Acidity is one of the primary flavor characteristics that coffee experts assess when scoring coffee. Acidity adds vibrancy and fresh fruit notes that may either appeal to or offend certain consumers.

Coffee samples with various roast degrees from Brazil and Kenya were spiked with nine organic acids identified via chromatography, then tested for their sensory detection threshold and recognition ability. All acids except formic acid generally decreased with increasing roast degree; however, variances did not correspond directly with sample origin.

Acids in Coffee

Acidity is an integral component of many highly esteemed coffees around the world. Acids provide a bright and clean element to overall flavor profiles and boast anti-oxidant properties, but not all acids have equal effects on our bodies; something more acidic may lead to inflammation or even heartburn in some people.

Coffee contains many organic acids, including citric, malic, lactic, tartaric and acetic acids as well as several others such as citric, malic, isomalic phenolic acids such as mangiferin isomangiferin scopoletin coumarin acids scopoletin scopoletin scopoletin and carotenoids like flavonoids lutein quercetin and kaempferol that exhibit antioxidant, lipid-lowering hypoglycemic and neuroprotective activities. These phenolic acids possess antioxidant, lipid-lowering, hypoglycemic and neuroprotective activities

There can be significant variation in acid content among various coffees and roast levels, due to different growing elevations, soil types and processing methods used. Coffee grown at lower elevations generally has lower acid contents than its higher-altitude counterparts while soil types with volcanic composition tend to have a lower acidic profile than nonvolcanic soil types; finally the type of roasting process chosen can have a profound impact on its acid levels.

Therefore, finding a clear trend in research regarding coffee acidity’s relationship to roast level was challenging. Our findings do indicate some general trends. First of all, sensory detection thresholds indicated that only citric acid could be detected above its average measured value, suggesting that individual organic acids might not provide the optimal sensory experience.

Second, chlorogenic acids–considered the primary acid responsible for acidity in coffee–were unaffected by sample origin. Thirdly, pH measurements on all five samples revealed a consistent trend: acid concentration decreases from lighter roast to medium roast and darker roast coffees.

Acids in Water

Coffee’s acidity comes from its plant roots and plays an essential role in its health and flavor profiles, but some chemicals used during bean production may have their own impacts. One such chemical contaminant is acrylamide produced during roasting of beans at high temperatures. Although toxic in high doses, acrylamide consumption at smaller levels is usually considered safe; its presence can be difficult to identify since there’s no noticeable odor or visible trace within a cup of coffee.

Acid concentrations were determined using HPLC on a Dionex Ultimate 3000 system comprising of an LPG 3400 pump, WPS 3000 SL autosampler and TCC-3000SD column oven. Organic acids were analyzed using an anion exchange column (Bionature EVOLUTE AX 50 mm 100 mg/3 mL from Uppsala Sweden) preconditioned with 3 mL of methanol followed by 25 mL of ultrapure water in order to remove protons before being dried with heated desiccator before reconstituition into mobile phase of acetone/water for analysis at 20 degC. Peak areas were measured using Dionex Mass Spectrometer software software.

Thirteen coffee experts were tested for sensory detection thresholds of five organic acids present in water and brewed coffee, using ISO standard 3972:2011’s identification of tastes test. Their solutions were then evaluated blindly using ISO’s Identification of Tastes Test; immediately prior to testing they received 30-min intensive training on organic acid recognition; the 2-AFC tests demonstrated that only citric acid could be correctly identified at concentrations higher than its average measured value in coffee; while acetic and chlorogenic acids couldn’t even be identified at all!

Chlorogenic acid concentration decreased by 0.4 mg/mL when roast level changed from lighter to medium and continued decreasing when switched to darker roast level, contrary to expectation. Although sample origin may have played a factor, postharvest processing and altitude may play more of an impactful role when it comes to acid composition in coffee beans.

Acids in Milk

Acidity is an integral part of coffee’s flavor profile, providing brightness and fresh fruit notes that many enjoy. But for some individuals with stomach conditions such as heartburn or acid reflux, high levels of acid may cause discomfort; in such instances low acid coffee varieties should be recommended instead.

Numerous studies have explored how proteins found in milk interact with certain compounds found in coffee known to possess antioxidant properties and reduce oxidative stress in the body, such as polyphenols. One such investigation conducted at Copenhagen University tested what happens when polyphenol-rich coffee and protein-rich milk are combined; researchers demonstrated that their combination enhanced its anti-inflammatory benefits.

Scientists compared total acids and organic acids present in brewed coffee samples from Brazil, Bolivia and Kenya. Although concentrations of individual organic acids varied significantly across samples from each origin due to small variances between measured values, significant proportions of differences could be explained by chlorogenic and citric acids which were significantly different between Brazilian and Bolivian samples, and malic and acetic acids which showed differences between Kenyan samples and others.

To further investigate the relationship between specific organic acids and acidity, researchers added a sample of each coffee with an average concentration of the five specific acids present in their water solution. They then asked a panel of 13 coffee experts (mean age 29; 46% women) to evaluate each acid-spiked sample using a taste identification test based on ISO 3972:2011; this required choosing from one of five possible organic acids before identifying which specific acid had been added.

Results revealed that none of the five acids were correctly identified by coffee experts when spiked to average concentration levels for their brewed samples, making any focus on specific acid types inappropriate. Nonetheless, all five were positively correlated with perceived acidity of coffee beans and therefore do contribute towards overall perceptions of its acidity.

Acids in Citrus

Acidity in coffee is often considered desirable as it adds brightness, sweetness, and fresh-fruit characteristics. However, too much acidity may become unpleasant or overwhelming and turn off potential consumers.

At Cafe Altura, our aim is to provide our customers with a variety of coffee choices so that they can find one that meets their individual preferences and acidity requirements. Whether it be light roasts with delicate citrus notes or dark roasts without any acidity whatsoever – there’s sure to be something perfect here for them all! We promise!

Recent research investigated the concentrations and pH values of chlorogenic, malic, citric, formic and acetic acids as well as sensory detection thresholds and identification tests for these organic acids present in coffee samples from three lighter specialty roasting degrees and five coffee origins.

Results demonstrated that acid concentrations varied significantly among sample groups. Average chlorogenic acid concentration in Brazilian coffees was significantly higher than Kenyan samples, while citric acid levels were comparable across Kenyan origins. Furthermore, formic acid presence was slightly greater among M roast compared with L and D roasts; similar observations were reported by Rodrigues et al.

Coffee experts typically believe that geographic origin can be distinguished through concentration differences of organic acids, particularly citric acid. Unfortunately, however, sensory detection thresholds and identification test results from this study show that these organic acids don’t differentiate a coffee’s origin to any significant degree.

Note that the organic acids measured in this study were measured following roasting coffee beans, so their concentration may differ from those in green beans. Furthermore, their concentration could change depending on factors like temperature and brew duration – more research needs to be conducted into how these may impact organic acid concentration in brewed coffee.