The project is now well underway.

Here we are, still in our oversized island that is Australia, able to play with this amazing raw material that has been our single-eyed focus since starting our business back in 2009. It’s one thing to read about the various ways to process coffee and quite another to actually do it for ourselves.

Each day the Zest team has been hard at work picking cherries from early morning. The drying beds have been built and the first natural lots are already drying under the warmth of the North Queensland sun.

Now we are keen to get further experimental lots started. Washed, honey process and more fermentations are on the schedule for today.



The honey process is one that has always piqued my interest and I’m very keen to see it happen in real life. To me it at least sounds better and tastier than washed or natural. But what is it really? Actually, it’s something of a hybrid of the washed and natural processes.

We know the natural process produces fruity notes, strawberries, blueberries, blackberry flavour in coffee, and it encourages a heavier body or mouthfeel, with less acidity compared to washed process. With the washed process, on the other hand, we expect high acidity and we should experience higher clarity of flavour, a result of using lot of water to wash the beans – it’s a cleaner cup of coffee. Flavours would be more like citrus, lemon, lime, peach, pear.

With the honey ‘hybrid’ process we can expect some flavour characteristics from both washed and natural to be present – not as clean as the washed, and not as heavy or fruity as a natural. Less acidity than washed coffee and more sweetness, while it borrows some berry flavours from the natural. We hope our honey process will yield some complex, interesting flavour notes from this Australian-grown Catuai coffee.

In this process we will remove the skin and flesh of the cherry by depulping the fruit but we will leave the sticky mucilage around the seed and put the coffee straight out to dry without any fermentation or washing. The fact is that an extended fermentation (or oxidation) will happen on the drying beds as the sugars in the mucilage break down.



We are using a nice little red and green depulper which we were lucky to pick up second hand. It’s a solid piece of engineering that has originated from the faraway coffee growing country of Colombia sometime in the distant past. The job of the depulper is to separate the coffee seeds from the skin and flesh of the cherry. This depulper is driven by an electric motor – very different to the hand cranked versions our guys have used in PNG and Peru. This should be much, much faster and a whole lot easier on the arm muscles!

We haven’t had any opportunity to test this depulper yet so we all gather round with bated breath as we prepare to flick the switch and run our first bucket of cherries through the machine. Will it do the job?

It whirrs into action and the first red cherries crowd into the hopper on top of the machine where they are very quickly swallowed by an auger screw that feeds them into the fast spinning depulper head. The narrow space between the head and the casing and kitchen grater-like blades on the rotating head quickly rips the skin from the seed. Sticky seeds shoot out a spout into a bucket while the red skins drop into a crate underneath the machine.

The first bucket is done before we know it. But we do notice that quite a few coffee seeds have found their way into the waste skin bucket too. Too many to waste so there’s another painstaking step for someone to carefully extract as many coffee seeds from the skins as possible. Too precious to waste after all the effort of picking!



After a number more buckets are depulped, we have a good quantity of coffee seeds ready to transfer to the drying beds.

I have heard a lot about honey processing but to actually feel these sticky beans in my own hands is a new experience for me. Slimy, silky, sticky. It’s almost as if they are covered in a layer of viscous goo. This slimy substance is made up of a variety of proteins, sugars and pectin. If left on the bean as in this honey process, this is what will ferment and oxidize while drying to impart a sweeter flavour to the final coffee product.

We split the beans between two drying bed compartments. We’re keen to discover the difference in flavour between a yellow honey and a red honey process.



In some areas the difference between yellow and red process is defined by how much mucilage is left on the seed before putting it out to dry. We, however, are using exactly the same beans straight out of the depulper with the same amount of mucilage to produce both types. The way we will achieve the difference between yellow and red is only in the way we dry the lots.

In the yellow honey process the sticky seeds are spread out over the drying bed or patio in a thin layer from the beginning of the drying process to the end. The beans are turned often on the beds. This is the fastest way to dry honey processed coffee. Oxidization (which is the chemical process that darkens the colour of the mucilage around the bean) is limited because of the spread of the coffee. Drying is accelerated because the maximum surface area of the beans are exposed to the dry, warm air. This should result in a batch that is quite yellow in colour and exhibits clean but sweet and complex flavour profiles with some muted acidity.

Red honey, on the other hand, is the result of a slight variation to the drying method. Instead of leaving the beans spread out over the drying bed for the whole drying period, after a couple of days we will heap the coffee into piles. This slows the drying and reduces exposure to the air. It also produces heat in the body of beans and thus enhances conditions for increased oxidation of the mucilage. These piles are turned less often than the yellow lot. The red gets its name from the colour of the mucilage at the end of the drying process which should be deep red – distinctly darker than the yellow. And the flavour? We expect a more full-bodied coffee with flavours of darker forest fruits, plum and prunes in the cup. And with less acidity than the yellow. Will it happen? At this stage we have no idea. Both lots start off looking exactly the same.

