S2: Episode 11: Why Coffee Is Blooming Lovely
In this episode we explore the phenomenon of the coffee bloom. It might sound floral but in fact it has nothing to do with flowers. The bloom is actually something that happens during the brewing process. As it tells you a lot about the freshness of your beans and can affect the extraction of the coffee it's a useful thing to get your head around. In this week’s FACQ we take a look at how the bloom can be controlled when brewing espresso coffee.
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Hello and welcome to The Coffee Drinker’s Guide, a podcast for the coffee curious where I explore and explain the world of specialty coffee to make your daily coffee better and more satisfying.
I’m Angela Holder a coffee roaster and writer on a mission to fight back against bad coffee by giving you the knowledge you need to help you get good coffee and a happier (coffee) life in coffee-break sized episodes. So grab your coffee, pull up a chair and take a break…
This week's episode is all about the topic of coffee blooming which has nothing at all to do with flowers but is actually an important element of the brewing process…and later I’ll be answering a question about how the bloom is managed when brewing espresso - so if you are intrigued, stay tuned for that…
‘Coffee blooming’ may sound like some seasonal event on a coffee farm but in fact it happens whenever you brew a cup of coffee. What it is referring to is the noticeable puffing up and bubbling of the coffee grounds when they come into contact with hot water. This lively reaction is down to gasses which have been held within the beans being rapidly released. OK, so this may sound weird, given that I am a professional coffee roaster but I have to confess I worked in the coffee industry for years before I truly understood the significance of ‘the bloom’. Of course I knew that when I brewed my filter coffee the grounds puffed up and bubbled - and that this was a Good Thing as it signalled fresh coffee, but I didn’t fully appreciate its role in the brewing process for quite a while. In my defence the state of knowledge about coffee back then - even in the specialty coffee world - was not as extensive as it is today! So without further preamble, lets get into what we now know about the coffee bloom…
Firstly the bloom and the bean
So what is happening when ground coffee blooms on contact with water? When the beans are in their whole form the carbon dioxide produced during the roasting process protects the volatile oils required to brew your coffee from reacting with the oxygen in air. It almost forms an invisible shield around each bean as the beans slowly degas after roasting. When coffee is ground the carbon dioxide rapidly escapes the grounds and when these are soaked in water the escaping gas causes the visible puffing and bubbles to appear. As the gas leaves it allows the water full access to the coffee oils enabling their extraction from the grounds. For an even extraction this protective gas must be allowed to escape at the start of the brewing process - which is why bloom management is included in modern brewing methods. While blooming may sound like it's a problem when brewing coffee, in fact it is good sign: it indicates that the coffee is fresh. If coffee doesn't bloom it means that enough time has passed since roasting to lose much of the protective carbon dioxide that prevents the volatile coffee oils being lost to the air. In filter brewing if the grounds don't bloom and instead form a concave shape in the filter paper when the water hits them then the coffee is stale. My heart always sinks when I see this as I know then that this brew is a lost cause!
Next the bloom and the brew
If you brew with a filter or cafetière you'll probably have noticed the phenomenon of the coffee bloom. Its especially obvious when brewing by filter. The ground coffee puffs up when the hot water first hits it, then starts bubbling. Sometimes the bubbles are small and rapid, at other times you may see one enormous bubble appear, slowly grow and hold its structure apparently indefinitely. It's a bit mesmerising. When brewing with cafetière the grounds expand and produce a froth or thick crema on top as the water fills up the jug. Good brewing technique involves managing the bloom at the beginning of the brewing process to ensure the best extraction of the coffee. In filter brewing this is achieved by fully wetting the grounds with a small amount of water, allowing the bloom to occur for up to 30 seconds then continuing to add water. Stirring the water in a cafetière before inserting the plunger has the same degassing effect. These small but important steps make the world of difference to the final result.
Finally the bloom and the taste
Ensuring that coffee grounds fully bloom at the start of the brewing process to release the gas they hold means that the coffee oils will be more fully and evenly extracted. This should produce a full flavoured and balanced brew with increased complexity and nuance due to the better extraction of the coffee’s aromatic flavour compounds. Or in other words - it tastes better! Not allowing the coffee to bloom and degas properly results in uneven brewing. This produces an unsatisfactory brew which may be sour, thin and unbalanced. If the coffee doesn’t bloom at all it is a sign that it has already completely degassed and its likely that oxygen in the air will have done its work of robbing the coffee of most of its lovely flavour. Not only will the coffee not taste good, it may even have absorbed undesirable aromas from where it was stored. Yuk.
And now its time for a Frequently Asked Coffee Question…
And this episode’s question is…
Do coffee grounds bloom during espresso brewing?
Yes they do - which is a bit of a problem as the speed of the espresso extraction means that the carbon dioxide gas can really mess it up. Automatic espresso machines manage the bloom by performing a short low pressure pulse of water to wet the grounds before continuing the pour. This allows the grounds to expand a little and degas at the start. A low tech way to reduce the impact of blooming on your espresso shot is to let the whole bean coffee sit for up to two weeks after roasting while it gradually releases stored carbon dioxide. This is euphemistically called ‘resting’ the coffee and is a common practice in specialty coffee cafes. But it results in a more consistent extraction and a better tasting espresso shot. So: happy days!
Thank you for listening to this episode of The Coffee Drinker’s Guide and that was all about the coffee bloom. Do you have any tips for managing the coffee bloom during brewing? Let me know by using the ‘send me a text message’ link in the show notes. Unfortunately, I am unable to reply to text messages but you can also get in touch via Instagram @thecoffeedrinkersguide or email me at thecoffeedrinkersguide@gmail.com if you have a question about coffee. In the next episode we are getting into home espresso brewing and if you are thinking about buying an espresso machine there’s some stuff you need to consider so be sure you hit follow so that you don’t miss it. If you have a friend who also loves coffee please tell them about the show and rate and review this podcast wherever you listen to your podcasts to help other coffee curious people find the show too. Thanks to my executive producer Viel Richardson at Lusona Publishing and Media Limited. You can find him at lusonapub.co.uk. Until next time I’m Angela Holder thanks for taking your coffee break with me - the best way to tackle life is one coffee at a time and here’s to better coffee!
The Coffee Drinker’s Guide is a Blue Sky Coffee Project