Comprehensive Learning Evaluation of Italian espresso espresso

The birth time of Espresso is around 1946; and this year is regarded as the official birth year of espresso. Since then, this unique coffee drink has been popular in Italy, Spain, Portugal and other southern European countries. But it wasn't until around 1986 that espresso was introduced around the world by Starbucks. Since then, people in the coffee industry around the world began to know and understand this kind of coffee. It was only about a decade earlier than the Chinese people came into contact with espresso. So the more popular and reasonable way to name it is espresso.

Espresso is a kind of life

In Italy, Espresso is simply a local life concerto. In the morning, drink a latte (Latte); then, people like to drink Espresso in the store, everyone waits in front of the bar, and after getting the first-hand coffee, they drink it in three sips. The guests in the shop knew each other and talked to each other, and even the coffee maker (Barista) took part in the chat, so the cafe became a social place.

In the United States and Taiwan, Italian-style cafes are littered with places for young people to date and chat. Most of them don't drink Espresso, only cappuccino or latte with milk. Most of these young people don't know the delicacy of Espresso. They just come here to see the atmosphere of Espresso. Presumably, this is also a kind of Espresso life!

Italian espresso Coffee: a small, heavy magnetic cup with a capacity of about 50 milliliters; filled with dark coffee with a thick layer of bright reddish brown foam on the surface of the half-full cup. A chemist will not like such a description, but will choose words that are less poetic but clearer. However, the above definition does fully describe the characteristics of a cup of espresso coffee, at least from a macro point of view:

Small volume: this means that the brewed coffee is stronger than normal.

The physical nature of the composition: the foam part of the coffee is as important as the liquid part.

These characteristics are of course the result of using a special way of percolation to brew coffee. In the following article, we will describe the characteristics of espresso coffee in detail with physical and chemical data from a sensory point of view.

Sensory characteristics of Espresso Coffee

The warm hue of foam, the strong and wonderful fragrance, the soft and smooth liquid like velvet, and the strong and persistent taste, all of which are presented in a well-brewed cup of espresso coffee, provide the drinker with the pleasure of smell, taste and vision. Only hearing is excluded from this multi-sensory experience. Between the complex chemical composition of coffee and its multiple sensory systems, a connection is created by sipping this small cup of coffee.

Visual features

What attracts the most visual attention of a cup of espresso coffee is the foam. The beautiful scenery of the foam is made up of tiny bubbles captured by sticky liquid and tiger skin markings formed by fragments of the cell wall floating on top of the foam.

The color and texture of the foam are very important to the drinkers of espresso coffee, because for the drinkers, the perfect foam represents the perfect coffee brewing process. Any errors in grinding, cooking, temperature or extraction will be immediately revealed by the color, texture and persistence of the foam. For example, if the foam is thin and shows a light color, uneven texture and gradual disappearance, it means that the cup of espresso coffee is not extracted enough. This may be because the grinding particles are too coarse or the water temperature is too low; if the color is dark and there is a hole in the center of the foam, it means that the porosity of the coffee pressed powder is too low or the powder content is too much. The reason for a cup of over-extracted espresso coffee is that if the water temperature is too high, it will appear white with bubbles; if it takes too long to brew, there will be white spots in the center of the foam.

Foam is also a cover for the aroma of coffee because it captures the volatile chemicals that make up the aroma of coffee. If the bean formula is suitable for brewing espresso coffee, the aroma will be pleasant, otherwise it will be disgusting. Foam is an amplifier that magnifies both the advantages and disadvantages of coffee.

Taste (mouth feel)

Texture is another important feature of espresso coffee. The oil droplets in coffee not only dissolve many flavor chemical molecules, but also increase the viscosity of coffee. Another form of tactile sensation is astringency, which has always been hated and thought to have something to do with drugs. The existence of astringency is related to the existence of immature beans, immature beans will contain polyphenols, these substances will cause oral mucosal bitterness and will interact with soluble proteins in saliva.

