IF I’M A HOME ROASTER

 

ROASTING ISN’T ROCKET SCIENCE. IT IS MUCH, MUCH EASIER. IN FACT, IT IS SO EASY THAT ANYONE CAN DO IT, EVEN AT HOME. WHILE HOME ROASTING IS VERY SIMILAR TO WHAT TRANSPIRES IN A COMMERCIAL ROASTERY, THERE ARE A FEW EXTRA TIDBITS THAT MAY BE HANDY TO KNOW IF YOU INTEND TO TAKE YOUR COFFEE HABIT TO THE NEXT LEVEL. BOTH INVOLVE THE TWO ESSENTIAL ITEMS YOU NEED TO MAKE IT HAPPEN: GREEN COFFEE AND A ROASTER.

Acquiring green coffee is pretty easy these days. If you were to walk into a roastery and ask them to sell you small amounts of green coffee, they most likely would do so. There are also a number of different online retailers that will sell you green coffee for home roasting. What really matters with green coffee is storage. While it can be a stable product, with the ability to last relatively unchanged for well over a year after harvesting, it must be stored properly. 

Basically, this means green coffee must be kept dry and at a cozy temperature. If the humidity is high, the coffee will absorb moisture. If it absorbs enough moisture, microorganisms may start chomping on it and growing, running the risk of ruining the coffee. Higher moisture contents may also facilitate natural degradation of the green bean, as will storing the coffee at temperatures that are too warm.

When green coffee doesn’t age well and it isn’t caused by mold, it develops a flavor known in the industry as “baggy”. It got this name because for most of recent coffee history, green coffee has been stored in jute bags and the baggy flavor tends to be woody/cardboard/grassy, not so unlike the way we imagine jute might taste. 

Fortunately, storing small amounts of green coffee properly in your home is simple. If the climate in your home is controlled throughout the year to make you comfortable (i.e., you use air conditioning and heating), then the coffee will likely stay fresh for many months, even for more than a year, assuming you don’t store it, say, next to the shower. If the conditions aren’t that controlled, then merely keeping the coffee in airtight containers (plastic, glass, or metal) will also do the trick. 

There’s also anecdotal evidence that storing coffee in the freezer is an excellent way of preserving it with no known side effects (while crystal formation doesn’t seem to be a problem, the same risks that apply to storing roasted coffee in the freezer would apply to green coffee, as well). 

Once you’ve got the green bean storage situation figured out, all you need is something with which to roast them! As a home roaster, you will be constrained by the tools available, thus, don’t expect to be manipulating the roast profile too much; home roasting machines aren’t as sophisticated as commercial machines. 

This isn’t to say you can’t create an excellent coffee at home, just that you may not get to explore the finer points of roasting too much. You can roast coffee with pretty much any tool you have that will transfer heat to the coffee. Most people start roasting coffee at home the way it is typically done in Ethiopia— on a skillet or other heated pan. 

This works, but roasting the beans evenly is very tricky, even with constant stirring. Other people start with hot air popcorn poppers. They hold only a small amount of coffee but hot air is a very efficient way of transferring heat to coffee. Commercial air roasters do exist, but they are much less popular than drum roasters, which are just large, metal cylinders that are heated externally and transfer the heat through the drum. If home roasting becomes a bigger part of your life, you can purchase an actual home roaster. 

There are several different types available, each with its own pros and cons. Both air and drum roasters are manufactured. Of course, if you like to work with your hands, you can always just build your own home roaster!

A DARKER ROASTED COFFEE? DO DARKER ROASTS HAVE LESS CAFFEINE?

 

The answer, unfortunately, is not clear. The available data are all over the place. Some research shows that the concentration of caffeine increases with darker roasts while other research shows that it decreases. Some research even shows no changes at all! What are we to make of all this—how can we see completely opposite patterns with something that seems so cut and dry? If we consider what we know about roasting and add to it some details of how caffeine behaves in the universe, we might be able to guess at the answers. 

As coffee is roasted longer and darker, it loses mass: gaseous molecules are created during roasting and they leave the bean. Longer roast times produce more gases, which mean lower weights. Some molecules in the beans, however, don’t change at all during roasting. Consequently, as roast levels darken, these static compounds increase in concentration. We can demonstrate this with an example using mythical compound q. Let’s say the concentration of q in the unroasted bean was 5 parts q to 100 parts bean. 

In a light roast, some of the bean vaporizes leaving only 85 parts bean but q stays the same. So, now the concentration is 5 q/85 bean. If the roast darkens a lot, the bean may only have 75 parts left, making q much more concentrated merely because it could tolerate the heat! This behavior would certainly help explain how the concentration of caffeine increases in darker roasts. Its actual content remains constant while lots of stuff around it is leaving. If this were always the case, then we’d always see an increase in caffeine concentration with darker roasts. But, that’s not what we find. Caffeine seems to be a fairly stable molecule in coffee. In other words, it doesn’t seem to combine or interact with other molecules, though there isn’t any research exploring whether this is true or not. 

However, it does have a quirky trait whereby it tends to not obey the typical transition steps between phase changes. So, instead of changing from a solid to a liquid to a gas, it often skips the liquid phase and turns directly into a gas, a process called sublimation. Sublimation for caffeine can begin at 178°C (352°F). While it is very difficult to measure the actual internal bean temperature during roasting, it is simple to measure the temperature of the mass of beans, which is probably near the temperature inside a bean. 

