The most common customer request commercial coffee roasteries get is for low-acidity coffee.
Before you run down that rabbit hole, here are a couple of things you and your customers should know.
The real reason people request low-acid coffee is because the bitter taste of coffee stimulates the production of stomach acid. Bitterness in coffee comes from all of the stuff that makes coffee taste like coffee.
All of the acids that make up the bulk of the fruit flavors identified in coffee also have an underlying note of bitterness. Chief among them are quinic, chlorogenic, caffeic, citric, malic, lactic, pyruvic, and acetic acids.
Many of the roasted malt, graham, grain, tobacco, vanilla, and caramel scents in coffee are a function of stuff that tastes bitter too: 5-hydroxymethylfurfural; methyl furan; furfuryl mercaptan; trigonelline; pyrazine; thiazole; quinoline; phenylpyridine.
Finally, caffeine, the entire reason we drink coffee in the first place just happens to be intensely bitter.
To put too fine a point on it, acidity in coffee is “perceived acidity” only. It’s the flavor of acidity, it’s not actually acidic. Brewed coffee is 98% water. On the pH scale, coffee is nearly neutral. For coffee to actually be acidic, the water would have to be acidic and you’d have a much bigger problem.
The real culprit is under-extraction.
Coffee extraction is complicated. In the 3-4 minutes it takes to brew a cup or a pot, a lot of things can go wrong. Water-to-coffee ratio, grind size, water temperature, flow rate, and brew time all need to work together to get the most delicious balance of solubles out of your coffee. Then too, the extraction needs to stop before you start to pull out undesirable flavors. When you grind too coarse, dose too much coffee, use too little water, or pour for a short amount of time, you under-extract your coffee beans.
Underextraction tastes terrible. Syrupy, salty, viscous, but above all: sour. The acidity overwhelms the cup. This is because the compounds that taste acidic in coffee are the easiest and fastest to extract. They’re simply the first to join the party. But no one wants to go to a party with just the early birds.
When you brew a balanced cup of coffee with the correctly calibrated variables, you extract sweetness to balance the acidity. You also extract bitter compounds that provide a lingering finish.
Proper extraction will also help with body and mouthfeel, creating a brew that’s properly diluted and enjoyable to drink. Next time you’re tasting too much acidity in your coffee, try simply brewing it a little longer, adding more water to your recipe, or grinding a little finer to extract more solubles and bring things into balance.
Still curious about a totally acid-free cup of coffee? Time travel with me back to the 1960s when the Toddy Brewer was first released. The innovative cold brewing method was initially marketed as a “low acid” cup of coffee. The Toddy brewer, still seen in cafes across the country today, was used to brew a coffee concentrate that could be added to a cup of hot water.
The cold water and long extraction time (12-24 hours) will eliminate perceived acidity in your final brew and leave you with a coffee that tastes chocolatey and smooth. What’s the drawback? You tend to lose origin characteristics and start to experience oxidation in this long extraction process. This is why, no matter what bean you start with, most cold brew tastes like cold brew.
Of course, not all coffee problems are extraction problems. If you’ve chosen a very intensely acidic green coffee, there are ways to balance acidity in your roasting process as well. Planning for a proper development time ratio in your profile and ensuring an even roast with a well-developed center seed will vastly improve your chances of a pleasant cup.
For more tips on sourcing and roasting consistently high-quality craft coffee, you’ll have to join us for class.