Espresso and espresso-based drinks became extremely popular worldwide in the 20th century. The espresso itself is a small and strong drink prepared by forcing hot water under high pressure through a finely ground coffee.
What Is Espresso and What It is Made Off?
You may consider Espresso to be both a brewing method and a beverage. It has an Italian origin and is made by forcing a small amount of water under a high pressure of 9 to 10 bars heated to a temperature of around 90 °C (190 on Fahrenheit scale) through finely-ground coffee beans. The extraction time varies from 20 to 35 seconds.
The espresso is characterized by a high viscosity in the range of warm honey and dense brown foam bubble layer over the liquid coffee, known as the crema. You can understand all these aspects in detail in later sections. Let us first understand the impact of temperature, pressure, and the thickness of the espresso grind on the brewed coffee.
The role of temperature Setting
This temperature of 90 °C is closer to the boiling point of water at the atmospheric pressure. Actually, the ideal temperature for brewing depends on many factors like the coffee you are using, the flow rate of the shot, and your taste. Ideally, it should be in the range of 185 °F to 204 °F.
- Lower temperatures result in under-extracted espresso with a sour taste.
- Setting very high temperatures gives bitter and woody flavors.
- As you increase the temperature, you can observe an increase in solids extraction and body, but flow rates decrease.
The costlier espresso machines have PID controllers to regulate the temperature within close limits.
The Role of Grinding
A good quality shot of espresso requires finely ground beans for the following reasons:
- The grinding process results in an increase in the specific surface area (SSA) of the particles. The finer the grinding, the more the surface area per unit mass.
- The higher SSA, the smaller particle size, and the closed packing among them produce a high value of hydraulic resistance. The water flow rate through the coffee bed must overcome this resistance.
- The increase in SSA causes a rapid washing of the solids from the surface of the ground coffee.
- There is accelerated wetting because of a shorter mean path for water diffusing out and the solubles diffusing out of cells.
- The large soluble molecules and colloidal materials get shifted to the extracting water.
If you are using an average-quality espresso beans grinder, it can either generate more heat and spoil the coffee flavor or produce a too-fine grind, clumps, or a poor distribution of the coffee grounds. These problems will be difficult for you to overcome.
Ensure that your grinder has sharp burrs to avoid these issues. In addition, the proper rotational speeds and the surface areas of the burrs that result in bimodal/trimodal particle sizes without clumps vital requirements are desired.
The role of Pressure Setting
As seen in the last section, finely ground coffee makes tight packing. The espresso machine has to push hot water against its hydraulic resistance. The water percolates down the coffee bed, causing erosion of the solids and oils from the particle’s surface during this downward flow before eventually landing in your cup of coffee.
The flow rate of water through the coffee grounds is determined by the pressure your machine applies, the mass, and the fineness of the grind. Hence, a finer grind or higher mass results in a larger resistance to flow and, consequently, a slower flow rate. While other components of the machine, such as pipes, valves, fittings, etc., contribute to the pressure drop, the governing resistance comes from the coffee bed.
Higher applied pressure will result in a higher flow rate and vice-versa till a certain point. Any further effort to increase the pressure will, in fact, decrease the flow rate.
The Phases of the Percolation
There are three phases of coffee percolation described as under:
- The Preinfusion Phase: This involves a slow flow of water at a low pressure to wet the entire grind and organize it.
- Rise in Pressure Phase: The coffee bed gets compacted by the rise in pressure, and eventually, the flow rate increases as the resistances are overcome.
- Extraction: The forcing of hot water causes the erosion of the solids from the surface of the grounds in a process known as extraction. It is basically the removal of the mass from the grounds.
History & Origin of the Espresso
Italians get the credit for the origin of the espresso. The first machines for preparing the beverage were patented by Angelo Moriondo, followed by Luigi Bezzera. With urbanization, consumption increased and spread within Italy, followed by their colonies.
In the English world, its variation, in the form of Cappuccino, found favor due to its fondness for steamed milk and milk foam. In the United States, other variants, the Lattes, became popular.
What is an Espresso Shot?
The way to consume an espresso is vastly different from other coffee drinks. You are supposed to casually sip it without adding or mixing anything to it. Its smaller size and higher concentration of flavors and chemicals earned it the name espresso shot. But you cannot drink it in one sip like other shots. The act of brewing espresso is known as “pulling.”
Espresso shots can vary in size and length. However, each cafe will standardize its shot in terms of size and length. They only vary the number of shots in their espresso drinks without affecting the extraction.
To change the number of shots, you only need to change the filter bucket size. The change in length may lead to a change in the grind. Let us understand them in a bit more detail below.
The size can vary between a single, double or triple shot with 7 gms, 16 gms, and 21 grams of the ground coffee bean, respectively. A typical single-shot espresso drink weighs around one ounce. The term Doppio is often used for the double shot (two ounces). Solo (Single Shot) and triplo (Triple shot) are less common.
For double shots and triple, you need to use bigger filter baskets of the corresponding sizes. The baskets for the single shots have a high degree of taper, the double baskets are gently tapered, and the triple baskets are straight. This is to accommodate them in a comparable depth with a comparable resistance to the water pressure.
You will often find the portafilters with two closely spaced sprouts and a double filter basket. This allows them to dispense the double-shot coffee brewed into two separate or one single cup.
The length of the shot has three variations given below. In any cafe, the three variations use the same mass of espresso bean, but the amount of water varies, resulting in different espresso brewing ratios. As expected, the Ristretto uses less water than the Normale, while the lungo requires more.
- Ristretto or reduced – Also known as the short shot, it has half the volume of the water in the Normale. It is a smaller and more concentrated form of coffee drink than normal espresso. It requires a finer grind than Normale to keep the extraction time the same. This ensures the shot is not under-extracted.
