It has happened to me on a few occasions and still happens to come across a dissatisfied customer who says that my coffee is not good, that my grind is not good, that it gives off an unpleasant smell when it is opened. of the bag. After checking with the customer, we can see the coffee coming out and overflowing the filter, and making a big mess around his coffee maker, which according to the customer is a grinding problem. As for the smell, it's difficult to verify since the mysterious smell disappears when I put my hand on the bag, but the customer swears to me that there was an unpleasant smell. After suspecting the water, the coffee maker, the dosage, the size of the filter, etc., I was always very embarrassed in front of the customer and offered him a new bag (same batch, same roasting but packaged a day later) and Everything was wonderful there, the coffee tasted what it should. It took me 5 years to understand (I had the answer in front of me every morning): it's the damn CO2!!! Why, I didn't think of that before!!!!
It all depends on our production organization, roasting at the start of the week and delivery Thursday and Friday. Our coffees are packaged quickly after roasting, in special bags with a valve that allow the coffee to emit CO2 through the valve without bringing oxygen and the roasted bean into contact. Except that sometimes, the number of orders received is difficult to predict, especially online, and we sometimes roast a few hours before delivery to customers. In short, the pinnacle of freshness but which can prevent you from tasting the coffee properly.
When I'm working on tasting the batches coming out of the roaster, I use a plunger. When I pour the hot water over the grounds, a neck of swelling foam is created, formed from the ground coffee, which bubbles and threatens to overflow. I use a coarser grind and an immersion time of around 6 minutes, during which I pour in the water gradually. I had never lit up and made the connection between this chemical reaction and my unhappy customer.
This effervescence reaction, called in English "blooming effect", comes from the release of gases trapped in the ground coffee bean (mainly CO2) in contact with hot water. Contact with water simply allows us to see the reaction between the oils and the gas seeking to escape, creating this famous pass.
To quickly explain it, the roasting process produces gases inside the bean due to several chemical reactions including:
- Maillard reaction http://fr.wikipedia.org/wiki/R%C3%A9action_de_Maillard
- Drecker degradation
- Pyrolysis. ( http://fr.wikipedia.org/wiki/Pyrolysis )
It is the Pyrolise, which can be described as an incomplete combustion of the bean (that's what we want, we don't want to calcine it!!) which creates gases. In some areas, this process is done intentionally to obtain other products (gas or material). In the case of coffee, this phenomenon is temporary collateral damage since the majority of the gas escapes from the bean in approximately 72 hours. But even after 72 hours, even after several months, well-packaged, sealed coffee beans will be full of CO2. It is also a very important indicator of freshness.
So, if I roast at 8 a.m. and deliver the coffee to my customer at 11:30 a.m. and when he returns from lunch he takes the bag, opens it and takes a good whiff of the aromas of the coffee, what he breathes in will be a mixture of CO2, a small amount of CO and very little of the coffee flavor. Not a very pleasant smell and since the ideal coffee should taste like what it smells like, it doesn't come off very well. Subsequently, the customer fills with doubt, puts his filter in his coffee maker, puts in the coffee and starts the machine. And there you have the coffee that swells, overflows from the filter, brews too quickly, and doesn't taste very good. And there, we call Dany. And Dany turns the team upside down by checking the batches, delivery dates, roasting dates, sends back a new bag, calls the customer back, etc. I think you understand the phenomenon, when I see that the roasting is very close of delivery, it is a case of effervescence (bloom effect).
In short, that brings me to the notion of freshness. Fresh coffee, we even had it written on our coffee bags. What is fresh coffee? We often tend to put coffee in the same category as bread. A fresh bread, straight from the oven, hence the appearance of a roaster in certain supermarkets. But in my opinion, coffee straight from the roaster is not immediately ready for consumption. We have to let it rest, degas. But not in the open air. Hence the importance of sealable bags equipped with a valve. The coffee should be isolated from oxygen by packing it as quickly as possible in this type of bag or an airtight container. This will allow the grains to rest without deteriorating too much, because by evacuating the gases, we also evacuate certain aromatic compounds.
The ideal is consumption 3-4 days after roasting. And grind 5 minutes before preparation. I regularly taste our coffees after a considerable period of time. Some even, after a few months. And the coffees are delicious. This morning I drank a Kenya AA roasted September 16, 2009. Sealed bag. And last week a Papua New Guinea Sigri AA, roasted the same date, sealed bag. The Papuan had developed a very pleasant sweet and fruity molasses taste. Two excellent coffees that could be considered not fresh…
If you brew coffee and the effervescence is strong, you have fresh coffee. It's a good sign. You can pre-infuse the coffee for 1-2 minutes, moistening it completely. In addition to improving your preparation, pre-infusion will help control effervescence by forcing the evacuation of CO2. It depends on the preparation method used, I obviously recommend full immersions (Piston, Clever, Aeropress) with a slightly coarser grind to prolong the coffee water contact. Using a plunger, mix the coffee well with a spoon at the beginning and end of the infusion. This will reduce the neck which forces the piston to pass coffee beans over the top. If using a cone filter method (V60 or other), pre-infuse and pour the water slowly in a circle to tame the effervescence and brew evenly. And if you have a good quality filter coffee maker, activate the pre-infusion or “pulse-brew” function.
Finally, effervescence is not a negative phenomenon in itself. We must fully understand its origin and know how to counter this effect in the preparation. It also allows us to objectively measure the freshness of the coffee. This phenomenon also helps differentiate coffee from other food products valued for freshness. Fresh coffee is not the same as fresh bread. These are two different products. Very, very, very different...
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