So you’ve decided to buy yourself an espresso machine. Now it's time to start recreating your coffee shop favourites at home!
Often the first few shots that people pull from their espresso machine are a little underwhelming. People often find that their home machine pulls shots that are unpleasantly sharp compared to what they get in a coffee shop. In this article we’ll review how you can avoid the “sour shot” trap and make the best possible espresso with a home set up.
What Causes Sour Tasting Espresso Shots?
Before we talk about how to improve your espresso shots, it's worth understanding why espresso shots can sometimes taste sour. The most common cause of sour shots is that not enough of the flavorful, soluble compounds in your ground coffee has dissolved into your brewing water. The sweeter soluble compounds in coffee dissolve more slowly than the sharper compounds, so if limited extraction has occurred then there will not be enough sweet notes in your final drink to balance out the sour notes.
This lack of dissolving is commonly referred to as “under extraction” and almost always has one of three causes:
Not enough of your ground coffee’s surface area has come into direct contact with your brewing water
There has not been enough direct contact time between your ground coffee and your brewing water
Your brewing water is not hot enough
As you’ll see, each of the techniques that we talk about in this article will address at least one of these issues.
Anyway, on with the tips!
Espresso Brew Tips
1. Brew With Coffee that Has Been Roasted Specifically for Espresso
Coffee roasters understand that you need to get your ground coffee to extract into your brewing water faster when brewing espresso compared to other brewing methods. Roasters will therefore prepare espresso roasts in a way that helps ensure that they extract as quickly as possible. A good example of this is our Honey Process Espresso Roast. This coffee is naturally sweeter than washed or natural processed coffees which makes them very forgiving for beginner espresso makers (any acidity due to under extraction will be balanced by the coffee’s natural sweetness.)
We highly recommend this for beginner and experienced espresso brewers alike.
2. Warm Up Your Espresso Machine Prior to Brewing
As we mentioned earlier, one of the most common causes of under extracted coffee is that your brewing water is not hot enough. Extraction is the process of the soluble compounds in your coffee beans dissolving into your brewing water. Soluble compounds dissolve faster in hotter water than cooler water. The ideal brewing temperature for espresso is 92-96 degrees Celsius. While most espresso machines will initially heat your water to this temperature, this temperature will drop significantly once it flows through the machine’s internal pipes and makes contact with your metal portafilter basket. You therefore need to heat these internal pipes and portafilter before you pull your shot. The easiest way to do this is to run a couple of “blind shots”, that is espresso shots without any ground coffee in your portafilter, before you pull your actual shot. These “blind shots” will ensure that your espresso is being brewed at the right temperature.
3. Use a Pressurised Portafilter Basket if You Brew with Pre Ground Coffee
Most espresso machines will come with two types of portafilter baskets: pressurised and non pressurised baskets. If you are brewing with pre ground coffee then we’d always recommend brewing with pressurised portafilter baskets.
The difference between the two basket types lies in the number of holes they have in their bottom. Pressurised portafilter baskets only have one hole in their bottom. Non pressurised portafilter baskets have hundreds of such holes. The red circle in the above image shows the pressurised basket’s singular hole. The pressurised portafilter basket’s singular hole in its bottom means that your brewing water is forced to run through your puck of ground coffee much more slowly compared to a non-pressurised basket. You want this slower flow when brewing with pre ground coffee because the longer coffee is ground before brewing, the faster water will naturally flow through it. Pre ground coffee brewed with a non pressurised basket will often come out under extracted (and therefore sour). Non-pressurised baskets allow you to “dial in” your espresso (more on this later) with more control than pressurised baskets so should be used with freshly ground coffee.
4. Weigh out Your Quantities of Ground Coffee and Liquid Espresso
The only way to accurately measure brew ratio is to weigh out your ground coffee and your final espresso.
One of the most important variables in espresso brewing is your “brew ratio”. This refers to the proportion of ground coffee that you initially brew with to the amount of liquid espresso that ends up in your cup. You generally want to aim for a brew ratio of 1 part ground coffee to between 2 and 3 parts liquid espresso. The exact ideal brew ratio depends on the type of coffee that you use. Beans designed for espresso will often have a recommended brew ratio printed on their packaging. The only way to accurately measure brew ratio is to weigh out your ground coffee and your final espresso. You should measure both of these by weight - measuring your liquid espresso by volume and then assuming that one millilitre of espresso weighs one gram will not work because espresso has crema on it which significantly increases its volume without increasing its mass. You will need some brewing scales that can fit under your cup when brewing to do this. Once the liquid in your cup matches your brew ratio then you know to finish pulling your shot.
5. Use Grind Size to Fine Tune Flavor
If you are buying whole bean coffee and grinding it yourself, then it's better to change your grind size, rather than your brew ratio, to adjust your espresso’s flavour. Small adjustments to your brew ratio will cause huge changes in your espresso’s taste. Adjusting grind size allows you to alter your espresso’s flavour with far more accuracy. A finer grind will expose more of your coffee’s surface area to your brewing water, therefore increasing extraction.
As a general rule:
If your espresso is slightly too sharp then you want a finer grind size
If your espresso is slightly too bitter then you want a coarse grind size
In most cases, grinding as fine as you can until your espresso is too bitter, and then going back one setting, will produce the tastiest espresso. This process of finding your ideal brew ratio and grind size is what people refer to when they talk about “dialling in” your espresso.
Brewing espresso at home is a little bit trickier than other brewing methods. Your biggest challenge is getting your coffee to extract sufficiently into such a small quantity of water. Hopefully these tips can help you create better espresso at home, regardless of whether you brew with pre ground or freshly ground coffee.