The Secret to a Perfect Cup of Coffee Lies in the Quality of the Water

Brewing coffee is often described as an art form, but to achieve the perfect cup you also need to understand some of the science behind it.

In the guide below we have highlighted some of the most important scientific explanations behind coffee brewing - so put on your white lab coat and safety goggles and let's brew a great coffee! You will learn the most important processes and how they influence the taste and aroma of your coffee.

Coffee beans (roasting, storage and grinding)

Whenever possible, use whole beans roasted within the last two weeks. The type of roast - light, medium or dark - depends on your personal preference. Keep in mind that the more the beans are roasted, the more the caffeine content of the original coffee beans will be reduced. A dark roast has a less acidic taste, but will lose some of its original sweetness and natural aroma as the sugars in the coffee caramelise during the roasting process.

Store beans in a sealed container, away from direct sunlight. If you are storing them for longer periods, consider freezing the beans.

Grind your coffee just before the brewing process. This helps to release the full aroma of the beans, as grinding them too far in advance leads to greater exposure to oxygen, breaking down the aromatic chemical compounds in the coffee beans.

The brewing process involves water penetrating and extracting the soluble flavours from the coffee beans. For this reason, it is better to achieve a finer grind, making sure the beans are ground evenly - this will maximise the surface area of the coffee for the extraction process.

Water and its specifications (composition, testing and purification)

A cup of coffee is 98% water, yet this element is often overlooked in favour of more commercially attractive components.

To brew the perfect coffee, your water source will ideally contain small amounts of calcium and magnesium, which help extract the flavour from the coffee beans. However, chlorides and sulphates can negatively affect the flavour of the coffee, resulting in a bitter-tasting brew.

Quick or laboratory water tests can indicate the levels of these chemical substances in the water you use. Many people living in areas with "hard" water are encouraged to use a reverse osmosis system to purify the water and turn it into the ideal water for flavourful coffee. 

The three factors that are most important for the extraction process are pressure, time and agitation during brewing. There is a wide variety of different brewing methods that make use of these three factors, all of which require hot water to extract the flavour from the coffee beans.

Although this varies greatly depending on preference, a water-to-coffee ratio of 1:15 - 1:18 (approximately 20g of coffee to 300-360g of water) is considered the best ratio for extracting flavour from the beans, though this varies depending on the brewing method used.

Water temperature is extremely important in this process, as it determines which solids are dissolved - too hot and the coffee will be sour, as too many acids will be released - too cold and the coffee will be weak, as not enough solids will be dissolved. The ideal brewing temperature is between 91°C and 96°C, which means it is best to let boiling water rest for a minute or so before pouring it over ground coffee.

Milk and other flavourings

Milk is not, of course, essential for a coffee. Many coffee lovers would say it diminishes the flavour of the coffee, but for many of us it is an essential ingredient.

The most important factor in milk is its fat content, which helps mask the naturally bitter and acidic taste of coffee beans. The fat globules in milk create a rich, sweet taste by coating the tongue, perfect for those who love a creamy coffee. Lower-fat milk does not deliver this flavour as well, which is why some baristas now use milk with 12% fat content (regular whole milk contains around 3.5%) to create the perfectly creamy latte or cappuccino.

Another key ingredient in milk is the protein level. Protein helps create the small foam bubbles that are so important for cappuccino and other frothy coffees, and is a major reason why plant-based milk alternatives, such as almond milk, do not perform as well when heated.

Milk also consists of lactose, a natural milk sugar. By increasing the temperature of the milk through frothing, you increase the solubility of the lactose, making the coffee perfect for those who enjoy a sweeter drink.

The perfect coffee recipe

A partial understanding of the science behind coffee helps you refine your own process, but keep in mind that there is no one-size-fits-all approach. Like any scientific experiment, the process needs to be perfected through multiple attempts. The key to success lies in making small adjustments to suit your taste buds - we wish you the best of luck in creating your perfect concoction! If you think we have missed something or you have your own tips, feel free to contact us. Also, if you would like to transform your water into the ideal water for drinking and brewing coffee, please do not hesitate to contact us. As the ideal filtration system for brewing coffee, we recommend FILTRO INFINITY