The Coffee Brewing Control Chart 2.0

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The Coffee Brewing Control Chart has long been the go-to guide for those looking to perfect drip coffee, yet it hadn’t been updated since the 1950s – until now.

The coffee industry is constantly evolving, with innovations such as super-automatic espresso machines revolutionising brewing efficiency and consistency. From new technologies to sustainability efforts, coffee professionals are breaking new ground in every aspect of the industry.

Yet despite these advancements, one corner of the industry has remained untouched since 1957.

In the realm of drip coffee, professionals have used the Coffee Brewing Control Chart (BCC), developed by Ernest E. Lockhart of the Coffee Brewing Institute almost 70 years ago, to perfect their craft.

The chart illustrates how adjusting brewing variables – such as brew strength, extraction yield, and brew ratio – can alter the flavour profile of a coffee. While it has guided the sector in producing drip coffee aligned with consumer preferences, the evolving needs of the industry calls for a chart better aligned with the modern consumer’s discerning palate.

In 2023, Professor Jean-Xavier Guinard of the University of California, Davis alongside a research team brewed something fresh.

According to Prof Guinard, who is also a member of the Institute of Food Technologists, an updated chart was necessary because sensory and consumer science has evolved into a full-fledged scientific discipline since the creation of the BCC. He believes the specialty coffee industry is eager to embrace science and technology to innovate and continuously improve the quality of its coffees.

“That has meant the development of many methods which, combined with statistics, have afforded us the ability to profile the sensory attributes of a food or beverage and to understand how they may drive liking by consumers,” he says.

The original BCC features objective sensory attributes of coffee such as bitterness, acidity, sweetness, roasted flavour, and astringency. However, Prof Guinard and the research team understood that the BCC was limiting, and consumer preferences were much more complex than the chart allowed.

The new BCC has not only expanded these sensory attributes to include a broader range of characteristics such as citrus, berry, and dark greens, but it has also been combined with consumer preferences to offer a more complete picture of how brewing variables influence both sensory profiles and consumer liking.

In the sensory and consumer science area, Prof Guinard and his team first developed the Coffee Taster’s Flavor Wheel as a tool for the characterisation and quantification of coffee flavour by descriptive analysis. They then partnered with their engineering colleagues to link the process of brewing coffee to its sensory profile and consumer acceptance in the new BCC.

The result was two charts: the objective Sensory BCC, which maps sensory attributes such as bitterness, sweetness, and acidity based on brewing variables, and the Consumer BCC, which identifies consumer preferences and how they relate to these sensory attributes.

These were combined to form the new BCC, effectively merging objective sensory data with consumer preferences to provide a more comprehensive understanding of coffee liking.

The new Sensory BCC includes sensory attributes such as bitter, acid/sour, citrus, roasted, viscous/thick, astringent, ‘sweet’, burnt/ash, black tea, dark greens, berry, and dried fruit, with each attribute’s position and font size on the chart reflecting its intensity and maximum expression.

“Those attributes included in the Sensory BCC are key coffee attributes and are positive or negative drivers of consumer liking. This was confirmed through extensive research linking TDS (total dissolved solids), extraction, and brew ratio to sensory profile and consumer acceptance,” says Prof Guinard.

Meanwhile, the Consumer BCC maps consumer preferences and shows how different sensory attributes influence overall liking, based on consumer responses.

“Within a population of California black coffee drinkers, we basically found two groups of consumers with different likes and dislikes,” he says.

“One group would probably be found anywhere in the world where people drink coffee.”

This group included consumers who like some ‘sweetness’ in their coffee and do not prefer bitter – and possibly astringent – coffee.

“For this group, liking increased as we moved towards the bottom centre of the Sensory BCC, at low TDS and medium extraction,” says Prof Guinard.

The other group was more likely specific to the consumer population that was studied.

“In a complex and convoluted way, the group equally liked coffees on the left and right sides of the BCC, with very different sensory profiles, but this could be explained from familiarity and liking for both specialty coffee and dark roast espresso,” he says.

Prof Guinard says the references of a group like this would vary around the coffee drinking world based on the specific local coffee landscape as exposure drives liking for flavour – particularly the way it smells.

The integration of the Sensory and Consumer BCC allows for a deeper understanding of these variations.

“The beauty of the Sensory and Consumer BCC is that it combines both the sensory and the consumer information on the same chart so that one can move around the chart through the use of specific brewing practices and alter the sensory profile in the desired way and tailor to the preferences of this or that group of consumers,” he says.

The research was essential in helping understand consumer preference clusters, so products can be tailored and targeted to its markets.

“Baristas know how to use brewing variables to manipulate the TDS, extraction, and yield of the coffee. Now they can do so to best express their desired sensory profile and understand how it may or may not appeal to different consumers,” says Prof Guinard.

“We no longer look at the average liking for a product and go with the highest because, as consumers, we often like and dislike different things.”

It is critical to uncover that preference segmentation first, then figure out which sensory attributes drive liking for each preference segment, so that baristas can create the right coffee for them.

“It’s also important to understand the consumers, in terms of their demographics, psychographics, and usage characteristics, so that we may market that coffee more effectively to them,” he says.

In the future, Prof Guinard hopes to see research exploring and mapping consumer preferences for espresso. The variables involved have the potential to unlock new insights into taste profiles, allowing for more personalised brewing methods and a deeper understanding of what shapes consumer satisfaction in espresso to help drive the specialty coffee market.

“I would love to do for espresso what we have done for drip coffee: design a brewing control chart that would relate sensory properties and consumer acceptance of espresso to espresso brewing variables, which are notably different from those that are most relevant to drip coffee,” he says.

The updated BCC is anticipated to influence the coffee industry, not just in terms of product innovation but also consumer satisfaction.

“Judging from the interest in our research, the new Sensory and Consumer BCC is fast becoming a critical tool for baristas across the world,” he says, “not so much because it is such a breakthrough – that was the feat of the original BCC – but because it brings the latest science to the art of making a great cup of coffee.”

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