Coffee acidity and bitterness – how to choose the perfect beans for your taste

Why is coffee sometimes bitter or sour? This question often comes up – especially among those who are only just starting their adventure with speciality coffee. Some people think that sour coffee from an espresso machine is a brewing error, others believe bitterness means strength. In fact, both these qualities – coffee acidity and bitterness – are completely natural elements of the flavour profile, giving your brew its character and depth.

In this article, we explain what coffee acidity really is and how it differs from an unpleasant sour taste. You will also learn why coffee sometimes turns bitter and how to choose the perfect beans – from delicate Brazilian types to fruity, expressive Kenyan coffees – so your cup always matches your taste.

Summary:

1. What is coffee acidity?
2. Why coffee is sour?
3. Low acidity coffee beans – how to choose the right ones for your preferences?
4. Bitter coffee – when is it a flaw and when a virtue?
5. How to brew coffee to achieve the perfect balance of acidity and bitterness
6. How to find the perfect coffee for your palate?

What is coffee acidity?

When we talk about coffee acidity, we don’t mean the unpleasant sour taste reminiscent of lemon. In the world of coffee, the term “acidity” refers to the liveliness, freshness and aromatic complexity of the brew. Thanks to this, coffee tastes more interesting – it can surprise you with notes of berries, red apple, maple syrup or juicy citrus fruit.

In contrast, sour coffee is a result of an error: grinding the beans too coarsely, using water that’s too cool, or not extracting long enough. Instead of a pleasant acidity, the drink will exhibit an intense, raw, flat sour coffee flavour. So if you wonder why coffee is sour from an espresso machine, the parameters of brewing – rather than the beans themselves – are probably to blame.

How is coffee acidity labelled?

On coffee packaging you’ll often see the acidity rating shown as a scale or graph (for example, from 1 to 5). It indicates how intense the freshness and fruitiness of the brew will be. This scale is usually part of the sensory profile, where producers also present the levels of bitterness, sweetness and body. For example:

• 1–2 – low acidity coffee, usually from Brazil or India: delicate, nutty and chocolatey;
• 3 – balanced, classic in flavour – like Colombian or Nicaraguan beans;
• 4–5 – high coffee acidity, typical of East Africa: juicy, fruity, slightly wine‑like.

It’s worth noting that low acidity coffee beans do not imply lower quality – they simply represent a different style. It all depends on your preferences: if you enjoy a smooth taste without fruit notes, choose low acidity coffee. If you prefer a bright, complex profile, go for beans from Guatemala, Kenya or Colombia.

Low acidity coffee vs. sour coffee – what’s the difference?

These two terms are often used interchangeably, but they are not the same. Low acidity coffee has a balanced, velvety flavour profile – no dominant fruity tones, yet still pleasant, subtly sweet and harmonious. In contrast, sour coffee results from a brewing mistake, not the bean’s natural character.

The sourness may be caused by:

• ❌ Under‑extraction – the water doesn’t stay in contact with the coffee long enough;
• ❌ Grinding too coarsely – a common issue with automatic espresso machines;
• ❌ Water that’s too cool – hot, but not boiling, is essential;
• ❌ Stale beans – old coffee loses its flavour balance.

If you notice a sour taste in coffee right after brewing, check your brewing parameters before blaming the beans. You might find that your cup – instead of being sour coffee from the espresso machine – becomes vibrant and well balanced.

Why coffee is sour?

Have you ever brewed a cup that, instead of pleasant freshness, surprised you with intense sourness? Sour coffee is one of the most common problems coffee lovers face. Although the causes may vary, they share a single underlying factor – an imbalance in extraction, the process by which water dissolves and draws flavour compounds from ground coffee.

If you’re wondering why coffee is sour, consider three main factors: the quality of the beans, their freshness and your brewing parameters.

Remember, a sour coffee taste is not always a flaw – it can simply mean the beans were not suited to your chosen brewing method. Beans with naturally high coffee acidity, such as those from Guatemala or Ethiopia, shine in pour‑over methods, whereas for espresso it’s better to select espresso‑dedicated coffees from Brazil or India. These offer sweetness and a silky body without the excessive acidity.

In contrast, low acidity coffee has a smooth, pleasant profile with no sharp citrus notes. You’ll find plenty of such beans at Coffee Broastery – see our range of coffee beans; each is described by its level of acidity, bitterness and aroma, helping you pick the ideal taste profile.

Sour coffee from an espresso machine – what causes it?

