Why does coffee bleed? What does this mean for baristas and roasters?

The fresher the coffee, the better,right? Yes... But not really.

No one wants to drink coffee aged, butbrewing it right after roasting can also lead to disappointing flavors due tothe coffee exhaust factor. Whether you're a roaster or a barista, you need tobe aware of this. So let's explore what coffee exhaust is, how it affects yourbrewing and what should be done about it.

What is coffee exhaust?

Exhaust refers to the gas that isreleased from roasted coffee. When coffee is roasted, gases form inside thebeans (including large amounts of carbon dioxide).

Large amounts of these gases arereleased in the first few days after roasting. As you brew your coffee, theescaping gases can cause small bubbles. These air pockets can break the contactbetween the grounds and the water, which can lead to uneven extraction of theflavor and aroma compounds in the dried coffee.

In other words, if you brew coffee thathas just been roasted, it may negatively affect the flavor and flavor of thecoffee.

For this reason, it is best to wait afew days after roasting before brewing your coffee. This time period, and thechemical release that occurs during it, is called venting.

Why is carbon dioxide always present incoffee?

During the roasting process, coffeebeans undergo many different chemical reactions. Complex carbohydrates arebroken down into smaller molecules, beans begin to brown, and large amounts ofwater vapor and carbon dioxide are produced.

When you hear or see a burst, it'sactually a buildup of gas that causes enough pressure to break down the cellwalls of the bean. But the gas production continues throughout the bakingprocess.

Ensei Neto is The founder of The CoffeeTraveler. He told me, "The most important chemistry happens near the endof the roasting, because that's when the saccharification happens. "Whenthe energy is released, it creates gas.

Coffee exhaust: 'just in time'

However, the carbon dioxide in coffeebeans is not a bad thing: it plays an important role in coffee quality. "Itis an indicator of freshness, plays an important role in shelf life andpackaging, influences extraction processes, is involved in the formation ofoils, and may influence cupped sensory data," says a 2018 report inAgricultural and Food Chemistry.

When coffee has too much exhaust, itsflavor diminishes. The trick is to allow it to exhaust sufficiently withoutBrowning the coffee beans. As Juan Mario Carvajal, co-founder of Latam SCA,told me :" The gas that is still being released is an indicator offreshness, but when the beans are too fresh, it prevents the grounds from beingfully extracted. ' '

If the coffee you use has not beenvented long enough, it may take longer to extract the espresso because thegases can impede the flow of water. These gases create bubbles, so they help toproduce impressive oils. But the taste is not ideal because they also interruptthe extraction.

He uses the award-winning Behmor 1600Plus as an example of how to roast Guatemalan coffee. After 72 hours, it willtake on a rubbery flavor, he said. But after 96 hours, the chocolate tastebecomes more distinct and "coffee characteristics have established",he said.

How long does it take to exhaust?

Therefore, venting allows the carbondioxide produced during baking to disperse. But we don't want all that gas todisappear. Instead, we should brew it when sufficient quantities are present.The right amount of carbon dioxide will give coffee a richer flavor.

However, how long it takes to ventafter roasting depends on several factors. Typically, some time between threedays and two to three weeks after roasting is considered a good time to brewcoffee. But every coffee is different, and the amount of venting time requiredwill vary. Brewing method, handling method, and roasting curve all affectventing time.

"Harvesting is always differentthan washing, drying is always different, and the amount of water in beans isalways different," said Sharavah Harper, co-founder of Uncharted Coffee Coin Pueblo, Colorado. "So I'm sure that's why the [exhaust] changes...Different sizes of beans have different amounts of water and gas."

How to brew

You can use them as soon as possible,within a few days of baking, if you are hand rinsing or French pressing them. Thisis because the coffee stays in contact with the water longer.

By contrast, when we do espresso, theextremely short brewing time means that the CO2 bubbles have a greater impacton extraction.

"Espresso is special," Joetells me. It needs a break. You will not see an espresso made right after thefresh roast.... The standing of the coffee is crucial, and venting has a majorimpact on the flavor of the coffee. "

Mark Michaelson is the head roaster atAgate Coffee LABS and the 2017 National Roaster Champion. He told me :" Weusually want to start making espresso five to seven days after the coffee hasbeen roasted, mainly because it's easier to extract. For pour-over coffee, ittakes one to two days. ' '

He also explained that whenself-roasting coffee is used in competitions, it usually takes between 10 and21 days of roasting exhaust time. "Because it's easier to pull, it'seasier to extract," he said. ' '

How to handle it

Washing, sun exposure, honey treatment:The way the coffee is processed can also affect the exhaust. "We'venoticed that sun-baked coffee takes longer to exhaust than washed-upcoffee," says Mark.

"I've noticed that sometimes younotice a decrease in freshness after three to five days. Compared to washablebeans, sun-cured coffee takes more time to vent. ' '

Baking Overview

Deep roasting speeds up the ventingbecause the sugars in the coffee beans have more conversion and reaction, andthere are more tiny cracks that can release carbon dioxide.

Sharayah told me, "When you bakelighter, you keep more beans." That means shallower roasts take longer tovent.

Ensei cautions me that if bakedunevenly, it can lead to internal layering of the beans. These layered partscan react at different times, depending on their level of development, whichalso changes the rate of venting.

How do you keep your coffee beans fresh

How can you be sure that your coffeehas been vented to the right degree?

Sharayah recommends setting up a goodsystematic arrangement so that roasted coffee doesn't last too long."Keeping reliable records helps us a lot, especially when we roast a lotof coffee," she says. ' '

He usually fills the coffee bags, whichhave exhaust valves, within 20 minutes to an hour after roasting. "Most ofour coffee travels at least three days to reach customers. We just want toallow the venting, especially in transit, to 'calm' the coffee down abit."

We often see airtight containersrecommended as the ideal coffee storage tool to "keep it fresh". However,when you use fresh home-baked beans, the container should allow carbon dioxideto escape. And, you should consider roasting in batches so that you can use allof your coffee before it becomes obsolete.