There’s a lot of very strong opinions out there about how long it takes for a coffee to reach its peak after roasting. Some say a couple of days, some say eight weeks. In this article we test and document what we found out regarding what is the actual peak time to drink coffee after roasting and how long coffee stays fresh for.
In order to find out long coffee stays fresh for, we’ve documented the variables that will have an impact and advise you on how you can keep your coffee fresher for longer. With that being said – let’s talk about ageing.
What is coffee ageing?
So what is ageing? And what is staling? What, chemically, is happening there?
Well I suppose there are two main processes or two main phenomena that are happening inside of a bag of coffee as it’s sitting there over time.
The first thing is that coffee degases. So when coffee is roasted, often a lot of co2 is produced and a whole lot of volatiles (volatiles being very very small molecules that exist in a gaseous state). It’s all trapped inside the coffee matrix. As the beans are a porous matrix, there’s some space inside of them and that’s where a lot of these things sit. Over time these things start moving out of the coffee and into the headspace.
There’s a process called degassing and we’ve often found when roasting our own coffee beans that a coffee requires about five days after roasting to get to a point where it’s not degassing significantly anymore.
We found that if you use a coffee within that five day period the extraction is quite bubbly and a little bit more inconsistent because more CO2 is degassing as you grind the coffee.
So that’s one process we call degassing, the other process that’s happening is…let’s just call it ‘coffee chemistry’ because there are lot of different reactions involved. In this is what we would consider the staling or ageing process.
Inside a coffee bag we’ve got the coffee and we’ve got the atmosphere around the coffee and the proportion of that atmosphere of oxygen and water will have a huge impact on how fast or how slowly that coffee ages. There are whole lot of reactions I could go into but it’s suffice to say that oxidation is one of the primary mechanisms in there.
All these reactions happen in concert to change the flavour of coffee over time. So ultimately it’s a balance – that’s why we say ageing and staling – it’s actually a balancing type equation that’s happening. Chemistry is happening, degassing is happening – all of it’s happening at the same time.
Really the only way to tell when the best time to drink coffee is not through chemical modelling (although that would be kind of fun and interesting) it’s actually to taste the coffees at different times with particular standards to understand really when coffee is at its peak.
What influence does packaging have on the coffee?
So how did we test what is the optimum time to drink your coffee? Well it’s important to note that there are a couple of different ways that coffee has been packaged.
Above, we mentioned the atmosphere doing some chemistry. Well, if you flush it with nitrogen, a lot of those oxidation reactions are minimised or the kinetics is significantly lowered because you’ve got an atmosphere of nitrogen not oxygen (or very minimal oxygen) so that’s called nitrogen flushed packaging. And we found that typically over time that preserves coffee for longer.
Hand packed coffee
The other way companies package coffee is to literally do a hand pack. They have an open bag, they shovel coffee and then they seal the coffee.
Because they are exposed to more oxygen than the gas flushed versions, they typically age faster so it’s an important point to note.
Taste test results
So what are the results? So we used a medium roasted coffee in both gas flushed and non gas flushed bags.
For gas flushed coffees we found that their peak flavour was at around two weeks (well between 1.5 and two weeks) and actually maintained this peak right through to eight weeks. Now we didn’t test this at six months but we do have evidence to suggest that at six months this peak is relatively maintained but from the experiments that we did over eight weeks we found that it maintained its peak consistently.
Interestingly enough when we tested the non gas flushed version (the same coffee, same packaging, just without that nitrogen atmosphere) we found that the peak was reached significantly earlier at around 1.5 weeks. And that peak interestingly enough, amongst all the tasters that were involved with the experiments said they all agreed that the flavour was superior at that one and a half week period.
So non-gas flushed coffee has a slight superiority in terms of taste but that superiority, or that peak in flavour, dropped off quite dramatically after about two and a half weeks.
So in other words, non-gas flushed coffees have a better taste at their peak but that peak freshness isn’t maintained for long. Gas flushed coffees hit their peak at around 2 weeks and can maintain their freshness for at least 8 weeks.
The other findings that we found is that using coffee within five days of roast date generally results in a fairly inconsistent extraction and a fairly harsh flavour. So essentially we would never recommend drinking coffee within five days of roast date, especially where consistency is concerned.
How long does coffee beans stay fresh?
Coffee beans that are not gas flushed will hit their peak 1 and a half weeks after they’re roasted and will stay fresh for a further 2 weeks. After this period, the freshness begins to drop off quite dramatically.
For gas flushed coffee beans, peak flavour will be 2 weeks after roast date. They can stay fresh for at least 8 weeks and in some cases even longer.