Popcorn Popper roast vs crema
I have recently begun home roasting using popcorn poppers. I love the whole process and the fact that it is considerably cheaper. I have been noticing lately though, that my latte art has taken a turn for the worst. I could previously pour decent hearts and monks heads using freshly roasted PURCHASED beans. However, since switching to my home roasted beans, the crema required to pour designs is lacking. Does the nature of popcorn popper roasting cause issues with crema production? I will purchase 250g of beans this weekend and test my theory...
Any info is appreciated. Thankyou in advance for your time and knowledge!
Hello Ben, I'm a little surprised that some of our more experienced roasters have not chipped in here. I'm not nearly as well qualified as many others on CS, but since no-one else has replied, here's my two cents worth.
I have not noticed much difference between my popper roasts and commercial beans when comparing the crema. The amount of crema I get seems to depend more on the freshness of the beans, the dose/tamp/grind, and the pressure of the pour. The colour of the crema varies a little with the depth of the roast.
I roast with poppers, but mine are heavily modified, so my profiles are not the short steep profiles that one would get with a stock standard popper. It may be that a short fast roast doesn't allow the development needed to produce lots of good crema. However, this is pure conjecture on my part, I really don't know if this is the case, or not.
With winter on the way you should be able to stretch your roasts out a bit more, so if time is a factor you may see a difference as the weather cools.
I'm currently brewing most of my coffees on manual lever machines. They produce a bit less crema than my pump driven machine, but I see no less with my own beans than those from professional roasters.
I would be interested to hear the result of your trial with a bag of bought beans, and whether you get better results if you are able to slow your roasts down a bit. I can tell you that it will definitely improve the flavour, even if it doesn't help the crema.
I reckon deegee is on the money - in standard form a popper gives a pretty 'light n fast' roast, where stretching them out can help to build the body and possibly maintain /protect the oils and sugars? This could explain the lack of crema and body. Could also be that you are roasting lighter than commercial beans? A darker roast would also give you a darker crema…?
I'm actually at a bit of a loss to explain what might be going on as we really don't have enough information. If you could give us some idea of the profile - Time to 1st-Crack, time to 2nd-Crack and/or when dumped and cooled; the finished colour, the presence or not of any surface oil, how long have you rested the beans, etc and any other information related to your roasts that might be relevant....
Without some basic info such as this, we're only guessing...
The length of the roast definately sounds like the culprit. Theres a good article by Illy & Navarini in 2011 that outlines what is known about crema ("Neglected food bubbles: the espresso coffee foam").
I haven't read it in a while but the most important factor seemed to be carbon dioxide formed during roasting - perhaps a short roast doesn't provide enough time to develop the inside of the beans? If you had a freshly roasted commercial bag for comparison you could observe how much degassing occurs?
Modding your popper or moving to a corretto should help the quality of your roast regardless