so I could actually follow what you were saying. We need to get some college kids to do the IPA/PTC study as a senior thesis. Can’t imagine it’d be hard to convince them.

Thanks a ton for sharing.

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