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Quite a few friends have reported that they boughtespresso blend coffee beans, and after grinding and extracting at home, they couldn't get any crema, and the espresso came out tasting overall bland and watery. When this problem occurs, Front Street's baristas always suggest adjusting the grind size. This article will discuss how to determine theespresso grind size.

First, before adjusting the grind size, we need to choose freshly roastedespresso coffee beans

First, when choosing a product, make sure it clearly states the roast date (not the expiration date or shelf life), and buy from professional coffee roasters with brand credibility that emphasize fresh roasting.

In addition, good coffee packaging bags usually have a "one-way exhaust valve" (a button-shaped small hole at the top of the coffee bag) designed to let the coffee beans release naturally produced carbon dioxide. Point the one-way exhaust valve toward your nose, gently squeeze the coffee bean bag, and smell the gas that comes out. If it's an inviting, rich coffee aroma, then freshness is not an issue. Conversely, if it doesn't smell rich enough, or even has a rancid oily smell, that means this bag of coffee has long gone stale and lost its flavor, and you should avoid buying it. Every bag of coffee beans sold by Front Street Coffee (FrontStreet Coffee) uses one-way exhaust valve packaging, guaranteeing that every bag of coffee beans reaches the buyer in the freshest condition.

Choose a grinder that cangrind espresso coffee grounds

For commercial use, you can buy an espresso-type grinder. The biggest features of espresso-type grinders are extremely fine grinding, fast speed, and large burrs. Uniformity is a hard indicator for judging whether a coffee grinder is good or not, and espresso-type grinders typically achieve an extremely fine grind size that other grinders cannot match. If you want to achieve espresso coffee grounds' grind size for home use, we should choose a flat burr grinder. Front Street Coffee (FrontStreet Coffee) currently uses a Feima 600N flat burr grinder to grindespresso coffeegrounds.
 

Why does Front Street recommend using a flat burr grinder?

Working principle of flat burr grinder: It consists of two burrs, upper and lower. The base is fixed to the motor. When the motor starts, the upper and lower burrs rotate to produce a cutting action. When coffee particles fall from the middle, the rotating lower burr pushes the coffee beans to the outer edge and pushes them into the toothed burr section for grinding. The upper and lower burrs of a flat burr grinder are arranged in parallel, so coffee beans need the rotational force of the lower burr to push them into the burrs. Therefore, the weight of the coffee beans placed on top will affect the uniformity with which the coffee beans enter the burrs, further affecting grind uniformity; in addition, the pushing and squeezing increases the number of collisions between coffee beans, which in turn increases the proportion of fines produced. This is the common reason whyflat burr grinders produceslightly less uniform particles and more fines. It quickly increases coffee liquid concentration and extraction yield in a short time, allowing the coffee aroma to be noticeably enhanced within a short period.
 

Advantages of flat burr grinders: clearer positioning, and output quality is proportional to the grinder's grade and burr diameter. Disadvantages: slightly less uniform grind particles and more fines, because the flat burr blades cut the coffee beans arbitrarily, which easily leads to under-extraction or over-extraction during brewing. In addition, friction from flat burrs generates heat, especially when a flat burr grinder has been running for a long time, producing an obvious burnt and bitter taste.
 

What is the grinding principle of a coffee grinder?

When coffee beans enter the grinder, the blades inside crush the coffee beans into powder. The smaller the distance between the blades, the finer the coffee beans are ground. The finer the grind particles, the more tightly packed they become, making it harder for water to pass through, thus greatly extending the extraction time. Conversely, if the distance between the blades increases, the grind particles become coarser, water passes through more easily, and the extraction time becomes faster.
 

How do we determine the grind size suitable for our ownespresso machine?

When adjusting thegrind size, Front Street first sets a parameter using the golden ratio and golden time for espresso extraction: a 1:2 ratio (20g of coffee grounds extracting 40ml of coffee liquid) with an extraction time between 25 and 28 seconds, then judges the grind size adjustment through observation and tasting.

If the grind is too coarse, water will pass through the portafilter too quickly, the flow will be thick, extraction will be shallow, the crema color will be pale, and the flavor will be sharply sour, because the extraction is incomplete and only the surface and easily extracted acidic substances are extracted. If the grind is too fine, it will first clog the filter holes, so water won't come out or the stream will be thin, the crema color will be dark, and there will also be over-extraction on the surface and under-extraction inside, manifesting as sharp sourness because sweetness is insufficient, followed by burnt bitterness and off-flavors.

If you want to test more rigorously whether this espresso has reached the standard value, we can first calibrate the concentration tester. The vast majority of espresso concentration is between 7% and 12%. Use pure water to zero the standard. Then stir the completed pour-over coffee, use a titration tube to extract the coffee liquid, place it into the coffee concentration tester, press the measurement button, and try measuring multiple times until the value stabilizes.
 

Front Street Coffee (FrontStreet Coffee) espresso extraction parameters

To make espresso, use Front Street Classic Espresso Blend. This is a recipe combining three origins—Brazil, Indonesia, and Vietnam—so it has both the caramel aroma of American coffee and the wild character of Asian coffee. In order to highlight the coffee's mellow aroma to the greatest extent and also let everyone easily extract rich and dense coffee crema, Front Street Coffee uses a dark roast. It is very suitable whether for making an Americano diluted with water or a latte with milk. You can place an order at Front Street's Taobao store or Front Street's Tmall flagship store.

Front Street espresso extraction parameters:

Grinder: Galileo q18

Grind size: 2.0 setting

Pressure: 10 bar

Temperature: 94°C

Time: 25~30 s

Dose: 20g (double espresso)

Extraction yield:40mlExtracted espresso flavor: smooth mouthfeel, medium body, with an obvious chocolate aroma accompanied by a light caramel note on the nose, and a smooth nutty cookie mouthfeel on entry, very rich and full.
 

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