Galla Coffee Blog

What is Under and Over-Extracted Coffee?

James — Sun, 29 Aug 2010 14:45:55 +0000

It’s something the coffee industry is obsessed with (and its something I talk about a lot too). But what is under-extraction and what is over-extraction? To put it simply, it’s a taste perception. We call coffee that tastes: flat, boring or lacks flavour; as under-extracted and coffee that tastes: burnt, bitter or overpowering as over-extracted.

To be more exact, around 30% of the grounds we use to make coffee are soluble in water. But not all of this 30% is desirable. There are flavours we would rather leave behind as they don’t taste so good.

Since the 1950s various coffee related bodies have conducted studies into consumer preferences to coffee and it’s been found that an 18-22% extraction range is the most popular. So we could say that anything below this range is under-extracted and anything above as over-extracted. However, taste is a personal perception and there would have been people in these studies who found coffee at a 16% extraction tasted good and coffee at 20% over-extracted.

How Flavours are Extracted from Coffee?

The different flavours that make up your cup of coffee all have different levels of solubility. Some extract quickly, others extract much slower. Ted Lingle identified four broad groups of solubility based on the molecular masses of each flavour.

If you imagine that these different groups of flavour form an orderly and patient queue, waiting to be extracted. Only after the previous group has been fully dissolved can the next group start. So the first flavours are ‘delicate’, then ‘mid-tone’, followed by ‘sweet’ and finally ‘bitter’. Think of the bitter group as that last 8% of solubles in coffee (i.e. from 22-30%).

The Sweet Spot

Extraction is more to do with the balance of flavours than simply the strength of the coffee solution. This is why things can get a little bit complicated. If we use too little coffee then the solution has a weak taste, but it’s the bitter flavours of over-extraction that we will detect. If we use too much coffee then the solution will have regular strength, but we be lacking in flavours. Some coffees with fruity notes may even taste sour or sharp, like unripe fruit, if under-extracted.

Imagine we had a specific volume of hot water which has the capacity to dissolve 12g of coffee solubles in a 4 minute brew time and we assume that all four groups of solubles are of equal size. If we use only 40g of coffee then are cup will contain 3g of solubles from each group (i.e. 30% of 40g divided by 4).

But if we use just over 53g of coffee we avoid over-extraction as the water will have been too preoccupied extracting the first 3 groups of flavours to have time to dissolve the final group.

And to complete the set, if we used 80g of coffee we’d end up with under-extracted coffee.

A good starting point on how much coffee to use is 60g per 1ltr of water. You can use our coffee calculator to calculate the exact quantity of coffee by entering the volume of water you’re using.

Uneven Extraction

Now that you understand extraction its time to throw a spanner in the works: a cup of coffee can be under and over-extracted at the same time!

Your cup of coffee is made from hundreds of coffee grounds. So when we brew, rather then one big (all encompassing) reaction we have hundreds of tiny reactions between water and each individual ground. As well as variations in each ground’s size (grinders produce a range of sizes rather than one uniform size); factors inside the brewing device will affect the speed of extraction. So some grounds will be extracted from quicker than others leading to some being under-extracted and others being over-extracted.

Is this something we should worry about? Personally, I think not. While we can take steps to minimise the differences in extraction rate it would be impossible to ensure a completely even extraction. The best we can do is concentrate on how the overall cup tastes and make adjustments from there.

Aerated Coffee – Sweeter with Greater Clarity of Flavours

James — Mon, 16 Aug 2010 15:59:34 +0000

Earlier this year, James Hoffman wrote a post on his blog about his experiments with a wine aerator. He found by pouring brewed coffee through such a device made the coffee taste sweeter and gave the flavours greater clarity.

How does an aerator work?

