Coffee bean preparation
I worked as a professional coffee scientist for several years and sometimes people ask me for coffee advice. I’ll briefly share some tips here. We’ll go over the process of coffee-making, from start to finish. There are four main parts: bean quality, storage, preparation, and brewing. For the best cup of coffee, you want the freshest coffee beans, ground right before you brew them, using the best water temperature.
First, the quality of your beans affects the flavor of the cup. Unfortunately you can’t tell what quality of beans you are getting unless you buy green beans and roast them yourself. If you are buying pre-roasted beans you have to trust that you are getting what you paid for.
What do I mean by quality? Coffee is a commodity and traded based on the quality of the green beans.Each lot of coffee starts with a perfect score and points are removed for visual defects (e.g., insect damage, broken beans) and flavor defects like sour, moldy, or rancid beans. No one would sell a cup made from bad tasting beans, but some companies blend the bad tasting beans in with good tasting beans so that no one will notice. Even if they coffee does not taste bad, it does not taste as good as it would otherwise. In general, you are going to get average coffee since most coffee available on the market (85% to 90%) is of average quality. If you like your regular coffee you can save some money by staying at mainstream quality. If you find your coffee lacking try drinking a more premium quality bean, whether you buy and roast it yourself or you buy it from a company you trust.
For the best quality coffee, you need to have fresh beans. Once you roast your coffee the oils will start to go rancid. What does this mean? The wonderful roasted coffee aroma breaks down and goes away leaving you with a stale bland cuphe only way to get around this problem is to buy and consume your coffee as quickly as possible. Buying the highest quality beans and letting them go stale is a waste of money and could be worse than buying lower-quality beans that you consume quickly. Only buy as much coffee as you can drink in about two weeks.
What causes your coffee to go stale?
- Oxygen. Oxygen in air causes the oils in coffee to rancid. Most sellers seal their coffee under Nitrogen and add a one way valve to keep the package from blowing up like a balloon. This allows them to pack the coffee immediately after roasting, while it’s still off-gassing, minimizing the amount of oxygen in the package. Unfortunately, this isn’t a perfect solution. The valve lets out the aroma and there is always some residual oxygen that will slowly make your coffee go stale.
- Light. There is a reason no one sells coffee in clear containers, other than the bulk bins at supermarkets. Not only is the coffee open to the air, but it is exposed to light. Light breaks down oils in coffee making them go rancid. On top of that some stores don’t clean the bins so you have old oil that gets rubbed onto the fresh coffee. Stay away from buying coffee in bulk bins, since you have no idea how long it’s been sitting there, UNLESS you know for a fact that the coffee is freshly roasted.
- Moisture. The more moisture in your coffee the faster the coffee will go stale. Plus, water is used as a cheap filler. Who wants to pay top dollar for water instead of coffee? While you can’t check the moisture content of your coffee without lab equipment, in general, cheaper coffee contains more water. Also, the longer your coffee sits around in your cupboard (or the fridge), the more moisture it will pick up from the air. Store your coffee in a dark, dry environment, ideally with no oxygen.
- Cleanliness. Regularly clean your brewer and other equipment. Coffee residue on your brewing equipment will get stale the same way old coffee will and this will affect the flavor of your brew. If you are not cleaning your brewer regularly, you will be contaminate your new brews with old coffee.
- Grind Size. The larger the surface area to volume the faster your coffee will go stale. Another way to put this is once you grind coffee you speed up how fast it will go stale. The best thing to do is to buy whole beans and grind them immediately before brewing for the freshest cup. If you don’t think it matters try an experiment where you grind coffee, let it sit a week, a day, an hour, or a few minutes, and grind some fresh beans. Brew all of them and compare the flavor. If you are not sure what size you should grind to it varies based on the brew method. For best results use a high quality burr grinder, but any burr grinder is better than a blade grinder. A blade grinder cuts the coffee, heats it up more, and gives an uneven grind.
- Water. If your water doesn’t taste good enough to drink straight from the tap, don’t brew coffee with it. Whether you use hard, soft, or distilled water affects the flavor because of the minerals, salts, or the lack thereof. Filtered, cold water is considered the best for coffee flavor. If you are not sure what tastes best experiment with your tap water vs. filtered to see which one you like best.
- Time & Temperature. One of the most important things about choosing your brew method is the water temperature, followed by the extraction time (how long the water touches the coffee). The best temperature is between 195 – 205 degrees Fahrenheit. If the water is too cold, the coffee will taste flat. If the water is too hot, it extracts bitter flavors that you don’t want. The ideal time depends on the equipment you are using–too short and you don’t get all the nice flavor and too long and you get the bitter flavors. Aim for a happy medium ~2-6 minutes.
- Coffee Quantity. The standard amount of coffee is one to two tablespoons per cup (177 ml or 6 oz). Once you find the amount you like, try using a scale for more consistency. Coffee is measured as 6 oz. per cup instead of 8 oz. for historical reasons, back when people used to drink smaller cups.