Now it’s just a waiting game.

Just on an aside, if we had had enough cherry, we would have liked to do a black honey too. A black honey? What’s that? Well, apparently, in a black honey the fermentation and drying process is slowed even further by covering the pile of coffee beans with plastic sheet or tarpaulin. This increases the heat generated in the pile of coffee even further, slows the drying and allows for even greater fermentation of the mucilage. In fact, in turns quite black, hence the name of the process. The result? Anticipate deep boozy fruit flavours closer to the natural process.



With the honey process lots now on the drying beds, we turn to our next objectives. Some interesting lots that will be fermented in sealed tanks.

This has always been of interest to us. We have conducted fermentation experiments in PNG, Sumatra and Peru. Fermentation is the introduction of another step in the coffee process. It’s another flavour influencing step. A step with as many variables and options as you can dream of. Which is why we’re interested. At Zest we’re fascinated with flavour. Fascinated with the nuances that we can draw out of the humble coffee bean.

The fermentation process occurs when microorganisms (yeast, bacteria, and fungi) that naturally occur in the coffee fruit and microflora acquired from the environment, degrade the mucilage surrounding the coffee seed by producing various enzymes, alcohols, and acids. Several factors impact the initiation and progress of the fermentation. Environment, temperature, pH, acidity, ethanol, sulfite and availability of nutrients are all important for the growth and metabolic activities of the bacteria.



Just to take you behind the scenes for a minute… We’re using these amazing terracotta coloured barrels as our fermentation tanks. A robust black screw on lid firmly seals the drum and locks in the desired environment. We have added taps in the sides and a valve in the lid. We found these drums very cheap second hand actually. Recycled! Just what we needed for our project.

We received them at our roastery in Victoria. To our horror, as we undid the lids and poked our noses into the drum cavity, a strong and pungent odour overwhelmed our senses… Olives. These were obviously olive drums in a former life and while the construction and physical features of these containers suited our purpose perfectly, this lingering odour did not…

What followed was a very time consuming cleansing process. We read up to find that the use of bicarbonate of soda had been proved to purge unwanted odours from plastic containers so the local supermarket shelves were severely depleted of this essential ingredient as we soaked, washed, soaked and rewashed our precious tubs.

After shipping to far north Queensland, we repeated the process on the farm until we were all entirely satisfied (after much communal sniffing of drums) that they were uncontaminated from that really persistent olive odour and fully ready for our equally sensory orientated fermentation trials.

A lot a background work and effort did go into giving this project every chance of success!



Our fermentation experiments are to include both natural and washed lots. We are committed to doing at least four fermentation lots in total. Why? To explore! Explore the potential of this Australian coffee from every possible angle and dimension.

Today we are going to start a standard washed, a yeast fermentation and carbonic maceration lot.



The standard washed process is probably the most commonly used method across the coffee producing world. It relies on a 12-24 hour fermentation step to separate the pectin rich mucilage from the bean which is then washed off with water before the coffee is dried. It uses the most water of all the processing methods and produces the cleanest flavour of all processes.

As with our honey process lots, we have floated and depulped the coffee cherries allocated for this standard washed process batch. We then put these sticky goo-covered beans into a tank with no water for 24 hours. This is called a dry fermentation. Just the time and temperature of these coffee seeds being in close contact with each other should work an amazing biological reaction to loosen the mucilage from the surface of the bean. Tomorrow we will open the tank and wash the coffee three times to remove the mucilage before transferring the parchment to the drying beds.



The next process is more exciting. It called a yeast fermentation.

We started our experimentation with coffee yeasts in 2019 when we went to Peru working with Bosques Verdes. We used the same yeast we have here today which is called Intenso and is made by a Canadian company, LalCafé. We got pretty good results in Peru so we have decided to try this here at Jack Murat Coffee farm to see if we can draw more red fruit and tropical fruit flavours out of the coffee. Our good friend, Christopher Feran from Phoenix Coffee Co. in the USA has helped us get our hands on a bag of Intenso yeast at very short notice. Thanks Chris! Fingers crossed we are going to achieve a great result!

The process is as for the standard washed coffee. Except that we are going to add coffee yeast to the fermentation. The whole idea behind using a coffee yeast is to provide more control over the flavour creation process as the coffee ferments. In the standard washed process, you still have the same fermentation period and method but you have no control over the type or quantity of yeast or bacteria fueling the fermentation. It is just what happens to occur naturally in this coffee and on this farm. By adding a specific known strain of coffee yeast, we are going to achieve more consistency in the flavour development as the added yeast will dominate over other naturally occurring bacteria and yeasts so that they don’t get a chance to contribute to the flavour.