Water (which makes up a large percentage of both coffee and wine) naturally contains dissolved oxygen molecules. It’s these molecules that support marine life in rivers and seas. Water gains most of its oxygen from the atmosphere and can only store a limited amount. There are two factors which affect the capacity of water to hold oxygen:

Pressure – higher the pressure the higher the saturation point
Temperature – higher the temperature the lower the saturation point

An aerator works by increasing pressure on the wine and then exposing it to air to increase the saturation of dissolved oxygen. This is only a temporary measure as when the pressure on the wine returns to normal it will slowly release the extra oxygen molecules until it reaches the original saturation point. But in this short time, the increased oxygen has already sped up the oxidation of the wine.

Oxidation of wine either by an aerator or by decanting is a controversial subject among the wine community. It can have both positive and negative affects. Daniel Sogg wrote a good article about this in the Wine Spectator.

Oxidation is usually considered a bad thing in coffee as it leaches away flavour. But this is concerned more with storage rather than actual brewing. Oxygen is said to be the worst enemy of roasted coffee beans as it shortens their shelf-life. However, the general consensus is that oxygen in the water used to brew coffee is a good thing as it helps extract the flavour. This has scientific grounding as oxygen atoms are very reactive and aren’t particularly choosey about what they react with. So it’s reasonable to expect oxygen to assist in breaking down the compounds in the coffee grounds into some that can be more easily dissolved in water.

Why did aeration make the coffee taste sweeter and give the flavours greater clarity?

When James wrote his post, he wasn’t sure what chemical changes occurred in his coffee to make it taste better. To be perfectly honest I’m not either. I’ve been searching around the internet for a while and haven’t come up with any answers. I guess that as oxygen is highly reactive it could have any number of affects on brewed coffee’s chemical make-up. I’ve come up with two theories which may (or may not) have something to do with it.

Aeration could alter the pH of brewed coffee. High levels of CO₂ are trapped inside the coffee bean when it’s roasted. While most of this disperses into the atmosphere a couple of days after roasting, a small amount is still contained. When we brew coffee we see CO₂ escaping, bubbling out of the bloom. Some CO₂ won’t escape though. It will be dissolved in water and form carbonic acid. By increasing the dissolved oxygen level in water, it should dispel more CO₂ and will reduce the presence of carbonic acid and therefore raise the pH (slightly).

Other acids may also be broken down by oxidation; and many of the flavours in coffee come from acids. So fewer acids, equals fewer flavours, which in turn gives greater clarity to those flavours remaining.

James also had an interesting discussion on his blog about why coffee changes taste as it cools. Oxidation of acids may be another piece in this jigsaw.

Oxidation could break down complex sugars. Have you every noticed how a stale biscuit tastes sweeter. This is because oxidation breaks down starch into simpler sugars and it’s these sugars we can taste. Coffee doesn’t contain starch, but it does contain other polysaccharides which aren’t soluble in water. It’s possible that these complex sugars could oxidise and break down into simple sugars which are then soluble.

In Scott Rao’s new book ‘Everything but Espresso’ he talks about a scale in coffee with clarity on one end and body on the other. Greater clarity equals less body and vice versa. Now much of the sensation of body in the cup is caused by insolubles. So one thing is for certain; for James to have achieved greater clarity, some of these insolubles must have been transformed by aeration into solubles.

Simple steps to aerate coffee

Wine aerators aren’t the cheapest of items to purchase and some of you might think that pouring your coffee through an aerator before drinking is a bit of a faff. So here are some simple things you can do to increase the dissolved oxygen content of the water you use to brew:

Use freshly drawn water – use water freshly drawn from the tap. Re-boiling water is a big NO NO!
Boil the water as quickly as possible – as I mentioned earlier the higher the temperature of water the lower the saturation point of dissolved oxygen. However, this isn’t an instantaneous reaction. The loss of oxygen occurs slower than the rise in temperature. So the quicker we boil water, the greater the level of dissolved oxygen, as it takes time for oxygen levels to fall and reach equilibrium with the higher temperature of water.

