In our previous two articles, we have created a general perspective on water and briefly talked about the chemistry of water and its solubility effects. Water is a polar molecule, the charges in the molecule are distributed asymmetrically. This helps water molecules to hold onto each other by forming hydrogen bonds and contributes to the properties of water. Water is a highly reactive substance. Therefore, it can react with other substances such as acids and bases. This causes the pH level of water to change, and this situation reveals many more properties related to water. In our previous article, we also talked in detail about what pH is, and in this article, we will talk in detail about the relationship between water and coffee, salts, SCA's assumptions and ideals. When we say the solubility effect of water, we accept that the expression of how the dissolving capacity of a substance in water changes depending on temperature, pressure and other factors has now been made. This effect affects the interaction of many different substances with water and the chemical properties of water. If these factors are examined under headings with small explanations below,
Temperature effect: Temperature has a significant effect on the solubility effect of water. In general, a substance becomes more soluble as the temperature increases. This is because the mobility of molecules increases as the temperature increases, allowing the solvent molecules to move more, facilitating dissolution. However, the solubility of some substances in water may decrease as the temperature increases (sucrose, fructose).
Pressure effect: Pressure also has an effect on the solubility effect of water. Increasing the pressure causes the solvent molecules to become more concentrated and therefore able to dissolve more substances. Decreasing the pressure has the opposite effect.
Other factors: The solubility effect of water also depends on pH, ionic strength, polarity, and other factors. For example, the more polar a substance is, the more easily it dissolves in water. Additionally, some substances can interact with other substances and affect the solubility of water.
The reason we focus on the solubility effect is that the coffee brewing process is completely dependent on solubility rates. We want coffee that dissolves well in ideal water, and for this, we try to create certain recipes by examining everything from water chemistry to the way water is poured.
The most basic thing to know about solubilities and water quality is the hardness of water. Water hardness is the name given to the total concentration of calcium and magnesium ions in water. Hard water is water that contains high levels of calcium and magnesium ions. These minerals can reduce the solvent power of water by preventing other substances in the water from dissolving and can cause lime stains.
The hardness of water is measured by the concentration of calcium and magnesium dissolved in the water. Usually, hardness is expressed in milligrams per liter (mg/L) or parts per million (ppm).
The hardness of water can be interpreted as follows:
0-60 ppm: Hardness is low and water is considered soft.
61-120 ppm: Hardness is at a moderate level and the water is considered slightly hard.
121-180 ppm: Hardness is high and water is considered medium hard.
181 ppm and above: Hardness is very high and water is considered hard.
The hardness of water can be measured by various methods. We can concretely see the effect of water hardness in the event we call lime. Lime, namely CaCO3, when dissolved in water, turns into hydrogen carbonate ions (H2CO3) as a result of the reaction of bicarbonate (HCO3-) ions in water with carbon dioxide (CO2) depending on the pH value of the environment. As a result of this transformation, when hydrogen carbonate ions combine with calcium ions and precipitate, CaCO3 sediment is formed. This sediment accumulates over time and forms solid layers called lime. If the chemical formula is written,
Ca(HCO3)2 → CaCO3 + CO2 + H2O
Since water hardness directly affects solubility, hard water takes us far away from ideal coffee brewing water, so water must be softened by various methods. Water softening is a process designed to remove or replace calcium and magnesium ions in water. This process is carried out using an exchange resin that can bind to calcium and magnesium ions in water. The softening process is carried out by passing water through resin beds. Resins are loaded with sodium ions, and they release sodium ions into the water instead of calcium and magnesium ions, reducing the hardness of the water. During this process, the resin beds begin to lose sodium ions and may need to be renewed.
Another softening method is reverse osmosis. In this method, a semi-permeable membrane is used through which water can pass under high pressure. This membrane allows only water molecules to pass through, allowing minerals such as calcium and magnesium to be removed. Osmosis is the process of a selectively permeable membrane between two solutions with two different salinity levels, where the salty solution passes towards the side of the solution with the lower salinity level. Reverse osmosis reverses this process and forces the solution with the higher salinity level towards the solution with the lower salinity level. In short, with this method, unwanted substances such as ions, organic substances, bacteria and other small particles in the water are filtered and cleaned. During this process, the water is passed through a pressurized membrane filter and only water molecules can pass through the filter, while larger molecules are left behind. In this way, cleaner and purer water is obtained.
We are closing the topic of the advantages and disadvantages of ion exchange and reverse osmosis methods for water softening to be opened in the next article.
Let's continue our topic with the ideal assumptions of coffee water.
