Thursday, May 12, 2011

Coffee Acidity

One thing was painfully clear at the SCAA show in Houston, acidy coffee is in! Really! I even heard one coffee described as having "aggressive acidity." Dark Roasts are out, Light Roasts are in. Light Roasts are complex, refined, have good acidity. Dark Roasts, well, Dark Roasts just aren't cool anymore. I mean, Starbucks over roasts their coffee. And we all know that Starbucks is not cool. Light Roasts are Third Wave and Third Wave is in.

Along with the trend towards Light Roast is this new found appreciation for Acidity. Acidity is what gives a coffee its brightness, its liveliness. Good Acidity can be likened to carbonation in a soda, without it the beverage is flat. Something I heard repeated time and again was the necessity of educating the customer about coffee acidity. But not all acidity is good, and a lot of what I tasted was acids due to defects in the coffee.

Of the plus 1000 different chemical compounds identified in coffee about 50 or so are acids. Many of these are volatile compounds and diminish in roasting. Light Roasts tend to emphasize these acidic compounds and bring them to the fore. This is why coffee tasters in the import/export trade roast their samples very light to expose these particular defects. Trade Cupping or Defect Cupping is a necessary skill for any coffee professional but one would be remiss into assuming that this is some higher form of taste.

Coffee's acidity comes from a combination of its inherent acidity along with the coffee bean's production cycle: growing, processing, and roasting. Coffee's inherent acidity is chlorogenic acid, which, along with caffeine, is part of the plant's defense against insects. Chlorogenic acid breaks down in roasting into quinic and caffetic acids depending on the amount of time the coffee is exposed to heat. Roasting machines with poor heat transference produce more of these acids resulting in a tinny, bitter taste. I have written more extensively on this acid in "Bitterness and Acidity in Coffee."

One of the more oft quoted acids is Citric Acid. This acid is usually associated with fresh crop coffee and indicates new harvest. Experienced cuppers will tend to opt away from these lots and wait for later deliveries, giving the coffee a chance to mature. If the flavor persists it is an indication that too many immature green coffee cherries are making their way through. I have notice in my own travels that first time cuppers often take a liking to this taste largely due to the fact that it is the first taste that they learn to identify. This acid is less volatile than other acids and so cannot be "roasted" out. Its easy to identify, since most of us are familiar with citric acid from citrus fruits.

Another common acid is malic. I have noticed an increase in this acid over the years as sun grown coffee has become more commonplace. It is due to excessive day/night time temperature deviations. Shaded coffee farms have more stable temperatures which benefits the plants night time expiration. This acid has a distinct tart apple peel taste that lingers on the palette.

Acetic acids come about from the just pulped coffee beans sitting in the fermentation tank. The time in the fermentation tank is critical since the enzymes break down the silver skin on the coffee beans. Too much time, or if the temperature is too high, however, results in a vinegar like taste. Sometimes this is confused with wineyness.

Most of these acids will decrease in roasting, aside from the Quinic, but as more roasters opt for a Light Roast these acids come to define the coffee's flavor. I hear a lot of pontificating about this coffee's blueberry taste, or apricot, plum, or jammy, as if they are talking about their favorite wine. The one thing that these acids have in common is that they invariably lead to a soury cup. You can mask some of these flavors by increasing the brew temperature, but as the cup cools so returns the sour. What's more, these acids tend affect a person's body, resulting in an edgy, uncomfortable feeling. Some assume it is caffeine, but it is these acids.

In my years of roasting I have never had a customer come in and ask for an acidic coffee: you know, something that tastes like fresh squeezed lemons? Something that will sour my stomach and make me feel all jittery?

Maybe its time the customer educated us.

11 comments:

sandhiya said...

Excellent view!Great Article.This is possible only when we have a good quality Coffee Equipment

compmuseme said...

