by Mike Grubbs July 05, 2018

 

 

Coffee brewing methods at the basic level are similar, but if you want to brew an espresso versus a sipping Americana, you may select a different brewing method and device to achieve the best and easiest result. In this part of the series, we will start by providing some background on the basic factors that affect the brewing cycle to help you select a brewing method and make some choices on how to brew your coffee.

There are many different brewing methods and they can all produce good results depending on the type of coffee and the result you are looking for.  They all do basically the same thing: use water as a solvent to extract the soluble components of coffee beans that make what we call coffee. There is a lot of complex chemistry behind the extraction process that we won’t go into here.  We will save the details and science for another article.  There are some basic factors that affect what gets extracted into your cup of coffee.  The various brewing methods provide ways of controlling these factors.  These are the basic variables in brewing coffee:

  1. Dose
  2. Grind Size
  3. Time and Flow
  4. Temperature and Pressure

You will also find that different coffees and roasting levels may also affect the result of the brewing process.  Some brewing methods are more suitable and optimized for specific types of coffee.  This article will get you started and then we encourage you to start experimenting and find your personal best.

Extraction Basics

Brewing coffee is about controlling the process of extracting the right compounds from coffee at the best concentrations while minimizing the compounds or reactions that are undesirable.  The four key factors listed above have a significant impact on this process.

How Much Coffee to Use or "Dosing"

The dose is simply the ratio of coffee to water.  The amount of coffee you use will need to be matched to the brewing method and the desired result.  The dose not change the rate of extraction but it does affect the level of extraction for a specific brewing method assuming the other factors are equal.  A higher dose will yield stronger coffee and a lower dose will yield a lighter brew assuming everything else is the same. 

Coffee should be measured by weight and not volume for dosing since different coffees, roast levels, and grinds have different densities.  That is why we put a scale in the list of things you need to brew great coffee at home.  The water measurement can of course can go either way but some people prefer to do their water by weight as well.  Since water was used as the basis for fluid units and weight units in both English and metric systems, weight and volume is fairly interchangeable.  1 US fluid ounce of water (fl-oz) weighs 1 ounce by weight (oz-wt) and the equivalent in metric units is 29.57 ml = 29.57 gramsThe same is not true for coffee.  1 ounce of coffee by volume does not equal 1 ounce of coffee by weight.

Dosing can be stated in either a ratio like 1:16 (one ounce of coffee by weight for every 16 ounces of water) or by weight/volume like 55g / 1L (55 grams of coffee for every 1 liter of water).  That ratio (55g / L) is called the “Gold Standard” by the Specialty Coffee Association of America and is specified for “cupping” coffees along with a very specific set of other extraction factors.   

Summary: Dosing affects the level of extraction in coffee and will be matched to the brewing method and other extraction factors in the brewing cycle.

Grind size and consistency

Grind size and consistencyare also major factors in the speed and level of extraction.  Grind size determines the total surface area of the coffee exposed to the water.  The finer the grind, the larger the surface area from the same weight of coffee.  This makes sense because with whole beans, the surface area is just the external surface.  As you grind it, all of those surfaces are still there but you open up more internal surface area to water contact.    Fine grinds extract more compounds faster than coarse grinds because there is a lot more coffee surface area.  If the brewing method is such that water is in contact with the coffee longer, such as “steeping”, you will typically use a coarser grind size to slow the extraction.  If the water flow is fast, such as espresso, you will typically use a fine grind so it will extract faster. 

The consistency of the grind size is also very important.   If the grounds have some fines and some coarse then the finer grounds will extract quickly and the coarser grounds will extract more slowly.  This can produce an unusual case of both under and over-extracted coffee in the same brew.  This can be less flavorful (under-extracted) and bitter (over-extracted) at the same time.

Summary:  Grind size and consistency affect the rate and balance of extraction.  The grind size will be matched to the brewing method and consistency is very important.

Time and Flow

The time and flow of water in the brewing process is a major factor affecting the level of extraction.  Some compounds in coffee extract faster than others.  For example, acids are extracted very fast at the beginning of the cycle and some of the more complex aromatic compounds are slower. To provide an example of the effect of each of these on the taste of coffee, one of the characteristics of a coffee taste profile is acidity. Acidity is important to flavor and balance and is usually described as “tartness” and “mouth feel”, but acids also provide important flavor components.  Some of the naturally occurring acids produce citrus and fruit flavors while others are sour and bitter.   Some of the other important compounds in coffee, like aromatic phenols that produce berry and floral notes, are extracted more slowly.  So if the brewing process is too short, the full flavor profile may be under-extracted.  It will also have a higher concentration of sour acids and less of the more aromatic compounds causing it to be less flavorful.  While some people may like sour, especially when combined with sweet, sour and less flavorful is usually not our goal.   However, if the brewing process is too long it may be over-extracted and some compounds or reactions that are less desirable in the flavor profile may cause bitterness.  If you are interested in a bit more background and detail on acidity, read the Science of Brewing notes.

Summary: The rate and length of the brewing process can dramatically change the balance, flavor, and acidity. 

 

 The Science of Brewing: Acidity

 

Coffee beans have natural levels of acidity that are important components of the taste of your brew.  You may already be familiar with some of them like citric acid (citrus flavors like orange and lime).  If you are a flavor aficionado you may know about malic acid (the pleasant tartness in apples and pears) and tartaric acid (found in grapes and wine).  But some acids, like carbonic acid, make coffee taste sour.  The roasting process of coffee embeds carbon dioxide (CO2) in coffee beans. The darker the roast, the higher the level of CO2.  CO2 reacts quickly with water early in the brewing cycle to form carbonic acid which is rather sour and bitter. 