According to the SCA, the “ideal” water used to brew quality coffee must have certain characteristics. These characteristics are:
Hardness: The hardness of coffee brewing water should be between 50-150 ppm. The solubility of water in this range is ideal and the taste and aroma of the coffee is better.
pH: The pH of coffee brewing water should be between 7.0 and 8.5. It is thought that water in this range supports the taste and aroma profile better.
Total dissolved solids (TDS): The TDS of coffee brewing water should be in the range of 150-300 ppm. Water in this range is thought to better support the taste and aroma profile of the coffee.
Oxygen: Coffee brewing water should be as oxygenated as possible. Oxygenated water better supports the flavor and aroma profile of the coffee.
According to SCA, having these features of quality coffee brewing water can improve the coffee flavor and aroma profile and make the coffee experience more enjoyable. What we expect from coffee experts is that the pH range of 7-8.5 can actually determine which bean, which harvest, which roasting and grinding degrees are at which ideal pH. As can be seen, SCA has given quite wide ranges, while pH 7 is neutral, pH 8.5 is quite alkaline water and which of these should be used in which coffee is the part that really requires expertise and is open to experimentation. Because coffee matter is quite flexible in terms of its structure, it is a magnificent structure that should not be fallen into concepts such as “THE RIGHT ONE” or especially the “IDEAL ONE” that I have quoted above, it gives very different answers to the experiments made and grinds the teeth of researcher souls. Therefore, if you are someone who is reading this article and taking new steps towards becoming a coffee expert, first of all, “THE COFFEE WATER SHOULD BE AT THIS PH, THE COFFEE SHOULD BE ROAST AT THESE DEGREES, …. You should stay away from capitalized sentences like “THE COFFEE GRINDING RANGE FOR THIS IS”. If you are an expert, you already know these because you have enough experience.
Let's continue with our topic…
According to SCA standards, we talked about the chemistry of water hardness and what methods can be used to soften it, we talked about the concept of pH in our previous article in the most understandable way possible, let's examine the oxygen part a little. In the meantime, we prepared another understandable article for TDS.
Oxygen…
Of course, here we will talk about the effects of oxygenation during coffee brewing and in water, rather than the general structure of oxygen.
The oxygenation of water is very important for coffee because during the coffee brewing process, aroma compounds are formed using oxygen. When volatile compounds in coffee beans come into contact with oxygen, they oxidize and change their smell and taste. Oxygen causes chemical changes in some compounds in coffee aromas. For example, when oils in coffee come into contact with oxygen, oxidation reactions can occur. What we normally call oxidation is also responsible for the loss of the fresh aroma of a coffee that has been aired. However, oxidation can also create pleasant smells and tastes in coffee. In general, we can summarize that having enough oxygen in the brewing water is very important due to its effects such as reacting with the oils in the coffee and forming compounds. But the most important and not emphasized part is melanoid oxidation, which consists of many intermediate reaction steps. Melanoid oxidation is a chemical reaction in which sugars react with amino acids, leading to the formation of brown pigments called melanoidin. In general, compounds called glycosylamines are formed as a result of the reaction of sugars with amino acids. These compounds then undergo oxidative decarboxylation, and the reaction produces melanoidin pigments. The melanoidins that form contribute to the aroma, color, and flavor of coffee. Oxygen is a component of this reaction because it is used in the step called oxidative decarboxylation. The presence of oxygen increases the rate of the reaction and causes more melanoidin pigment to form. Melanoid oxidation can occur at around 90-96°C, which is the temperature at which coffee is brewed. This temperature is sufficient for the sugars and amino acids in the coffee beans to react. As a result of this reaction, the aroma and flavor of coffee are created. Moreover, these flavors are released without the unpleasant side effects of any combustion process. At the same time, the mixing of oxygen into the coffee water helps to break down and eliminate organic substances that give the water bad odor and taste.
Can water be made more oxygenated?
Yes.
The following methods can be used to create more oxygenated water:
Water fluidity: As water fluidity increases, more oxygen is mixed into the water. Therefore, methods such as dropping water from a height or spraying air into the water can be used to increase the fluidity of water.
Agitation: Stirring or shaking the water will allow oxygen to be better distributed. Therefore, shaking or pouring the water to agitate it will allow more oxygen to be mixed into the water.
Oxygen rich environments: In oxygen rich environments, water can come into contact with more oxygen. For example, in high altitude areas where water is in contact with air, water can become saturated with more oxygen.
Water purification systems: Some water purification systems have the ability to add oxygen to the water. These systems can add oxygen to the water using methods such as ozonation or UV light.
