Using the converter “Converter of pressure, mechanical stress, Young’s modulus. What is measured in pascals

Length and distance converter Mass converter Bulk and food volume converter Area converter Volume and units converter in culinary recipes Temperature converter Pressure converter, mechanical stress, Young's modulus Energy and work converter Power converter Force converter Time converter Converter linear speed Flat Angle Thermal Efficiency and Fuel Efficiency Converter Number Converter to various systems notations Converter of units of measurement of the amount of information Currency rates Sizes of women's clothing and shoes Sizes of men's clothing and shoes Angular velocity and rotation frequency converter Acceleration converter Angular acceleration converter Density converter Specific volume converter Moment of inertia converter Moment of force converter Torque converter Specific heat of combustion converter (by mass) ) Energy density and specific heat of combustion converter (by volume) Temperature difference converter Coefficient of thermal expansion converter Thermal resistance converter Specific thermal conductivity converter Specific heat capacity converter Energy exposure and thermal radiation power converter Heat flux density converter Heat transfer coefficient converter Volume flow converter Mass flow converter Converter molar flow rate Mass flow density converter Molar concentration converter Mass concentration converter in solution Dynamic (absolute) viscosity converter Kinematic viscosity converter Surface tension converter Vapor permeability converter Vapor permeability and vapor transfer rate converter Sound level converter Microphone sensitivity converter Sound pressure level (SPL) converter Sound level converter pressure with the ability to select reference pressure Brightness converter Luminous intensity converter Illumination converter Resolution converter in computer graphics Frequency and wavelength converter Optical power in diopters and focal length Optical power in diopters and lens magnification (×) Converter electric charge Linear Charge Density Converter Surface Charge Density Converter Volume Charge Density Converter Converter electric current Linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Converter electrical resistance Electrical Resistivity Converter Converter electrical conductivity Electrical conductivity converter Electrical capacity Inductance converter American wire gauge converter Levels in dBm (dBm or dBmW), dBV (dBV), watts and other units Magnetomotive force converter Voltage converter magnetic field Magnetic flux converter Magnetic induction converter Radiation. Ionizing radiation absorbed dose rate converter Radioactivity. Radioactive decay converter Radiation. Exposure dose converter Radiation. Absorbed dose converter Converter decimal prefixes Data Transfer Typography and Imaging Unit Converter Lumber Volume Unit Converter Molar Mass Calculation Periodic Table chemical elements D. I. Mendeleev

1 pascal [Pa] = 1.01971621297793E-05 kilogram-force per square meter. centimeter [kgf/cm²]

Initial value

Converted value

pascal exapascal petapascal terapascal gigapascal megapascal kilopascal hectopascal decapascal decipascal centipascal millipascal micropascal nanopascal picopascal femtopascal attopascal newton per square meter meter newton per square meter centimeter newton per square meter millimeter kilonewton per square meter meter bar millibar microbar dyne per sq. centimeter kilogram-force per square meter. meter kilogram-force per square meter centimeter kilogram-force per square meter. millimeter gram-force per square meter centimeter ton-force (kor.) per sq. ft ton-force (kor.) per sq. inch ton-force (long) per sq. ft ton-force (long) per sq. inch kilopound-force per sq. inch kilopound-force per sq. inch lbf per sq. ft lbf per sq. inch psi poundal per sq. foot torr centimeter of mercury (0°C) millimeter of mercury (0°C) inch of mercury (32°F) inch of mercury (60°F) centimeter of water. column (4°C) mm water. column (4°C) inch water. column (4°C) foot of water (4°C) inch of water (60°F) foot of water (60°F) technical atmosphere physical atmosphere decibar walls on square meter barium pieze (barium) Planck pressure meter of sea water foot of sea water (at 15°C) meter of water. column (4°C)

How does a Geiger counter work?

The Science of Coffee Making: Pressure

High pressure is often used during cooking, and in this article we will talk about what pressure is used when brewing coffee. We'll look at the espresso technique, which uses hot water under pressure to prepare coffee. First, we'll talk about coffee preparation in general, what substances are extracted from coffee beans during the brewing process, and the different methods of preparing coffee. After that, we'll discuss in detail the role of pressure in making espresso, and also see how other variables affect the taste of coffee.

