Espresso, the heart of coffee culture, is a true work of art. Recognizing a good espresso and understanding its nuances can elevate your coffee experience. In this guide, we'll delve into the characteristics of a great espresso and tackle common problems like bitterness and sourness.

Recognizing a Good Espresso

You can recognize a good espresso by analyzing several aspects. Here are top things to look out for: 

1. Perfect temperature: 

Touching the cup should reveal a pleasant warmth without burning your fingers or feeling cooler than your hand.

2. Perfect crema: 

A quality espresso has a persistent, closed, and shiny crema with a rich brown hue, never a dull gray.

3. Enticing aroma: 

Upon stirring, an enticing aroma should gently waft into your nose, free from unpleasant notes like burnt, rubbery or ashy notes.

4. Persistent crema: 

Once stirred, the crema should close again. 

5. Balanced taste: 

A sip reveals a nicely balanced taste where bitterness, sweetness and acidity are harmoniously combined. 

6. Pleasing aftertaste: 

The coffee leaves a pleasing aftertaste on your palate, with a full taste and texture that lingers.

7. Desire for more: 

Craving a second cup? That's the sign of a fantastic espresso.

Fixing Bitterness

When preparing coffee, we aim to extract aromatic compounds responsible for flavour from the coffee with water as well as the maximum of sweetness and the right amount of acidity and bitterness. Unfortunately, along with the good compounds, bitter substances can also be released. This specifically happens when the coffee is over-extracted.  

If your espresso taste too bitter, there could be various factors at play. The fundamental cause is typically an excessive extraction of compounds, which impart a high level of bitterness to the brew. Let's explore why your espresso might taste too bitter and some crucial factors to monitor:

1. Aim for 7-10g of coffee in your basket for a single espresso of 25-35ml. 

The more espresso ml you want to achieve, the higher your dose and vice-versa and make sure to use the right basket size. If you used too much coffee, the water cannot flow through as easily. This leads to over-extraction.

2. Adjust your grind size until you get an extraction time of 20-30 seconds for a 25-35ml of espresso.

During the coffee extraction process, water goes through the ground coffee, drawing out its soluble compounds. If the coffee is ground too finely, it obstructs the water's flow, causing it to move more slowly through the coffee grounds. This extended contact time between coffee and water results in an increased dissolution of substances, including bitter compounds.

3. Don’t tamp too strong, 15-20 kg of force is enough. 

When making espresso, too much tamping pressure can also result in a bitter espresso. If the coffee is too compressed, the water does not pass through the coffee as quickly and more bitter substances are dissolved.

4. Ensure the water temperature is between 89 and 93 degrees Celsius. 

This is important as the bitter substances contained in coffee dissolve more easily at a higher temperature. 

Tackling Sourness in coffee

The process of coffee extraction entails dissolving flavors from ground coffee using water. At first, highly soluble substances like organic acids dissolve, followed by less soluble flavors. When coffee isn't fully extracted, leading to a condition known as "under-extraction," it typically has a sour and weak taste. Under-extraction can be attributed to various factors. Here are some key considerations:

1. The water-coffee ration. The ideal ratio is 60g of coffee to 1000ml of water for filter coffee and 7-10g of coffee to 25-35ml of water for a single espresso.

If you don’t have enough coffee grounds for the amount of water used, not enough tasty compounds can be pulled out. The water flows through the coffee very quickly and only the more easily soluble substances are released from the coffee. 

2. Check the grind size: 

If it's too coarse, water flows through the coffee grounds too quickly. This primarily dissolves organic acids, resulting in an overall lack of substances in the brief extraction period. Consequently, the coffee ends up tasting sour and weak.

3. Don’t tamp too light: 

If the ground coffee in the portafilter is not compacted firmly enough during espresso preparation, the water has less resistance to pass through the ground coffee. This also leads to a shorter extraction time and an under-extracted coffee.

4. Verify the water quality, especially the hardness of the water. 

It is recommended to use soft, but not distilled water: 3-6°dH total hardness, 2-4°dH carbonate hardness. Too hard water could ruin the extraction of compounds and turn the espresso into a more bitter and too heavily bodied espresso, whereas distilled water could make your espresso too sour.

5. Check the water temperature: 

A low brewing temperature can result in an acidic coffee. This is due to the fact that the solubility of substances contained in the coffee generally increases at higher temperatures. Thus, if the coffee is brewed at a low temperature, not enough sweetness and pleasant bitterness can be extracted turning your espresso watery and acid. 

Brewing the perfect espresso requires finesse. Armed with the knowledge to recognize a good espresso and troubleshoot common issues, you're on your way to becoming a true espresso connoisseur. Remember, it's all about the balance of flavour, influenced by parameters such as grind size or water temperature, that makes each cup a masterpiece.