First off, your coffee should not taste sour. Period. There are a variety of factors that can cause this and we’ll cover those here very briefly. There’s no point in getting into all the chemistry, grinds and roast methods too deeply just suffice it to say, coffee should not taste sour.
Of course there is the usual question, “What if I like the sour taste?”. Well then you may want to stop reading here and just stick with what you are doing now.
First: Where does the sour taste come from?
The common term you will hear most often is under extraction. But that’s an insular descriptor and only part of the story. It more often than not actually starts way back at the roasting phase.
Coffee is complex. In fact more complex than red wine (@100+ components) with most Arabica coffees pegging the flavor meter at about 700+ flavor components or chemically speaking “constituents”.
The sourness comes from the first flavors apparent which are not surprisingly, citrus notes. Those flavors come from acidic compounds found naturally in the bean.
But like any food or beverage, the flavor is actually a sensory balancing act between your nose and tongue called the chemosensory system. Just hold your nose the next time you drink your favorite soda or a slice of pizza and you’ll see what I mean. It’s very hard to discern specifics without both systems feeding data to your brain.
When we cup coffees (taste test various coffees and roasts) here at our roastery:
- The first thing we do before we add water is smell the ground coffee in the cupping device.
- Then after the crust forms, again we smell and
- Again when we break the crust.
At each stage you’ll pick up different aromatic constituents. But you won’t normally be able to smell sourness, like taking a whiff of a fresh cut lemon…it doesn’t smell sour but may actually have a pleasant aroma. That’s because you have to include the taste buds in the equation for that to come out.
But when we clear away the crust and slurp the first taste of the coffee, the constituents are dispersed around the tongue and now combined with the olfactory senses give you the overall sense of what this coffee is about.
Here’s where the under extraction case for sour coffee falls short.
Yes if you let the coffee sit in the cup for too short of a time, it will taste sour. That is classic under extraction. If you let it sit too long it will become more bitter. This is classic over extraction.
However if you cup as we do, and as is common practice, you should always use the same time for every cupping. You don’t let one cup sit two and half minutes and another three and half. No you allow every coffee to sit for the same specified time.
The problem begins with under roasted coffee also known as blond or light roasts
Following this practice of maintaining consistent brewing procedures (whether cupping, french pressing, etc) you will in fact get sour notes in coffee from time to time which indicate that the coffee has been under roasted (aka light roast). If you are a regular drip brew of pour-over aficionado again, the key is consistency in your measure and timing. That is the only way to determine if your various coffees are on or off target.
The blond roasts made popular today by Starbucks® and others attest to this fact. The high acidity of “Blonde Roasts” is generally perceived as a lemony, citrusy or sour taste, and seems to be craved by some people. It’s not new either, in fact for years it was called a Cinnamon Roast. But because of the obvious confusion, many people believing that meant it would have a cinnamon flavor, the term blond roast came into fashion.
Another reason blond or light roasts have become popular with large companies is this: This roast is rarely used outside of low cost, commercial coffees. That said a batch of coffee roasted to such a light degree will result in a larger amount of brewable (and saleable) coffee, as the batch will lose less weight from loss of moisture.
But let’s call it what it is, a blond roast or a cinnamon roast is under roasted coffee by most measures and will tend towards sour flavor. It goes like this:
Under roasted = light roast = blond roast = sour coffee
How does under extraction factor in? Yes it is a factor but secondary
Now keep in mind even if you have a properly roasted coffee, you can still get sour notes, but that is truly caused by the go-to term used globally by so many bloggers as under extraction. Under extraction simply means that the water washes over the coffee so fast or quickly that only the easiest flavors (citrus, sour notes) are extracted or removed and flow into your cup or pot.
Under extraction of a properly roasted coffee though can have several legitimate causes and here they are:
- The coffee was ground too coarse
- All things being equal if your coffee is ground too coarse, there is less surface area exposed to the water and less extraction of the symphony of constituents that balance out a proper cup.
- Brew time was too short
- Similar to the coarse grind issue, except even if the coffee is ground properly, but say for instance, in the case of a french press, you let it steep in the water for too short of a time, again not enough of the various constituents will be extracted or pulled out of the coffee to produce a balance cup. Y0u’ll just get sour notes.
But just remember, a coarse grind and/or to little time for the water to do it’s leaching of the flavor components will produce a sour cup.
Add under roasted, blond roast coffee and you have a miserably sour cup.
KEY POINT: Always start with properly roasted coffee. (PS: Infrared is better too)
The reality is most of us don’t vary or coffee preparation day to day, we are creatures of habit. Therefore, if you try a new coffee and it tastes sour, all things being equal you have an under roasted coffee. It may be called a light roast, or even medium roast, but if it’s sour, it’s under roasted.
Under roasted coffee is also highly acidic and can upset sensitive stomachs.
Our infrared roasted coffees on the other hand by the very nature of the infrared roasting process, are thoroughly and evenly roasted from the inside out .
Most coffee roasters are what are known as flame bed roasters. Flame bed roasters transfer heat to the bean in these type roasters by conduction: the bean touches the hot metal of the roaster drum and heat is transferred the outside of the bean. You can easily get burnt spots which produce the burnt taste so many people dislike.
In the end it’s all about balance: It’s like a Tootsie Pop®
Think of a good cup of coffee kind of like a Tootsie Pop®, sweet candy on the outside with a Tootsie Roll® center. What’s the best part? When you finally bite down on the hard candy outside and crush it together with the Tootsie Roll® center. That marriage of the candy flavors with rich chocolate is what most of us think of when we think about that candy.
It’s the same with coffee. You have the citrus notes early on but if properly extracted and married you get dozens of other flavors and that marriage is a good cup of coffee however YOU like it. Some prefer medium bodied coffees others prefer bolder bodied coffees, but they should never drive your taste buds to either extreme or sourness or bitterness.