Exercise 3 - solution

Roasting changes the total caffeine in a bean very little: caffeine is stable up to 200 C and breaks down around 285 C, which roasting rarely reaches. So "much less caffeine" is not true beans-for-beans, by weight.

It is roughly true by volume: darker beans are less dense, so a scoop of dark roast holds less coffee by weight, and therefore somewhat less caffeine, than a scoop of light roast.

To compare fairly, weigh the coffee (for example 20 g of each) instead of measuring scoops.