Coffee

People enjoying coffee at least from the fifteenth century, and perhaps even earlier, although we do not have precise data on earlier coffee preparation. Historians claim that the people of Ethiopia were the first to drink coffee, and that from there this drink spread to Yemen and other neighboring countries, and from these countries it already came to Europe. According to some reports, Sufi Muslims used coffee in religious rituals. For many years, coffee was banned in the Arab world by conservative members of the Islamic clergy due to its unusual properties, but the ban was eventually relaxed. The Church in Europe also disapproved of coffee for some time due to its popularity in the Muslim world, but soon came to terms with the growing popularity of the drink in Europe. Since then, coffee has been popular all over the world. Coffee is probably the first thing that comes to mind when you think about a typical morning. So what is coffee, how to prepare it, and why do we love it so much?

Coffee beans are the seeds of the berries of a plant in the madder family ( Rubiaceae). There are many different plant species in this family, but the most widely used for making coffee is the Arabian Coffee Arabica(Arabica variety) and Congolese Coffea canephora coffee tree (robusta variety), with the Arabica variety being more popular. IN English coffee berries are sometimes called cherries for their color and shape, but they have no relation to the cherry tree. The coffee beans are first cooked, that is, roasted, and then prepared into coffee, and during these processes, various substances, including aromatic oils and solid particles, are extracted. These substances create the special taste and aroma of coffee and give it invigorating properties.

As far as we know, one of the first methods of preparing coffee was to boil coffee beans in water. While trying different brewing methods, people noticed that if coffee is in contact with hot water for too long, the drink becomes bitter, and if, on the contrary, the coffee is not brewed long enough, then it becomes sour. Therefore, they were developed various ways preparations that ensure the best extraction. Trying different methods preparation, bartenders in coffee shops noticed that pressure improved the preparation process and the taste of the finished drink, and thus the espresso technique was born.

Coffee has been prepared for centuries in different ways, and everything we know about making coffee comes from hundreds of years of experimentation in the kitchen. It was thanks to these experiments that coffee lovers determined optimal temperature, roasting and brewing times, grind size, and the use of pressure during the brewing process.

Substances that are obtained by extraction from coffee beans during the preparation process

The taste of coffee and its special properties depend on the chemicals that are obtained during the extraction process of roasting coffee beans and preparing the coffee itself. In this section we will talk about the main substances and how different preparation methods affect their extraction.

Caffeine

Caffeine is one of the main substances obtained during extraction from coffee beans. It is thanks to him that coffee gives those who drink it a boost of energy. Caffeine also gives the drink its characteristic bitterness. When coffee is prepared using the espresso technique, more caffeine is obtained from the ground coffee compared to other preparation methods. But this does not mean that if you drank one shot of espresso, you received a greater dose of caffeine than if you drank a cup of coffee, for example, prepared in a drip coffee maker. After all, espresso shots are much smaller in volume than portions in large cups in which coffee prepared in a drip coffee maker is served. Therefore, although espresso coffee has a much higher concentration of caffeine, the total amount of caffeine in a shot of espresso is less than in coffee prepared by other methods, since espresso is drunk in very small portions.

Trigonelline

Trigonelline is one of the substances that gives coffee its special rich caramel aroma. The flavor is not obtained directly from trigonelline during preparation, but during roasting of the coffee beans. Due to heat treatment, trigonelline breaks down into aromatic substances called pyridines.

Acids

Coffee contains acids. You've probably noticed this if you've ever poured cream into your espresso coffee and it curdled. The three main acids in coffee are citric, quinic, and malic. There are other acids in coffee, but in very small quantities.

Quinic acid makes coffee sour if it is kept at temperatures above 80°C for a long time, for example if it is left in a warming pot.

Malic acid gives coffee notes of apple and pear and improves its taste. It also adds sweetness to the coffee.

Some other acids that get into the finished drink due to extraction are: phosphoric acid, which gives coffee fruity notes, acetic acid, which gives notes of lime, and tartaric acid, which gives coffee a grape flavor.

Carbohydrates

Coffee contains a number of carbohydrates that make coffee sweet. You probably haven't even noticed before that coffee is actually a little sweet, especially if you think of coffee as a bitter drink. But there is sweetness in it, and you can notice it with practice, especially if you drink espresso good quality, brewed by a person who knows how to make coffee properly. Brown roasted coffee - also thanks to carbohydrates. When cooked, coffee beans change color from green to brown, as the Maillard reaction occurs in carbohydrates under the influence of temperature. The color of golden brown bread, fried meat, vegetables, and other foods is also the result of this reaction.

