Researchers at the University of Oregon and Drexel University used cyclic voltammetry to test coffee quality. By dipping a platinum electrode into black coffee, they measured chemical composition and roast levels. Sunalini Menon said, "I thought it was a very beautiful concept." This method replaces traditional, complex lab testing tools.
"As long as there was coffee in the world, how bad can things be?" asked American author Cassandra Clare. And if you are a true connoisseur of the beverage, you would likely agree.
But as much as a cup of great coffee can lift your spirits, a bad brew can crush it. How do coffee roasteries and brewers get it just right?
Beverage strength and the degree of roast determine flavour and, hence, commercial value. Optical refractometers can measure coffee concentration, namely the quantum of dissolved solids, but cannot differentiate between a light and dark roast, Arabica and Robusta varieties, and washed and natural processing.
What is the alternative?
Enter cyclic voltammetry (CV), an age-old principle in electrochemical science that helps observe molecular behaviour as they add or shed electrons.
A paper published earlier this year by researchers at the University of Oregon and Drexel University demonstrated this simpler method for coffee testing.
Instead of adding chemical reagents or sending samples through lengthy lab processes, researchers dipped a platinum electrode directly into a cup of fresh, undiluted black coffee. Brewed coffee is naturally conductive -- it can pass a current between electrodes. Moreover, its pH remains steady no matter how long current flows through it, a property called self-buffering.
Both these properties are critical when assessing quality. Voltage changes induce electrochemical reactions at the electrode's surface, causing a small current to flow. By measuring how this current rises and falls, the researchers could quickly determine the liquid's chemical composition.
"I thought it was a very beautiful concept," says Sunalini Menon, President of Coffelabs Ltd and a board member of the Specialty Coffee Alliance.
Data points in a shot
Menon says a traditional roastery or lab must use an optical refractometer to measure beverage strength and an Agtron colour meter to gauge roast darkness. Cyclic voltammetry combines both in a single device. When electric potential is applied, the initial surge of current measures the movement of free protons in the liquid, which indicates the strength of the brew. Alongside this, key organic molecules in the coffee, such as caffeine and chlorogenic acids, adhere to the platinum electrode surface. The speed and degree of the coating, which suppresses the current, indicate the roast level and chemical composition of the liquid.
Further, optical refractometers and colour meters record only surface reflection and cannot tell whether a roasted bean may be undercooked inside. CVs can detect this -- the undercooked parts change the coffee's organic chemistry and, thereby, the coating on the electrode, which helps flag a less-than-perfect batch.
The cost of a CV is on the higher side, hindering widespread adoption. However, large roasteries, speciality brands and quality labs stand to benefit by consolidating two instruments into one automated and more accurate chemical readout.
As Menon recalls, "In my tenure at the Coffee Board of India in 1985, we introduced the Washed Robusta. There was initial high resistance, but ultimately it helped elevate Indian Robusta to world-class status."
New concepts such as CVs may help push the envelope further.