8 Common Mistakes to Avoid in Home Roasting

Mistake 1: Not preheating the roaster

Depending on where we roast, and what time of year it is, the temperature of the roaster will naturally fluctuate. Setting up a preheat program helps us ensure consistency when baking several batches.

The equipment should always be preheated before roasting so that when we put green coffee into the roaster, we get a more consistent roast quality and can be sure that the temperature readings we get are the actual temperature of the roaster. If you don’t preheat your roaster, you end up with uneven heat distribution.


Mistake 2: Not taking notes

Roasting coffee at home understandably involves repeating many processes and steps, so it’s easy to think we’ve memorized all the relevant stuff. However, without proper documentation, we may find that the next batch of coffee beans tastes completely different from the last batch.

It is very important to keep detailed records. When we roast, we record the temperature from the beginning to the end, starting from the input temperature and ending with the temperature when the beans are poured from the roaster drum to the cooling tray (ie, the oven temperature). All changes in heat supply and airflow should also be recorded.

If we were using a program like Artisan or Cropster, we could annotate these changes and the temperature throughout the roast would be recorded automatically. If we record the temperature manually, it is recommended to record it at least every 30 seconds, or the recording frequency can be higher.


Mistake 3: Want to drink coffee right away

After roasting, there’s always an urge to try the latest batch of coffee beans right away. While freshness is important, roasted coffee needs to release carbon dioxide to be truly drinkable.

Each batch will act differently; how long the beans will age depends on many different factors, including roasting conditions, the type of beans, and the altitude at which they were grown.

We’ve found that finding a “sweet spot” in the bean can make the flavor of the coffee more clear when tasting. Ideally, roasted beans are aged for at least 5 days. A good rule of thumb is that dark roast coffees can be kept for a shorter time, while light roast beans can be kept longer.

Raising beans is very important! Because there is still some residual carbon dioxide in the cell walls of the coffee. The carbon dioxide released when in contact with water interferes with the brewing process. However, we don’t want to exclude all carbon dioxide, as this gas also strips volatile aromatics.

Mistake 4: Underroasting and Overroasting

This common home roasting mistake is one of the hardest to fix. Knowing what we are looking for in a roast will help us identify under-roasted or over-roasted coffee by its appearance.

It’s important to note that this is a good way to judge home roasting. Sometimes, it’s also down to personal preference.

We need to look for signs to tell if our coffee is under-roasted or over-roasted. Physically, under-roasted coffee is slightly lighter in color and cannot be crushed when we press down on the bean with our thumb.

Over-roasted coffee beans will have oil on the surface, and if it is very over-roasted, we can even use it to write or paint because the coffee components have been reduced and carbonized!

In terms of flavor, an under-roasted coffee may have a grain or bread-like flavor and a somewhat broth-like consistency when brewed. Over-roasted coffee, on the other hand, will have a thinner texture and a bitter taste when brewed.

Learning to avoid this basic mistake takes time. While there’s no substitute for home baking experience, there are plenty of educational resources and courses in the industry to choose from for those who want to learn.

Mistake 5: Don’t know the green coffee beans you use

When we buy new beans for home roasting, it can be difficult to create a roasting plan to match. But when we know more about the coffee beans (variety, planting height, processing method, etc.), we can roast them well.

Small variables can make a huge difference, and no green bean is exactly the same. Each bean will be different. Mastering the idiosyncrasies of each coffee is half the fun of roasting. “

Here are some basic tips: “Coffee beans with a larger mesh will take longer to heat in the roaster. Coffee beans with a lower density will absorb heat more easily at the beginning of the roast. However, denser coffee will absorb heat in the later stages of roasting and develops its flavor in the post-crack development stage.

Coffee with a high water content requires more energy to reach the first crack. Kenyan coffee sometimes even reaches the first crack earlier than coffee from any other origin. These tiny differences are endless, and it just takes time to get used to them. This is where taking notes can really help. “

However, apart from taking notes, there is no alternative to simply roasting different coffees from multiple origins.

Mistake 6: Baking

“Bake” is a common term for roast defects that can destroy the complex flavors contained in green coffee beans. If heat is removed from the roast at the wrong time, the temperature of the coffee beans can stagnate and not change as much as it should.

About the roasting process. The general consensus is that “baking” occurs when the rate of rise (°C/min) stagnates or drops to negative values late in the roast (usually before first crack).

This means we either keep the coffee at the same temperature or lower the temperature before the sweetness of the coffee is properly developed.

How to avoid the occurrence of “baking” phenomenon? Avoid letting the temperature rise before the first crack, so that it is possible to avoid a baked situation. However, if you are not careful, there may be baking phenomenon in the development process after the first crack.

Mistake 7: Burnt

Roasting occurs when the rate of heating plateaus or drops, and bean burnt occurs when we use too much heat in the early stages of roasting. Charred beans have been seared by the heat on the outside, but are still raw on the inside.

Here are some suggestions for everyone to avoid burning. Scorching generally occurs at the beginning of roasting, because the coffee beans absorb too much heat; that is to say, the temperature of the drum is too high when feeding, and the heat will not enter the center of the beans, and the surface of the coffee beans has been due to Baking becomes brittle and causes charring.

The main culprit of burnt coffee beans is too much heat at the beginning of the roast. But we can also burn the coffee late in the roast by applying too much heat too quickly. Pay special attention to this in roasters equipped with powerful burners.

Mistake 8: Not keeping the equipment clean

While many of the mistakes mentioned in this article can lead to bad coffee, not cleaning your home roasting equipment properly can be extremely harmful.

In addition to cleaning your home roaster regularly, you should also utilize a vacuum cleaner to keep your baking area clean and tidy. Silverskin in particular is a highly flammable substance.

The importance of good health and safety procedures cannot be underestimated. Seemingly innocuous waste can become dangerous if ignored. The greatest danger in coffee roasting is fire. Silverskin buildup anywhere in the roaster can be a major fire hazard

Silverskin is a bigger problem on some coffee beans. For example, more silver skin is always attached to natural or honey-processed coffee beans. The coffee beans that have been washed or wet planned have less silver skin and are slightly safer.

Remember to keep the roaster clean at all times, just like in a restaurant kitchen. Even though it might already look clean, there’s no harm in cleaning up a little more. “

Not only that but keeping our equipment clean can help us avoid the leftovers from previous roasts that can affect the flavor of the next batch of coffee beans.

In the end, practicing your home roasting skills takes time. But eliminating some of these mistakes can put us in an excellent position to roast a variety of coffees and unlock their true potential. At the same time, it is possible to improve the consistency and repeatability of roast quality.

Although everyone’s roasting technique is different, there is no substitute for experience and roasting time. Keep practicing, make every roasting note, and use a variety of different green bean raw materials, I believe everyone will taste the difference soon.

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