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Homeroasting Chapter 2

Written by colin newell

Home Coffee Roasting Chapter 2 - The Bean basics -

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I have been roasting coffee, on and off, for over 10 years. More off than on lately I must admit.

I am not entirely sure what happened to my enthusiasm for roasting very small quantities of the little green bean.

I think roasting my weight in green coffee, one afternoon, at Every Day Gourmet Coffee Roastery may have had something to do with it. At least a small part anyway. I mean, after you have driven the big rigs, it is hard to get back on the Tonka Toy version of coffee roasting. Seriously.

Now far be it for me to diss a legitimate learning method in the world of specialty coffee. Because I am not. Honest, I am not. I will be the first to admit the rush I felt when I first saw green beans transformed into the chocolate brown nuggets we know and love today. Unless you witness this process first hand, or over the shoulder of a master roaster... even if it is at a small cafe roastery or Whole Foods store, you will not completely get it - if you know what I mean.

So. What of the home roasting process as a home hobby? Well, like many men (and women) of hobby obsession age (I know, this only really applies to men!), my introduction to home roasted coffee was a gradual and tantalizing one. I approach every other hobby(and I have many), by stalking my prey through the underbrush of reading... reading every book on the subject available for the aspiring home roaster. I read Corby Kummers "Joy of Coffee" as well as others. I camped out on the USENET newsgroup, alt-coffee - where all coffee experts are born!

Coffee is a very complex subject involving some pretty mind bending food chemistry. So do not short change yourself by not being informed as to what is taking place during the roasting process. Read!

So back to the books for a moment. There is only one really good book for the home roaster. (Hello Kenneth Davids!)

Yea. His book. Kenneth Davids is one of the first coffee authors for me when I really started to take this coffee fascination seriously. His roasting compendium: Home Coffee Roasting: Romance and Revival is required reading for anyone remotely interested in approaching this age-old domestic task -- with at least a little caution in mind and an interest in avoiding some of the pitfalls

Anyway. Kenneth and one or two timely internet resources got me modifying one particular model of a home corn popper - a unit that set me back all of 14$ at a local small appliance general store. As I recall, the modifications called for one specific Taylor thermometer which I mounted according to the attached photo.

Voila! I was now a home roaster. But wait, there are more details... much more it would turn out.

There are a couple of things about home roasting and green coffee that most newbies are not aware of.
Coffee roasting, of any quantity of green bean, is a smokey and messy business.
Two things:

Roasting smoke
Chaff

Roasting coffee produces smoke and fumes and lots of both. You would not think 4 ounces of green coffee could be disruptive to the community around you - but it is. The smell, which starts somewhat grassy, slowly evolving into something reminiscent of toast, then dark toast, then burning toast and then, well... you get the idea.

Roasting coffee does not smell like coffee. At least, right away that is.
Roasting coffee makes the environment in which the coffee is roasted, smell like coffee for days.
And you might think you will like that smell 24/7 but trust me, you won't.
And neither will your spouse, family, house pets or neighbors.

a modified home roaster gadget

Coffee is one of the World's most recognizable smells... and one of the most cloying.

Hence there is only one solution to the smell dilemma: Build a roasting shack. Or use the garage. Or the Balcony. The outdoors is the very best place for roasting smoke. Keep in mind that home-roasting requires an ambient temperature of at least 60 degrees (F). Roast coffee in a cold environment and risk pre-maturely burning out your home roaster.

Now about the Chaff: What is it? Chaff is the silverskin that remains after green coffee is dried and de-hulled.
Lighter than the finest onion-skin, chaff is released from the green coffee bean as it is roasted. It floats. It floats everywhere. Thank-fully, some of the homeroasting units available today have chaff collection gizmos - that hopefully work. The chaff collection on my Hearthware roaster worked like a charm. In professional roasters, there is a chaff collector built into the system. It has to be emptied regularly and must not collect into the roaster drum or air column proper because it poses a fire hazard.

Did I mention that roasting coffee creates a fire hazard? When roasting coffee, the temperature of the beans approach upwards of 470 degrees (at the extreme end of the dark roast) and this is what we call in the fire prevention business - Flash point. Now for some science-guy talk:

Coffee roasting is a chemical process by which aromatics, acids, and other flavor components are either created, balanced, or altered in a way that should augment the flavor, acidity, aftertaste and body of the coffee as desired by the roaster.The first stage of roasting is endothermic (beans absorb heat), where the green beans are slowly dried to become a yellow color and the beans begin to smell like toast or popcorn.

The second step, often called the first crack, occurs at approximately 205 °C (400 °F) in which the bean doubles in size, becomes a light brown color, and experiences a weight loss of approximately 5 %.

In the next step the temperature rises from 205 °C to approximately 220 °C, the color changes from light brown to medium brown (Agtron # 60-50), and a weight loss of approximately 13% occurs (Davids, Roasting, 68). The resulting chemical process is called pyrolysis and is characterized by a change in the chemical composition of the bean as well as a release of CO2.

The second step is followed by a short endothermic period, which is followed by another exothermic (beans release heat) step called the second crack. This second pyrolysis occurs between 225-230°C, and the roast color is defined as medium-dark brown. The second pop is much quicker sounding and the beans take on an oily sheen. Roasting well into the second pop or darker is not favorable since volatile aromatic compounds are stripped off and oils on the outside of the bean are more easily oxidized. Unfortunately, in America the trend is to roast to a dark black, with a bright-shiny surface, and a final temperature of 240°C. This type of roast is often preferred since it masks poor blending, dirty machines, and stale coffee. --full article

Still awake? Thought I lost you there for a moment. Bottom line here is - there is a lot of time tested science with coffee roasting - 500+ years actually. Anyway, it will not take that long to teach you the basics. So...

In the next chapter we focus on the facts and fiction of home coffee roasting - Roasting your first beans!

Colin Newell lives and works in Victoria, B.C. Canada - His website, CoffeeCrew.Com is Canada original resource for the coffee lover.

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