November 11, 2019

Common Mistakes That Roasters Make & How to Avoid Them


Mistakes happen in the roastery. Whether they’re caused by humans or are equipment-related, they happen. The good news is that there are ways to limit, mitigate, and sometimes completely avoid these issues altogether. 

Understanding the errors that are made during roasting and guarding against them is a large part of helping your green coffee beans reach their full potential.

Read on to learn more about common mistakes roasters make and how to avoid them.

Lee este artículo en español Errores Comunes al Tostar Café y Cómo Evitarlos

Roasters checks the development of the roast profile.

Roaster checking the progress of his roast. Credit: Battlecreek Coffee Roasters

Mistake #1: Starting With Inexperienced Roasters

Experience is a large part of any skill set, and coffee roasting is no different. According to Rob Bathe, owner of Folly Coffee Roasters, “A common trend we’re seeing is cafes beginning a roasting program with an inexperienced roaster. The customer suffers because they’re paying the same price as an expert roaster and getting coffees that are being roasted by someone learning on the fly.” 

Without an adequate baseline of roasting knowledge, the coffee produced can be subpar. This will be off-putting for clients, negatively affect your brand, and put your expensive equipment at risk.

If you’re transitioning into roasting, take your time with a new roastery startup. Utilize all the literary and online resources available and hire experienced roasters – even if just to mentor your staff. This will ensure your clients get quality coffee. Your company will be rewarded with brand loyalty and ultimately, increased sales.

You may also like Practical Tips For Quality Control in The Coffee Roastery

Roaster releasing roasted coffee into cooling tray

Freshly roasted beans being dropped into cooling tray. Credit: San Franciscan Roaster Co.

Mistake #2: Losing Focus

Every roaster out there has had the batch that got away from them. Preparing the next load, getting preoccupied with packaging, and falling down a social media rabbit hole are all things that can take a roaster’s attention away from the task at hand. 

Focusing on the beans is the roaster’s primary job. If multitasking is necessary, keep it to a minimum. Minimize potential distractions in your immediate proximity, keep your phones off, and close unnecessary windows on your computer. The benefits for the coffee produced and the minimized green bean wastage are worth these small sacrifices.

For larger companies, it’s the management’s responsibility to keep from rushing the roasters. Allow sufficient time for the roasters to do their job. There’s a finite amount of coffee a roastery can produce given the equipment and staff on-hand. Understanding that and allowing some buffer time keep staff from becoming overwhelmed increasing morale will produce a more consistent, better quality roast.

Roasted coffee beans in grinder hopper

Roasted coffee beans in a grinder hopper. Credit: KML

Mistake #3: Rushed Warm-ups

Experienced roasters know the challenges of the day’s first roast. The machine needs to be brought up to the same charge temperature that it will be run at for the remaining days batches. According to Scott Rao, the author of The Coffee Roaster’s Companion, “every roaster I’ve ever asked has admitted to having difficulty with the quality of the first few batches of a roasting session. The problem is usually caused by inadequate warming up of the roasting machine”.

Knowing your machine well is important during warm-up. While temperature probes can quickly read the correct charge temperature, they don’t take into account the thermal energy of the entire roaster. Rushed warm-ups will cause a lower heat drop then expected when beans are loaded, requiring heating compensation or having to extend the overall roast. This will change the entire roast profile.

There are several ways to ensure a more complete warm-up. You can heat the drum well above charge temperature, and then allow it to cool multiple times before the first load. Alternately, you can let the machine idle above charge temperature for 15 to 20 minutes before dropping to charge temperature. 

Whatever your technique, your roaster warm-up should never be rushed, or your coffee quality will suffer.

Close-up of roasting machine

Coffee beans being roasted. Credit: Battlecreek Coffee Roasters

Mistake #4: No Between Batch Protocol (BBP)

To achieve a consistent quality coffee, a roaster needs to identify all the variables at play, so they can be controlled and standardized. 

In my interview with Dudley Powell, Assistant roaster, QC and Training manager at Horsham Coffee Roaster, he told me, “Something we’ve been working on really hard here at Horsham Coffee Roaster is our Between Batch Protocol (BBP), and ensuring our roasting workflow is consistent with regards to stable and correct charge temperatures”

BBP is important for a constant roast and to minimize defects. If the drum is too hot when your next batch of green beans are loaded, scorching can occur. If the drum is allowed to cool too much, it will take longer to achieve first crack and alter the roast profile of the next batch. A consistent BBP is a big part of a consistent roast profile and minimizing roast defects.

Sample roaster sat on a table top

Sample roaster at Matraz Café in Guadalajara, México. Credit: Ana Valencia 

Mistake #5: Not Cupping Your Roasts

A solid quality control regime requires continual cupping of your production roasts. However, cupping can serve to check more than just the treatment of your particular roast.

According to Jeff Mooney, Folly Coffee Roasters green buyer, “Tasting coffees next to other coffees from roasters you enjoy allows you to note the differences and whether those are good or bad and adjust the roasting process or green selection”.