Taste (taste)

Sweetness is an important trait when appreciating a cup of espresso coffee, but sour taste is not. Consumers in different countries show significant differences in the ratio of bitter taste to sour taste of espresso coffee. Consumers in southern countries prefer bitterness and focus on texture, while in northern countries they prefer a more balanced sense of taste and think that too much bitterness is a disadvantage. This difference can also be seen in the concentration of espresso coffee, espresso in southern countries is small and strong and drinks without milk, while in northern countries, it is more diluted and served with milk or whipped cream. Unfortunately, however, it is quite difficult to brew a cup of espresso coffee with more than 50ml without over-extraction, which is why most northern espresso coffee tastes woody or astringent, which is often described by drinkers as bitter, because when a large amount of coffee is extracted, some soluble and unpalatable substances are also brought out. The degree of roasting of coffee beans can change the ratio of bitter to sour taste of espresso coffee; deeply roasted washed coffee beans have an irritating burning taste, which is usually unpopular. Very fast baking can cause an unpleasant taste with astringent, bitter and metallic flavors.

Feeling after drinking (aftertaste)

The liquid property of Espresso coffee is quite special, its high concentration is caused by high density and high viscosity, on the other hand, the surface tension of espresso coffee is reduced by the existence of natural surface tension agent. The existence of these conflicting characteristics explains the strong taste and long-lasting taste and flavor of espresso coffee. When drinking, the surface of the tongue is bathed so that the coffee is caught by the taste buds, while the oil droplets in espresso coffee attach to the mucous membrane of the tongue, slowly releasing volatile aromatic molecules, so these tastes and flavors can still be felt after drinking coffee for a period of time (up to 15 minutes). The fact that the tongue is covered with coffee can explain the decrease in bitterness, which can be indirectly confirmed by the following experiment: a group of subjects were asked to drink quinine solution and set the degree of bitterness at 100. then they drank quinine solution with 1% concentration of colloidal polysaccharide (carboxymethylcellulose, carboxymethylcellulose), and the subjects felt only 40% bitterness.

The conclusion of this experiment is that colloid can block the bitterness receptor of taste buds and reduce the bitterness perception, and the emulsified oil droplets in espresso coffee may reduce the bitterness sensation by acting like colloid. However, diluted espresso coffee increases the bitterness, because it contains hundreds of millions of bitter molecules, but the number of oil droplets is only one thousand or 1/10000, so when espresso coffee is diluted, it increases the chance of bitter molecules being caught by the receiver, resulting in the phenomenon that diluted espresso coffee is more bitter.

In general, a good cup of espresso coffee must taste sour at first and then bitter and sweet afterwards. And in the taste to have a thick texture, in the sense of smell can smell a strong aromatic flavor and can happily last for a period of time.

Espresso coffee brewing method

Espresso espresso is a small and strong cup of coffee, based on the unstable nature of espresso coffee, must be ground roasted coffee beans freshly made, hot water under pressure conditions through the coffee pressed powder, so that the water pressure can be distributed in the coffee pressed powder.

The way of brewing is to extract the ground roasted coffee beans with hot water under pressure for a short period of time.

Scale range of cooking conditions:

Coffee powder 6.5 ±1.5 g

Water temperature 90 ±5 ℃

Water pressure 9 ±2 bar

The cooking time is 30 ±5 seconds

Italian espresso coffee is a multiphase beverage made only from ground roasted coffee beans and water. Italian espresso coffee is composed of foam layer and liquid layer, the foam layer has fine foam and shows tiger skin stripes, under the foam layer is an emulsion liquid layer composed of tiny oil droplets, which contains carbohydrates, acids, proteins and caffeine, as well as evenly distributed bubbles and solids.

The values of Italian espresso coffee analysis are:

Viscosity at 45 °C > 1.5mPa.s

Total solids 20-60 g / L

Total lipids > 2 mg/ml

90% of the oil droplet size