The big freeze: why there’s no longer a barrier to coffee freshness

Imagine going into a café in five years time and asking the barista for a look at the vintage menu of coffees on offer: a 2013 Panama Geisha, Sasa Sestic’s 2015 World Barista Championship (WBC) winning carbonic maceration-processed coffee, or perhaps the number one Brazil Cup of Excellence coffee from 2018 is more to your liking. 

By traditional standards, consuming such coffee years later would prove stale and lifeless in the cup, but what if they were frozen? It’s a concept Ona Coffee is exploring in order to preserve and extended coffee’s shelf life, and by all accounts, it’s got potential. 

George Howell saw that early on. He started freezing green coffee in 2001 to help preserve freshness and flavour, and at Re;Co 2017 he presented a series of vintage harvests from 2012 and 2013 to demonstrate how freezing coffee could preserve its integrity, telling the audience “by all standards, these coffees should have been dead and buried”. But they weren’t. They were very much alive.

Mike Chapman of 1914 Coffee Company in Squamish, Canada has also been serving a frozen coffee menu for several years. Mike has been collecting a vintage freezer menu for more than two years that’s over 100 coffees deep, and now, Ona Coffee wants to lead the way for Australian roasters to start the same experimentation. 

“I want to prove that freezing coffee is no gimmick or WBC trend,” says Hugh Kelly of Ona Coffee’s Research and Development team. “It can actually preserve a coffee’s flavour, extend its expiration date, improve sustainability, and make a huge different to the industry.”

freezing coffee beans
Ona Coffee vacuum seals its espresso coffee in-store, 14 to 16 days post-roast, and placed in a chest freezer at -19°C.

What the freeze?

Put simply, Hugh says the process of freezing coffee involves putting a roasted bean into a frozen state or freezing the cell wall structure of the bean. 

At Ona, individual doses of coffee are placed into vacuum sealed bags and placed under varying temperatures between -32°C to -86°C. 

“Research is still needed to understand how long we can keep roasted coffee frozen and retain a level of freshness, but what we do know is that freezing coffee allows us to stop the cellular activity in coffee particles completely,” Hugh says. “This means that we can capture or lock in the peak flavour window of the coffee, freeze it at that point, and stop the age-old problem of coffee going stale.”

When removed from the freezer, Hugh says the key is to grind the coffee straight away.

“Coffee is extremely volatile and its cellular structure changes very quickly. It can collapse quickly if it’s not treated right,” he says. 

Coffee at room temperature is more pliable and requires more energy to break down into smaller pieces. Pair this with a warm grinder and we generate more static electricity. Frozen coffee, however, has a completely different molecular structure that shatters more easily. Also, small amounts of condensation help to neutralise static buildup. 

Coming from extremely low temperatures like -86°C, coffee grinds remain cold as they enter the hopper. Any heat damage from the grinder is thereby minimised because the coffee particles shatter so easily under a blade. 

“The biggest difference when grinding frozen coffee compared to room temperature coffee is a narrower and overall finer range of particles,” Hugh says.

As such, frozen coffee needs to be ground coarser for espresso. In a side-by-side comparison of an espresso using room temperature beans and frozen beans of the same recipe, Ona Coffee Trainer Matthew Lewin says frozen coffee will taste better. 

“The frozen coffee will have more definition. Freezing the coffee makes it taste super charged with extra flavour and higher extraction yield. It’s more vibrant, sweeter, and more transparent. More everything,” Matthew says.

freezing coffee beans
Freezing coffee can stop the cellular activity in coffee particles and prevent ageing.


Variables 

The moment a bag of vacuum-sealed coffee is taken out of the freezer, there’s a number of variables which can affect the flavour outcome if not treated correctly. Get it wrong, and the result is dismal. Get right, and what you get is a “smoother transition of flavour on the palate”.

“You can get a drastically different extraction thanks to the temperature of your shot if you’re not in control of the variables,” Hugh says.

This includes room temperature, placing the coffee on a bench for 30 seconds and the temperature of the hopper or a utensil it comes in contact with. The list goes on.

To manage variables, Hugh first recommends placing the correct dose volume of coffee into a vacuum-sealed bag to avoid mixing it with additional beans in the hopper that brings its own set of variables. Vacuum sealing essentially sucks out or forces any extra carbon dioxide on the surface of the coffee that would normally be left to release naturally. But this also removes oxygen which would otherwise oxidise the coffee over time. Another tip is to keep the same roasted batch of coffee together on the freezer shelf – temperatures vary from the top to the bottom shelf.