As most roasts easily exceed bean mass temperatures of 215°C (419°F) and can go as high as 235°C (455°F), it is perfectly reasonable to suspect that some caffeine in the bean sublimates and drifts away from the bean. If this happens, then it explains the caffeine decrease as roasts become darker. In fact, some research does indeed show that total caffeine content decreases with darker roasts. 

What about the data that demonstrated no change in caffeine concentration in either direction? Well, it is possible that both of those phenomena occurred simultaneously at just the right levels as to maintain a constant caffeine concentration. I don’t think it is that straightforward, though. 

There are several reports where beans were processed differently or were of different quality grades and their caffeine contents were different. This suggests that some kind of interaction between caffeine and biological and/or chemical processes exists. The effect of this interaction may be the unpredictability of how caffeine behaves during the roasting process. At the end of the day, all this discussion of how the caffeine concentration is changing is probably moot. In all cases, the changes in concentration are pretty small, amounting to 0.1 percent or less of a difference from the lightest to the darkest roast.

 Thus, in a practical, real-world sense, on a per-cup basis, the amount of caffeine in a cup produced from a very light roast compared to that of a cup produced from a very dark roast is pretty small. It is so small, in fact, that a person who drinks a cup of coffee a day would probably experience no physiological difference between the two cups based upon their caffeine content! 

HOW IS COFFEE DECAFFEINATED?

MORE THAN A FEW PEOPLE OUT THERE CAN’T FUNCTION WITHOUT A CUP OF COFFEE A DAY, IF NOT TWO OR THREE CUPS. MOST COFFEE DRINKERS NOT ONLY RELY ON THE CAFFEINE IN COFFEE BUT THEY RELISH THE ENERGY AND AWARENESS IT BRINGS. HOWEVER, THERE’S A DEDICATED GROUP OF DRINKERS WHO EITHER DON’T WANT THE CAFFEINE OR PHYSICALLY CAN’T TOLERATE IT. SO, THEY DRINK COFFEE FROM WHICH THE CAFFEINE HAS BEEN REMOVED.

As of now, there are no arabica varieties in cultivation with caffeine content that 68 meets international standards for what constitutes decaffeinated coffee. Thus, all decaf coffee comes from manually removing it from ordinary coffee. There are four commonly used solvents for doing this: methylene chloride, ethyl acetate, carbon dioxide, and water. No matter which solvent is used, the beginning of the process is the same. Green coffee beans are steamed or soaked in water to make the caffeine more available to the solvents and to make it easier for the solvents to penetrate the beans. From here, two main pathways exist: direct solvent extraction or indirect extraction. 

In direct extraction, where methylene chloride and ethyl acetate are used, the wet green beans are treated directly with the solvent for some eight to twelve hours. Then, the solvent is removed and the beans are steamed (to help drive off any remaining solvent) and dried before roasting. Unfortunately, these solvents don’t extract just caffeine. Thus, other compounds, which may be related to quality, may also be extracted. This is one reason why decaf has a historically bad reputation for quality (the other reason is that low quality coffees were often used: junk in, junk out). 

Carbon dioxide is a terrible solvent for caffeine under normal conditions as the solubility of caffeine in it is low. This is not surprising, as carbon dioxide is a gas at room temperature! However, if carbon dioxide is taken to its supercritical state— where it has liquid and gaslike properties simultaneously—it improves, and if a bit of water is added, it becomes much better. To take carbon dioxide to its supercritical point requires special equipment to significantly increase temperature and pressure. The great benefit is that supercritical carbon dioxide seems to selectively extract caffeine and not much else. 

The indirect method allows for water to be the only solvent in direct contact with the beans. Water can be used to extract the caffeine and other compounds and then the water solution is treated with a solvent or passed through a filter to remove the caffeine, pulling it away from the beans. The other compounds can then be returned to the coffee beans before drying them down. When water is the only solvent used, a clever trick is employed to prevent compounds other than caffeine from being removed. 

The process begins with soaking the wet green beans with water and then removing the caffeine from the solution, as in the indirect method. Then, the beans are discarded! The solution, sans caffeine but with the other stuff, is then the solvent used to extract the caffeine from the next batch of coffee. Doing it this way means very little noncaffeine material is extracted by the solvent. Now, nothing has to be returned to the coffee and it is believed that the end result tastes better. 

There will always be a place for decaf coffee, as there will always be someone who loves the taste of the coffee at all hours of the day but doesn’t want to deal with the physiological effects of the caffeine. Modern decaffeinated coffees can have excellent quality. Like all technology, the methods for removing caffeine are continuously improving. Thus, expect the quality to improve even more. “I was taken by the power that savoring a simple cup of cof ee can have to connect people and create community.”

Raspberry Coffee Recipe

Take a well-deserved break day or night and spoil yourself with a raspberry infused coffee. 

Makes: 6 

Preparation Time: 5mins 

Total Prep Time: 5mins

Instructions: 

1. Put the ground coffee along with the brown sugar in the brew basket filter of your coffee making machine. 

2. Add the raspberry extract to the empty coffee making machine. 

3. Pour in the necessary amount of water and brew according to the manufacturer’s instructions. 

4. When brewed, pour the coffee into your favorite mug, sweeten with sugar to taste and garnish with whipped cream.