Coffee descriptors

Back in September of last year I was thinking a bit about the words we use when we describe coffee.  Out of interest I went to a few US roaster’s websites and copied all their coffee descriptions into a text document and ran it through wordle.

I then went to Starbucks website and did the same thing with all their descriptions.  The results are interesting, I think and you can click to enbiggen:



Now don’t take these too seriously – this is hardly the most incisive bit of research.  I’d like to ask if the same thing stands out to you as it does to me – but then I have to ruin the question by giving my own answer.

Speciality  1 likes to use nouns.  Solid, statement-of-fact nouns:  This coffee tastes like blackberry.

Starbucks surprised me, not only by their consistent use of acidity which confuses me on a couple of different accounts, because they don’t use as many nouns.  Lots more descriptive words, more adjectives and adverbs.  Are they harder to argue or disagree with?  Perhaps a more accessible way to describe coffee to their customers?

Is there something in the way they do this we can learn from.  I’m not suggesting we spruce up our descriptions with meaningless words, and I will admit that I am uncomfortable with labels when flavour descriptors start verbing, but would describing those factual flavour nouns in our labels a little more be beneficial?

  1. how uncomfortable I am with this term  ↩︎

Brewing Espresso at Altitude

There has long been discussion about what happens when you brew espresso somewhere at relatively high altitude. This has become, and will become even more, relevant as the WBC is taking place in Bogota this year. Bogota is the third highest capital city in the world, some 2625 metres above sea level (approx 8,600ft).

At this altitude water will boil at 91.2°C/196.2°F – below the 93.5°C/200°F that the Aurelias will be set to. What follows is mostly personal opinion 1, coupled with a possible experiment that might answer some questions.

When we’re brewing espresso the system is under pressure (9 bars mostly), rather than the much lower atmospheric pressure. One of the unique aspects of brewing under pressure is that water is able to dissolve a lot more CO2 than it usually can at atmospheric pressure. When the coffee liquid leaves the basket we see that it is unable to retain that CO2 which forms bubbles that get trapped by various surfactants as a foam: crema.

People will often remark that at altitude the coffee acts like it hasn’t had a chance to rest/degas. The espresso tends to have very large bubbles, and lacks strength – often disappearing very quickly. This is, of course, similar to brewing very fresh coffee (up to 48-96hrs post roast) at sea level.

What doesn’t make sense to me is that surely CO2 would be more likely to be drawn from the coffee bean when stored at low pressure than at higher pressure?

My guess (and it is a guess) is that the pressure change from the bottom of the basket to atmosphere is much larger than normal when brewing at altitude. I would guess that the saturation point for CO2 in water at 2625m is significantly lower than the saturation point at sea level. The liquid loses more gas, and we see this as bigger bubbles. With foams in liquid the strength is dependent on bubble size (the smaller the stronger – think good milk foam), so these larger bubbles of crema will disappear faster.

What does this mean for competitors? Here is my advice:

Bring scales. I know a lot of people don’t like it (though I don’t really understand why), but your espresso volume is going to be radically different for an identical flow rate at sea level. Know your brew recipe before you come, and before you start freaking out about how things taste, check whether you are brewing on spec. Espresso is a recipe that is based on weights and flow rates. Going by eye is tough. I’ve tried, when I was there in 2007, and it took a while before things made sense!

Pulling shots in Bogota

Another question remains – should espresso be aged longer for brewing at altitude?

This is a good question, and one I think we need to do a few experiments on. Ageing espresso will certainly reduce the amount of CO2 left in the coffee beans, but surely at the expense of some loss of pleasing aromas and the potential development of negative flavours. I’d like to run a two way experiment, but it needs participants who have access to coffee machines at different altitudes.

Take two bags of espresso from the same roasts/blending batch. Store one at sea level, store the other at high altitude. Ideally in similar temperatures. After 10 days bring both back down to sea level and observe variations in volume for a fixed weight of coffee, liquid and brew time. Based on my amateur theorising above – there should be no detectable differences, or – if anything – the coffee stored at altitude might have less crema/volume when brewed.

Then take two bags of identical espresso and store both for 10 days at sea level. Then brew one at sea level and one at altitude. Record variations in volume for fixed weight of coffee, liquid and brew time.

This way we’ll know whether the issue is ageing of brewing. I would predict that when brewed identically the high altitude espresso should be just as delicious as the low altitude one – but I am very happy to be proven wrong.

One aspect to consider is when the brewing liquid might reach boiling point. If someone is pulling very fast shots, where the brew water doesn’t lose much heat to the coffee – then I’d expect to see some issues towards the end of the shot as the exit liquid from the basket will be very close to boiling, if not boiling at high altitude. Properly brewed espressos shouldn’t (in theory) see the same problem. Anyone have video of a naked portafilter at high altitude?

