By definition, this everyday phrase means to “become aware of the realities of a situation, however unpleasant.” For many of us, the reality of a new day does not begin until we have had a cup of coffee, in my case, at least two, before I can start to function. It is nice to know I am not alone: an estimated 2.25 billion cups of coffee are drank across the globe every day, with over 60% of these being consumed in the morning.
So, what is it about coffee, aside from the caffeine boost? What is it about coffee’s flavour and aromas which are so synonymous with awakening the senses? Let’s look at some coffee chemistry and coffee analysis.
Q: What is the chemical formula for “coffee”?
Actually, it all starts with a green coffee bean and some carbohydrates.
The raw coffee bean is at least 50% carbohydrate. When roasted, the carbohydrate’s carbonyl groups react with amino acids in the bean under the Maillard reaction. This network of reactions produce a wide range of compounds across the five flavour notes: woody/smoky, roasty/burnt, caramel/nutty, bouillon and meaty/animal. The next step is caramelization, where starches are broken down into simple sugars, changing the colour of the bean and developing the flavour. Caffeol oil is released, an umbrella term for the coffee aromas we all know and love.
Coffee chemistry is complex, but the origins begin with coffee carbohydrates. Analysis of these can be used to profile your coffee and test its authenticity. The AOAC (Association of Analytical Chemistry) Official Method 993.5 details the analysis of coffee carbohydrates in extracts and products by Ion Chromatography using high performance anion exchange with pulsed amporemetric detection (HPAE-PAD), the ideal technique for sugar analysis. As we like our coffee “to go”, faster IC methods have been developed and you can learn about the comparison of the two methods in this application note also discussed in this video from the AOAC Annual Meeting 2016.
Skinny malate or double shot of quinate?
It’s true, we love coffee! In the UK alone, the number of coffee shops has doubled in the last decade and estimates are 1 coffee shop for every 3000 people, rising every year. Why so many? What are the differences and why do we all have our preferences? The answer may well lie in the profile of inorganic and organic acids.
Like what you are learning?
The two most commonly cultivated coffee plants are Coffea Arabica (Arabica) and Coffea canephora (referred to as Robusta). Arabica accounts for 75-80% of the world’s production. It contains more sugar making it a more aromatic brew and the connoisseur’s choice, but is more expensive as it is difficult to farm and sensitive to insects thanks to its lower Chlorogenic acid content. Robusta has higher caffeine content, making it more bitter in taste, but is easier to cultivate and gives higher yields. This makes Robusta a cheaper option and is more likely to be found in your jar of instant or is often blended with Arabica to make a more cost effective product.
Inorganic and organic acids give brewed coffee its acidity with each coffee type having a different profile. Organic acids such as malic, quinic, acetic, formic and citric determined by Ion Chromatography allows us to understand the maturity of the bean and also the extent of roasting. As volatile compounds, their concentrations are decreased during the roasting process, so if you prefer a darker roast then it will be less acidic. A mature fruit will have a higher malate concentration, with immature fruits being higher in quinate. If decaffeinated coffee is your choice, then your preference is for a lower quinate, malate, citrate and lactate concentration as determined in Application Brief 135.Something to think about next time you‘re queuing in the coffee shop.