BETTER BREW COFFEE

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Understand Strength, Extraction Yield and Taste to improve your Home Brew

Can you define what makes your home brewed coffee any good? 

Do you know what you like about it and how to repeat it? Can you define what you don’t like about it, and what to change the next time?

Understanding your brew in specific ways will help you make better coffee. Brewing blindly will doom you to repeated the bad brews. 

Here are some coffee concepts that helped me better understand my own brewing methods and results.  

Think about Coffee as a Solution

Coffee, the drink, is a solution. A “solution” is a liquid mixture that has a soluble substance mixed into the main solvent. Coffee is mixed into water to make a coffee flavoured solution. 

That “solution” has characteristics. 

The solution can have a strength that is defined by how much coffee was dissolved into the water. 

The solution can have a yield that is defined by how much drinkable coffee comes out of the process. That is, how much black coffee do you end up with after discarding the grounds. 

The solution can have a taste. It will be more or less like coffee, but with some flavours as well. 

All of these characteristics can be optimised to improve your brew. We’ll explore coffee strength, extraction yield and flavour along with their relationships and some tips to optimise your coffee. 

Note: for this article, I am strictly referring to brewed coffee (immersion or percolated) in the examples and not espresso. However, the basic concepts still apply. 

Improving the Strength of your Brewed Coffee

The generic definition of strength is as “the potency or degree of concentration of a drug, chemical, or drink”.

When brewing, you would take coffee grounds and saturate them with water. Parts of those coffee grounds are solid, they end up in the trash later. But some parts of them are soluble. Those parts will dissolve in the water. The strength of the coffee is determined by how much soluble coffee dissolves into the water. 

The concentration of dissolved coffee in the water defines how strong your brewed coffee is. 

More dissolve coffee into a certain volume of water results in a stronger brew. 

The total amount of dissolved coffee in the brew is a concept used by coffee professionals to understand and test their coffees and espressos to confirm if it falls within the known acceptable parameters for strength. Let’s get a little science-y now. 

Professionals refer to this as Total Dissolved Solids, abbreviated to TDS and measured in percentage. Generically it is a term referring to the amount of inorganic and organic substances that are dissolved in a liquid, and therefore become a part of the solution. 

For coffee, when the coffee grounds are immersed in water, the soluble parts of the coffee grounds that come into contact with the water eventually dissolve. The solids that dissolve will accumulate in the water is measurable (the TDS of the coffee) and if you can measure it and interpret the reading it can influence and improve your coffee making process. 

I came across coffee TDS many times when researching to improve the coffee I was brewing. I initially struggled with the concept. When I finally understood it and how to apply it to my brew, I found it very helpful.

Professionals use expensive refractometers to measure the TDS of their espressos and brews. 

That reading is a percentage (the % of coffee in the solution) and is compared to acceptable norms for coffee strength, typically between 1% and 2%.  

For the home brewer, we don’t need to invest in such expensive testing devices to help us use the TDS concept. Having an understanding of TDS can influence your brewing practices, help you better describe your coffee and improve your brews in general. 

Simply put:

  • More coffee dissolved in the water = stronger, higher TDS

  • Less coffee dissolved in the water = weaker, lower TDS

Summary: the ratio of coffee to water influences the strength


How do you change the strength of the coffee-water solution? You adjust the ratio of coffee to water for the brew. When you do that you change how much coffee dissolves into the water. 

Here is an example, using a standard 250g of water for the brew.

Option 1 - 250 grams of water added to coffee dose of 15 grams of coffee results in a ratio of 16.6 grams of water for every 1 gram of coffee.

Option 2 - 250 grams of water added to coffee dose of 10 grams results in a ratio of 25 grams of water for every 1 gram of coffee.

The brew in option 1 has less water for every gram, meaning there is more coffee going into the brew. More coffee means more brew strength.

The brew in option 2 is the weaker brew. Less coffee into the solution means a weaker brew strength.

Changing the brew time can also affect strength. More time in the water means that more parts of the coffee grounds are exposed to the water, and the water will have extra time to dissolve soluble parts so a 2-minute brew will be weaker than a 4-minute brew (of the same ratio).  

One last option is the grind size. If the water can get to more coffee grounds, in the time it has, it can dissolve more. One way of using the same weight of coffee but getting more contact with the grinds is by adjusting your grind setting. Finer grinds mean the water has more contact with dissolvable coffee. 

Here’s a simple graphic to represent this.


Typically, the percentage of dissolved coffee in a brew ranges from 1% to 2%. So that means you are drinking 98% water… That's coffee. 

I’m going to use an analogy here:

Say you are making a class of juice using a juice concentrate. You add the juice concentrate to a glass of water. You add a specific amount to get an end result that is a juice of your desired strength. That would be a specific ratio of juice concentrate to water. More juice concentrate added to that same amount of water will result in a stronger juice… less concentrate will result in a weaker juice.

But let’s say you froze the concentrate into ice cubes. You take the same amount of water as mentioned above and you start dropping the juice cubes in, but it’s the same amount of concentrate you wanted in the example above. You start drinking immediately. The frozen concentrate has not dissolved from its solid state yet, so the juice solution is weak. You are drinking more water than juice, so it is a less concentrated juice solution. Give the water time to dissolve the iced cubes and then you’ll get the strength you want. Or, make smaller iced cubes of concentrate, giving the water more surface area to work with and it will dissolve the smaller cubes faster. 