Comments, thoughts, accurate science and brutal critiques of the above welcome!  Thanks to Brent Fortune for setting my brain off!

  1. Warning: Amateur Science Alert!  ↩︎

8 steps to develop your coffee palate

This post is really for coffee consumers who want to develop their palates, which leads to coffee becoming more enjoyable.

I had been in coffee well over a year before I really began to develop my vocabulary and descriptive skills, and that is probably more embarrassing as I had done some work in wine beforehand.

What does the coffee professional have access to, that the consumer doesn’t, that allows them to progress so fast?  It isn’t cupping bowls, or spoons.  It isn’t scoresheets, or large amounts of data about where the coffee is from.  It is regular opportunities for comparative tasting. Continue reading “8 steps to develop your coffee palate”

CoE Colombia First Harver 2007 Top 10 Descriptor Cloud

I thought this might be more interesting than it turned out to be. I had to mash words together to get the generator to see them as one descriptor. This might be more interesting with a better generator and with easier data to work with – it would also be interesting to compare a cloud from one auction to another.

greatchocolate creamymouthfeel brightacidity brightcherry delicate round cedarwoodaromatics sweet creamybody darkchocolate buttery chocolatespicearoma peanuts sweethazelnut peach almonds cherry floralnote syrupybody notablyclean chocolate smoothsweetmouthfeel orangeblossom coconut richbody crisp notablysweet sweetchocolate caramelaroma longcreamyfinish sweetmilkchocolate delicatefloralaromatics brightfruitacidity complex richcreamybody floral milkchocolate honey vanilla roses pleasantblackpepperfinish citric balanced longcomplexfinish sugarcane caramel winy jasmine creamy veryclean cleanandbright syrupymouthfeel sweetmelon sparklingfinish brightlivelyacidity citricandcomplex smoothfinish cherryfloralnotes chocolatecaramel redwinenotes lemon blackberry verysweet wellbalanced roundmouthfeel juicy peachandapricot citrus smoothbrightacidity creamysilkymouthfeel blueberry crispacidity

“…Coffee: The Chemistry behind its Magic” by Marino Petracco

I came across this 7 page article by one of the main guys behind the chemistry research at illycaffe whilst searching for new reading material and it is an interesting overview, though no doubt familiar to those who own “The Science of Quality”.

One section seemed relevent to discussions going on around these parts of late:

“To the young food chemist, espresso could be a challenge for deeper research, because its structure of a polyphasic colloidal system along with its complex composition may be seen as the quintessence of all other techniques by which coffee can be brewed.  Knowing espresso is to know coffee in all its forms.”
Link to the pdf here.

[tags]coffee, chemistry, coffee chemistry, espresso, illy, marino petracco[/tags]

Research into coffee – who is it for?

There is a huge amount of money spent on researching coffee.  This isn’t just the latest study telling you whether it is good or bad ( article – you may need to use for you, but also the many papers published that are of interest to the industry – ASIC’s conference has just finished (how I would have loved to go and just been totally outnerded!)

What I wonder is who is the research actually for?  Does it make its way into the hands of the farmers and certainly with the espresso research (I am fascinated to see if many papers submitted to ASIC this year are espresso based) – is it being read by baristas?

Often the answer is no – the language of the papers seems impenetrable to most of us.  So – I thought I would try and find a few papers (I have a few I have bought but I am not sure if I am violating copyright by making them free to download – I assume it is wrong but any advice welcome) and take them apart to see if there is anything contained within them that is of practical use to the person making coffee.

It may be a wasted exercise or I may find a few gems of information buried away in there.  We shall see…..

[tags]coffee, espresso, research, scientific papers[/tags]

Beyond the Taste Buds

Listening back to a rather good little show broadcast this week on BBC Radio 4

“Claudia Hammond tickles her taste buds and looks at the science of taste. Scientists are now discovering that our perception of taste and flavour does not just come from the tongue, but our eyes, nose and even our ears all play a crucial role.

She also discovers how the top scientists in the field can make her like the food she hates.”

Lots of interesting guys on this, such as Tony Blake who has done some really interesting stuff with the Fat Duck

Also a segment on supertasters, superfeelers and tasting PROP, which is perhaps of interest to WBC judging hopefuls.

You can listen again to the show here
I love Radio 4.

[tags]taste, flavour, food science, aroma[/tags]

Some thoughts on brew temperature

I am fully expecting to have this picked to pieces or just generally rubbished, but I thought I would jot down a few thoughts having read a post over at Coffee Aspirations

Let’s treat something going into solution as a chemical reaction (because it is), and let us also assume that this means that increased heat will result in more chemical reactions, or more compounds going into solution. (This comes under the banner of Arrenhius’ Equation I believe, and no I am not going to try and explain it right now!).

