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Experiment on the detection threshold of acid in coffee


When discussing the crucial factor that contributes to making coffee lively, acidity naturally stands out as indispensable – something that can significantly alter the sensory experience of coffee. Not everyone can detect the various acids in coffee, and not all types of acids are easily identifiable. Experts are continually refining their expertise, techniques, and perceptiveness to enhance their ability to “pinpoint” the dynamically changing acids within each cup of coffee.


The expertise in detecting acidity in coffee among professionals


The ability to detect acidity in coffee by experts is crucial. Through various types of acids, experts can evaluate the flavor and quality of coffee brews, thereby adjusting roasting methods, brewing techniques, processing, etc., to create desired flavor profiles. The ability to detect and name acids becomes a criterion for evaluating experts. They continuously strive to refine their senses to become even more sensitive while enriching their acid dictionary, which is always present in their minds. This forms the basis for professional, technical assessments such as “this coffee exhibits a pronounced sourness of malic acid when hot and then citric acid as it cools…”.

The Specialty Coffee Association (SCA) and the Coffee Quality Institute (CQI) have sensory evaluation tests that use various levels of different acids to “challenge” the sensitivity of experts. The standard procedure for testing the ability to taste acidity in coffee used by both SCA and CQI involves “spiking” brewed coffee with organic acids. SCA uses citric, malic, lactic, and tartaric acids in their Sensory Skills Professional test, while CQI tests citric, malic, acetic, and phosphoric acids as part of the Q grader exam.

Experiment on the detection threshold of acid in coffee

Acids contribute to making coffee more enticing, with layers of intertwined flavors.

Each place has its own testing method, where trainers typically add 0.4 grams of each acid per liter of brewed coffee (or 0.5 grams in the case of lactic acid). For CQI courses, trainers will select two out of four cups and ask students to identify which two cups have been spiked with acid (the “pair match” test). SCA certification goes a step further by testing students’ ability to identify which type of acid has been added to the cup. The purpose of these tests is to ensure that the added acids are detectable SCA guidelines instruct trainers to “adjust to taste” if necessary, to ensure that students can perceive the differences between the cups.


Detection threshold of acidity in coffee


A recent scientific paper titled “Acids in brewed coffees: Chemical composition and sensory threshold” revealed that the concentrations of many organic acids in brewed coffee are so low that they are undetectable.

Sensory experiments on acidity are based on the assumption that common organic acids significantly influence the flavor of coffee and help distinguish between different types of coffee. However, many of these acids cannot be detected at low concentrations in brewed coffee. Researchers brewed coffee extracts with different doses of acids and tested them on a group of coffee experts – in this case, barista managers from the Copenhagen Coffee Collective roastery. All participants had prior training on how to recognize organic acids, as well as 30 minutes of intensive training immediately before the test.

Experiment on the detection threshold of acid in coffee

Many types of organic acids exist in coffee at concentrations lower than the detectable threshold

They found that at the concentrations commonly found in coffee, participants were unable to identify any acids in the experiments. In fact, for most acids, participants couldn’t even discern whether any acid had been added or not. When tasting acids in plain water instead of brewed coffee, participants could only accurately identify acetic acid.

By adding different amounts of each acid type to coffee, researchers calculated the amount they needed to add to the coffee to detect a difference in the cup – or the “detection threshold.” According to the research group’s results, the average concentrations of malic, lactic, and acetic acids in brewed coffee were below the detection threshold, while the average concentration of phosphoric acid was slightly above the detection threshold. The only acid type that could be clearly detected at the concentrations found in coffee was citric acid.

The News section has provided readers with a study from a scientific journal on the detection threshold of acidity in coffee. Although acidity levels can be measured, our perception of acidity is highly subjective. Visit XLIII Coffee to experience the acidity in each cup of coffee for yourself!

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