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 Roasting coffee transforms the chemical and physical properties of green coffee beans into deliciously caramelized and aromatic roasted coffee products.

more of its "original flavor"  - the flavors created in the bean by the soil and weather conditions in the location where it was grown. Coffee beans from famous regions like Java, Kenya, Hawaiian Kona, and Jamaican Blue Mountain are usually roasted lightly so their signature characteristics dominate the flavor.

As the beans darken to a deep brown, the origin flavors of the bean are eclipsed by the flavors created by the roasting process itself. At darker roasts, the "roast flavor" is so dominant that it can be difficult to distinguish the origin of the beans used in the roast. These roasts are sold by the degree of roast, ranging from "Light Cinnamon Roast" through "Vienna Roast" to "French Roast" and beyond. Many consider that a "full city" roast is a great roast because it is "not too light" and "not too dark".

In the 19th century coffee was usually bought in the form of green beans and roasted in a frying pan. This form of roasting requires much skill to do well, and fell out of favor when vacuum sealing of pre-roasted coffee became possible. Unfortunately, because coffee emits CO₂ for days after roasting, the coffee must be allowed to get slightly stale before it can be vacuum sealed. For this reason two technologies have been employed: pressurized canisters and bags featuring built-in pressure relief valves.

Today home roasting is becoming popular again. Computerized drum roasters are available which simplify home roasting, and some home roasters simply roast in an oven or in air popcorn poppers. Once roasted, coffee loses its flavor quickly. Although some prefer to wait 24 hours after roasting to brew the first cup, all agree that it begins to get off-flavors and bitterness about 1-2 weeks after roasting even under ideal conditions like being stored in an airtight container or de-gassing valve bag.

The Professional Coffee Roasting Process

The coffee roasting process consists essentially of cleaning, roasting, cooling, grinding, and packaging operations. Bags of green coffee beans are hand or machine-opened, dumped into a hopper, and screened to remove debris. The green beans are then weighed and transferred by belt or pneumatic conveyor to storage hoppers. From the storage hoppers, the green beans are conveyed to the roaster. Roasters typically operate at temperatures between 370 and 540 °F (188 and 282 °C), and the beans are roasted for a period of time ranging from a few minutes to about 30 minutes. Roasters are typically horizontal rotating drums that tumble the green coffee beans in a current of hot combustion gases; the roasters operate in either batch or continuous modes and can be indirect- or direct-fired.

Indirect-fired roasters are roasters in which the burner flame does not contact the coffee beans, although the combustion gases from the burner do contact the beans. Direct-fired roasters contact the beans with the burner flame and the combustion gases. At the end of the roasting cycle, water sprays are used to "quench" the beans. Following roasting, the beans are cooled and run through a "destoner". Destoners are air classifiers that remove stones, metal fragments, and other waste not removed during initial screening from the beans. The destoners pneumatically convey the beans to a hopper, where the beans are stabilized and dried (small amounts of water from quenching exist on the surface of the beans). This stabilization process is called equilibration. Following equilibration, the roasted beans are either ground by multi-stage grinders or packaged as whole beans. Roasted whole beans can be considered fresh for up to, but not exceeding one month. Once coffee is ground it is only good for about 24 hours. Unroasted beans boast all of coffee’s acids, protein, and caffeine—but none of its taste. It takes heat to spark the chemical reactions that turn carbohydrates and fats into aromatic oils, burn off moisture and carbon dioxide, and alternately break down and build up acids, unlocking the characteristic coffee flavor.

Darkness

Roasting Coffee at Home

Up until the 20th century, it was more common for at-home coffee drinkers to roast their coffee in their residence than it was to buy pre-roasted coffee. During the 20th century, roasting coffee in the home faded in popularity with the rise of the commercial coffee roasting companies. In recent years home roasting of coffee has seen a revival, and while there may be economic advantage, primarily it is a means for connoisseurs to achieve finer control over the quality and characteristics of their coffee.

Home roasting is the process of buying green coffee beans and roasting them in your own home. Roasting coffee in the home is something that has been practiced for centuries, and has included methods such as heating over fire coals, roasting in cast iron pans, and rotating iron drums over a fire or coal bed. The majority of coffee roasters will agree that once coffee is roasted, it is only good for a maximum of one month.

The roasting process is about as varied as the latte orders you might hear in line every morning. There are easily half a dozen different methods for how to roast coffee beans, each of them with their own merits. Before we get to the methods, there are a few basic requirements for roasting coffee.

Coffee Roasting Requirements

• Generally the beans are roasted at very high temperatures, between 460F and 530F.
• The beans must move around! This is to avoid uneven roasting or worse, burnt beans. Air, stirring and tumbling are common ways to keep the beans on the move.
• When the roasting is done, the beans must be cooled promptly.

How to Roast Coffee - With a Coffee Roaster

There are two types of roasters for home use: fluid bed and drum roasters. Each machine roasts the beans and makes sure they are cooled properly.

Because of the quick heating times of the fluid bed roasters, coffee roasted with this method tends to be more acidic, while drum roasted coffee is often fuller in body. Personal preference will help you choose.

The best home coffee roasters today, using one of these two methods can reproduce and surpass many professionally roasted beans on the market.

Drum Roasters: The drum roaster is a method that relies on the constant movement of the coffee beans. These machines are fairly simple to operate. Often it is simply a matter of loading your fresh beans into the roaster and setting a time. With some experimentation, you'll decide how long you want your beans roasted. Obviously less time for a light roast and longer for dark roast coffee.

Fluid Bed: Fluid bed roasting utilizes air flow instead of bean movement, allowing for substantially faster heating times (hence the acidity). However, the ability to adjust fluid levels, airflow, and time spent in the roaster make fluid bed roasting slightly more adjustable for the home coffee roaster.

How to Roast Coffee - Without a Coffee Roaster

I do not recommend the following methods but wanted to mention them. Espresso uses a very dark roast and if you cross that line, the beans will burn and possibly catch fire. These methods also produce smoke and the smell can radiate through the whole house for days! Never leave roasting beans unattended! If you try these methods, you are on your own!

Popcorn Poppers: A popcorn popper will provide the even air flow and high temperatures needed for a nice clean roast. And it’s fairly simple, merely tossing your green coffee beans into a popcorn popper and keeping a close eye on them. Because this technique uses air to roast, the chaff (outer skin of coffee bean) will come flying out of the popper. You may want to roast outside, if possible. This one can get messy!

Oven Roasting: Another simple method is the use of an oven. Ovens offer ample space, easily controlled temperatures, and efficient venting when experimenting with how to roast coffee. While this method requires patience and careful attention, properly oven roasted coffee beans can have a quality of taste that very few other beans carry. To cool the beans, dump into a metal colander and stir. The chaff of the bean will come off so either stir over a sink or outside.

Frying Pan: How about the frying pan method? If done properly, a frying pan can give you perfectly roasted beans. Because the temperature is never quite as high with stove top pan-frying, you will need to constantly move the beans, never setting the pan down or walking away. To cool the beans, dump into a metal colander and stir. The chaff of the bean will come off so either stir over a sink or outside.

When learning how to roast coffee, there are multiple options, from the oldest in the book – pan frying – to the best home coffee roasters on the market. No matter what you decide though, you’ll be getting coffee that’s fresh and roasted to exactly how you like it.