So – the hotter my brew water the more I will dissolve from the surface of the ground coffee particles, and this seems to manifest itself to me in the cup. Typically we see it as a bell curve wth cup quality increasing quite suddenly around a certain temperature and dropping off quite radically either side.

Here is a hypothetical espresso extraction, with brew temperature and also exit temperature measured:

(please note this is a very approximate graph – it is just for illustration)

We would expect to see an exit temp lower than the brew temp – energy having been lost through heat loss (radiation, conduction etc) as well as having been spent dissolving lots of wonderful things for us to drink. The shaded section’s surface area should correspond to energy spent.

So if we increase the brew temperature by a small amount (be it 0.1F or 1C) then we are inputting more energy into our little graph:

Question 1 – Do we expect the exit temp to rise by that amount also?

If so – then surely the amount of energy spent (the difference between input and output) would be the same, so therefore would there have been the same reactions occuring regardless? Or would more reactions have occured in the top section of the puck, where the coffee is exposed to the most heat?

Question 2 – Can we compensate? If we are stuck with a lower brew temp can we come close to achieving a similar result by creating a brew time that gives a matching surface area or would the different dose or grind necessary influence the quantity of solubles going into the cup too much?

Other thoughts:

Occaisonally it seems ridiculous that a 0.1F difference in brew temp can change an espresso’s cup quality. Yet if you read about the aromatics present in coffee (and we, as an industry, often talk about the incredible numbers of volatiles in roasted coffee, as if the cells of the bean can barely contain them) you realise that whilst there may be several hundred different ones there are not present in very great quantities. They are capable of having being a character impact odorant (one of the ones that give a product a distinctive taste) at concentrations of parts per million or part per billion.

This being the case then suddenly a subtle shift in chemistry from a subtle shift in temperature could easily mean a big chance in perception. Though perhaps this begs the question of – if I get red fruit notes at 91C but chocolate tones at 93C, why do I not also get a stronger red fruit note at the higher temperature?

Perhaps it is down to the complex relationship between what we taste and the flavours we percieve. Paul Songer briefly spoke to me about how the level of percieved acidity can influence the flavours/aromas you are better able to pick out crediting the brain’s expectation for the difference.

And yet if espresso really is this picky, the cup quality balanced on such a knife edge – how then do people have similar taste experiences with a blend? Perhaps they don’t – I know this is something that is bugging Stephen Morrissey at the moment. Or perhaps the cleverest blends are ones that contain character impact odorants in great abundance, so wherever you hit the shot (within a certain sensible tolerance) you get strong tastes of caramel or whatever they intend.

I also think that the taste of a coffee – its balance of sweetness, bitterness, acidity and on occaison saltiness – is less temperamental. I often find that a coffee will exhibit the same feel and taste in the mouth from brew to brew whilst the flavour/particular aromatics may vary. (This could easily end up spiralling back into earlier thoughts though….)

I seem to have posted more questions that musings, but that is inevitable with any post about espresso these days….

[tags]coffee, espresso, food science, aroma chemistry, taste perception, barista[/tags]

Maillard Reaction, Strecker Degredation and Caramelisation

In the next of my apparent series of articles on all things coffee and chemistry I am going to tackle in a pleasant (I hope) depth these three types of reactions as they appear all the time in coffee articles. Obviously we are going to need to get into a bit of chemistry but hopefully it will remain understandable!

All of these are forms of non-enzymatic browning – opposed to reactions causing foods to go brown because of one of many enzyme actions, such as your apple turning brown when bitten into and left for a bit. This seems an obvious distinction, but I think it is important to include.

As usual – questions or mistakes in the comments!

The Maillard Reaction

Luis-Camille Maillard was the chemist after whom these particular reactions are named, as he was one of the first to investigate them in 1912. The term describes a very specific set a reactions – browning reactions occuring between amino acids and reducing sugars.
Amino acids are the building blocks of proteins, and just as the 26 letters of the alphabet can be used to write an infinite number of different texts, the 20 standard amino acids are put together to create a potentially infinite number of different proteins.
I won’t dwell on the chemistry but all amino acids have the same end to the chain:

The R symbolises the rest of the chain, and obviously this is the bit that is different from amino acid to amino acid.
So anything with protein in it is a candidate for the maillard reaction. All we need now is the presence of a reducing sugar.

The term reducing sugar implies something more interesting than what we find. Simply put a reducing sugar is any sugar with an aldehyde group. We often talk about aldehydes in coffee’s complex aroma chemistry (such as benzaldehyde – which has the characteristic smell of bitter almonds, and is used in just about any almond syrup), but to be an aldehyde means you have to have this arm tacked onto the molecule somewhere:

(again R is the the Rest of the molecule)
A list of reducing sugars is full of familiar names: fructose, glucose, lactose and maltose to name a few.
However, and this is important, sucrose – table sugar – is not a reducing sugar and takes no part in the Maillard Reactions (but does get involved in caramelisation).

