Where Does Mocha Originate From, and What Is a Standard Espresso Extraction?

A traditional single shot takes about 7 grams of freshly ground coffee, water near 92°C, roughly 9 bar of pressure, and 20 to 30 seconds, yielding 20 to 30 milliliters with a crema layer on top. Many specialty shops now dose higher and stop by weight instead.

One common modern recipe uses 19 grams in and 38 grams out at a 1:2 ratio in about 28 seconds. Shops switched from milliliters to grams because crema varies in density and volume, so weight gives a repeatable result. Espresso is the base for drinks such as mocha, which traces back to the port of Mocha, as well as cappuccino and latte.

Espresso is the soul base of flavored coffees like mocha, cappuccino, and latte, but how many milliliters should a qualified espresso actually be? What parameter standards should be followed during extraction? In this article, Front Street will systematically sort out the definition and technical specifications of espresso, analyze the reasons for the evolution of measurement from milliliters to grams, and provide cause analysis and solutions for common phenomena such as under-extraction, over-extraction, uneven flow, clumped crema, and tiger-striped crema. It will also share how to choose beans suitable for making espresso, helping coffee lovers replicate coffee-shop-level rich flavor at home.

For friends who regularly drink espresso, espresso serves as the common base of drinks like mocha, cappuccino, and latte, and its status is self-evident. So how many milliliters does a cup of espresso need to meet the standard? Below, Front Street will provide a popular science explanation around common extraction questions about espresso.

What Is Espresso

Espresso is called "Espresso" in English and originated in Italy. It is both a classic local coffee drink and the base of many Italian-style coffees. It uses high pressure to complete extraction quickly in a short time, and the capacity of a traditional single shot is about one ounce.

According to internationally accepted technical specifications: take about 7 grams of freshly ground coffee powder, use hot water at about 92°C, extract under about 9Bar pressure for 20–30 seconds, and finally obtain 20–30ml of coffee liquid, with a layer of crema covering the surface.

With the popularization of the specialty coffee concept, new theories continue to emerge, and with independent cafés springing up everywhere, their respective espresso extraction plans also have subtle differences. Taking Front Street's standard output as an example, one espresso is based on 2 shots (1 serving of espresso), using 19g of coffee powder, extracted at a ratio of 1:2 to obtain 38g of espresso liquid, taking 28 seconds.

Why do most coffee shops in China no longer measure in milliliters today, but instead use grams? This is related to density. A cup of espresso consists of dark coffee liquid and crema floating on top, while crema has low density and large volume, and it cannot be guaranteed that the crema state of every cup is exactly the same, so measuring by weight is more accurate.

Which coffee beans produce richer crema when making espresso?

In fact, in addition to controlling various parameters, Front Street believes that choosing the right beans is equally key, because it directly determines whether the coffee tastes good. If you want to replicate coffee-shop-style espresso at home, Front Street Classic Espresso Blend is recommended. This recipe is composed of three origins: Brazil, Indonesia, and Vietnam, combining the caramel aroma of American coffee with the wild character of Asian coffee. In order to highlight the mellow aroma to the greatest extent, and to allow everyone to easily extract rich and dense crema, Front Street Coffee uses dark roasting. It is suitable whether making an Americano diluted with water or a latte paired with milk, and can be purchased from the Front Street Taobao store or the Front Street Tmall flagship store.

How should we understand under-extraction and over-extraction of espresso?

Over-extraction often shows as coffee liquid and crema (Crema) having a dark color, and sometimes obvious large bubbles float on the surface of the liquid. A common feature is excessively long extraction time (such as more than 1 minute), and the first drop of coffee liquid appears only after more than 10 seconds. There are many causes of over-extraction, such as coffee powder being ground too fine, water temperature being too high, extraction pressure being too high, tamping force being too strong, etc. When tasting, it is usually accompanied by burnt bitterness and astringency.

Under-extraction is the opposite of over-extraction. It usually means that a large number of aromatic molecules in the coffee powder have not yet been released, but the preset extraction time has already ended, that is, the extraction yield is lower than 18%. When under-extracted, the coffee liquid may be light yellow and lack crema, and the extraction time is often too short (such as completing in 15 seconds). When pressurized, the coffee liquid gushes out like a stream of water, rather than the viscous feeling of honey flowing down during normal extraction—these are all signs of under-extraction.

In addition to the above theoretical issues, some practical situations are also often encountered when extracting espresso, for example:

When using a double-spout portafilter to extract espresso, why does the coffee liquid always drip from one side first?

There are mainly three reasons. First, confirm whether the shower screen of the brew head is blocked by coffee residue, and observe whether the water flow from the brew head is evenly distributed. If the water flow favors one side, it is necessary to clean the brew head and shower screen.

Second, check whether tamping is level. If the puck is high on one side and low on the other, water will penetrate too quickly from the lower side, causing the liquid to flow toward one side first during extraction.

Third, observe whether the coffee machine or tabletop is level with the ground. In many cases, the first two situations do not exist, but the coffee machine or table is uneven, causing the body to tilt, so the liquid first flows to one side during extraction.

What causes clumped coffee crema?

The formation of crema comes from the high temperature and high pressure during brewing, which causes air to combine with soluble fats in coffee. If the coffee beans are too fresh, their internal gas content is relatively high, and the crema will appear overly thick. Moreover, too-fresh beans are very unstable in condition, and the crema pressed out will also be rough, and after sitting for a long time it will solidify and clump.

So once clumped crema is found, it is most likely that the coffee beans are too fresh. The best way is to store them for a few more days and use them after the resting period has passed.

Is tiger-striped crema on the surface of espresso normal?

Tiger-striped crema refers to crema with dark spots on the surface, resembling tiger stripes. These dark spots are actually some extremely fine particles. The causes may be too many fines produced by the grinder, the basket holes becoming coarser, excessive extraction pressure from the coffee machine, or coarse grinding combined with heavy tamping, causing fines to easily move downward and pass through the basket into the espresso cup, so dark tiger stripes appear on the surface of the Crema, and the overall color also appears darker.

In fact, whether tiger stripes are present has little effect on the flavor of espresso. Espresso with tiger stripes has a fuller body, but if there are too many fines, it can also backfire and create a rough mouthfeel.

The above content is compiled by CoffeeHunters, a coffee news website.