BeanScene Magazine


Zest’s micro-lot flavour creation in PNG

From the August 2017 issue.
Zest’s micro-lot flavour creation in PNG

Rob McDonald talks about Zest’s Project Raggiana, and the making of micro-lots using low-oxygen fermentation.

By Rob McDonald, Creative Director at Zest Specialty Coffee Roasters.

It’s around a one-hour drive from Mount Hagen airport to the Sigri Coffee Estate, located in the Wahgi Valley of the Western Highlands in Papua New Guinea. For the most part, the road is newly laid or well maintained, however, there is a section of road that passes by a pineapple market that slows the traffic to all but a crawl.

Our Land Rover Defender navigates a path between the crater-like potholes and cut-out ruts, past the line of pineapple vendors. Their faces filled with eager expressions.

“You can’t be serious,” I say. “There is no way a group of pineapple vendors could band together, hire earthmoving equipment and get away with destroying a 150-metre stretch of newly-laid road for the sole purpose of increasing pineapple viewing time and upping their sales?” But that’s exactly what they did.

“Welcome to PNG,” says Sajith Shankar, Sigri Estate Manager, as we pass by the mounds of tasty-looking fruit. Sajith was not only my Sigri Estate guide, but welcomed me into his home for a delicious Keralan curry.

The purpose of my visit to PNG was to help produce micro-lots for Project Raggiana, and capture the beauty of the Sigri Estate farm and its workers in a cinematic film. But the real backbone of my visit was a fermentation experiment in which I hoped to uncover the potential of PNG coffee to produce a top-tier specialty and micro-lot drinking experience.

Fermentation, within this context, is the process in which a sticky, sugary layer of mesocarp, called mucilage is removed from the coffee seed before it is dried. It is also the process in which microorganisms, mainly bacteria and yeasts, consume sugars and produce organic acids, carbon dioxide and ethanol.

The exciting part of the experiment, is that by controlling and designing the fermentation environment, you can have a large influence over the coffee’s final flavour.

To this day, PNG is relatively unexplored in terms of producing small lots of specifically processed coffee, which is quite remarkable because PNG has some of the most environmentally ideal coffee-growing conditions on the planet.
Also, historically, much of PNGs original coffee farms were planted with the seeds of the world-famous, high quality Jamaica Blue Mountain Typica. This variety still remains the dominant coffee grown by small holders and plantations throughout the PNG Highlands.

However, the biggest attraction I have with PNG coffee, is its flavours. Every now and then, our sensory team will hold a cupping of PNG samples, in which the odd, rare cup reveals jaw-dropping flavours, such as jellybean-like sweetness, and a unique sparkling acidity. It was the lure of these tasting experiences that planted the initial seed in my mind to venture to the remote highlands of PNG and explore the flavour possibilities.

Despite PNG’s close proximity to Australia, the overarching reason the country has remained relatively unexplored in terms of specialty micro-lots is because the Papua New Guinean people have a strong culture of tribal warfare, which can create a security risk for foreign travellers. During our visit we didn’t encounter any negative or dangerous situations, but we did make a very active effort not to be in the wrong place at the wrong time.

The aim of our fermentation experiment and the Project Raggiana micro-lots was not only to produce coffee from carefully selected, ripe Typica cherry, but to push the boundaries and really understand the impact of controlled, low-oxygen fermentation on the coffee flavour profile.

By boundaries, I’m talking about the length of time spent fermenting and the degree of pH (potential of hydrogen) reached before washing the coffee, and ending the fermentation. Basically, we wanted to determine how long and how low the pH could go before things went sour. In planning the experiment, we consulted coffee fermentation experts, such as Felipe Sardi from La Palma & El Tucan in Colombia, and learned that a low-oxygen environment would slow the metabolic rate of fermentation and allow more scope for flavour creation. We also learned that a low oxygen environment enables a desired microbial community to become dominant. This dominant community has a strong correlation with great tasting, fruity cups with a high lactic acidity.

Our fermentation protocol was to monitor the pH, Brix sugar content, and temperature of each of the fermentations three to four times a day. From this information, we could map the metabolic rate and better understand the different stages of the fermentation as well as correlate our tasting experience with different lots and finally, hypothesise the causal flavour impacts of fermenting for longer times or to different levels of pH.

This article features in the August 2017 edition of BeanScene Magazine.

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