Acidity

Let's be clear: beer is an acidic beverage.  You like acidity.  And if there's one factor to a mixed-fermentation beer that determines whether I readily go for that fifth and seventh sip... it is your artful restraint.  I even think about acidity in the brewers toolkit when tasting draught Guinness, how a lower pH adds to the balance of each sip, and ends up rounding out other qualities.  

pondus Hydrogenii (pH)

We measure our mash pH, we might measure our post-boil pH, and we make fairly banal comparisons in sour beer.  It's an incredibly useful measure in the brewing process and the overall success of a beer.

Cascade Brewing will always get credit for breaking me into the style as a local thought leader in my mid-20's, when I couldn't afford the good European stuff.  They (in)famously "don't use brett" (though that seems to be debunked), putting an emphasis on their LAB cultures and running a solid oak aging program.  I recall leaving a bit of their Rose City Sour out, then measuring a pH of 3.25.  No wonder these things are so puckering sour!

Would you be terrified to learn that Coke has a pH around 2.52?  I hope not, but it does beg the question... why isn't Coke sour?  How can a bone-dry mixed ferm saison at a meager 3.25pH make your mouth pucker for hours?

When you are planning your day and have a look at the weather forecast, do you look at the temperature?  Of course, but it's not all you care about.  Asking pH to give the full picture of a beer's acidity like getting dressed based on temperature alone.  Well, what if it's rainy, windy, or humid?  There's more to acidity than free hydrogen ions.  

Titratable Acidity

Titration works by comparing the measure of a known quantity (for example, Sodium Hydroxide or NaOH) to an unknown one, like how much lactic acid is in our clean kettle-soured beer.  I don't want to get into number crunching and quantitative guides on how to measure TA, this post is all about qualitative assessment.  But let's suffice to know we can objectively measure acidity.

Beer consists of many acids, especially something like a barrel aged, mixed fermentation fruited beer.  In it, you'll certainly find lactic (think tangy yogurt) and acetic (think sharp vinegar), but also citric (think lemon juice) and malic (think berries) acids.  Let something carbonate and you have carbonic acid adding a little Zing! to the tongue.  In wine you'll find tartaric acid.  You'll also find fatty acids drive a lot of the flavors you may not have known.  Understanding the presence and concentration of these acids allows us to see the trees apart the forest.  

You know how some beverages will now say their caffeine content in milligrams?  Imagine if a Berlinerweisse listed their x.xx% total acidity as lactic acid, or 15g/L TTA.  It would be interesting, like IBUs in the Oughts.  Total Titratable Acidity is a pretty meaningful number, much like barometric pressure across weather systems can tell you a lot about what to expect.  

Do We Have a Coke Problem?

So... how does a Coke with a pH of 3.52 and a TA of 18.3g/L generally in the form of phosphoric acid not present itself as instantly puckering and off-putting?  

Sugar.

Yes, those 55 grams of high fructose corn syrup make a big difference.  Our palate is pretty easily tricked.  Acidity was evolutionarily advantageous, think about what it meant for the hunter-gatherer to come across a big patch of wild berries.  Super sour, super sweet, what a boon!  How do your teeth feel after drinking a Coke?  A bit like the enamel was stripped off?

Applied to beer, it's a reason why there is an acidity arms race among the fruited berliner and sour smoothie crowd, and how lactose and fructose can balance those... also why fruit sugars left unfermented is desirable by the brewer and consumer, even if the yeast doesn't agree.

Cudgel!  Wait, no... Scalpel!

Now for the practical advice.  If I'm three sips into your sour beer, and I'm wondering where the nearest Tums are, that's not good.  While I find acetic acid and assertive lactic can really benefit something like a Peche, it's rare that I want to be unable to reacquaint my mouth to other foods the rest of the day.  No, wait, it's never.  I never want that feeling; it never helps my drinking experience.    Some people will complain their esophagus is burning even having a mildly tart beer, say 3.6pH.  I can only speak for my palate which tends to check out around 3.35.  

And that palate enjoys acidity that it doesn't have to get past.  The vuvuzela might be a wonderful instrument with rich history, but I'll never forget the fucking noise during those 2010 world cup games.  I don't want to have to recalibrate my sensory to try to seek out the better qualities in a beer.  

For this reason, I coast my mixed ferm beers a stop somewhere between 3.45 and 3.75 pH, with a TA around 7-12 g/L (that's mostly lactic acid).  Funny enough, this is about the range for red wines.  Coincidence?  Importantly - many of these beers finish out between 0.5 - 1.5°P (1.002-1.006 SG), and those unfermented sugars can offer body and balance against.  It's why blending and barrel care are so important - why I rarely hang onto a stock that has noticeable acetic acid.

A Pledge; A Plea

It's kind of tragic that a 7 day grain-to-glass Gose, and a 4-year Lambic call get bundled under the umbrella of "Sour Beer."  But that framing seems to be more of a consumer warning label than a useful category.  I don't ask lay drinkers if they like sour beer, I ask if they like dry cider, wine, or kombucha?  These are a much better predictor of how they'll take to a dry, tart, funky beer.  

So I urge my cellar kind to show restraint, let sour be your bandmate and not the solo diva.  Use hops, temperature, fermentable sugars and blending as your levers.  Consider whether a beer will have much perceivable sweetness to balance (e.g. a champagne-dry nectarine beer).  And for god's sake, pair Pediococcus with Brettanomyces.