These methods can help make water more oxygenated. However, oxygenated water has a limited life span because oxygen is lost over time. Therefore, it is recommended to choose a fresh and renewed water source. As can be seen, the oxygen issue is also a very sensitive and important issue and is a completely solid parameter. Let's continue with our last topic by adding a title to the 4 main titles written by SCA above.
Alkalinity…
Alkalinity is a subject that is often confused with water hardness and unfortunately not thought about much. Here we will briefly talk about what the subject is and its importance for coffee.
The alkalinity of water is a term that refers to the concentration of basic compounds or bases (hydroxide, carbonate, bicarbonate, etc.) in water. These compounds can be caused by alkaline substances added to water, mineral sources, or spring water. Alkalinity is a factor that affects the pH value of water. As the alkalinity level increases, the pH value of water also increases. Therefore, waters with high alkalinity levels are basic, while waters with low alkalinity levels are acidic. Alkalinity provides important information about the chemical structure and mineral content of a water source.
The level of alkalinity in coffee can affect the taste, aroma and quality of coffee. Coffees with high alkalinity levels are less acidic, while coffees with low alkalinity levels are more acidic. Some coffee experts believe that the minerals in the soil of the region where the coffee beans are grown affect the alkalinity of the coffee beans. The level of alkalinity in coffee can vary depending on the brewing method. Coffee beans naturally contain coffee oil (triglycerides). Unfiltered brewing methods, especially the French Press method, allow the oils in the coffee beans to pass into the coffee, which leads to the presence of coffee fatty acids in the water. These acids increase the hydrogen ions in the water and lower the pH level, i.e., reduce the alkalinity in the water. However, some compounds in the coffee beans (such as caffeic acid) can neutralize these acids, which causes the alkalinity level to increase. Unfiltered brewing methods can result in higher alkalinity levels because more compounds are soluble in water and become more active in the coffee water.
In filtered brewing methods, especially the paper filter brewing method can reduce the alkalinity level in coffee. In these methods, as the water flows over the coffee grounds, the paper filter retains the coffee oil and some aroma compounds and allows only the liquid part to pass. This process causes the oil and some aroma compounds in the coffee to remain in the filter. These compounds can contribute to alkalinity, so the filtering process reduces the alkalinity level.
Therefore, the alkalinity level of coffee can vary depending on factors such as the coffee's brewing method and the alkalinity level of the source water.
In general, filtered brewing methods result in a lower alkalinity level compared to others, while unfiltered brewing methods may result in a higher alkalinity level.
Below we have listed the changes in alkalinity levels according to coffee brewing methods:
Low alkalinity:
Filter coffee (using filter paper)
Aeropress
Chemex
Origami
V60
Kalita
Orea
High alkalinity:
French Press
Turkish coffee
Mocha pot
Espresso
But of course, other factors such as brewing time, quality of coffee beans and water hardness also affect alkalinity levels.
Brewing time: As contact time with coffee beans increases, the solubility of compounds in the coffee increases. Therefore, longer brewing times generally lead to a higher level of alkalinity.
Bean quality: The quality of coffee beans affects the type and amount of compounds they contain. Higher quality beans tend to have higher alkalinity levels. Higher quality beans tend to have higher acidity levels (not to mention the acidity you can taste). This is due to the presence of higher amounts of organic acids. Many of the organic acids increase alkalinity levels by lowering the pH of the compounds in the coffee. Therefore, higher quality beans tend to have higher alkalinity levels. However, there are variations in alkalinity levels depending on the type of bean, the processing method, and other factors.
Water hardness: Hard water can dissolve fewer compounds during coffee brewing, which can result in a lower level of alkalinity. However, water hardness can also indicate the presence of other minerals, which can lead to different flavor notes.
Top of Form
Alkalinity and water hardness are different concepts that should not be confused. Alkalinity refers to the presence of bicarbonate ions (HCO3-) in water, while water hardness refers to the presence of calcium (Ca2+) and magnesium (Mg2+) ions in water. Some waters can have high alkalinity and hardness together. In other words, there is no inverse/direct proportion between them. In this case, bicarbonate ions can neutralize calcium and magnesium ions dissolved in water and reduce hardness.
In this article, we tried to look at other parameters that we did not mention in our other two articles about coffee water with a very broad perspective. With this article, a summary was created for the first, second and expert level with the questions about the chemistry of coffee brewing water, its variables, and the concept of "ideal". Enjoy reading.
DUYGU KURTULUŞ
Co-Founder / Chemist / Nanotechnology Engineer / Hazardous Chemical Consultant / Chemical Evaluation Specialist