Competition

Hugh learned about variability the hard way. Two weeks before competing at the WBC in Seoul 2017, Hugh found his shot variation to be unpredictable: one day good, the next day not.

Hugh was ranked first place after the first day of heats. After the finals, that ranking slipped to fifth place, and no-one could understand why. What Hugh later discovered was that his coffee kept ageing, and on the third day of competition the coffee had gone well over its peak window of freshness. 

“The truth is, if we had more control of the ageing process of that coffee we could have made it taste like it had on that first day,” Hugh says. “At this point I was using frozen coffee to improve the grinds and flavour profile, and not to lock in its quality.”

Since then, his colleague Matthew Lewin has been driven to find a solution to avoid coffee going stale.

Experimentation

Matthew turned to influences from medical science such as cryogenic freezing, and the commercial food industry such as tuna fishermen and sashimi chefs to see how they utilise freezers to keep their produce fresh. He even referred to chef Heston Blumenthal who freezes black truffles to keep them fresh year-long when out of season. 

A common trait was the use of Ultra Low Temperature (ULT) freezers that can reach temperatures as cold as -86°C, opposed to dry ice that reaches -73°C, and commercial freezers that hit -30°C.

It is possible to put coffee beans straight into a ULT freezer provided you put the frozen coffee straight into a grinder when you’re going to use it. This is Ona’s most commonly used method. The other, is to approach it in two stages. First, use a blast chiller, then a ULT freezer.

Isaac Kim has helped introduce a Reserve Range of frozen coffee to Ona Coffee Marrickville’s menu.

“The faster you freeze coffee the better. In the freezing process, small ice crystals will start to form. The importance of this process is that the cystals won’t burst and saturate the coffee when thawing out – imagine how damp a piece of steak is when it defrosts – but they will help stop the cellular activity of the coffee cells,” Matthew says.

Blast chilling doesn’t take long at all – just 10 to 15 minutes. Matt used this process for the Fushan Cup because he couldn’t have a freezer on stage. He used the blast chiller to freeze his coffee before the competition, and thawed it out on the day. 

In the second stage of freezing, coffee is transferred to a ULT freezer. The longest Ona Coffee has kept coffee inside a ULT freezer is four months, a point where Matthew says coffee’s aroma, texture, and flavour has been “impressive”. 

“In theory, there’s the potential to keep coffee in a ULT freezer for years and retain 90 per cent of the original flavour profile of the coffee. We just need time to explore it further,” Matthew says.

The challenge, he adds, is to freeze the coffee before it goes into its peak flavour window. “For example, for some coffees, the nine to 10-day mark post-roast is when you start to see the flavour potential, and that’s when you vacuum seal it. That’s when you can lock in those amazing flavours,” he says.

With rare and expensive coffees such as Geishas, Matthew says the freezing process gives baristas the ability and the confidence to serve a coffee at its optimum.

“There’s more opportunity to deliver on a price point and flavour that will enhance the specialty coffee experience and education for consumers,” he says.

“So many customers have lacklustre specialty coffee experiences because we have the toughest time trying to control so many variables. It’s hard to get it right consistently, but this method of freezing will reduce that unpredictability. It will also become less challenging to deliver on a $10 tasting experience with the promise of how good a coffee can be.”

Origin

Matthew has been freezing coffee for the past two years. When he competed in the 2017 Australian Barista Championship final, he placed second to Hugh Kelly using liquid nitrogen to freeze his coffee on stage to make the flavour of his coffee taste better. It’s for this reason alone he is determined to “go down the rabbit hole” to see how freezing coffee can be beneficial, not just for the consumer, but coffee producers as well.

“We need to look at the macro point of view. If we get this right, we have the ability to help the next generation of coffee farmers facing climate change. There’s the potential to freeze coffee and deliver particular cultivars even when they’re not in season and halt wastage,” Matthew says. “There’s no need to throw out roasted coffee any more just because demand didn’t meet supply. We can freeze it from the start to extended the period of time we have to sell it. We have control.”

Café application

With the potential of freezing coffee realised, how to apply it to a café environment was the next step. Ona Coffee Marrickville Manager Isaac Kim was tasked with that responsibility for the opening of Ona’s first Sydney café. 

This article appears in the August edition of BeanScene. To read the story in FULL, subscribe now.

For more information, visit onacoffee.com.au