The balanced extraction of all these and several other components produces the diverse and unique variations of coffee taste and aroma that we love so much. Below we will look at a number of methods for achieving a balanced taste. It is worth noting that the concentration of each substance depends on its content in the coffee beans. This content depends, in turn, on the soil and other factors related to the growing conditions of the coffee tree.

Espresso preparation procedure

The technique for preparing espresso coffee includes the following steps:

Roasting coffee beans.
Grinding grains.
Coffee dosage.
Pouring ground coffee into the portafilter basket.
Tamping coffee in a portafilter. This step also includes breaking up any clumps and leveling the coffee inside the portafilter basket.
Pre-wetting, which is only possible in some espresso coffee makers.
Espresso coffee extraction. In English, this process is also called pulling, since in early manual espresso machines the barista pulled the handle to get a shot of espresso.

In this article, we'll focus on the pressure-based steps of espresso preparation, including tamping, pre-wetting, and brewing the coffee itself.

Tamping

When preparing a shot of espresso, pressurized water is forced through a portafilter. In this case, substances are extracted from ground coffee that give the drink its properties and taste. If the coffee tablet in the portafilter is not compacted uniformly, water will flow through the points of least resistance. The coffee at these points will be over-extracted, while at other points it will be under-extracted. This will have a bad effect on the taste of the coffee. To avoid this problem, the lumps in the coffee are loosened and then tamped or, as they now say, tamped with a special device called a tamper.

There are several ways to get rid of the areas of least resistance in your ground coffee. One method called Weiss distribution technique, is used to break up lumps caused by the oils that coffee releases during grinding. They do this as follows:

Add coffee to portafilter;
Use a makeshift funnel for the portafilter basket to prevent the coffee from spilling out when stirring. To do this, you can attach a yogurt cup or a plastic juice bottle with the bottom cut off to the portafilter;
Stir the ground coffee well with a thin stick, such as a chopstick or a thin wooden skewer;
Tap the edges of the plastic nozzle to release all the coffee back into the portafilter basket.
The next step is the compaction itself.

Tamping is the process of uniform compaction of a coffee tablet. The pressure exerted by the tamper on the ground coffee must be sufficient to form a dense tablet that traps the flow of pressurized water. What exactly the pressure should be is usually determined by experimenting with different pressure values. You can first try the recommended values for pressure, and then experiment, observing how changes in pressure affect the taste of the finished drink, and in what concentrations each component is extracted at a certain pressure. Typically, the literature for espresso coffee lovers recommends the following:

Start tamping the coffee, applying about 2 kg of pressure.
Continue compacting using 14 kg of pressure.

Some experts recommend first using a scale or a tamper with a dynamometer (professional, read: expensive solution) in order to know for sure that the tamping was done at the correct pressure, and to feel with what force the tamping should be done. To apply even pressure across the surface of the coffee tablet, it is important to use a tamper that is the same diameter as the portafilter basket. It is usually difficult to tamp coffee neatly using the standard plastic tamper that comes with some espresso machines, as it is difficult to keep perpendicular to the surface of the coffee, and often its diameter is too small and the pressure is uneven. It is best to use a metal tamper, the diameter of which is only slightly smaller than the diameter of the filter.

Pressure in espresso coffee makers

As their name suggests, espresso coffee makers are designed specifically for making espresso coffee. There are many ways to extract the various aromatics from coffee beans to make this drink, from cooking on the stovetop in a pot or drip coffee maker, to using pressurized hot water through a coffee pellet, as in an espresso maker. The pressure in coffee makers is very great value. More expensive coffee makers are equipped with pressure meters (pressure gauges), and in coffee makers without pressure gauges, amateurs often install homemade pressure gauges.

To make delicious espresso, you need to extract enough solids and aromatic oils through extraction (otherwise the coffee will be watery and sour), but it's important not to overdo it (or the coffee will end up too bitter). How much parameters such as temperature and pressure affect the taste of the final product depends on the quality of the coffee beans and how well they are roasted. The espresso technique tends to extract more acids from light roasts, so dark roasts are typically used for espresso. Light roasts are more often used in drip coffee makers.

Typically, both home and commercial coffee makers use a pressure of 9-10 bar. One bar is equal to atmospheric pressure at sea level. Some experts advise varying the pressure during cooking. The Italian National Espresso Institute advises using a pressure of around 9±1 bar or 131±15 psi.

