In Focus: Acids in Coffee

Posted by Stella Cochrane on

Our CMCR KL Academy Trainer, Pablo Bialaszynski, took some time our his busy schedule recently to investigate the complex effect of acid in coffee. Here's what he found:

'When we think of acids, we often think of a pH level chart and reminisce school science experiments with lemon juice and vinegar. In this case, we’re going to focus deeper into the source of coffee’s acids and the sensorial experiences that come with them.

This post aims to provide a perspective that simplifies acidity, rather than complicate a topic that is already tricky. You might even find a greater appreciation for your cup of specialty coffee with a little more understanding.

There are a few stages of a specialty coffee’s journey that could alter acidity in the final cup, inevitably how we sense and perceive it. It could be the type of Arabica, the environment of where it’s grown, the method of processing, as well the effects of roasting.

yellow bourbons   coffee cherries    drying coffee

There are two main groups of acids, known as 'organic acids' and 'inorganic acids'. 'Organic acids' - as the name would suggest – can be easily considered as naturally occurring to the plant and fruits development, via cellular respiration. While 'inorganic acids' are acids present that could be a byproduct of for example, a fertilizer or soil rich in certain minerals.

Organic acids are more prominent in gradually higher altitude Arabica; and there are over two dozen of acids! Different cultivars can be composed of different levels of these same acids. An effective analogy is the one of apples. Have a look at these different apples below, could you try to imagine how they taste individually?


Now what’s remarkable is that you didn’t need to be an aficionado of apples to know which of these would be the juiciest and sweetest, or has a tart sourness and crisp feel.

These apples – like specialty Arabica – are rich in acids and sugars. In this case, over 90% of apples acids are malic acid. And while an orange would also have malic acid, we would never compare 'an apple-like flavour' to that of an orange simply because of it’s undeniable character rich in citric acidity, or citrus. In fat, stone fruits like peaches have almost equally both malic and citric!

Of course we couldn't take about acids without considering the environment that the coffee grows in as this is a big factor effecting it's end quality. Higher elevations (thus lower levels of oxygen) promote the maturation of harder and denser seeds within the fruit and the cool nights slow down the ripening of the fruit. Bright citric acid slowly matures into sweeter malic acid and ultimately changes how acidity can differ in presentable flavour.

Altitude map

Different processing methods will also effect the acids in the coffee. Washed processed coffees are higher in perceived acidity this is attributable to the removal of mucilage which contain most of the fruit’s sugars. A 'natural' or 'dry' processed coffee retains the mucilage and therefore has a greater presence of sweetness which can mitigate perception of acidity. An easy analogy is that of making lemonade. We know drinking lemon juice concentrate isn’t a delight, and diluting it with water might make the sourness less painful, but all it takes is some sugar to turn it into something more palatable.

Now that we have some good understanding of how certain acids form, let’s look at how roasting coffee can alter that. The concept of roasting can be viewed simply, a light roasted coffee preserves acidity while a darker roasted coffee degrades specific acids and increases a handful of others. There are many chemical reactions in roasting; as well there are many ways to go about it.  

roasting stages of coffee

The fruity acids like citric and malic degrade at higher temperatures and longer roasts, while certain groups like chlorogenic acids have components that break down and increase during the roast. Quinic and caffeic acids are a result and commonly associated with the bitterness, astringency and body found in darker roasted coffee. Naturally, we wouldn’t want acidity to be the only character, it would overwhelm the drink, nor do we want a cup full of bitterness. This is in the roasting to change.

Here are the few acids that we can easily identify in taste!

Citric acid – as you would find in oranges and lemons, it is easily detectable. While it’s known for bright and juicy sensations, this acid has one of the greatest presences in green coffee. It reduces in darker roasts.

Malic acid – quite like the crispy joy of biting into a green apple or sweet pear, this is a tart and lingering acidity. A prized quality in specialty-grade Arabica coffee.

Acetic acid – the taste of vinegar, how delicious. A common byproduct of washed coffees that contribute to a rounded, clean tasting cup. Poor fermentation can accentuate this acidity but the right amount of it makes for nice complexity.