Acids are extracted very quickly in the early stages of the brewing process.  They also lower the pH (a measure of acidity). Our taste organs are very sensitive to even slight changes in acidity.  pH is measured on a scale from 0 to 14 and in taste tests the difference between “best” and “worst” was only 0.3 pH points.  Tiny changes can make a big difference.  

We add lime to unflavored carbonated water (and some beers) to offset the sour carbonic acid taste.  Carbonated water drinks have been “engineered” with flavors to mask or incorporate the sour carbonic acid to create a tasty flavor profile. 

In coffee brewing, the natural flavors in the beans are extracted in the right proportions to achieve a desirable balance of aroma, flavor, level and mix of acidity in the brew.  This balance can be adjusted by changing the various factors affecting extraction in the brewing cycle.  Also see “blooming” in Part 5.  This technique is used to outgas excess CO2 at the beginning of the brewing cycle to reduce carbonic acid.

 

Temperature and Pressure

Temperature and pressure are two other major factors that affect extraction.  Higher temperatures will cause a faster extraction and, at temperatures that are too high, some reactions that alter the chemistry result in characteristics that are undesirable.  However, low temperatures slow extraction and some important flavor producing compounds may be missed at lower temperatures.  Adding pressure (such as in some espresso methods) also increases the rate of extraction and chemical reactions.

Since temperature and pressure affect the rate of both extraction and chemical reactions, rather small changes in temperature can significantly affect the brew. The equivalent of the “Gold Standard” for temperature is 200 degrees Fahrenheit or 93 degrees Centigrade.  To illustrate the sensitivity, varying water temperature 5 degrees in either direction will change the result in ways you can taste.  This is why a thermometer or a temperature controlled water heating method is in the list of required items. 

Summary:  Temperature and pressure affect the rate and level of extraction and change the balance, flavor, and acidity.

Brewing Basics

Now that you know about the major factors that affect the brewing cycle of coffee, it may seem very complicated and that you need to set up a science lab in your kitchen to brew a good cup of coffee.  The good news is that very clever folks have created a variety of brewing methods and devices that let us brew a great cup of coffee with ease and precision without a lab and a PhD in chemistry.  These brewing devices provide ways of controlling the rate and level of extraction without having to know exactly what is going on in the chemistry of extraction and reaction process. They range from hooking up a water supply, pouring in some coffee beans, and pushing a button to much more “hands-on” methods.

Brewing devices range from hands-on pour-overs and presses to push-a-button

Despite the very large array of brewing devices available, there are really just three basic brewing approaches commonly used for home brewed coffee:

  1. Pour and Drip: There many variations but the common characteristic of this type of brewing is that hot water is poured through the coffee grounds at a specific temperature and time. These include: drip coffee makers and various “pour-over” methods.

 

  1. Steeping: Again, there are many variations but they all use a common approach where water is mixed with the ground coffee, allowed time to extract in solution, and then filtered or strained after some period of time. These methods include the French Press and AeroPress.  A very basic form of steeping is also used for “cupping” coffee (official taste testing) to determine the profile and quality of specialty coffees.

 

  1. Espresso: This method forces water and steam through finely ground and compressed coffee under pressure. This produces a more highly concentrated extraction because less water is used in the extraction process. That is why espresso is also used in coffee drinks where it is diluted with something (like milk).

 

There are of course other methods, but most common home brew methods fall into one of these categories.  Cold Brew is a variant of steeping but with a very long extraction time due to the low temperatures used.

Each brewing method has a different level of precision and convenience but all of them can produce a good homebrew.  Each method has specific ways of controlling the extraction process by varying the basic factors: dose, grind, water flow, temperature, and time.   

I wish we could provide a simple and perfect recipe for all these methods but each brewing method is different.  Brewing devices come with instructions, recommendations, and some of them have videos, recipes, and even international competitions with published winning recipes.  I recommend you start with the instructions provided for your brewing device and then make small adjustments to one factor at a time to suite your personal tastes.  Make small adjustments and take notes on what you do so you can reproduce the results.

Filters –The filtering method and material can affect subtle complexity and flavor components. There are three basic types of filtering: Paper, stainless steel mesh, and none.

Paper - Paper filters produce a “brighter” coffee by removing both the particulates and some of the natural oils in the coffee.  You should always rinse the filters prior to brewing to remove any residual chemicals used in the manufacturing process and any aromas that may have been picked up along the way.  Filters are odor magnets in your kitchen so keep them in a sealed bag.

Mesh – The most common mesh filters are made from laser perforated stainless steel.  These are popular because while they filter the particulates, they do not filter out the oils, and they are reusable.  Mesh filtering generally produces coffee with more “body” and a heavier “mouth feel”. 

None - When we do a coffee tasting (“cupping”) we simply pour hot water into a glass or cup containing coarse ground coffee, wait for a bit, break the “crust” (floating grounds and CO2 bubbles), skim off the top, and sip it from a spoon with lots of slurping and air noises, wait for a bit, and do it some more.  That is so that we taste all the components of the coffee at different levels of extraction and temperatures.  That is also related to how my grandfather brewed coffee over a campfire (although it was a bit “chewy”).  None is not for everyone, and not how I usually do my morning cup of coffee, but it is a good way to get everything from the coffee without interference when you are taste testing.

The filter method is purely a matter of personal preference and even mood.  Experiment and discover what you like best with different coffees, food pairings, and even times of the day.

Summary: Coffee brewing involves adjusting and controlling the primary factors that affect extraction and chemical reactions during the brewing process including dose, grind size, time and flow, temperature and pressure, and filtering.  Select a brewing device and method that allows you to control the brewing cycle consistent with your preferences for convenience, time, and precision for a specific coffee and situation.  Experiment and become comfortable with more than one method and select them based on the circumstances.

www.truecoffeecompany.com

 

 


 

Mike Grubbs
Mike Grubbs


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