Eight common mistakes to be avoided in household coffee roasters guidelines for roasting coffee beans

Those who roast coffee at home know that it can go from a simple hobby to an obsession with everything in just a few weeks. It's like having a nice cup of fresh coffee at home and knowing you're the one who's roasting it.

But experienced home roasters will also know it has a steep learning curve. There are many common traps and obstacles, and many people become prey again and again.

Error 1: Do not preheat equipment

Depending on where you are baking or what time of year, the temperature of the equipment naturally fluctuates. Setting up a preheat program will help you ensure consistency when baking several batches.

"You should always preheat the equipment before baking," Evan explains. "This provides better consistency when you add green coffee to the roaster and ensures that the temperature reading obtained is the actual temperature of the roaster."

"If you don't preheat the oven, the heat will [eventually] be distributed unevenly."

Mistake 2: Not taking notes

Understandably, roasting coffee at home involves repeating many routines and procedures, so it might be easy to think that you've put all your energy into memory. However, without proper documentation, you may find that the next batch of beans tastes completely different from the previous batch.

Evan explains that it is important to keep detailed records. "When I bake, I record the temperature from start to finish, starting with the loading temperature and ending with the temperature at which I drop the beans from the roaster into the cooling tray. I also recorded all changes in heat application and airflow.

"If you're using a program like Artisan or Cropster, you can annotate these changes and the temperature will be automatically recorded throughout the baking process." If you want to manually record the temperature, it is recommended to do so at least once every 30 seconds, if not more frequently!"

Mistake 3: rushing for coffee

After roasting, it's hard to stop yourself from tasting the latest batch right away. While freshness is important, roasted coffee needs to actually release carbon dioxide to be truly drinkable.

Each batch will act differently; the length of time required to rest depends on many different factors, including baking conditions, type and altitude, to name a few.

Evan told me that he found that finding a "sweet spot" while resting beans can make you taste coffee more clearly. "I like to let coffee rest for a few days after roasting; ideally, at least five days. A good rule is to drink dark coffee [faster] and let light coffee rest longer.

"[It's important] because coffee has residual carbon dioxide in its cell walls. Carbon dioxide released on contact with water interferes with the brewing process. But you don't want to lose all that carbon dioxide because that gas also helps carry away volatile aromatic hydrocarbons."

Mistake 4: Underbaking and Overbaking

This common home-baking mistake is one of the most difficult problems to solve. Knowing what you are looking for in roasted coffee will help you identify the appearance of underroasted or roasted coffee.

It is important to note that these are great ways to bake at home. Sometimes it depends on personal preference.

Evan says: "You need to look for signs to tell if your coffee is under-roasted or over-roasted. Physically, under-roasted coffee will be lighter, and when you press up on the table, you won't be able to crush it with your thumb.

"Over-roasted coffee gets oiled, and if over-roasted, you can even write or paint with it because the coffee has reduced its carbon content!"

"In terms of flavor, under-roasted coffee may have a granular or bread-like taste, brewed with a certain broth consistency. Over-roasted coffee becomes thin and bitter when brewed."

Learning to avoid this basic mistake takes time. Although there is no substitute for the home baking experience, there are plenty of educational resources and lessons for those who want to learn more.

One such example is The Crown, an open source coffee education center in Oakland, California. In addition to operating a "tasting room" and coffee lab, it also offers online coffee resources and regularly hosts webinars.

Mistake 5: Not knowing your coffee

When you buy new coffee for home roasting, it can be difficult to establish a matching roasting profile. The more you know about coffee (variety, height, processing, etc.), the better you can roast it.

Evan told me that small variables make a huge difference and that no green bean is the same. "Every bean is different. Learning the idiosyncrasies of every coffee you work with is half the fun."

He gave me some basic tips: "Coffee with a larger screen size takes longer to heat in a roaster. Lower-density coffee tends to heat up more at the beginning of roasting. However, high-density coffee can be heated after roasting and blown up by post-crack development.

"Coffee with a high moisture content will require more energy to reach the first step. [I even found that] sometimes Kenyan coffee reaches the first crack earlier than coffee from any other source. These tiny differences are endless and take time to get used to. This is where taking notes really helps."

But there is no alternative to simply roasting different coffees from multiple sources, other than taking notes. While minimum order quantities for green coffee are generally higher for home roasters, some vendors have begun offering lower minimum order quantities to cater to this audience. Royal Coffee, for example, recently introduced 1-pound bags of green coffee as part of its Crown Jewels line.

Mistake 6: baked beans

"Roast" is a common term for roasting defects, which can destroy the complex flavors contained in green coffee. If heat is removed from roasting at the wrong time, the temperature of the beans may stagnate instead of changing as it should.

Evan explains the baking process. "The general consensus is that 'baking' occurs when the rate of rise (degrees per minute) of your late baking (usually before the first crack) stalls or drops to a negative value.

"This means you want to keep the coffee at the same temperature, or lower the temperature, until the sugar in the coffee is dissolved properly."

And how to avoid it? Evan says: "Avoid stopping the temperature before the first crack and it's possible to avoid roasting, although you can also roast coffee after cracking (if not careful)."

Error 7: Burning

Baking occurs when the rate of rise stagnates or falls, and scorch occurs when we use too much heat in the early stages of baking. Charred beans burn on the outside while the inside remains raw.

Evan has experienced all of this firsthand. He gave us some advice to avoid anxiety. "At the beginning of roasting, coffee heats up too quickly and can cause scorch. Higher charging temperatures may crispen the outside of the coffee, which then allows heat to enter the center of the beans, causing the coffee to burn.

"Too much heat is almost always the culprit at the beginning of roasting, but you can also sear coffee late in roasting by applying too much heat too quickly. Note this in roasters equipped with powerful burners."

Mistake 8: Not keeping equipment clean

While many of these mistakes lead only to undesirable consequences for coffee tasting, home roasting equipment that is not properly cleaned can be highly hazardous.

In addition to regularly cleaning the home toaster, keep it close to the vacuum cleaner to ensure that the baking area is clean and tidy. Chaff in particular is highly flammable.

Evan, who specializes in barbecue work, told me that the importance of good health and safety procedures cannot be underestimated. Seemingly harmless waste can become dangerous if ignored. "The greatest danger is fire," he explained. "When chaff accumulates anywhere,[it becomes a major fire hazard]."

Certain coffees are a bigger problem, he added. "The best coffee I've ever experienced has always been natural or honey processed," he said. "With these, the silver skin is still often stuck to the beans due to the processing methods used. Most washed or shelled coffee is no concern.

"Also keep it clean at all times, just like in a commercial kitchen." It may look clean enough, but a little more can't hurt."

Not only that, keeping your equipment clean also helps you avoid things left over from previous baking that affect the flavor of the next batch.

It takes time to hone home baking skills. However, eliminating some of these mistakes will put you in the perfect position to roast all kinds of coffee and unleash its true potential. They can also improve consistency and repeatability when grilled.

Although everyone has different skills, there is no substitute for experience and hands-on time in roasting coffee. Keep practicing, taking notes and working with different green beans, and soon you'll be able to taste the differences.