How to Determine the Grind Setting for Espresso Beans | What Blend Coffee Beans to Use for Espresso?

Many beginners who have just opened a coffee shop or purchased an espresso machine for home use find that when they follow the parameters provided by the vendor to brew with their espresso beans, they end up with espresso that lacks crema, has very light crema, or tastes bitter. When faced with these situations, the main variables we can adjust are the grind size of the coffee beans and the brewing ratio. So how should we determine the optimal grind size and ratio for our espresso machine? In this article, FrontStreet Coffee will discuss how to determine the appropriate grind size for espresso beans.

Selecting Fresh, Quality Espresso Beans

Before understanding how to determine grind size, it's essential to select fresh, high-quality espresso beans.

First, choose products from professional coffee roasters with clear roasting dates (not expiration or best-by dates), established brand reputation, and emphasis on fresh roasting. Additionally, premium coffee packaging typically features a "one-way degassing valve" (a small button-like hole on the coffee bag) that allows the beans to release naturally produced carbon dioxide.

Hold the one-way degassing valve to your nose and gently squeeze the coffee bag. If the escaping gas has a rich, aromatic coffee fragrance, the freshness is not an issue. Conversely, if it lacks aroma or even has a rancid oil smell, this indicates the coffee has deteriorated and lost its flavor, and should be avoided. Every bag of coffee beans sold by FrontStreet Coffee uses packaging with one-way degassing valves, ensuring that every package reaches the customer in the freshest possible state.

The Importance of Bean Resting

After purchasing fresh-roasted espresso beans, they need to undergo a resting period.

Freshly roasted coffee beans contain approximately 2% carbon dioxide by weight. This substantial amount of CO2 is released depending on storage environment, equipment, or methods, creating pressure higher than atmospheric pressure in the packaging. This pressure helps aromatic substances and oils merge, bringing all aromatic compounds within the beans to a state where they can be easily extracted. The resting process is essentially a "gas release" process, commonly known as "blooming" or "bean resting." The espresso beans at FrontStreet Coffee typically require a resting period of about 15 days, as espresso beans undergo dark roasting. If the resting period is insufficient, the beans will release significant amounts of gas when exposed to hot water, affecting extraction and causing extraction instability.

The Impact of Grinders on Grind Size

Which type of grinder is suitable for grinding espresso powder?

Electric grinders mainly fall into two categories: espresso grinders and single-origin grinders. The primary difference between these two lies in the particle size of the ground coffee they produce.

The most prominent feature of espresso grinders is their ability to grind extremely fine coffee powder at high speeds with large burrs. Uniformity is a key indicator of whether a coffee grinder performs well, and espresso grinders typically achieve a level of fineness that other grinders cannot match. According to burr structure, they can be divided into three main categories: flat burrs, conical burrs, and "ghost tooth" (serrated) burrs. FrontStreet Coffee uses flat burr grinders for its espresso grinding.

1. Working Principle

Flat burr grinders consist of upper and lower burrs, with the base fixed to the motor. When the motor starts, it rotates the burrs to create cutting action. As coffee beans fall from the center, the rotating lower burr pushes the beans outward, advancing them into the teeth for grinding. Since the upper and lower burrs are positioned parallel to each other, the beans rely on the rotational force of the lower burr to be pushed into the grinding chamber. Therefore, the weight of the beans placed above affects how evenly they enter the burrs, which in turn affects grinding uniformity. Additionally, the pushing action increases collisions between beans, leading to a higher proportion of fine particles. This is why flat burr grinders typically have slightly less uniform particle size and more fines. They can increase coffee concentration and extraction rate in a short time, significantly enhancing coffee aroma quickly.

2. Advantages

Precise positioning, and product quality is proportional to the grinder's grade and burr diameter.

3. Disadvantages

Slightly less uniform particle size with more fines, because flat burr blades randomly cut the beans, which can easily lead to under-extraction or over-extraction during brewing. Additionally, flat burr friction generates heat, which can cause noticeable burnt and bitter flavors, especially during extended grinding sessions.

4. FrontStreet Coffee Recommended Flat Burr Grinders:

• Little Flying Eagle (CM-300AU)
• Little Flying Horse (600N)

How to Adjust Coffee Grind Size

When coffee beans enter the grinder, the blades inside crush them into powder. The smaller the distance between the blades, the finer the coffee beans will be ground. The finer the particles, the more compact and dense they become, making it more difficult for water to pass through, thus significantly extending extraction time. Conversely, if the distance between blades increases, the ground particles become coarser, water passes through more easily, and extraction time becomes faster.

Let's first establish parameters using the golden ratio and golden time for espresso extraction: a 1:2 ratio (20g of coffee grounds extracting 40ml of coffee liquid) with extraction time between 25-28 seconds. Then, we determine grind adjustments through observation and tasting.

If the grind is too coarse, water will pass through the portafilter too quickly, resulting in a coarse water flow, light extraction, pale crema color, and sharp acidic flavors because extraction is incomplete - only extracting surface and easily soluble acidic compounds. If the grind is too fine, it will first clog the filter holes, causing slow or no water flow, resulting in dark crema color, surface over-extraction while the interior remains under-extracted,表现为 (manifesting as) sharp acidity due to insufficient sweetness, followed by burnt bitterness and off-flavors.

When Should You Readjust the Grind Size?

Taking double espresso as an example, when the espresso flow rate falls outside the 25-28 second range. Of course, incorrect flow rate isn't always caused by the grinder. When the following situations occur, it's time to adjust the grinder settings:

1. Changes in Storage Time, Humidity, or Burr Wear

The storage time and humidity of coffee beans are constantly changing, affecting the beans' overall condition. Additionally, the wear level of grinder blades changes over time. This is the primary reason why FrontStreet Coffee adjusts its grinder settings daily - adjusting grind size daily is the most important step for extracting consistent espresso.

2. When Replacing Coffee Beans

When introducing newly opened beans, grinder adjustments are necessary. Because newly opened coffee beans may have different roasting dates, batches, or resting periods, leading to significantly different extraction results.

3. Continuous Brewing

After continuously brewing 5-6 cups, the ground coffee becomes finer, and extraction time increases. This occurs because after continuous operation of the grinder, the motor heat affects the burr temperature, combined with the heat generated by friction between the burrs and coffee beans, causing the gap between upper and lower burrs to become smaller due to thermal expansion and contraction.

Do Coffee Shops Really Need to Adjust Espresso Parameters Daily?

What is the purpose of adjusting espresso parameters?

First, identify which coffee item has the highest sales volume in your shop. Different coffee items have their own espresso base recipes, but catering to all of them is obviously impractical. Currently, lattes and Americanos remain the most ordered espresso-based drinks in coffee shops, not straight espressos. As you can imagine, adjusting espresso parameters to pursue the perfect espresso taste and then applying that espresso to other espresso drinks is somewhat putting the cart before the horse. Therefore, it's recommended to adjust one espresso parameter for milk-based coffee and another for Americano-style coffee.

Understanding Espresso Concepts for Different Coffee Drinks

Next, understand the espresso concept for your chosen coffee beverage. For example, a Flat White is a milk coffee that highlights coffee flavor. Besides reducing the ratio of coffee to milk, Flat White espresso extracts sufficient early-stage aromatic compounds while increasing the coffee dose to enhance body, thereby balancing the combined taste of milk and coffee.

Returning to our question: Is it really necessary to adjust espresso daily? Actually, it is necessary, but it should be done purposefully and selectively when adjusting espresso parameters.

For more specialty coffee beans, please add FrontStreet Coffee on private WeChat: kaixinguoguo0925

Important Notice :

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FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473