A Pocket-Sized Guide To Achieving Consistent Roasts

Kahwei Yoong
April 2, 2021
consistent roasts

In coffee roasting, consistency is key. The ability to produce a quality cup of coffee that’s full of flavour and aroma is important for coffee roasters. However, being able to recreate the same experience and meeting consumers’ expectations at all times is just as important as it is to satisfy their taste-buds.

However, achieving consistency can be tough. Coffee roasting is a complex process, affected by many variables that can lead to a wide range of taste spectrum. This includes factors directly related to the roasting process like charge temperature, heat and roasting time, as well as indirect factors such as the quality and characteristics of green beans.

To find out more about achieving consistent roasts, I spoke with Matthew Deyn, Roast Master at pioneering Typhoon Roasters.

See also: Explaining The Importance Of Roast Curves For Coffee Roasters

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What is roast consistency & why is it important?

As a specialty roaster, your job is to unlock the full potential of green coffee beans. Each coffee is different, which means it’s up to the roaster to find the perfect flavour and aroma by applying their skills and expertise.

Once the desired roast profile has been achieved, the roaster then has a responsibility to maintain consistency. Roast consistency is essentially replicating the same roast profile for every batch of coffee.

When customers buy your product, they want to know that it will be the same as it was the first time they bought it. There’s nothing more disappointing for a consumer than revisiting a café or repeating a purchase of a particular bag of coffee, only to find the taste has changed. Similarly, it makes it difficult for baristas to work with as they have to constantly respond to differences in quality.

According to marketing firm Venveo, product consistency breeds consumer trust and loyalty. While changing things up every now and then has its advantages, customers are more likely to remain loyal to your brand if they know what to expect each time. 

As well as damaging consumer trust, inconsistent batches of coffee will often be rendered useless, thus hitting a roaster’s profits and wasting the time of producers. Therefore, achieving consistent roasts is in the interest of all those involved in the supply and consumption of coffee.

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What affects roast consistency?

Given the complexity of coffee roasting, there are many factors that can affect consistency. Understanding how these factors can influence the final outcome will allow roasters to prepare and control against any fluctuations in roasting results. Two of the main variables affecting roast consistency are the quality of green coffee and the charge temperature.

Green coffee quality

When cooking, the ingredients used will ultimately have the most significant influence on the final taste of the dish, regardless of the chef’s skill. 

Likewise, in coffee roasting, the characteristics of green coffee have a considerable bearing on the final outcome of a batch of coffee. The size, density, and processing method of green beans can all affect roast consistency if the roaster doesn’t take the necessary steps to accommodate these differences.

Matthew Deyn is Roast Master at Typhoon Roasters in Prague, Czech Republic. After honing his coffee knowledge in London with Perky Blenders and Brew Coffee Plus, he moved to the Czech capital to pursue a career in roasting. He explains that moisture content, in particular, can 

“Too much moisture content causes the beans to become mouldy,” he says. “On the other hand, low levels of moisture will lead to the beans roasting too quickly, resulting in grassy flavours.”

Charge temperature 

Charge temperature is the temperature the roaster uses before a batch of beans is dropped into the drum, setting the momentum for the rest of the roast. 

In his pioneering book on coffee roasting, Scott Rao explains that “charging at too low a temperature can limit bean development; charging too hot can burn a bean or blunt some of the delicacy of its potential flavour.” However, he also notes that there is no single optimum charge temperature as it can change based on a range of factors, from batch size to bean density.

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How to measure consistency

In order to successfully achieve consistency, roasters first need to know how to measure it. Matthew tells me that, in his experience, cupping has proved the most effective method.

“Taste is the main aspect that I focus on when trying to achieve consistency,” he says. “Data and numbers, meanwhile, tell me how to get there.”

He suggests that looking at coffee extraction level in particular is a useful way of determining consistency. To obtain the percentage of extraction level, simply multiply total dissolved solids (TSD) with coffee yield in grams, before dividing the result by coffee dose in grams. 

A refractometer is used to measure TDS, which indicates the concentration of coffee solubles in a cup of coffee. A comparison of extraction level allows roasters to examine roast development of different batches.

Scott Rao outlines another method of measuring consistency, involving the weight loss of the beans. He explains that knowing a roast’s weight loss percentage can help roasters determine how well they’re penetrating the bean core during roasting.

It’s important to keep in mind that the initial moisture level of the green beans can cause limitations to this method. Therefore, when comparing roast batches, roasters should ensure that the green coffee batches have similar moisture content.

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How to maintain consistency during roasting

Although there’s no one-size-fits-all solution to achieving roast consistency, there are a number of practices specialty coffee roasters can implement to help them.

Establish a system for roasting

Consistency is enabled by having a standard framework that informs the roaster whether a particular roast has met the required level of quality, according to Matthew. 

He says that although it may take time, roasters will eventually discover their own set of standards for the roasting process, which they can put in place to maintain consistent results. 

The idea is that a standard framework will provide space and flexibility for roasters to refine and improve, guided by available data and the roaster’s sensory input, including end temperature, rate of rise, or total roast time. 

Plan ahead & keep your equipment clean

Having a well-organised work space is the first step to creating a better workflow that allows you to focus on the job. A study on the performance of participants during simple tasks when put in either a tidy or messy work space suggests less error is committed in a tidy environment.

Furthermore, proper cleaning of equipment will reduce disruption to the roasting and cupping processes. For example, residue that builds up in a roaster can affect airflow, while a dirty grinder can affect coffee extraction for tasting.

Devising a cleaning plan and putting together a general schedule can help tackle these problems. Ultimately, a plan will allow roasters to work without distractions and help them focus on the task at hand. 

Not sure how to clean your roaster? Read our post on cleaning and maintaining your equipment

Don’t be afraid to ask questions

As a roaster, it’s important to stay on top of the latest trends in the coffee sector, keeping an open mind to the latest developments. To improve your knowledge of roasting, Matthew says it’s crucial to be inquisitive.

“Ask questions and use the data you have to guide your tasting process,” he says. “If you’re not sure of something, don’t be afraid to seek help. It will only ever make you a better roaster and reduce the inconsistencies in your day-to-day work.”

Build relationships with your green bean suppliers

By forming strong, working relationships with your green coffee suppliers, you’ll be able to communicate your needs more effectively and have more of an input in the production of the coffee you buy.

Defects in green coffee can pose a real problem for consistency. However, if you have a good relationship with your suppliers, you can look at ways of reducing the amount of defects and improve the overall quality of the coffee you buy. This could involve anything, from the processing to the way the beans are shipped.

Store your green beans properly

Once your green coffee beans arrive, it’s crucial to store them properly to reduce the development of defects or mould. Matthew says that establishing a storage system that prolongs the shelf life of green beans is just as important as the roasting itself.

“The way in which green coffee is stored is usually not given as much thought as it ought to be because roasters may be focused on setting up other aspects of their roastery,” he explains. “But having a staging room, or temperature and humidity controlled room will massively improve your roast consistency.

“This will help maintain consistency, particularly when there’s a seasonal change between summer and winter, as drastic temperature changes produce different roast results. meaning, roasters will need to adjust the profile.”

compostable coffee packaging

At MTPak Coffee, we understand all the hard work that goes into producing quality and consistent coffee. Our wide range of high quality packaging will protect your coffee and maintain its freshness, so that your customers can enjoy a consistently good cup of coffee every time.

For more information on our sustainable coffee packaging, contact our team here

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