Parameters affecting coffee preparation

Although we are mainly talking about pressure in this article, it is worth mentioning other parameters that also affect the taste of the finished coffee. We will also discuss how the choice of these parameters depends on the coffee preparation method.

Temperature

The coffee preparation temperature varies between 85–93 °C, depending on the preparation method. If this temperature is lower than it should be, the aromatic components are not extracted in sufficient quantities. If the temperature is higher than necessary, the bitter components are extracted. Temperature in espresso coffee makers is usually not adjustable and cannot be changed, but you should be careful with the temperature when using other brewing methods, especially those that can easily overheat the coffee.

Grinding

Pre-wetting

Some high-end espresso makers have the option of pre-wetting the ground coffee while brewing. This mode is used because it is believed that increasing the time the coffee is in contact with water improves the flavor and aroma during extraction. Of course, we could simply increase the time the water passes through the portafilter. This will increase the amount of water that flows through the portafilter, but this will result in a decrease in coffee concentration since the amount of ground coffee remains the same. On the other hand, during the pre-wet process, which occurs at low pressure, the amount of water does not increase much, but the water remains in contact with the coffee longer, which improves the taste of the finished drink.

Cooking time

When preparing espresso, it is very important to choose the right time so as not to overcook or undercook the coffee. You can navigate by the following parameters:

Find the optimal color where you like the taste of coffee the most. To do this, you can experiment by stopping the extraction for different stages until you make coffee you like.
Measure how long it takes to brew coffee of that color. This time should be between 25 and 35 seconds, and if it is different, then you need to change the grind.
If the time is less than 25 seconds, then the grind is too coarse and needs to be finer.
If the time is more than 35 seconds, then the grinding, on the contrary, is too fine and needs to be made coarser.

Do you find it difficult to translate units of measurement from one language to another? Colleagues are ready to help you. Post a question in TCTerms and within a few minutes you will receive an answer.

The operating principle of many modern hydraulic devices - lifts, brakes, presses, water supply systems - is explained on the basis of Pascal's law. In 1961, one of the SI units was named after this scientist, who made a great contribution to the development of physics, mathematics, philosophy and other sciences. What is measured in pascals?

Pascal

So, pascal (Pa) is a measure of pressure, mechanical stress, elastic modulus and some other characteristics used in technology. A pressure of 1 pascal is created by a force of 1 newton, uniformly distributed over an area of 1 square meter perpendicular to the direction of its action (1 Pa = 1 N/m2). Remembering that 1 N = 1 kg∙m/s 2, we can express the pascal in terms of SI base units: 1 Pa = 1 kg/(m∙s 2).

Pressure is a scalar quantity; it characterizes the result of the action of an external force on a surface distributed over its area. Let's explain this with an example: imagine a person who first moves through loose snow on skis, and then takes them off and falls deep into a snowdrift. In the first case, the force - the weight of a person - is evenly distributed over a relatively large surface of the skis, in the other - only over the area of the foot, which leads to an increase in pressure, and consequently to subsidence of the snow.

External forces acting on a body tend to shift the position of the particles of which it consists. In response to this, internal forces will arise within the body that prevent displacement. The measure of the result of their action is called mechanical stress, which is also expressed in pascals.

What else is used to measure blood pressure?

If we are talking about pressure in medicine or meteorology, it is more often assessed in other units - millimeters of mercury. And in technology you can find such pressure measures as bar or atmosphere. Therefore, it is important to be able to convert them to pascals.

A brilliant scientist, physicist, mathematician, inventor, writer, philosopher and religious thinker, Blaise Pascal was an unusually gifted person.

Pascal's father Etienne was the chairman of the tax office. He was well versed in mathematics and explored the 4th order algebraic curve, named after him “Pascal’s snail.” Etienne was familiar with such famous mathematicians as Fermat and Descartes.

It was Etienne who drew up a training plan for Blaise Pascal. According to this plan, from the age of 12 Blaise was supposed to study ancient languages, and he planned to introduce his son to mathematics at the age of 15. But Blaise’s acquaintance with mathematics happened much earlier. He was very interested in geometry. Although he did not know geometric terms and called a circle a “ring” and a straight line a “stick,” he began to find relationships between them, and was soon able to prove the Euclidean theorem on the sum of the angles of a triangle. After this, with the help of his father, he began to study the geometry of Euclid and became acquainted with the works of Archimedes.