Tartaric acid – the grapey and winey notes in coffee, which is understandable considering grapes, are rich in this acid. Too much however will be sour and unpleasant, this acidity is one of the main acids in wine.

Quinic acid – the byproduct of cholorogenic acid decomposing during roast. It increases in concentration in darker roasted coffee, stale coffee and coffee that was brewed and cooled or sat in a coffee pot too long over a hot plate. It does give coffee a clean finish but is better known for the sourness of coffee that turned cold.

Phosphoric acid – introduced during fertilization, this inorganic acid is commonly found in Kenyan coffees. With a hint of sparkling in texture, it’s the reason for the delicious currant notes. It’s believed that the larger presence of this inorganic mineral makes Kenyans so iconic.

As you can see, there’s much room for flavour expression in specialty coffee!

apples              citrus fruits

There is a plentiful of things for us at Common Man Coffee Roasters to consider. Tasting different coffees from one harvest to another, new and old cultivars from varying regions and countries, analyzing and improving our understanding of how different coffees react in the roast; inevitably how we brew and serve our consumers. It’s in our simplest intention, making delicious coffee common.

Next time you find yourself in a specialty café, look out for tasting notes in the coffee you ordered, even if they’re as funky as raspberry, cola, liquorice, banana or coriander. Thanks for reading, this calls for a great brew!

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Why Pay More for a Single Origin

Posted by Stella Cochrane on

It used to be that going out for a coffee was a bit of a treat but in recent years we have seen specialty coffee joints popping up all over the island so we are never far from a decent brew.

The so called third wave coffee movement hit Singapore in the late 2000s, a movement to elevate the status of coffee appreciation and promote sustainability by opting for direct trade which has been sweeping over the world for nearly two decades now.

Still in its teenage years here in Singapore, it's interesting to reflect on what was on offer, if anything(!), back then compared to what they offer now; and really evaluate whether it is worth spending your hard earned dough on a cup of joe.

A well-known US coffee chain first opened its doors here back in 1996, they offered branded coffee made on shiny espresso machines, meant to impress and wow the crowd with frothy milk techniques. It was really all about the brand and and selling this to the consumer, along with a fountain of other merc including t-shirts, caps, cup holders, pens, barista bears etc.

Then things started to change, a type of cafe started to emerge that cared more about the product than the fluff of the brand. What they wanted was fresh roasted specialty coffee made on good equipment by well trained, passionate people — and they were willing to pay for it.

Some of them lifted the price of their cups of coffee to better represent the quality they were offering and the additional (and significant) cost paid by them to achieve this higher quality. Some of the pioneers of the increased prices were slammed by the news media, but it appeared that what they were offering had already won the respect and appreciation of the discerning coffee-drinking public. If anything, the media attention, which was intended to be negative, had the opposite effect. The upshot of all of this is was consumers were getting a much better product than they were before, and they were happy to pay for it.

Much of the world’s Arabica comes from growers with very small levels of production. Historically, this coffee has been sold to mill/exporters who then load it into their vast silos, blend it in with all the other small lots and sell the blended result by the container load to everyone around the world. The main difference now is that cafe owners are collaborating much more closely with roasters, and roasters are collaborating more closely with the growers — mainly for the purpose of providing the end consumer with an opportunity to taste and enjoy specific coffee from specific growers.

Achieving this is not easy. Firstly, one of the main reasons for offering microlot coffee is for it to showcase the potential of a particular region — meaning that it’s all a waste of time and effort if the coffee isn’t excellent and doesn’t reflect the characteristics you might expect from the geographical location, growing conditions and processing methods. This needs people on the ground working with the grower to make sure that they are employing the best agricultural and processing practices possible, and that their coffee, once ready for sale, is kept aside from the rest of the tons of coffee going into mill/exporter production lines and is hulled, bagged and shipped separately as small, individual lots.

