Coffee is an incredibly popular product, even beyond the world of coffee professionals.
FILIP BARTELAK explores the findings of Dr. MACKENZIE BATALI’s recent work on fractionation and sweetness.
Many of us can’t imagine morning without cup of coffee. We frequently buy coffees from coffee professionals (you know them as baristas) in their specialized cafés. Our experience of coffee is dependent on our geographic region, but more recently, the Italian approach—espresso-based beverages—have become more and more popular, relegating “pour-over” brews, or those brewed without the nine bars of pressure in an espresso machine, to be thought of as “alternative methods” by the coffee-consuming public.
But this approach, even if it is not as “alternative” as it may seem, is gaining traction: in the specialty coffee sector, we look for the best baristas brewing coffee without an espresso machine in the World Brewers Cup. During this competition, baristas brew their coffee with drip brewers, immersion methods or, every so often, pressurized extraction methods but without the use of automatization. But I am slightly disappointed in the lack of new methods of brewing techniques that would affect the final brew. Competition routines seem to differ more in the coffees used, or the presentation style, where hospitality and professionalism play a major role in dictating the experience. What stays the same seems to be the brewing equipment or protocols. Rarely, from what I have seen, are judges challenged with presentations that include novel brewing methods. But have we really discovered it all?
The Current Approach
Drip brew method, where water is poured over ground coffee, is one of most popular among baristas worldwide. Pulled downwards by gravity, the coffee is extracted as the water filters through, leaving a coffee brew in a carafe or vessel beneath the brewer. This mixture contains approximately 98% water and up to 2% dissolved coffee solids, which are measured as “total dissolved solids,” or TDS.
Some baristas, when they brew with the drip method, like to include pre-infusion in their protocol. They pour small amount of water on ground coffee and wait certain time. This step works well when it comes to saturating grounds with water and pushing out excess of CO2, which still is locked in coffee. When coffee is fresh, the amount of CO2 in the roasted bean is very high. When coffee is ground, a vast number of gases are released together with volatile compounds—this is the reason why we enjoy the aroma of freshly ground coffee when we enter a café. Even though the gas is released while grinding, some of it is still locked in the pore structure of ground coffee; when in contact with water, it seeks its way out and creates spontaneous turbulence, affecting extraction. To avoid uncontrolled brewing, baristas often pre-wet coffee grounds to have better management of their extraction process.
Applying Research to Brewing Practice
A recent academic paper by Dr. Mackenzie E. Batali et al., “Sensory and monosaccharaide analysis of drip brew coffee fractions vs. brewing time,” was published in the Journal of the Science of Food and Agriculture. For me, the most exciting outcome was understanding better how the brewing process we typically follow results in a drinker’s perception of sweetness in a cup of coffee.
The coffee industry has long assumed that sweetness was not dependent on the actual number of monosaccharides (the most basic form of carbohydrate) in a brew, but rather on our impression of the brew which brings the memory of sweet foods. The SCA explains the sweetness attribute on the cupping form as:
“… refer[ring] to a pleasing fullness of flavor as well as any obvious sweetness and its perception is the result of the presence of certain carbohydrates. The opposite of sweetness in this context is sour, astringency or ‘green’ flavors. This quality may not be directly perceived as in sucrose-laden products such as soft drinks, but will affect other flavor attributes.”
Dr. Batali’s study interestingly showed that the levels of sugars present in most cases of brewed coffee are too little to be perceived by humans and give the impression of sweet taste. This means that if we are perceiving sweetness, it is through the recognition of aromatics of sweet fruits, vegetables, and other sweet foods represented by specific compounds coming from coffee itself and not the sugars.
This implication has two very significant aspects for me. First, the study underlines that what is enjoyable to each drinker is specific to their biology and personal preference: diagnostic instruments cannot tell us if people will enjoy a coffee or not. Second, it’s also important to understand that the perception of sweetness in brew relies on our personal memory associations with other sweet products and is playing a specific game with our perception. “Taste modulation,” where sweetness can be altered or muted by other tastes, is a good example of this. For example: saltiness will reduce the experience of sweetness. Taste modulation significantly influences flavor perception where no real volumes of particular compounds are significant, making it even more specific to the individual tasting or experiencing a cup of coffee.
Some other findings of the article are also important to me and made me experiment with my brewing routine—a finding on coffee brew fractionation and their assessment. From the article, it appears that brewed coffees with more TDS are perceived as less enjoyable while those (to some extent) with lower TDS are perceived as better.
Think back to the standard brewing method outlined above: most of the solids are released and dissolve in water in the first fractions of brew. The longer the brew, the fewer solids are being released and dissolving in the water.
I began brewing with different variables of extraction and I noticed that some brews tasted better when I got rid of the extracted coffee that filtered through during the “pre-infusion” brewing stage—after pouring small amount of water (app. 25-30mL for 18g of coffee), I waited 30 seconds for it to drip down onto the drip tray then placed the server in its position for brewing. In my opinion (and as was suggested by the study), this “defragmentation” of the extraction gave me cleaner cups, slightly sweeter but with less body.
The study also highlighted, surprisingly, that the bitter tones that we are more likely to perceive are more responsible for our enjoyment of a beverage than carbohydrates and monosaccharides. The threshold of bitter perception is much lower than sweetness and there is a lot of it in brewed coffee. Perceived bitterness is a result of caramelization and dry distillation/pyrolysis byproducts. If we roast too light to avoid the formation of bitter tasting compounds, then we risk not developing flavor properly and creating vegetal, grassy flavors instead. I was wondering if we can still develop the roast properly and minimize the impact of bitter compounds. I came to conclusion that I should brew coffee differently.
Brewing Method For Thought
My initial recipe for brewing included pre-infusion and disposal of its extraction, but I wanted to explore the findings of Dr. Batali’s study further. I wanted to have the final cup begin with a later brewing fraction, so I tried a pre-infusion with a larger amount of water than just for wetting grounds. My goal was to get rid of bitter tones without losing fragile volatile compounds, so I tried using cold water to “wash” the compounds from the first brew fraction. I really enjoyed the results of the coffees I brewed this way, and I feel it improved my perception of their sweetness. I did feel as if I lost the intensity of the “body,” but I was comfortable with this outcome.
In the end, I found my personal preference to be for room temperature water deployed at a ratio of 1:2 with the amount of coffee used (i.e., if I was brewing 60g of coffee, I would use 120mL of room temperature water for “rinsing”). I would leave the brewing device to drip all “rinsing” water for 2-3 minutes, empty the carafe, and then start brewing.
I also tried this method with same ratio of water to coffee as described in the Golden Cup protocol (8.25g/150mL) but I get better results with slightly less water (8.25g/130mL).
With this method of brewing, I feel I have rediscovered coffee attributes. It works very well for me with slightly faded coffees (past-crops) and lower quality ones. In my opinion, high-scoring coffees don’t profit much from this method, although it does offer another “face” of the coffee to enjoy.
Sweetness is an incredibly important experience for humans: the perception of sweetness indicates there are nutrients available. There is still so much for us to learn and explore in how we brew and present coffee, but I am excited to see pieces of research like Dr. Batali’s work help to explain a little more of this mystery, and I hope it will drive us to continue to explore new and different brewing methods.
FILIP BARTELAK is a green coffee buyer and roastmaster at Coffee Grange, a role he holds in addition to Q Grader, Q Instructor, WCE Certified Judge (WBC and WBrC), and Cup of Excellence Judge. He is the Coffee Roaster’s Guild Chair and Chair of the CRG Sustainability Committee.