Rosemary wrote:Does the degree of roast affect shelf life? Has this been a factor in the past that has led to the darker roasts being popular? Have the microroasters and their closeness to the consumption point aided the development of the lighter roasts?
I don't know, but my guess is that if anything, lighter roasts may stay aromatic longer, since they have more to start with. On the other hand, the taste may change less on darker roasts as they age.
Dark roasts were the rule in western countries until the beginning of the 20th century. Prior to that, most coffees were fairly low quality naturals, fermented and staled/aged by long sea voyages. Dark roasting was the way to get the funk out of the bean. Light roasts became popular with faster ship transport and the availability of Central American and East African washed coffees. In the US, as quality spiraled downward after the 2nd world war, the roasts stayed light. The first generation of West Coast specialty roasters (Alfred Peet and his trainees) used dark roasts to distinguish themselves. Espresso in the US, outside Italian enclaves, has a West Coast origin, and inherited this dark roast style. The East Coast founders of US Specialty coffee, Don Schoenholdt and George Howell, stayed with the light roasts, but weren't into espresso at all.
I think lighter roasts for US espresso happened almost entirely because of Barista competition, and the success of the Scandinavian countries. Many people who drank high end SOs as brewed coffee always used lighter roasts for these, but, at least on my part, it never occurred to me that these roasts were capable of being used in espresso. Personally, it took me a lot of time to get the required technique. That made knowing there was a payoff to the effort vital for undertaking it.