All of this costs a great deal. The labour inputs are much higher. For example, farmers need to employ more pickers over a longer period of harvest to ensure that they are only picking ripe cherries. The labour inputs are much higher for the mill, as they need to handle the small lots manually and keep the coffee off the automated hulling lines. This separate handling of the coffee continues all the way through the process right through to the cup.

I really enjoy walking into a cafe knowing that I have an opportunity to order a single origin, micro lot coffee. I must admit that I’m sometimes guilty of taking a choice of a micro lot for granted. As an insider, I know what additional costs have gone into taking coffee from the tree of a particular farmer and I love knowing that it’s the very same coffee in the hopper I’m about to order from.

Celebrate the grower and their efforts by ordering a micro lot single origin when you have the chance. Celebrate the cafe owner who has also gone to the effort and expense of giving you the bean.

After all, it’s all about the coffee.

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The Trouble with Soy

Posted by Stella Cochrane on

With the rise of so many different dietary intolerances any good coffee menu needs to include at least one diary milk alternative for their customers. The trouble is that many of these are extremely volatile to heat and don't make for a very smooth latte. Not ones to shy away from a challenge, our coffee partners over at Five Senses Coffee, set about investigating the chemistry behind this phenomenon and coming up with a solution which doesn't turn the stomach.

Following article by Jeremy Hartley, Five Senses Coffee

'“I'll have a decaf, no foam, skinny, tall soy latte.' It's a modern American cinematic cliche, a caricature of the fashion conscious urban coffee consumer with the conspicuously complicated demands! However, for the barista on the cutting edge of the speciality coffee industry, this order might present more challenges than just remembering the details. The trouble is that soy has a frustrating tendency to turn into tofu right before your eyes - and that's not a good look!

The problem is exacerbated for those of us working in the specialty coffee industry. As we push the envelope of lighter roasts to preserve the flavour of the beans, we also preserve more of the natural acids in the coffee. The same chemicals which make our brew brighter and clearer don’t play nicely with colloidal proteins. Stay with me here – with a little bit of protein chemistry it all makes sense.

Curds, whey and colloids
There is a lot to be said for proteins. If you have the right ones handy, you can make spider webs, enzymes, even antifreeze and, if you can suspend them in water, a refreshing milky beverage. The trick is to keep them suspended in water.

Proteins are large, bulky, sticky molecules and by rights, they should clump together and drop out of solution. The reason they don’t is that they are covered in charged (positive or negative) chemical groups. The electrostatic charges on the molecules repel each other and they can never get close enough to entangle and clump. When this is the case, protein strands will stay suspended in liquid indefinitely. It’s called a colloid. The protein isn’t dissolved in the water, rather it’s a solid which floats around in it and never settles.

It’s a fine situation for a refreshing milky beverage until you begin to add acid. The proteins in your drink are endowed with an overall negative charge. Acids are strongly positive. As you add more acid to the drink, the acid begins to cancel out the negative charges which are keeping the protein strands apart from each other. The protein strands link up and clump together. And voila, curds and whey. If you were the kind of kid who always wondered what Miss Muffet was eating, let me help you out; the curds are the chunks of coagulated protein and the whey is the watery stuff in between. I wondered for years.

It’s a very useful process if you want to get proteins out of water. Bacteria eat the lactose sugars in milk and excrete lactic acid, and you end up with yoghurt or, eventually, cheese. If you start with soy bean extract, it’s a step on the way to tofu. It’s not so handy if you’re pouring latte art.

In coffee, acid is only half the story. Not only are you adding acid in the form of your espresso brew, but the milk is heated as well. The heat speeds up the process of acid-induced coagulation, but also has its own effects. If you go far enough with your milk steaming, the heat can damage the protein structure (denature it) in a way which makes the clumping problem worse. It’s what you see when you cook an egg and it turns from clear and runny to white and chunky. So if you’re making cheese or tofu, a little acid and heats is OK, I’d even recommend it, but it’s a difficult balance for a smooth soy latte.