First scientific successes

In 1639, when Pascal was only 16 years old, he formulated one of the main theorems of projective geometry - Pascal's theorem about a triangle inscribed in a circle or any other conic section.

At the same age he studied conic sections.

2 years later, Pascal began work on creating the first computer. It was a box, inside of which there were gears connected to each other. Pascal's machine performed simple mathematical operations. It was a primitive adding machine that became the basis of most computing devices.
While studying the probability of winning, Pascal laid the foundation for the theory of probability, which he called “the mathematics of chance.”

Pascal and physics

Physics was Blaise Pascal's second hobby. He confirmed Torricelli's assumption that atmospheric pressure exists. In addition, he expressed the idea that with increasing altitude, atmospheric pressure decreases. And when in 1647 an experiment was carried out according to Pascal’s descriptions, it turned out that at the top of the mountain the atmospheric pressure was indeed lower than at the base.

Pascal proved that air has weight and calculated the approximate mass of the atmosphere. He proposed using a barometer to predict the weather, since he established that the barometer readings depend on the temperature and humidity of the air.

In 1653 Pascal formulated basic law of hydrostatics, according to whichthe pressure on the liquid is transmitted evenly without change in all directions. This law is called Pascal's law and himselfPascal is considered the founder of classical hydrostatics - the science of liquid or gas in a state of equilibrium (rest).

The ability of a fluid to transmit pressure in all directions without change was the basis for the design of hydraulic and pneumatic devices.

Hydraulic presses, hydraulic lifts, fuel filling units, sprayers, water cannons, pneumatic pipelines, etc. are built on the basis of Pascal’s law.

Unfortunately, the life of the brilliant scientist was short. His health had steadily deteriorated since 1658. Terrible headaches tormented him. Physically he became very weak, although he was only 35 years old. Doctors forbade any mental stress. And in 1660 Pascal looked like an old man.

Blaise Pascal died in 1662.

The SI unit of pressure is named after Pascal. One of the first programming languages is called Pascal. The university in Clermont-Ferrand bears the name of Pascal.

Pascal (symbol: Pa) is a unit of pressure (mechanical stress) in SI. Pascal is equal to the pressure (mechanical stress) caused by a force equal to one newton, uniformly distributed over a surface normal to it... ... Wikipedia

Siemens (symbol: Cm, S) SI unit of electrical conductivity, quantity reverse ohm. Before World War II (in the USSR until the 1960s), siemens was the name given to the unit of electrical resistance corresponding to the resistance ... Wikipedia

Sievert (symbol: Sv, Sv) unit of measurement of effective and equivalent doses of ionizing radiation in International system units (SI), used since 1979. 1 sievert is the amount of energy absorbed by a kilogram... ... Wikipedia

This term has other meanings, see Becquerel. Becquerel (symbol: Bq, Bq) is a unit of measurement of the activity of a radioactive source in the International System of Units (SI). One becquerel is defined as the activity of the source, in ... ... Wikipedia

This term has other meanings, see Newton. Newton (symbol: N) is a unit of force in the International System of Units (SI). Accepted international name newton (symbol: N). Newton derived unit. Based on the second... ... Wikipedia

This term has other meanings, see Siemens. Siemens ( Russian designation: Cm; international designation: S) unit of measurement of electrical conductivity in the International System of Units (SI), the reciprocal of the ohm. Through others... ...Wikipedia

This term has other meanings, see Tesla. Tesla (Russian designation: Тl; international designation: T) unit of measurement of magnetic field induction in the International System of Units (SI), numerically equal to induction such... ... Wikipedia

This term has other meanings, see Gray. Gray (symbol: Gr, Gy) is a unit of measurement of the absorbed dose of ionizing radiation in the International System of Units (SI). The absorbed dose is equal to one gray if the result is... ... Wikipedia

