There are more and more people willing to get some brewing tools and brew coffee at home or office since it is very convenient. Today, we would like to introduce the variables of coffee brewing to folks. Once we get familiar with those variables, it will be easier to brew your own cup of coffee at home or office.
To make a cup of coffee, the ingredients are simple: coffee grind and water. And so, the ratio or the recipe of these two could definitely affect the flavour of the coffee extraction. The smaller the ratio is, the higher the concentration, and vice versa. Generally speaking, we would suggest folks use the ratio 1:16, which means to use 16g of the water to extract 1g of coffee. For example, if you would like to make a 250ml of coffee, we would suggest you use 15.6g of the coffee grind. The brew ratio may be adjusted, according to the different origin, different roasting level, the freshness of the coffee beans, personal preference and the coffee culture in different countries. We could find that the variation could be from 1:13 to 1:20.
2. Grind Size
The grind size of coffee beans is an important factor in brewing coffee. Let’s take an example to explain:
There are 2 containers with same size: one with stones and one with marbles. There is a hole at the bottom of each container. If we pour the same volume of water into these containers, which will be faster to get all the water from bottom? Apparently, the water goes through container with stones will be faster. It’s because stones have a bigger particle size, water spends less time to go through.
We can see that the grind size of the coffee beans will affect the speed of extraction, and so the time. If the grind is too coarse, water goes through quickly. The contact surface between grind and water will be too less in getting flavour of the coffee.If the grind is too fine, water needs to spend more time and energy to go through the grind. As a result, It will lead to an over extraction and a bitter flavour.
If we use different brewing tools and methods, the grind size will be different. Take manual brewing as an example: Hario V60, Kalita, Aeropress, Chemex and Clever Coffee Dripper, the grind size will be medium- fine, coarser than table salt; grind size of French press will be quite coarse, it feels like coarse sand or sea salt when you hold it on hands.
3. Brewing Time
The longer the brewing time is, the longer the extraction, and vice versa. For general, using a 2- cup size hand drip dripper will not take over 3 minutes from start to finish. During the bloom process, The coffee grind gets in touch with hot water, the cell wall of coffee particles will open and release the CO2 faster, and therefore expand. This is to get ready for the coming extraction. This blooming process would take from 30- 45 seconds, depends on the situation of the bloom.
Moreover, there are different sizes of the brewing tools, from 1- cup size to 8- cup size. We will change the extraction time according to the sizes of brewing tools. If we use a bigger tool, the coffee grind and water we use will increase. That means the variable will increase as well. As a result, it’s difficult to control the brewing process and the brewing flavour when compare with a smaller brewing tool. Therefore we suggest folks to use a 2-4 cup size brewing tool.
4. Water Temperature
There is an old idiom in Hong Kong: You will get a cup of delicious tea if the water is boiled. But for coffee, it is not enough just to prepare the boiling water. There is something more that we need to pay attention. If we use a 100 degree Celsius of boiling water, it’s pretty sure the cup of coffee we get could be a bit bitter; and if we use the boiling water with less than 80 degree Celsius, the yield that we get may not have enough flavour. Actually, the higher the water temperature is, the higher the extraction rate is, and vice versa. Generally speaking, 90- 96 degree Celsius is a good range of water temperature when we use for hand drip or manual brewing.
To conclude, brew ratio, grind size of the coffee, brewing time and the water temperature are the variables we need to pay attention when making coffee. According to the characteristic, the roast level and the freshness of the green coffee, those variables could be adjusted. There is not necessary to just stick to one guide line. It’s not the matter of right or wrong, but more important is how we find other possibilities , or the best way to say, our cup of tea base on the basic, useful principles. Enjoy your coffee!