Unscrambling the egg

five senses coffee soy milk testing for common man coffee roasters
It’s not every day you get a chemistry problem to solve in your coffee, and reports of baristas fighting back tofu in their cups around the nation was too much chemistry for us to resist the challenge. We roasted coffee. We collected soy milk. We bunkered down in the Rockingham cupping lab and we went to work.

First up, we made few basic measurements. We tested the pH of soy milks straight out of the bottle. Then we added measured amounts of acetic acid to samples of each milk and streaked them onto a black sheet to visualise clumping. We certainly got very different results from each of the milks. Some went to yoghurt almost straight away (I’m looking at you So Good), some thickened a little but wouldn’t go fully chunky, even with the addition of lots of acid. I’ve never spent so long peering into coagulated soy milk. It’s not something I want to do again.

five senses coffee testing soy for common man coffee roasters

Next in line was the coffee. We brewed up a range of our roasts and measured the pH. The results were surprising. The short version is that you can’t reliably predict the acidity of a brew by the taste. Some of our least acid-tasting coffees measured as the most acidic with objective equipment. For these roasts, it seems that the acid in the bean is too well balanced on the palate to perceive it.

Then we put it all together. Shots were poured of both our most and least acidic coffees, and soy milk was steamed and poured into each. Importantly, a milk thermometer was used to keep the micro-foam temperature at a standard 65°C.

five senses coffee testing soy common man coffee roasters

The most surprising result was how few of the cups obliged with curds and whey. Only one of the milk brands tested separated to any real extent and the rest held together, even in our most acidic coffee. The milk which did fully separate, did so in all three of the coffees tested. But the separation was worse in the more acid one. It was a surprising result given how often one hears reports of curdling soy milk. I hypothesise that in many of these reports, overheating the milk is a factor. Alternatively, it could be that you’re using Pureharvest Nature’s Soy — whatever that turned to would probably have been delicious with oyster sauce.

The overall lack of curds isn’t to say that all the milks performed equally. Some definitely produced a more even and aesthetically pleasing micro-foam than others. The stand out performers were Bonsoy and Macro Organic Soy Drink. Some might be surprised that the ‘barista quality’ milks we tested were among the worst — they didn’t curdle, but it looked as if it was a real effort for them.

Finally we held the taste test. Have you seen those YouTube clips of babies getting their first taste of lemon? That moment when they realise just how horrible the world can be is comedy gold. You should stop reading right now and google it, or set up a soy milk taste comparison for two people with exquisitely sensitive pallets; it’s basically the same show.

I think the taste testers thought I was trying to poison them with burnt plasticine and acetone if you believe my cupping notes. Not cool “barista quality” soy. Not cool.

In an amazing stroke of fortune (or design), it turns out that the two most presentable drinks were also the ones which didn’t make anyone dry retch. This is not a product endorsement, but based on this experiment, next time we make a soy coffee, we’ll reach for the Bonsoy first, followed by Macro Organic Soy Drink.

So if you’re having trouble with curds in your soy milk, it might not be the milk which is the problem (unless you are using Pureharvest Nature’s soy, in which case it almost certainly is). Try keeping a better eye on your milk temperature and see if that solves the problem, you may be denaturing your proteins. If your milk still isn’t presentable, try reaching for the two milks which worked best for us, Bonsoy and Macro Organic. If all else fails, we can recommend a lower acid coffee from our range — it’s all in the chemistry!'

First appeared on Five Senses Coffee's blog.

Don't forget you can get a perfectly made soy drink at the CMCR cafes, just take a look at the microfoam on this beauty!

common man coffee roasters perfect soy cappuccino

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Why you need a Barista Course

Posted by Stella Cochrane on

There tends to be two types of people in the world - those who would openly admit that they could benefit from the excitement and vigour of a three and a half hour barista course, and of course, those who would not.

If you've identified with the first group, that's great! With the opening of the new CMCR Academy KL it couldn't be a better time to book yourself into a class. Don't waste your energy on another bad coffee!

However, if you are thinking to yourself, 'I already know how to make a damn good coffee at home' then this article, my friend, is directed at you.

