In home roasting, does the time spent roasting matter, or only the final temperature?

Question

I have a Fresh Roast SR500 home roaster and have had some success roasting mostly drinkable coffee. My first attempts, following the instructions enclosed with the roaster turned out horribly, tasting both charred and grassy at the same time. Yeechh. After doing some online reading, I've greatly lengthened the roasting process with mostly good results. I'm currently roasting batches of 90g of raw beans for between 12-17 minutes. My thinking is that this is giving the beans time for the proper reactions to take place inside the beans without charring the outside. But I've read that some commercial roasters might take 20 minutes or more to roast a batch. Of course they are roasting much larger quantities than I am but it occurred to me that perhaps this longer roasting time is intentional and has some beneficial effect.

I'm mostly aiming for a City or City+ roast level and want to know if lengthening the roast time beyond what I'm currently doing is a good idea? I would still stop the roast soon after First Crack, but I suppose I could stretch out the time to get there if that might produce a better product.

Answer 1

It does matter for a couple of reasons.

Drawing out the roast generally produces more even results.

Slower roasts mean that you have a better chance of stopping the roast at the target level and not over or under roasting.

You can search the online forums for some of the home roasting sites, but many people run their roasters at a higher setting, then turn down the heat once the roasting process is rolling. Some of the more expensive machines even have "roast profiles" preprogrammed to modulate the temperature up and down for desired results.

Personally I think there is a point of diminishing returns between the time dinkering with the roaster and the difference in the taste. Most of my roasting lands in the 15 to 16 minute range and comes out even enough that I feel good about it. I recommend drawing the time out just enough that the results are even enough for you and you are comfortably hitting your target roast level the vast majority of the time.