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As a coffee exporter, we have many green coffee beans to sample, and because we travel around the country a lot, we sadly we don’t always have a coffee roaster on hand. Since anyone here in Peru can get green coffee beans easily and inexpensively, I thought I’d share how we oven roast green beans in any propane fired home oven (all ovens here are propane, natural gas would work better!)
In case you don’t know, coffee leaves the grower in a green state. The bean is full of moisture and quite hard. In this green state, coffee can be properly transported and stored for over a year without significant change to the bean’s flavor profile. However, once roasted the quality of the cup diminishes significantly during the first week. After that, no matter how it is stored you have lost the subtle edges, the wonderful notes, the aroma, and most of the wanted flavor. That is why the specialty roasting business is booming all around the world. Drinkers are getting savvy, buying only a week’s worth of roasted beans at a time, and grinding them daily.
There are many innovative, complicated and more precise ways to roast beans, but this is my simple method. In 40 minutes, I have a week’s worth of coffee (about four pounds), roasted without any burned beans, and very little smoke in the kitchen or the rest of the house! A little bit of coffee smoke smells nice after an hour, but filling the house with lots of smoke is not healthy. So keep your windows open and the doors to other rooms shut.
Home Oven Roasting Green Coffee Beans Instructions:
Preheat oven to 190 degrees Celsius (375 degrees Fahrenheit). Evenly layer green coffee beans in a heavy baking sheet no deeper than 3/4 of an inch. Ensure that the coffee goes right to the edges, and the center is no thicker than the rest. Bake in your oven, and pull out every five minutes to stir, beginning after the first 10 minutes. If you hear a great deal of cracking or popping sounds, this is normal for regular roasting, but might indicate that either your oven is too hot or that you should just go ahead and give it a stir right away. Hearing 10 or so cracks is OK. This low temperature method has minimal cracking and minimal smoke, if you are experiencing great amounts of either reduce the oven temperature. You aren’t going to get anything near what an expert will get, with an expensive roasting machine. However, you also aren’t going to get burnt beans and in the end that will pay off. You will likely be soon having a really good cup of coffee!
Each time you pull the beans out, toss them with a spatula for about 30 seconds, smooth them out evenly again and put them back in the oven without delay. Be sure to dig the spatula all along the bottom, incorporating the sides and the center together.
Many people will tell you that roasting at higher temperatures will yield better results, and that can be true with the proper equipment, but only if you can somehow get all those beans to roast evenly. So this is why we are not roasting at the recommended higher temps. If you and your oven are able to get great results with higher temperature methods, by all means do it. When we are in the presence of a roaster we don’t use this method, so use the best method you can for the circumstances you are presented.
Ideally, let the beans rest (off gas) 12 hours for optimal flavor (I rarely wait, and I brew a cup ASAP). Grind the beans in a coffee grinder or blender (the food processor it too drastic) as needed just prior to brewing. Store the roasted coffee, after de-gassing for 12 hours, in an airtight, light proof, moderate temperature location. Store any ground coffee in the same manner, but use quickly, as grinding the coffee accelerates the degradation of the final cup.