To boil water quicker we can do the following:

Keep the kettle clean – limescale slows the efficiency of the heating element.
Use filtered water – the more impurities in water the higher the boiling point. Filters with an ion exchange, like a Brita one, are quite effective.
Only boiling the amount of water you need doesn’t just help save the environment!
Manually turn the kettle off yourself as kettle’s have the reaction of a sloth! They don’t really, but rather then use a thermostat to measure the temperature of water, kettles typically rely on a steam sensor to tell when water is boiling. As the old saying goes: there’s no steam without boiling water (or was that smoke without fire?). So there’s a 10-20 second delay between water reaching boiling point and the kettle turning itself off.

Hey you guys! Ok not this Sloth but the tree dwelling variety.

Of course boiling a kettle quickly only gives you a temporary advantage and if you then have to wait for it to cool before using (you don’t want to scorch those precious grounds), any advantage quickly diminishes. It would be much better if we could only heat the water to the desired temperature.

More and more kettles are now coming on to the market with built in thermostats. Some you can heat to anywhere between 60-100°C in 5°C increments. This would be ideal for making coffee. But are these kettles actually any good or are they a bit gimmicky? Speaking to someone actually in the industry (household appliance design that is) he said that the first kettles that came onto the market weren’t very accurate at all. The temperature could be as much as 5°C out. But I would love to hear the experiences of anyone with a more recent model. See if it tempts me to take the plunge and buy a new kettle.

How to Make the Perfect Coffee – A Lesson Learned from the WBC

James — Thu, 22 Jul 2010 23:04:24 +0000

Disclaimer: This post will not tell you how to make the perfect coffee – I was trying to think of a catchy title and “How to make your coffee taste better by making small adjustments to the brew variables from the standard method – a lesson learned from the WBC” was a little long winded. As in most cases perfection is something to aspire to, but in reality will never be achieved. If anyone can think of a better title please leave a comment.

Now I know that the WBC was quite a few weeks ago, but I thought I would write about it today as I think there is an important lesson to be learned that we can all employ when brewing at home. This lesson doesn’t just apply to brewing espresso, but to any coffee maker.

Stray from the standard brewing method

While the standard brewing method is a great starting point when learning to use a new coffee maker, it’s not a strict recipe that must be followed to the letter. To get the best out of your coffee (or to pursue perfection) you should experiment with the way you make it.

To illustrate this, I’ve picked on three of the performances from this years WBC (you can still catch the performances here). Each barista altered their technique slightly to highlight different flavours in their coffee.

Michael Phillips, who won the competition, used two coffees from the same co-operative, but which had undergone different processing after harvest. When making the espressos he used a different dosage and brew time (and I imagine grind too – although he didn’t mention this in his performance) for each coffee to extract the best possible flavour from them.
For Colin Harmon’s signature drink, he did something really simple but also very clever. For each judge he served two espressos, each topped up with a different type of water (two americanos if you like). The first used a soft water; the second used a more alkaline hard water. The soft water highlighted the floral and fruity flavours in the espresso, whereas the hard water accentuated the chocolate, nutty and earthy notes.
Raul Rodas used two different techniques to extract two different flavour profiles from his chosen coffee. One espresso highlighted citrus notes and a silky body, whereas the other which used more coffee and had a longer flush (to lower the water temperature) was full of cherry and juicy fruits.

It’s not surprising that small changes in a brewing method can make significant changes in flavour of the end cup. Over 850 flavour compounds have so far been identified in roasted coffee and many of these compounds are volatile (i.e. can easily be lost). By making adjustments, the method can be made more favourable to extracting some compounds while leaving others behind.

Experiment with your coffee

So when you use the standard brewing method for your coffee maker, ask yourself: “Does the coffee I’ve tasted in the cup have all the flavours I smelt in the fresh grounds before brewing? Does the coffee have depth in flavour? Is the coffee balanced?”

