You will often heard it said that the mark of a great espresso is the ‘crema’ but what does this mean?
Crema is produced during the the high pressure brewing technique required in making an espresso. Brewing extracts insoluble oils which produces the crema, a rich velvety cream that sits on the top of the coffee. It is in effect the product of the co2 in the beans which escapes in the form of thousands of tiny bubbles under high pressure. These are coated by melonoidins in the coffee which keep them from bursting.
So putting it bluntly crema is really a very robust type of bubble! But it won’t last forever. Ideally you need to add your milk to your latte in just 10 seconds.
Why is Crema Important?
It enriches the flavour and texture of the coffee and also indicates how fresh the beans are. CO2 starts to escape after roasting so beans roasted a long time ago will be less gassy and thus produce less crema.However do remember that different coffee varieties produce different amounts of crema and dreadful tasting coffee can also produce crema.
If your crema has little brown flecks in it don’t panic, it is in fact a sign of good extraction. They are actually tiny granules of coffee forced out during the brewing process.
This can look lovely and smooth but a yellow crema can be an indication that the shot was too quick which will result in an under extracted brew.
Deep Brown, Black Spots
This is the opposite of the above. A dark brown crema can indicate over extraction and a shot that has been pulled too long.