Cupping is important for more than just ensuring adherence to your own roast profiles. It can act as a ‘meta-cupping’ to check that your roast profiles are in line with your preferred and respected flavor profiles, and your roastery’s vision as a whole.

Cupping bowls and kettle on a table

Cupping table at The Fix coffee in Madrid, Spain. Credit: Fernando Pocasangre

Mistake #6: Complacency

According to Rob, “The larger a roaster is, the easier it is to fall into your own routine. Success can build complacency, but can slowly create loss of customers.” Just because you’ve been roasting a certain way for many years, doesn’t mean it can’t be done better. Questioning and refining your own process will only benefit your roastery and ultimately produce a better coffee. 

To be the best roaster possible, you have to be aware of what’s happening in the industry. With all the platforms available for staying connected, there’s no excuse not to. Between social media, podcasts, industry publications, events, and print media. It just takes a little effort to continually learn and refine your techniques. 

Dudley says “we gather information from everywhere to help us with this, be it drawing influence from the big players in coffee by reading their blogs and attending their talks, or from talking to people who know as much, if not more, but are less active on the internet.”

Roaster using roasting machine

Roaster working with a roasting machine. Credit: San Franciscan Roaster Co.

Mistake #7: Overloading And Underloading

Understanding the equipment you use and its capabilities comes with experience. Knowing the load capacity of your machine is essential.

A common mistake made by new roasters is not understanding the optimal batch size for your roaster. Overloading a machine will make the roast take longer than it should and produce a baked, bland coffee. 

Underload a roaster and the roast will be more difficult to control due to increased sensitivity to heat. This will result in less bean mass, and an improper bean probe reading.

Bags of green coffee next to roasting machine

Roasting machines and bags of green coffee at a roastery. Credit: Peter Bösken 

Mistake #8: Roaster Maintenance

Purchasing a roaster is a significant investment, and poor roaster hygiene puts both the health of the equipment and the quality of the coffee produced at risk. Roasted coffee produces oils that can spoil and become rancid. The off-gas from roasting can also get messy and fill the ventilation with thick tar. 

Operating a dirty roaster is very hard on the machine. Oily build-up strains the motors, making them prone to breakdown. Airflow is reduced as material builds up in the ventilation. Even more serious is the risk of fire due to build-up of combustible materials in the roaster and ventilation system.

Run a batch of coffee (especially a lighter roast) through dirty equipment and the beans will pick up an array of negative flavors.

Set a maintenance schedule according to your manufacturer’s recommendation and your machine usage, and then stick to it.

Roasting machine and cooling tray

Red and silver coffee roaster. Credit: Nate Dumlao 

Mistake #9: Not Dealing With Defects

Often, you’ll find physical flaws in the beans themselves resulting from defective beans or roasting errors. Although not the primary focus of this article, it’s necessary to mention them. 

Sam Kayser, owner of Lone Oak Coffee Co., summarizes roasting defects well. “In my experience, some common mistakes could be: Tipping, scorching, baking, underdevelopment. Those are specific to the actual roasting process…the coffee itself will taste ‘off’ if any of these have occurred. Ashy, burnt, woody, green, or grassy flavors would be apparent if such a mistake were to be made. Experience, proper staff training, roast profile software, and rigorous quality control will keep the majority of these defects at bay.” 

Defective green beans on a tray

Tray with defective beans. Credit: Ana Valencia 

A Step-By-Step Guide to Managing Your Roast

1. Apply sufficient heat at the beginning of the roast

It’s crucial that you apply sufficient heat to the beans at the beginning of the roast. According to Scott Rao, doing this “is essential to achieving optimal flavor and proper bean development”.

This is not to say drop the beans into a super-heated drum, as this will cause scorching and tipping defects. Rather, have the roaster at the predetermined charge temperature, load the beans, and then keep the heat high enough to reach a strong rolling first crack in a reasonable amount of time. 

Bean development happens after first crack, so lengthening the time between loading and first crack will do nothing for its development. It will only extend its overall roast time, which will result in a baked and bland coffee.

2. Allow enough development time

A common issue that Dudley has noticed is “the prevalence of underdeveloped roasts, which seem to actually be more common now more than ever before. This might be because there are more people roasting lighter which I think is generally positive, but does push some people closer to not developing coffees well.”

Underdeveloped roasts are dropped shortly after first crack, and have a green, grassy, and often peanut-like taste. It’s possible to get a well developed light roast without these unsavory flavors by slowing the rate of roast after first crack. 

Cutting heat and increasing airflow after a strong first crack will stretch out the time in between first and second crack. This will give the beans more development time, without heading hard into a dark roast. Precise timing will vary depending on your machine and batch size. With a little experimentation and cupping one can easily find the sweet spot of a well-developed light roast.

Close-up of roasted coffee beans

Person holding a roasted bean. Credit: Daniel Ramirez

Roasting coffee is an art. Creativity in the blends and subtle adjustments in the roast process makes for vastly different coffees. This is what keeps the industry exciting and inspiring. Use the advice above as your base line for quality and then play with the space in between. 

Your customers are sure to be impressed and keep coming back for more!

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Feature photo: Freshly roasted beans cooling down. Feature photo Credit:  Moritsz320

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