Let’s get one thing straight. If you have already perfected the process of making great coffee at home, you can answer this one question: Can you explain why your coffee is so good? If you are confidently able do this, you are most likely on your way to understanding what truly equates to mastery in the cup.

If you can answer that question, then you must already have the ability to:

  • Describe the history of coffee
  • Understand the development of coffee throughout the world 
  • Describe ideal growing conditions
  • Explain processing
  • Discuss what affects flavour during each level of production
  • Differentiate the flavour characteristics of origins
  • Provide a general roasting overview and even…
  • Explain body, texture and acidity

But do you also have knowledge of proper dosing, reading and interpreting colour changes, splitting techniques and machine parts and maintenance? If so, then we will assume that your shots are sorted and your milk is mastered.

If the thought of discussing the aforementioned information is like yesterday’s bak ku teh, then please accept our apologies for wasting your time with this useless text.

However, if you think you could afford to learn a few more things about products and equipment, if you’d like the opportunity to experiment with volumetrics and temperatures with an unlimited amount of milk and coffee, and you think it’d be kind of cool to dazzle your friends with your ability to manipulate speed and length to suit their individual tastes, then the CMCR Academy would love to hear from you. Don't forget you'll get an industry recognised certificate and a special something at the end of your class not to mention a plethora of new coffee knowledge from our friendly trainers.

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Eat Chocolate, Drink Coffee - Hello Chocolate and CMCR

Posted by Stella Cochrane on

The similarities between these coffee and chocolate are quite astounding from bean to bar, fruit to cup it really is an amazing adventure to follow. It's firstly important to understand the global shift in the way that we consume products which has greatly influenced both industries. This shift has seen more and more people demanding transparency in production processes and encouraging an emphasis on artisanal or handcrafted products.

common man coffee roasters online store specialty coffee and chocolate event

This is something we have seen in coffee with the so called 'third wave' coffee movement hitting Singapore a few years ago now and we are starting to see this trend spread throughout the Southeast Asian area. However, it is not just coffee that this movement has effected, from beer to packing boxes to specialty eggs (yes really, UK online shopping site Ocado has a whole aisle dedicated to them!) the trend is here, and looks likely to stay.

This focus on quality and traceability has been at the core of CMCR's business since the beginning as we strive to bring you an a-grade product every time. Our ethos is know the farmer, the exporter, the roaster and the brewer and support each step to your cup. We want to live up to what specialty means - a person or place known for making something very well.

common man coffee roasters online store specialty coffee and chocolate event

With this premise, we hooked up with the good people at Hello Chocolate to pair together some of their delicious chocolate with our coffee. Their entire range is specially curated to bring together a range of craft chocolates which showcase different textures and flavours. They also only carry products which pay attention to the source of ingredients and show a strong sense of social responsibility towards everyone involved in the production process - just our sort of people!

common man coffee roasters online store specialty coffee and chocolate night

Just a brief comparison between the two industries, both coffee and chocolate are produced by tropical trees grown between 30 degrees north or south of the equator. Although they are grown at different altitudes (cacao in lower, warm climates whilst coffee much higher, cooler conditions), both trees are harvested for their seeds which then are processed (fermented, washed or sun-dried in most cases) to produce the beans we then roast to create the final product.

Interestingly there are also two original varietals of coffee (robusta and arabica) and cacao trees (criollo and forastero) with further species which are hybrids of these being found throughout the production region.

The night was filled with espresso and filter fun as we encouraged the guests to let the chocolate slowly melt on their tongues before letting the coffee flow over it bringing out all those delicious ever evolving flavour combinations.

common man coffee roasters online store specialty coffee and chocolate event

The best part of the night was that all proceeds from ticket sales where donated to The Leukaemia and Lymphoma Foundation Singapore who provide financial and emotional support for people with blood cancers and their caregivers.

Watch out for more events like these at the CMCR cafe both in Singapore and KL, and remember if you would like to host a party or a coffee appreciation workshop get in touch with us here.

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