How much water do you know we use to make coffee every day?

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Carbonate system generally refers to factors related to water quality: TDS, hardness (GH), acidity and alkalinity, pH value, buffer index (KH), metal content, especially calcium and magnesium. In order to test the use of water for brewing coffee, the above factors and their interactions must be taken into account when evaluating the use of water for brewing coffee.

Total dissolved solid (Total dissolved solids/TDS)

Also known as the total amount of dissolved solids, the higher the TDs value, the more dissolved matter in the water, including both inorganic and organic matter, measured in milligrams per liter (mg/L).

Milligrams (mg) / liter indicates how many milligrams of total dissolved solids are in 1 liter of water.

A unit of concentration per million of PPM solution. Refers to the number of milliliters of solute in 1 million ml solution or indicates the number of grams of solute in 1 million grams of solution.

Conversion relationship: 1mg/l=1PPM

If the TDS value of water is less than 1000mg/L, it is generally considered to meet the safety standard for drinking. Too high TDS value will definitely affect the taste of brewed coffee, because water does not have more "space" to dissolve substances that produce flavor. Experiments show that the quality of brewing coffee with water with TDs value 120-125mg/L is obviously better than that with TDS value 300mg/L. Brewed coffee.

On the other hand, different types of substances that produce flavor can also affect the hydraulic dispersion (hydrodynamic dispersion) when water permeates through the coffee powder layer (coffeebed) and individual coffee particles.

The higher the ppm value, the more soluble matter in the water, so the extraction rate of coffee will be lower.

The lower the ppm value, the less soluble matter in the water, so the higher the extraction rate of coffee.

According to the SCA study, the ppm value of water is between 125and 175. it is most ideal for coffee extraction. If the ppm value is less than 75, it is more likely to be overextracted. If the ppm value is higher than 225ppm, it is more likely to be underextracted.

Reasons for the formation of TDS in water

The groundwater (ground water) extracted from the underground storage layer or permeated through the soil contains high minerals (high TDS value), and the limestone in the aquifer is easy to dissolve to form hard water (hard water) in the acidic state, because the limestone is mainly composed of calcium carbonate.

On the other hand, surface water from lakes and rivers usually has a low TDs (not often in contact with soil minerals). But human factors can affect TDS. For example, acid rain caused by air pollution can cause the decrease of PH value and the increase of mineral content in lakes. Industrial and agricultural wastewater can increase the solid content in surface water. Despite municipal water treatment systems, in rural areas, water always carries the smell of algae, fungi, uric acid, the main nitrogen-containing end products of protein metabolism in mammals and some fish, and the smell of chemical fertilizers in the soil.

Water absorbs and dissolves pollutants in the atmosphere in the process of evaporation and rainfall; precipitation falls to the ground and dissolves dirt on the ground; surface water continuously dissolves minerals and chemicals in the process of infiltration into the ground or into rivers. Water dissolves calcium (Ca) and magnesium (Mg) ions in the water cycle, which will also affect the TDS of water.

Measuring TDS gives us an overview of how to use the total amount of soluble solids in water. Increasing the amount of ions in water limits the amount of soluble matter extracted from coffee. A higher TDs value will result in the extraction of a small amount of flavor substances. The primary purpose of water treatment is to debug the TDS value to an acceptable level.

Total hardness of water (GH)

The softness and hardness of water with the same ppm may be different. The hardness of water refers to the concentration of calcium and magnesium ions in water, and the unit of hardness is ppm,1ppm, which represents the content of calcium carbonate in water 1 mg / L (mg/L).

The hardness of water is related to the ppm value of water. The content of calcium and magnesium ions in water with high ppm value is relatively high, while in water with low ppm value, the content of calcium and magnesium ion is relatively low. However, when different water has the same ppm value, the composition of soluble solids in water may be different. In other words, the content of calcium and magnesium ions will be relatively different, so it will also have an impact on coffee extraction, just look at the TDS value is one-sided.

In the process of brewing coffee, some compounds or ions have a greater effect on the extraction than other compounds and ions. In the experiment, a single inorganic compound was put into distilled water to test the effect on coffee extraction.

The TDs value of coffee extracted by distilled water with sodium bicarbonate Sodium Bicarbonate was 1.29%. After dissolving in water, sodium bicarbonate is decomposed into sodium carbonate, carbon dioxide and water. The carbon dioxide produced helps fluffy coffee particles, diffuses soluble compounds in coffee and speeds up extraction. A high content of sodium ions will have a salty taste.

The TDs value of coffee extracted with distilled water added with calcium chloride (calcium chloride) was 1.04%. Calcium chloride is ionized in water to form chloride and calcium ions which react with soluble organic compounds and carbohydrates in coffee to form precipitation. Calcium ions can also combine with specific substances to produce new flavors during coffee brewing.

Hard water and soft water

Water is soft water and hard water. Water that does not contain or contains a small amount of calcium and magnesium ions is called soft water, and vice versa. The hardness composition of water, if caused by sodium bicarbonate or magnesium bicarbonate, is temporary hard water (precipitated by boiling temporary hard water, decomposed sodium bicarbonate, resulting insoluble carbonate, and water changes from hard water to soft water); if it is caused by sulfates or chlorides containing calcium or magnesium, it is permanent hard water and cannot be removed after boiling. The above two kinds of hardness are collectively called total hardness.

Total hardness of water = calcium hardness + magnesium hardness = carbonate hardness + non-carbonate hardness = temporary hardness + permanent hardness

According to the total hardness of water, the total hardness 0-30ppm is called soft water, and the total hardness above 60ppm is called hard water.