Great, the bit about the acids reveals what I was searching for in the variety and roast of coffee. I have been trying to discover what I like in a black cup of coffee, so far only pleased by the the Whole Foods brand City Roast.
After several days of being quite annoyed with Mr. Overly for distracting me from working, and recalling the not so pleasing mochas from Kaladi Brothers around 2009-2010, I was forced into my car, perhaps an entire mile. In the past, I was not crazy about the chocolate sauce, caramel sauce or the flavor imparted by the black lids on the cups (yes, yes, not even tasting the coffee). However, today's cup of Indian, unadulterated, was the best cup of coffee I've had from a coffee shop (and I came in with the attitude of "you talk a good game, so you better impress me with flavor, not spin, lol). Socratic contrarianism is totally acceptable when it heralds true quality and the display of technique in product, rather than trumped up, unfounded snobbery.

Alexander Nordenson said...

I almost can't drink coffee due to this acidity. I'm one of the rare super-tasters in the world, and I can taste these acids to extremely keenly that unless I neutralize them with a lot of milk and/or cream it's like drinking caffeinated vinegar to me.

Finn Felton said...

In Africa country, coffee beans are soaked in water mixed with spices and served as candy to chew.

Kopi Luwak

Its me Finn or is it Jake said...

Great post. Before coming here, I also read from What exactly is coffee acidity? the brewing process, location, and processing method also affects the acidity of coffee

Emo said...

This post is extremely informative. I think you are right on about the fact that people only seem to "like" acidity merely because it is tricky to first identify. But the third wave seems to be taking acidity out of control. Thanks for the post

Domenceus Priest said...

I enjoyed reading this post; I have recently become interested in coffee and it is fun to read your insights.

I have a question about acidity: I have noticed that coffees with higher acidity - whether from location (like Central America) or lighter roasting - tend to give me a piercing headache after I drink them. I use French Press and Clever Brew, and prefer to drink my coffee black (but I only drink about 3 oz at a time) because the flavor is so good on its own. I don't have these problems with med or dark roasts and in fact they help me with migraines (I started drinking coffee for this reason).

I haven't been able to find anyone discussing this, so I was hoping that with your greater exposure to coffees of various sorts, you might have seen or heard something about this. Thanks!

----------------------- said...

Walked into a new coffee shop in Raleigh, NC the other day. Asked for a dark, smokey roast and after they looked at me funny, offered me the "closest thing". Took much care with the pour-over brew and later asked me how I liked it. I told them it was fresh but too acidic. I then received a lecture from the barista half my age (I've been drinking coffee since before he was born) about how light roasted acidic coffees contain more of the original coffee flavor. I said that I did not agree; that I was overwhelmed by the acidic tartness and that what he was saying just didn't sound right. I knew in my gut that their take on things was a sham, but it wasn't until reading this article that I knew the reasons. Thanks.

Courtney said...

I have a sensitivity to citric acid. Swollen throat inflamed glands..I am discovering the amounts I can tolerate and I was just crying "say it ain't so!" about having to give up coffee. The description of the jitteryness matches my reaction to the coffee I have been drinking..Thank you. I will try your advice on the roasting level. I may just have to get my own roaster. Or "gasp" the unthinkable, give up coffee.

Jasper Beyan said...

I used to be very proud of Sydney as a city of good coffee.
3 good modern breakfasts from 3 young cafes in a week and I was left befuddled.....
I came looking for answers
A good friend warned me "They have a boutique roast here"
The coffee was acidic swill under roasted bitey bilge.
I have witnessed this movement grow since 3 or 4 years ago. At Bondi I was boasted to 'We have to change our grinding wheels every 6 weeks.
To prove it they kept the old ones kicking around as talking points.
I took them for nutters- , but they have made their mark.
The wheel was not broken it did not need re-inventing but somehow the generation that decided trousers were made to hang off your buttocks have now got their hands on the tiller and coffee drinking has gone back to being the risky venture that it used to be when traveling.
Look out for the tea revival!

0s0-Pa said...

Anyone know any good places to buy gourmet coffee online?