If your answer is ‘no’ to any of these questions, then it’s time to experiment and make some adjustments to the way you brew. To help you experiment I’ve come up with the following lists: which are by no means definitive, just a bump start in the right direction.

Delicate flavours (i.e. floral & fruits)
If your cup is lacking in floral or fruity flavours (or tastes bitter) you can try the following to increase their presence:

lower water temperature
increase brew ratio (i.e. use more coffee or less water)
increase grind size
reduce brew time

You’ll know if you’ve taken things too far if your coffee starts to taste sour or astringent (like unripe fruit).

Mid-tone and Sweet flavours (i.e. nuts, chocolate & caramel)
If you cup is lacking sweetness or balance (or tastes sour) do the opposite of above:

raise water temperature
decrease brew ratio (i.e use less coffee or more water)
decrease grind size
lengthen brew time

You’ll know if you’ve taken things too far if your coffee starts to taste bitter or burnt.

Tip: Only alter one variable at a time otherwise you won’t know which one has had a positive affect (if any).

I hope this post has got your palate excited in anticipation. Now go do some experimenting and feel free to share your results.

Where England Went Wrong in The World Cup – Explained Using Coffee (Beans)

James — Mon, 12 Jul 2010 19:29:45 +0000

Sorry for the lack of new posts recently. I’ve been distracted too much by the World Cup. Hopefully now it’s finished I’ll get back to blogging on a more regular basis.

Speaking of the World Cup; now I know this post is a little off topic, but I couldn’t really resist talking about the finals (I’ve also tried to justify it a little by using coffee beans). England’s performance was at best, very frustrating and anxious to watch and at worse a humiliation. The press are very keen to blame everyone and anyone for what went wrong, provided that it sells newspapers.

The Formation

To me the underlying problem for all England’s woe seems to be their formation. A 4-4-2 formation without a proper left winger (no offense to Steven Gerrard) didn’t work. The basic principle of an attack is to stretch the defensive team and so create space for goal scoring opportunities. The problem with England when they attacked was they didn’t keep a good shaped. Other than the occasional width provided by the full-backs getting forward, England kept to the middle of the pitch. This made it easy for the opposition to defend against (particularly as most had 10 men behind the ball), as they weren’t stretched at all. It also made it frustrating for the England players as their bunched up shape left no easy passes on to teammates.

England's 4-4-2 formation: Gerrard drifts into the middle from the left while Rooney comes short looking for the ball. Defensive players have an easy time as they can keep a compact shape. England players have a tough time finding passes to teammates.

How many times did we hear Mark Lawrenson (or another commentator) use the phrase ‘Hollywood pass’ as Lampard or Gerrard tried and failed to split the defence with a near impossible ball? Some of the intricate play between Rooney and Gerrard was impressive, but it never resulted in chances as 3 or 4 defenders could afford to close them down without leaving space behind for other England players to exploit.

Many of us will remember when Ossie Ardiles managed Tottenham; how he emphasised a triangle passing system, where the player on the ball always had two options to pass to. The truth is that in any formation, if you keep a good shape, these triangles of players exist naturally within. If England kept a better shape there would be easier passes on, they’d keep the ball much better and the players wouldn’t feel anxious. When on the ball they’d know that they’d always have two easy passes on. So they wouldn’t have to worry about threading the ball through the eye of a needle or having to take a man on just to make some space.

England with a 4-5-1 formation (Joe Cole in and Defoe out). See all the triangles of players there are if they keep their shape.

Now I know this is the same formation that saw England qualify top of their group with some ease. But their group was pretty easy. The likes of Belarus, Kazakhstan or Andorra hardly provided a tough challenge. Sir Alex Ferguson was recently quoted by the BBC as saying:

“They qualified from a group which you’d have to say was a million to one they wouldn’t qualify from. So it was an easy passage into the finals.”