Simply, if you adjust the coffee dose, the brew time and the grind size, in an informed way you can adjust the strength of the final brew. 

But how do you know what strength you want? That’s up to your personal taste. So, taste your coffee and think about it. 

When you drink your coffee, you need to be able to describe what you’re tasting. 

  • Words used to describe weak coffee include: watered down, watery, thin, empty.

  • Words used to describe strong coffee include: heavy, “too much”, overwhelming. 

  • Words used to describe regular strength coffee include: rich, full, full bodied, creamy. 

Think about this when you are tasting your coffee. Does it help you diagnose the strength?

Yielding the Right Amount of Coffee

When you mix your coffee grounds in water, you’re doing it to get a certain about of drinkable coffee out. The coffee you get out is known as the extraction yield. 

Again, extraction yield is a way of saying how much drinkable coffee did you get out of your brew. So, if you get 200 grams of brewed coffee (the actual yield), with a TDS of 1.5% (let’s call it regular strength since we don’t have refractometers), using a coffee dose of 15 grams, then the Extraction Yield is 20%.

Is this a calculation you’ll ever need to do when brewing? The answer is no. That’s because you will never know the TDS without a refractometer. But what I’m getting at, is that many people have studied this and found plotting the Extraction Yield against the TDS can lead you to adjust your brew in a way that results in an extraction sweet spot. That sweet spot is a cup of coffee at the right strength and good yield. 

The target Extraction Yield (in %) is said to be between 18% and 22% for brewed coffee. If your brew is in that range of yield then your flavour will have the potential to be well developed.  

Here’s a simple graphic to represent this.

But yield alone does not make the coffee taste good. 

Let’s say you did want to determine the ideal extraction yield of you brew, here’s the equation:

As you can see, there is a relationship between strength and yield, and you need to aim to get both into their respective sweet spots by adjusting the ratio.

Tasting for Strength, Flavour and finding the Sweet Spot

The problem with only thinking about strength and extraction yield is that it will likely result in extraction errors. By extraction I mean the taste and flavour result. You could end up with an under-extracted (sour) coffee or an over-extracted (bitter) coffee. 

Note though, that going overboard on strength for normal brews may also get a bitter taste. You can distinguish between bitterness due to strength and bitterness due to flavour extraction by diluting the coffee. If it is still bitter it’s not related to strength but related to the extraction. That’s good to know as a diagnostic point of reference.

To get the right extraction, that will result in a well-developed flavourful coffee, the extraction yield needs work with the strength. 

Flavour and taste is influenced by time… letting the water develop the flavour of the coffee in the time it has. 

An analogy to help… When you make toast, the toaster needs time to toast the bread. Leave it in too short, it’s under-toasted. Leave it in too long, it’s burnt. Leave it for the right amount of time and it's toasty!  😊

Though, my toast analogy won’t work to help explain what I’m about to say… sometimes changing the grind can also help flavour extraction. I know… I said the same thing about strength. But again, it’s about what the water can access in the coffee grind and what it can do with that access. If you’re limited by the brew time then more surface area is an option if you need more flavour extraction.

More coffee surface area could mean enhanced flavour development but overdoing it could take it to over-extraction levels. Too little surface area could mean under-extraction if the water is not given enough time to pull out the right flavour notes. So, you can manage your surface area by managing the grind size, or the amount of coffee used, in conjunction with the duration of the extraction. 

How does this help you? Well if you’ve hit your perfect strength level, with the correct yield range but the flavour is not correct, you now have 3 factors you can adjust to correct the flavour – time, coffee dose and grind size. And now, when you make adjustments to your brew, you can judge the strength and taste to hone in on your best brew.  

Bring Strength, Extraction Yield and Taste together for a Holistic Approach

Brewing coffee is about taste and at a personal level your own enjoyment of your brew. So, your own taste should lead you to your own coffee sweet spot. However; if you know that you want to make changes and can’t find your way to the sweet spot, assess your brew taste against the strength and flavour and you can apply some troubleshooting to find your way there.

Where does the sweet spot actually live? It’s easiest demonstrated on the coffee control brewing chart, which I was leading you to with my simple line diagrams.

If you put my line diagrams together, you get this:

The sweet spot can be found in the region of between 1.2-1.5% TDS and 18-22% Extraction Yield.

Here is proper the coffee control brewing chart, showing the sweet spot along with all the factors involved:

(reference: understanding-the-coffee-control-brewing-chart)

Conclusion

Ultimately when you are working on improving your brew, you can use the concepts in conjunction with what you are tasting to get you close to that perfect brew. Adjust grind size, coffee dose and brew duration individually in small measure and see where it takes you.

If you are planning on going on his journey to the sweet spot, make sure to record key elements of your brewing process so you can repeat a brew or judge what to adjust on the next iteration. Either keep a notebook handy when doing this or use an app to keep track.

Happy sweet spot brewing. 

If you want to learn more on this topic, check on this insightful and educational lecture by Barista Hustle on YouTube: https://youtu.be/2lPGf1gM9nA