- Normale or standard – A solo shot of Normale uses about 30 ml of water.
- Lungo or long – Known as the long shot, it uses 2 to 3 times the water in Normale. The resulting shots are much weaker, with a lack of body & mouthfeel and taste bitter. In modern times, baristas use a light coffee roast for the Lungo. The grind is coarse to allow a higher flow rate and over-extraction.
Espresso Characteristics and Taste
Any espresso or drip coffee has solids and gases dissolved in the liquid known as the solubles. The strength of the drink and its taste is the function of the soluble solids, while the soluble gases make up the aroma.
Not all solids get dissolved in the liquid. The large molecular proteins and the fiber fragments from the bean cell wall make up a large portion of insoluble solids. These solids and the oils in suspension (another insoluble part) combine into what is known as the brew colloids. The coffee liquid can hold the insolubles either in the form of a suspension or an emulsion.
The non-dissolving solids in the brewing process form part of the body but have no contribution to the flavor. The emulsion, formed by tiny oil droplets, makes up the body and gives rich flavor, taste, and aroma to the espresso. The insolubles can trap the soluble solids and gases and later release them to do so.
Crema: The Beautiful Espresso Topping
We had touched upon the high viscosity and the crema in earlier sections without detailing them. The high viscosity arises from a large proportion of the dissolved and suspended solids in espresso than the regular brewed coffee. This is due to the use of pressure in the espresso, like coffee, compared to other brewing methods.
Crema comprises dissolved Carbon Dioxide and water vapor bubbles that get wrapped inside a liquid film. The liquid film comprises an aqueous solution of substances known as surfactants that reduce the surface tension of the liquid and enhances its wetting properties and spread.
In addition, crema has suspended wall fragments, discussed above, known as fines and aromatic oils. Hence, in espresso, you encounter the three dispersed phases – an emulsion of oil droplets, suspended solids, and gas bubbles or foam layers.
The oil droplets give a creamy feel to the mouth contributing to what is known as the body of the drink.
Caffeine Content in Espresso Coffee
As espresso is very concentrated, it has a much higher caffeine content per unit volume of the drink than any other regular coffee. The caffeine in any drink depends on multiple factors like the origin and the size of the bean, the roast method, and profile, etc. A typical espresso coffee shot of one ounce may contain around 65 mg of caffeine.
Coffee Vs. Espresso Caffeine: Which Drink Has More?
Due to their large serving sizes, a mug of regular drip coffee has more caffeine than a single espresso serving. A typical serving of a drip coffee may contain anywhere between 150 to 200 mg of caffeine.
As indicated earlier, Espresso forms the base for many other coffee drinks. The most common of these mixed drinks have espresso with milk in either the steamed, wet or dry foamed form or mixed with hot water. These drinks are:
- Macchiato: This contains a shot of espresso mixed with a very small quantity of milk in steamed form with slight foam. The total volume of the drink may vary between 35 to 40 ml.
- Modern Macchiato: One or two espresso shots with an equal portion of milk. Total volume – 60 to 120 ml.
- Cortado: It contains one shot of espresso mixed with an equal volume of steamed milk and little foam. It is thought o have its origin in Spain.
- Cappuccino: You will usually read or hear about the rule of thirds related to the Cappuccino. As per the rule, you are required to mix espresso, milk, and foam in equal proportions of one-third of the total volume of the drink. In many places, a ratio of 1:2:2 in the total volume of 150 to 175 ml is followed.
- Latte: It started as a drink for customers who desired to enjoy coffee but with a less intense experience than drinking espresso. The Latte has more milk and less foam than the Cappuccino. The steamed milk may vary between the 1:3 to 1:9 ratios. Based on this, the total volume can range anywhere between 240 to 600 ml.
- Flat white: Flat white originated in Australasia. Cappuccinos had enormous quantities of dry foam and many consumers started asking for flat white coffee. It can be thought of as a small and stronger latte. It normally has a double ristretto or double espresso shot with a total volume of 150 to 175 ml and a very thin layer of foam. They may have a single shot, also. Hence, the ratio of coffee to milk varies a lot. 30 ml expresso mixed with 120 ml milk results in a 1:4 ratio, while 60 ml espresso in 90 ml milk is a 2: 3 ratio.
- Americano: It is believed that American soldiers in Italy during World War II diluted their espressos with hot water to match it to the regular strength they were habitual of. The Caffe Americano resembles filter coffee and usually has around three portions of water.
Espresso machine Salient Features
The main features of any espresso-brewing coffee machine are:
- The pressurization method: It varies between the steam, pump, or lever-based machines. The pump-powered machine consistently provides the required pressure by any espresso brewing method.
- Level of Automation: These range from semi-automatic to automatic to fully automatic (sometimes referred to as superautomatic). This includes all the features like those of coffee grinders, milk steamers, and pulling shots.
- Single/Double Boilers: The single boiler machine uses a single tank both for making espresso and steaming the milk. The problem originates from the difference in the ideal temperatures for the two functions. This means either of the two has to wait for the other to complete.
- Electronic Displays: To indicate the parameters of the brewing process like temperature, pressure, time, etc.
- Steam Wands: They should have the ability to be controlled manually, with 2 to 4 steam holes and swivels to provide the best angle for steaming.
Expresso Roast & Grind
There is no difference between espresso and other coffees as far as the selection of beans and their roast profile are concerned. You can use your regular coffee beans or bean blend for an authentic espresso roast.
In some areas of Southern Italy, dark roast beans are preferred over lighter or medium roast.
We covered the grinding requirements in depth in various sections of our article for the different shot lengths.
You can go through our other articles to have more in-depth knowledge about Espresso drinks. You can leave your comments in the section below if you desire any clarifications on the article or additional details.