simonc Ah, you have no doubt searched the internet and found it wanting…there are many problems in the information given on the internet.
- Some sites don’t say if the bean is roasted or not
- some quote per bean, mostly they copy from one another and depending on the source the number varies wildly. Who quotes per bean anyway and then equates it to a beverage, but they’re all copying..
- some sites say there’s less caffeine in darker roasts than lighter ones??? (mystery to me), logic would tell you it’s the other way round, if there is any difference
- some reference to certain drinks (often incorrectly), they don’t define the beverage…
So I will give you the best answer I can, based on my knowledge of coffee and logic and you can see if it fit’s or falls between any of what you read. You need to bear in mind that coffee is an organic product and different varietals, growing condition many have different amounts of caffeine in the bean. The preparation method is likely to affect things as well in the final beverage.
Using a paper from Belitz et al 2009, where they examined the unroasted coffee bean, both Robusta and Arabica types they measured caffeine levels of
- 0.8 to 1.4% of dry weight in Arabica
- 1.7 to 4.0% of dry weight in Robusta
This is quite a variance, so I’m going to suggest using a figure of 1.2% for Arabica and no more than 2% for Robusta as I am have read many papers than don’t show anywhere near double the caffeine in Robusta beverages
Allowing for 15% weight loss during roasting, the fact that caffeine is unaffected by the roasting process, plus the assumptions of 60% solubility in espresso due to contact time and 80% solubility in brewed. All for 12g per 200ml coffee for brewed and 16g of coffee used for espresso.
Arabica 163mg caffiene in the roasted bean approx :
- 97mg espresso
- 115 mg brewed
You can do the math for Robusta yourself, or scale it up and down for different weights of coffee.