Length and distance converter Mass converter Converter of volume measures of bulk products and food products Area converter Converter of volume and units of measurement in culinary recipes Temperature converter Converter of pressure, mechanical stress, Young's modulus Converter of energy and work Converter of power Converter of force Converter of time Linear speed converter Flat angle Converter thermal efficiency and fuel efficiency Converter of numbers in various number systems Converter of units of measurement of quantity of information Currency rates Women's clothing and shoe sizes Men's clothing and shoe sizes Angular velocity and rotational speed converter Acceleration converter Angular acceleration converter Density converter Specific volume converter Moment of inertia converter Moment of force converter Torque converter Specific heat of combustion converter (by mass) Energy density and specific heat of combustion converter (by volume) Temperature difference converter Coefficient of thermal expansion converter Thermal resistance converter Thermal conductivity converter Specific heat capacity converter Energy exposure and thermal radiation power converter Heat flux density converter Heat transfer coefficient converter Volume flow rate converter Mass flow rate converter Molar flow rate converter Mass flow density converter Molar concentration converter Mass concentration in solution converter Dynamic (absolute) viscosity converter Kinematic viscosity converter Surface tension converter Vapor permeability converter Vapor permeability and vapor transfer rate converter Sound level converter Microphone sensitivity converter Sound Pressure Level (SPL) Converter Sound Pressure Level Converter with Selectable Reference Pressure Luminance Converter Luminous Intensity Converter Illuminance Converter Computer Graphics Resolution Converter Frequency and Wavelength Converter Diopter Power and Focal Length Diopter Power and Lens Magnification (×) Electric charge converter Linear charge density converter Surface charge density converter Volume charge density converter Electric current converter Linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Electrical resistance converter Electrical resistivity converter Electrical conductivity converter Electrical conductivity converter Electrical capacitance Inductance converter American wire gauge converter Levels in dBm (dBm or dBm), dBV (dBV), watts, etc. units Magnetomotive force converter Magnetic field strength converter Magnetic flux converter Magnetic induction converter Radiation. Ionizing radiation absorbed dose rate converter Radioactivity. Radioactive decay converter Radiation. Exposure dose converter Radiation. Absorbed dose converter Decimal prefix converter Data transfer Typography and image processing unit converter Timber volume unit converter Calculation of molar mass D. I. Mendeleev’s periodic table of chemical elements

1 pascal [Pa] = 1.01971621297793E-07 kilogram-force per square meter. millimeter [kgf/mm²]

Initial value

Converted value

pascal exapascal petapascal terapascal gigapascal megapascal kilopascal hectopascal decapascal decipascal centipascal millipascal micropascal nanopascal picopascal femtopascal attopascal newton per square meter meter newton per square meter centimeter newton per square meter millimeter kilonewton per square meter meter bar millibar microbar dyne per sq. centimeter kilogram-force per square meter. meter kilogram-force per square meter centimeter kilogram-force per square meter. millimeter gram-force per square meter centimeter ton-force (kor.) per sq. ft ton-force (kor.) per sq. inch ton-force (long) per sq. ft ton-force (long) per sq. inch kilopound-force per sq. inch kilopound-force per sq. inch lbf per sq. ft lbf per sq. inch psi poundal per sq. foot torr centimeter of mercury (0°C) millimeter of mercury (0°C) inch of mercury (32°F) inch of mercury (60°F) centimeter of water. column (4°C) mm water. column (4°C) inch water. column (4°C) foot of water (4°C) inch of water (60°F) foot of water (60°F) technical atmosphere physical atmosphere decibar walls per square meter barium pieze (barium) Planck pressure seawater meter foot sea water (at 15°C) meter of water. column (4°C)

The Science of Coffee Making: Pressure

Coffee

People have been enjoying coffee since at least the fifteenth century, and perhaps even earlier, although we do not have precise records of earlier coffee preparations. Historians claim that the people of Ethiopia were the first to drink coffee, and that from there this drink spread to Yemen and other neighboring countries, and from these countries it already came to Europe. According to some reports, Sufi Muslims used coffee in religious rituals. For many years, coffee was banned in the Arab world by conservative members of the Islamic clergy due to its unusual properties, but the ban was eventually relaxed. The Church in Europe also disapproved of coffee for some time due to its popularity in the Muslim world, but soon came to terms with the growing popularity of the drink in Europe. Since then, coffee has been popular all over the world. Coffee is probably the first thing that comes to mind when you think about a typical morning. So what is coffee, how to prepare it, and why do we love it so much?

Coffee beans are the seeds of the berries of a plant in the madder family ( Rubiaceae). There are many different plant species in this family, but the most widely used for making coffee is the Arabian Coffee Arabica(Arabica variety) and Congolese Coffea canephora coffee tree (robusta variety), with the Arabica variety being more popular. In English, coffee berries are sometimes called cherries for their color and shape, but they have no relation to the cherry tree. The coffee beans are first cooked, that is, roasted, and then prepared into coffee, and during these processes, various substances, including aromatic oils and solid particles, are extracted. These substances create the special taste and aroma of coffee and give it invigorating properties.

