Schoolboy Chemistry Lesson Part 1 September 18 2017
Which brew method has the highest concentration of caffeine?
My son Henry is in his second year studying A level chemistry, something I can claim much interest, alas not a huge degree of personal success (I scraped a pass -- just!). Over the dinner table, he mentioned that he had to pose a chemistry question and then design an experiment to get some answers. I was delighted to hear he wanted to do something with caffeine!
This is Henry hoovering under our 1 tonne Probat roaster while an under-qualified forklift driver (thats me) lifts it into position in the new Dusty Ape roastery, so we can be relieved it's a not a physics experiment that's required here.
The budding chemist suggested getting some supermarket brands to test relative caffeine levels in but I explained that no sub-standard coffee would be coming through these doors, besides which most supermarket declare little more than a country of origin. Latching onto this, he then suggested that different producer countries where compared. We quickly dismissed this given that, even amongst similar arabicas -- varietal, processing, geography and environmental conditions - particularly plantation altitude - play a significant role in caffeine content. High quality coffees, typically higher grown for flavour characteristics produce lower levels of caffeine since they are less prone to pests at higher altitudes.
Selfishly thinking of Dusty Ape's customer I suggested he analyse the impact brew method has on caffeine in the cup. We agreed to look at 3 of the most popular brew methods: cafetière, V60 (filter) and espresso. Of course, each method has different brew ratio (coffee:water), but starting with the same dry weight, using best practice guidelines for each method (as in a speciality coffee house) - the question is which would have the highest concentration of caffeine?
The method is being written up over the next few days, and Henry has kindly agreed we can share here when complete. There have been a number of interesting challenges to overcome in terms of restrictions on dangerous substances in school labs and lack of accurate scales (somewhere between 50 - 175mg of caffeine per sample), but I'll save the detail until the method is published.
Preparation of the test samples has now been concluded. I'll cover each of the brew methods next.