These two react together and form new molecules with a brown colour – melanoidins (which you may recall being quite important to crema). Heat is not absolutely necessary, you could mix the two, put them in the fridge and they would turn brown – just very slowly! Heat helps speed the whole thing up. Equally they can happen with water present, but water slows it down. Without the sugar there can be no browning – this is why quakers stand out in roasted coffee, and are so pale.

Problems arise in the full description of reactions because different sugars and different amino acids produce different molecules, and then to complicate the picture these molecules begin to react and interact further. It is almost a cascading set of reactions. Therefore there are a great deal of different compounds created, both aromatic and non-volatile.

There is of course commonality between Maillard Reactions in different food products – coffee and chocolate share a great deal in terms of flavour as many of the same reactions have occured. Roast beef should also share some similar chemistry to roasted coffee, though whether there is enough commonality to make the combination palatable is debatable (though I have a collection of recipes for roasted and barbequed meat with a coffee crust!)
The Maillard reactions are the reason that milk left on a steam wand quickly turns brown.

These reactions are dependent on a few variables: the different amino acids available, the pH, the amount of water, any salts and the period of time held at a temperature.

The Strecker Degradation

This is one I thought I should include because I see it referenced quite a lot, in any text concerning roasting chemistry and is instrumental in the creation of the brown pigment as well as a myriad of volatile aromatics. It falls under the umbrella of, and requires compounds created by, the Maillard Reactions. Unfortunately this one isn’t so simple to explain.

It involves amino acids again, but instead of reacting with a sugar it is reacting with a molecule with two carbonyl groups, which look like this:

The compounds begin to trade parts of themselves, one of the carbonyl groups ending up on the amino acid (the acid having lost on carbon from its chain) creating an aldehyde as wll as an amino ketone. This is an intermediary stage and reactions continue to create many different volatiles.

I have refrained from making explicit descriptions of groups of aromatics. Ketones could be broadly described as having buttery, caramel flavours but key aromas in both raspberries and grapefruit are ketones.
Therefore I don’t think it is terribly helpful for me to claim that furans taste of this, and aldehydes taste of that….
Perhaps a description of each group of aromatics – esters, phenolics, terpenoids and thiols – would make an interesting article.


Much slower than Maillard reactions, and requiring much higher temperatures these reactions begin exclusively with sugars. They really begin up around 150C to 180C, with water being lost from the sugar molecule beginning the chain of events. In all cases the sugar is converted to a furfuryl. These are a type of furans that have a caramelly, slightly burnt and also slightly meaty notes. The same compound is produced via a different route in the Mailllard reactions. However it is with prolonged high temperature that many other types of aromas are generated.
Caramelisation is more predictable than Maillard reaction due to less variation in the starting compounds. Without the sulphur or nitrogen found in the amino acids caramelisation is unable to produce flavours as meaty as Maillard reactions

It is interesting to note how the sugar solutions taste changes in caramelisation. A sugar solution initially will be sweet with no aroma. Through caramelisation it becomes both sour and a little bitter, as a rich aroma develops. Generally the longer sugar is caramelised the less sweet it tastes.

Extended Reading:
General Book: The Maillard Reaction
Website: Course Information and A nice Diagram
Coffee Specific: The Science of Quality

Hopefully this will give the reader an insight into the basics of the different types of chemistry going on when you apply heat to food and it turns brown. Because of the broad range of applications I haven’t focused this one completely on coffee, though no doubt that will change when I come to review it. Any mistakes or obvious omissions then please let me know!

Lecture in Dublin

Got back yesterday from Dublin, having given a talk for the SCAE Irish chapter, and being hosted by Marco.

I hope the lecture went well (I get my feedback forms soon, so I will know for sure then!) I think I achieved what I set out to do, and that was to show people something that they would struggle to see anywhere else. I wanted people to go away with a lot of questions about their coffee, to talk less of strict rules and more of the guidance of taste.

It was a fairly well attended talk, with 40 of the top coffee people in Ireland there.

Joe Smith introuduces me:

It would have been nice if I could have spent some time with the coffee I was using before hand to get to know it a bit better. However it was nice to introduce the concept of brew recipes particular to every coffee to some people there.

What tied in with all this was the book I read on the way over. I picked up a collection of short works by Richard Feynman. (Perhaps I thought I could learn something of explaining difficult subjects to audiences from one of the great masters!). I can see why his style is often called infectious – it makes me want to be a proper scientist! What I really want to take away from it is his approach to science, the necessity of doubt – not only for progress but for integrity. Teaching as I do it can be all too easy to make bold statements of fact, and what I want to do is more actively question them, examine them and learn more. I identify quite strongly with the desire to have the experience of a new understanding, that incredible pleasure from finding something out.