As far as we know, one of the first methods of preparing coffee was to boil coffee beans in water. While trying different brewing methods, people noticed that if coffee is in contact with hot water for too long, the drink becomes bitter, and if, on the contrary, the coffee is not brewed long enough, then it becomes sour. Therefore, various preparation methods have been developed to ensure the best extraction. Trying different preparation methods, bartenders in coffee shops noticed that pressure improved the preparation process and the taste of the finished drink, and thus the espresso technique was born.

Coffee has been prepared in many different ways for centuries, and what we know about coffee preparation comes from hundreds of years of experimentation in the kitchen. It was through these experiments that coffee lovers determined the optimal temperature, roasting and brewing time, grind size, and use of pressure in the brewing process.

Substances that are obtained by extraction from coffee beans during the preparation process

Caffeine

Trigonelline

Acids

Quinic acid makes coffee sour if it is kept at temperatures above 80°C for a long time, for example if it is left in a warming pot.

Malic acid gives coffee notes of apple and pear and improves its taste. It also adds sweetness to the coffee.

Some other acids that are extracted into the finished drink are phosphoric acid, which gives coffee its fruity notes, acetic acid, which gives it lime notes, and tartaric acid, which gives coffee its grape flavor.

Carbohydrates

Coffee contains a number of carbohydrates that make coffee sweet. You probably haven't even noticed before that coffee is actually a little sweet, especially if you think of coffee as a bitter drink. But there is sweetness in it, and you can notice it with practice, especially if you drink good quality espresso, brewed by someone who knows how to make coffee properly. The brown color of roasted coffee is also due to carbohydrates. When cooked, coffee beans change color from green to brown, as the Maillard reaction occurs in carbohydrates under the influence of temperature. The color of golden brown bread, fried meat, vegetables, and other foods is also the result of this reaction.

Espresso preparation procedure

The technique for preparing espresso coffee includes the following steps:

Roasting coffee beans.
Grinding grains.
Coffee dosage.
Pouring ground coffee into the portafilter basket.
Tamping coffee in a portafilter. This step also includes breaking up any clumps and leveling the coffee inside the portafilter basket.
Pre-wetting, which is only possible in some espresso coffee makers.
Espresso coffee extraction. In English, this process is also called pulling, since in early manual espresso machines the barista pulled the handle to get a shot of espresso.

In this article, we'll focus on the pressure-based steps of espresso preparation, including tamping, pre-wetting, and brewing the coffee itself.

Tamping

Add coffee to portafilter;
Use a makeshift funnel for the portafilter basket to prevent the coffee from spilling out when stirring. To do this, you can attach a yogurt cup or a plastic juice bottle with the bottom cut off to the portafilter;
Stir the ground coffee well with a thin stick, such as a chopstick or a thin wooden skewer;
Tap the edges of the plastic nozzle to release all the coffee back into the portafilter basket.
The next step is the compaction itself.

Start tamping the coffee, applying about 2 kg of pressure.
Continue compacting using 14 kg of pressure.

Pressure in espresso coffee makers

As their name suggests, espresso coffee makers are designed specifically for making espresso coffee. There are many ways to extract the various aromatics from coffee beans to make this drink, from cooking on the stovetop in a pot or drip coffee maker, to using pressurized hot water through a coffee pellet, as in an espresso maker. Pressure in coffee makers is very important. More expensive coffee makers are equipped with pressure meters (pressure gauges), and in coffee makers without pressure gauges, amateurs often install homemade pressure gauges.

Parameters affecting coffee preparation

Temperature

Grinding

Pre-wetting

Cooking time

When preparing espresso, it is very important to choose the right time so as not to overcook or undercook the coffee. You can navigate by the following parameters:

Find the optimal color where you like the taste of coffee the most. To do this, you can experiment by stopping the extraction at different stages until you make coffee that you like.
Measure how long it takes to brew coffee of that color. This time should be between 25 and 35 seconds, and if it is different, then you need to change the grind.
If the time is less than 25 seconds, then the grind is too coarse and needs to be finer.
If the time is more than 35 seconds, then the grinding, on the contrary, is too fine and needs to be made coarser.