When you get sour coffee from an espresso machine, something in the brewing process has gone wrong. Although both automatic and manual machines can produce excellent results, even a single incorrect setting can make the brew overly acidic. The most common culprits are:

• ⚙️ Incorrect grind size – too coarse and the water passes through too quickly, giving an under‑extracted, sour shot. Try grinding a bit finer until the drink gains depth and sweetness.
• 🌡️ Improper temperature – if the machine doesn’t reach around 92–94 °C, primarily acidic compounds are extracted. Regular maintenance and cleaning help with temperature stability.
• 💧 Under‑dosing – too little coffee relative to water means the water flows too fast, again causing under‑extraction. Try a 1:2 ratio (for example 18 g coffee → 36 g espresso).
• 🚿 Lack of maintenance – residues of old coffee and limescale inside the machine distort the flavour of new brews; cleaning the brew group regularly is essential.

Manual espresso machines can suffer similar issues – if your espresso tastes flat and sharply acidic, you may be tamping too lightly or letting the water flow too quickly. Also check the water quality: overly hard or chlorinated water disturbs flavour balance.

Another thing to watch – beans that are too fresh. Coffee roasted only a few days earlier can taste sharp and sour because of carbon dioxide still trapped inside. Wait 7–10 days after roasting before opening the bag.

Experiment, observe and change only one parameter at a time – it’s the easiest way to find the perfect settings for your espresso machine, and that pesky sour coffee will be gone for good.

Low acidity coffee beans – how to choose the right ones for your preferences?

Not everyone enjoys coffee that bursts with fruity freshness and high coffee acidity. For many, the dream cup is low acidity coffee – smooth, sweet and without harsh edges. Finding such beans isn’t only about taste but about understanding their origin and roasting level – the two main factors shaping a coffee’s flavour and aroma.

If you wonder how to find low acidity coffee beans, start by considering their country of origin. Different regions of the world produce completely different flavour profiles – some chocolatey and nutty, others floral and citrusy. Also pay attention to the roast level: this determines whether a coffee will taste brighter and fruitier or deeper and more chocolate‑driven.

Where low‑acidity coffees come from – countries and regions

Some parts of the world are famous for their smooth, well‑balanced flavour profiles, where bitterness and sweetness create harmony. If you’re looking for low acidity coffee beans, pay attention to those from South America and Asia – this is where you’ll find naturally sweet, nutty and chocolate‑rich coffees.

• Brazil – the classic origin for gentle, low‑acidity coffee. Brazilian Arabica offers notes of chocolate, toasted almonds, hazelnuts and subtle orange. Expect a sweet, milky‑chocolate finish and medium acidity. Perfect for espresso and cappuccino.
• India – Indian coffee has a warm, rounded flavour profile dominated by nuts and chocolate, balanced by a hint of lemon. The acidity is sweet‑citrusy, giving a creamy, well‑balanced cup. Excellent for pressure brewing methods.
• Sumatra (Indonesia) – this renowned island produces some of the world’s lowest‑acidity coffees. They feature a heavy body and earthy, herbal, dark‑chocolate tones. These deep‑flavoured coffees shine in moka pots and French presses.
• Nicaragua – delicate and creamy, with notes of hazelnut, grapefruit and black tea. Despite the hint of fruit, the brew remains smooth and round – perfect for anyone seeking balance and restraint.
• Colombia – Colombian beans are known for their harmony: a combination of chocolate, caramel and red‑currant sweetness results in a cup with medium coffee acidity. A refined compromise between lightness and intensity.

Roast level and coffee acidity – how does it influence flavour?

Besides origin, the roast level significantly affects how the brew tastes. It determines whether the cup is fruity or chocolatey. The darker the roast, the lower the perceived acidity and the more pronounced the cocoa, caramel and bitter coffee notes.

Roast level	Flavour characteristics	Acidity level
Light roast	Fruity, citrus and floral notes. Best suited to alternative methods (drip, Chemex, Aeropress).	High
Medium roast	Balanced between sweetness and coffee acidity. Ideal for espresso machines or moka pots.	Medium
Dark roast	Deep flavours of cocoa, nuts and spices. Lower acidity, heightened bitterness and a full body.	Low

If you’re seeking espresso with a creamy texture and gentle bitterness, choose medium or dark‑roasted Coffee Broastery coffee beans. For alternative methods like drip or Aeropress, lighter roasts highlight natural coffee acidity and bring refreshing brightness to your brew.

Bitter coffee – how to tell when it’s a flaw and when a virtue?

Bitter coffee – to some it’s a symbol of strength and intensity, while for others it signals something gone wrong. In reality, bitterness in coffee is not bad in itself. It’s a natural part of the flavour balance that, just like coffee acidity, can be pleasant if kept in harmony. Problems start when bitterness overpowers all the other flavours and mutes their complexity.