Water with extremely high hardness indicates that it also contains other metal elements such as chloride, sulfate, carbonate and sodium bicarbonate. Chlorine and chlorine (chloramines) are used in municipal water system to remove harmful bacteria from water, which can cause the oxidation of aromatics and oils and destroy the flavor of coffee, which should be removed when making coffee. Too much iron in the water makes the coffee look green, hydrogenated sulfur makes the water smell like rotten eggs, and chlorine and sulfate make the water salty.

PH value

Also known as hydrogen ion concentration index: a scale of hydrogen ion activity in a solution, that is, a measure of the acidity and basicity of a solution in a general sense. Normally, the pH value is a number between 0 and 14. When pH7, the solution is alkaline, and when pH=7, the solution is neutral. Water is neutral at 25 degrees, corresponding to a pH value of 7.0. the stronger the alkalinity (the higher the pH value), the stronger the ability to counteract acid, the stronger the effect of reducing acid taste, the more alkaline the water used, the more acid-base reactions will occur in coffee, and coffee is more likely to dissolve in alkaline water.

When water dissolves carbon dioxide in the atmosphere, the pH value is low, and atmospheric pollution will further reduce the pH value of water. When water seeps through the soil and mineral layer, acidic water will dissolve minerals and the pH value of the water will increase. For groundwater deep below the surface, when it reaches the underground aquifer (sand aquifer), it has a high pH value and contains a lot of minerals. On the contrary, microbes in the soil are beneficial to the production of carbon dioxide, which dissolves in water to form carbonic acid, bicarbonate, carbonate, which in turn reduces the pH value of the water (acidity increases).

Mineral-rich areas, the hydrological ph will be alkaline, the typical African three lakes region ph value will be 8, rainforest areas, because there are a large number of fallen leaves and rotten trees, and then produce a lot of humic acid, so the water quality of Southeast Asia, West Africa, South American Amazon, and other rainforest areas is acidic.

Acids and bases in carbonate system

The pH value represents the total number of hydrogen ions in the solution. If the hydrogen ion and hydroxide ion in the solution are out of balance, the solution is either acidic or base bases (alkaline). High levels of any of the above ions will have an effect on brewing coffee.

Not all acids or bases decompose quickly in solution, but they decompose naturally in water or coffee, because coffee contains a large number of different compounds, including different amounts of ionic bonds.

People can neutralize the acid or base, such as adding acid to the solution with high pH value to achieve the neutralization effect, and the hydrogen atom in the acid and the original hydroxide ion in the solution form water molecules. The value of TDs will increase because of the new anions in the acid.

The total alkalinity of water

To obtain the expected pH value, it is not enough to measure the pH value of the solution. Also consider the total alkali (total alkalinity) and total acid (total acidity).

Total alkalinity: refers to the total amount of substances in water that can neutralize strong acids, including strong bases, weak bases, strong bases and weak salts. For example: hydroxide (OH-) hydroxide, carbonate (CO3- 2) carbonate, bicarbonate (HCO3-) sodium bicarbonate.

The total alkali content of water (solution) with the same ph value is not necessarily the same, because the ph value directly reflects the content of HB, or OH- in the water, and the total alkali content includes OH-, CO3- 2, HCO3- and other alkaline substances.

Ph values of solutions with the same alkalinity can be different: for example, NaOH solution of alkaline 0.1mmol/L, ph=13, NaHCO3 solution of alkaline 0.1mmol/L ph=8.3

PH and alkali affect the acidity of the solution in the opposite way, you

The alkali in the solution can neutralize the acid of the coffee and make the coffee particles expand. In the experiment, using carbonate-containing water to brew coffee tastes bitter, has a high ph value, tastes insipid, and prolongs the extraction process.

Buffer index (KH alkalinity)

KH is often misled as the hardness of water. In fact, this is wrong. The KH value only describes the acid carbonate (HCO3-) in the temporary hardness. Chemically, the KH value is defined as the concentration index of bicarbonate (HCO3-) in units of KH. Hardness (GH) is used to define the content of multivalent metal ions (magnesium ions, iron ions, etc.) in water, rather than describing the anions (bicarbonate, sulfate, etc.). Therefore, there is an obvious difference between KH and GH.

The influence of KH value and GH value on hedging brewing coffee

Because bicarbonate is the most important buffer material in water quality, it can neutralize any increase or decrease of free CO2 in water quality, and it can also restrain the fluctuation of hydrogen ions to maintain a constant pH value, so the control of kH is regarded as an indispensable procedure for water quality management.

If the KH is too low, it means that the natural buffer system in the water has lost balance, and the water quality will become acidified, which is easily affected by intermediate and acidic substances, resulting in a sharp decrease in pH value.

On the contrary, if the kH is too high, the water quality will tend to be alkaline, which is easily affected by alkaline substances, resulting in a sharp increase in pH value.

KH hardness completely refers to the expression of anion (HCO3-) content in water, which is called 1 degree (equivalent to 10ppm concentration) with 1 mg of HCO3- in 100ml water and marked as 1 degree kH. It is completely different from the expression of CaCo3 (calcium carbonate) hardness for the content of cations (Mg2+, Ca2+) in water.

The value of KH is closely related to the buffer capacity of the buffering system. Generally speaking, the larger the KH, the greater the buffer capacity of the water body, and the smaller the pH change caused by the entry and exit of high concentration CO2 into the water body. From this point of view, in theory, the bigger the KH, the better, but if the KH is larger, the pH of the water body will be higher.