In these finals, more than any other World Cup that I can remember, the lesser nations (normally the whipping boys) have been well organised. They’ve approached their games negatively, happy to play out for a draw, hoping to get a lucky break on the counter. Out of 48 group matches, only 13 had a two goal or greater winning margin (and this includes Mexico beating France 2-0)!

Number of matches with a two goal or greater winning margin in the group stage of each World Cup.

England struggled against Algeria and Slovenia because of their poor shape. They couldn’t pass the ball around to wear the opposition down and pull defenders out of position. They didn’t trouble the full-backs and fire in lots of crosses, which lets face it, is England’s life line of goals. 3 out of 4 (should have been 5 – thank you Jorge Larrionda) goals scored by England in the finals were from crosses.

Winter Break

One of the most popular theories for England’s failure is tiredness. The players were apparently too tired to perform after an extensive domestic campaign. Many newspapers and pundits alike have suggested the Premier league season should be altered to include a winter break.

Personally, I think they’re all barking up the wrong tree. Nearly 1 in every 7 players at the finals played in the Premier league. But no other team appeared as tired as England. Look at Landon Donovan: he’s hardly stopped playing in two years with two MLS seasons sandwiched between off-season loans to Bayern Munich and Everton. Not forgetting playing in the Confederation’s Cup last summer. Did he look tired at the finals? No – probably USA best player scoring 3 times.

To say all of England’s players were worn out from the domestic season doesn’t really ring true. Glenn Johnson only made 25 appearances in the league for Liverpool after sitting out the middle of the season through injury. Ashley Cole had two months off after breaking his ankle against Everton in February. Emile Heskey spent much of his season warming the Villa bench. So these players surely should be pretty fresh.

To me, what appeared to be fatigue was in fact anxiety: anxiety at not being able to win easy; at not being able to string easy passes together. This anxiety was caused by the formation not working. You could see the players wanted to win. You could see the determination in their eyes. But it was the basics they couldn’t get right: poor passes, poor touches and poor positioning. They wore their hearts on their sleeves and worked hard but unfortunately their anxiety inhibited their skill and ultimately made them look average.

John Terry tries to catch a bullet during the game against Slovenia.

World Barista Championship 2010 – The Results

James — Sun, 27 Jun 2010 12:37:17 +0000

If you haven’t heard already, the results for the WBC are as follows:

Michael Phillips (USA) 706 points
Rual Rodas (Guatemala) 691 points
Scottie Callaghan (Australia) 672.5 points
Colin Harmon (Ireland) 659.5 points
Soren Stiller Markussen (Denmark) 644.5 points
Stefanos Domatiotis (Greece) 632 points

Should you have missed any of the action, the videos for all the competitors are still available online here.

The whole event was done really well. The only disappointing thing for me was the drawn out announcement of the final results. Like many people I’m sure, after the final performance by Rual, I wanted to know the results as soon as possible. But instead, I had to endure each and every sponsor being invited onto stage, by the MC, to give a speech.

Could you imagine this happening in the FIFA World Cup? After England beat Brazil in the final (I wish), before Steven Gerrard can lift the trophy we have to hear a speech from all the sponsors.

MC: I’d like to welcome onto the pitch our ball sponsor Adidas.
Adidas: Thank you. This World Cup we at Adidas listen hard to what players and coaches alike wanted from a football. We then went incompletely the opposite direction and took inspiration for the Jabulani ball from those 99p plastic balls you find on the garage forecourt.
MC: Thanks Adidas. Now I’d like to welcome Ronald MacDonald…

Big respect must go to Stephen Leighton of Has Bean Coffee. As a sponsor he had the opportunity (and every right) to promote his company. I can’t remember his exact words, but basically when he was handed the mic he said “Just get on with the results”.

Update: Just watch the announcement back to find out what Stephen’s exact words were. What he actually said wasn’t crude like the words I suggested above – sorry. Light-heartedly Stephen said:

All the baristas rocked. Can we have the results please.