In speciality coffees, bitterness appears subtly – as gentle undertones of dark chocolate, cocoa or nuts. This kind of bitterness enriches the cup and adds depth. On the other hand, a harsh, ashy or burnt bitterness points to either too dark a roast or brewing errors such as excessively high water temperature or overly fine grinding.

• ❌ Over‑roasting – causes sugars to caramelise excessively, leading to burnt flavours that dominate the cup.
• ❌ Water that’s too hot – extracts excessive bitter compounds (mainly lignins and tannins) and strips the drink of sweetness.
• ❌ Grinding too fine – keeps water in contact with coffee for too long, leaching out extra bitterness and heaviness.
• ❌ Over‑extraction – leaves a distinct ashy or drying aftertaste.

It’s worth noting that bitter coffee from an automatic espresso machine often doesn’t result from poor‑quality beans but from over‑roasting or over‑brewing. If your espresso tastes sharp and lacks sweetness, lower the water temperature to around 92 °C and shorten the extraction time slightly – the improvement may surprise you.

How to balance bitterness and acidity in coffee to achieve the perfect aroma?

The ideal cup is one where acidity, bitterness and sweetness coexist in harmony. Achieving this balance is both craft and science – you only need to follow a few simple rules to obtain café‑quality results at home.

Remember that balanced bitterness doesn’t mean the absence of it. Gentle, velvety bitterness gives the brew body, depth and a lingering finish, whereas excessive sourness makes coffee taste sharp and thin.

How to brew coffee to achieve the perfect balance of acidity and bitterness

Even the finest beans won’t reach their potential if brewed incorrectly. That’s why brewing parameters – water temperature, grind size, extraction time and coffee‑to‑water ratio – play a crucial role in taste. These factors decide whether your cup will be balanced or lean too far towards sourness or bitterness.

By mastering these variables, you can coax out sweetness, creaminess and subtle bitterness while maintaining pleasant coffee acidity. A small misstep, however, can leave you with an overwhelming sourness or astringent bitterness.

If you’d like to understand in more depth how roasting affects flavour, read this article on our blog: 👉 “Light, medium or dark? How the roast profile influences the taste and aroma of coffee” – it includes practical examples and tips tailored to different brewing methods.

Once you understand how these parameters interact, you can deliberately “steer” the flavour – bringing out more sweetness, softening bitterness or toning down excess acidity. The craft of brewing lies in subtle awareness and small adjustments.

Temperature, grind and ratio – their influence on sour coffee

Excess acidity in coffee often stems from the wrong combination of these three factors: water temperature, grind size and brew ratio. Grasping their relationships is the key to creating a cup that’s full‑bodied, sweet and perfectly balanced.

• Temperature – below 88 °C produces sour coffee: watery and under‑extracted. For most methods, 92–94 °C is ideal. With highly acidic beans, try a slightly higher temperature to mellow the flavour.
• Grind – if your coffee tastes too sour, it’s likely ground too coarse. A finer grind allows better extraction of sweetness and creaminess. You can learn more from our blog post 👉 “Grinding coffee – why freshly ground beans change the flavour”.
• Ratio – too little coffee for the amount of water = excess acidity and lack of body; too much = overly bitter coffee. For espresso, stick to 1:2 (18 g coffee → 36 g shot); for filter brews, about 1:16 works well.

When these three elements are in tune, your coffee will shine with harmony: acidity bright yet pleasant, bitterness gentle, sweetness clear. That’s when the beans reveal their full character.

How to find the perfect coffee for your palate

After reading this article, you already know that the taste of coffee is a fascinating interplay between acidity, sweetness and bitterness. There’s no such thing as one “best” coffee – it all depends on which flavour notes appeal most to your senses. For some, perfection means a low acidity coffee with hints of nuts and milk chocolate; for others, a juicy, fruity Kenyan arabica with bright citrus refreshment.

The key to discovering your favourite flavour profile is experimentation. Adjust one brewing variable at a time – temperature, time, ratio or grind size – and observe how each small change alters the taste in your cup. Try coffees from different regions too: Brazilian arabicas are creamy and sweet, Colombian ones balanced and complex, while Ethiopian beans are floral with a subtle citrus tang.

Don’t be afraid to experiment. The world of speciality coffee is full of delightful nuances and endless possibilities. Your perfect coffee is the one that brings you pleasure – whether it leans more towards bitterness or coffee acidity. With time, you will learn to recognise what you truly love – and coffee will become more than a drink: it will be a daily ritual of flavour and aroma.

Find your favourite coffee, brew with passion and enjoy every sip – because a great coffee always begins with you!