First, we measure our yeast amount on a scale. We need to be precise, 15g of yeast is all we are using in this lot. The yeast is dry, fine and granular, almost white in colour and it pours easily into our measuring cup. We add this to a clean bucket (it is important to use clean vessels and tools so that we don’t unnecessarily introduce foreign yeasts or bacteria).

Now we must add water. But not just any water. Our coffee guru, Aryan, insists that we use rainwater from a tank on the farm. Why? We want soft water that will not interfere with the yeast activity and effect. And the temperature must be right too to activate the yeast. Aryan checks the TDS and temperature of the water. The temperature is 22 degrees and the TDS is 11ppm. Perfect.

We add the dry yeast to the water and stir vigorously with a somewhat oversized plastic paddle. We must agitate well for about 10 to 15 minutes to allow the yeast to dissolve and activate properly. As Aryan stirs, we can already smell the aroma of yeast. It smells a bit like baker’s yeast but this product has been developed especially for enhancing coffee flavour. It is designed to bring out red fruit flavours and increase the body of the coffee – make it a bit creamier and heavier. Soon we see bubbles forming on the surface of the water – a sign that the yeast is activated and ready to be added to the coffee in the tank.

We put the pulped coffee into the tank and then add the yeast solution. Looking into the drum we see a lot of bubbles on the surface of the water which shows the yeast has started doing its work. We need to ensure all the pulped coffee is submerged so we top up the tank with a little more rainwater – just enough to cover all the coffee seeds.

To enable us to monitor the fermentation process we add another smart little gadget to the tank – a wireless temperature probe called a Hobo (of all names) data logger which has been set up to connect via Bluetooth to Aryan’s phone. This little data logger will keep monitoring the temperature in the tank 24 hours a day and transmit it to us through the whole process.

With the data logger in the tank, we now screw the lid on. We then move the tank with a trolley into the warehouse cool room where we can control the external temperature. We will monitor internal temperature and pH to determine when the fermentation is complete. Then this lot will be washed and dried on the raised beds.



We feel a little shy using this term because, in coffee, it really has been made famous by another of our industry friends, Sasa Sestic of Ona Coffee. We’d like to give him and his team the credit. They have done an amazing job in researching and spreading the benefits in terms of flavour in the cup of this processing innovation. Of course, even before Sasa coined the term for his coffee process, this technique was well known and established in the wine industry where it has been used for years to make wines taste fruitier and soften the tannins.

Most wines turn grape juice into wine via a yeast fermentation. But in carbonic maceration the initial fermentation is not caused by yeast but instead occurs intracellularly, or from the inside out. This method involves filling a sealed tank with CO2 and then adding whole grapes. In this anaerobic (or oxygen free) environment the grapes begin to ferment from the inside using the available CO2 to break down sugars and acids and produce alcohol and flavour.

The process for coffee cherries works in much the same way.

We have followed the familiar protocol of picking and floating the cherries and we add them into a tank as whole cherries. We are doing a dry anaerobic fermentation so no water is added. We then remove the oxygen (by a very simple method of lighting a candle in the sealed drum which burns until all the oxygen is consumed). As bacteria and the yeasts in the tank digest the sugars in the fruit, this produces carbon dioxide which fills the whole tank. This environment contributes to the flavours produced as the coffee fruit ferments around the coffee seed.

We repeat this to process produce two lots. The first will be fermented for about 90 hours while we hope to be able to extend the second lot to about 140 hours. Again, these are variations of methods to explore the effect on final flavour in the cup.

Both lots will be kept in the cool room at 20 degrees for controlled temperature fermentation.

A tube is connected to a valve in the lid of the drum. The end of this tube is submerged in a bucket of water. This will ensure that CO2 can bubble out from the tank but no oxygen can enter. The pH will be monitored regularly each day by taking a small sample of water from a tap which we have installed at the bottom of the drum – the pH will .



A lot of effort is going into these lots. They are quite small which gives opportunity to give our full attention to each experiment. Hopefully we will produce some wonderful, exotic results but really at this point we can’t predict the outcome. We’re working with Australian grown coffee for the first time. A raw material that has, to this point, not yielded a really high scoring micro-lot. What we do know is that these coffees are going to be very scarce and very precious to us!



We’ve been busy and the day has passed quickly. Darkness descends on the farm and the birds chorus their last hurrah. A tired bunch of guys heads back to the motel.

Anton, fellow director of Zest, sums up the day – and the project – as if reassuring us it’s all worth the effort…

“Guys, what we’re trying to achieve is a great tasting Australian coffee. We don’t know everything, but we’re learning together. It just an experiment, you know, we’re trying a whole lot of different methods, and at the end we’ll say, hey, that one worked! How can we scale it up?”

He’s right. We have no basis or desire to be arrogant. We are just thankful for this opportunity to live what we love…

Exploring exceptional coffee flavour.


Blog written by Rod Greenfield
Director Zest Specialty Coffee Roasters