Spontaneous fermentation, as defined by Milk The Funk Wiki, is simply, “The inoculation of wort for fermentation with local ambient microbes.”

As brewers, we all know this method of fermentation is nothing new. But long before humans understood what bacteria, yeast, or social media was all alcohol was made by leaving sugary liquids hanging around for varying time durations until something happened.

It wasn’t until the 17th century when Dutch scientist Antonie van Leeuwenhoek, respectfully known as “the father of microbiology,” discovered microbes. He first referred to what he had found as “dierkens”, or “small animals,” which he was able to discover through the use of his self-designed single-lens microscope.

Let’s fast forward to 1859, Louis Pasteur has just discovered how yeast works and revolutionized modern brewing and the role yeast plays in fermentation. Over time, the more we have learned about the behavior of yeast, the more regulated and controlled fermentation has become.

Brewers learned that the more yeast was refined and isolated, the easier it was to replicate their recipes and make consistent products.

But hey, just like punk rock – look around you! It should be apparent that there is something innately rebellious in being a brewer.

Reviving an ancient art

Spontaneous fermentation never went away, as seen with the lambic beer from the Pajottenland region of Belgium, but over the past ten years craft brewers have started to restudy and embrace these ancient fermentation methods. Some have even created their own regional spontaneous wild yeast programs.

Spontaneous fermentation is created by a balance of obsessive science and blind trust, with the result being a product of both the brewer and the environment in which it was made. A symbiotic relationship, if you like.

When I think of spontaneous wild ales, there is no easier way to describe them but “complex.”

The interaction of climate and terroir (a French term used in wine-making to describe the environmental factors that affect a crop’s phenotype) make wild ales, by definition, regional. Therefore, no two are alike. For instance, a wild ale brewed in Belgium will most definitely not taste the same as one brewed in Asia.

The components of wild ales can include hints of everything from “musty hay,” to “moldy cheese,” all the way up to the differences in the acidity of citrus fruits. These characteristics are among the short list of phrases to describe the taste of wild ales.

A trip to the islands

Lamma Island is situated a short 3 km boat ride southwest of Hong Kong Island, comfortably nestled in under the Tropic of Cancer. According to a study conducted in 1999 by The Chinese University of Hong Kong, 648 plant species were recorded on the island with 151 of those classified as rare or very rare (for a more complete and detailed look at the many species of plants indigenous to Lamma Island, please click on the link for Able Charity HK: http://ablecharityhk.com/flora/)

Luke Yardley, has called Lamma Island home since 2010 and so has his brewery, Yardley Brothers Craft Brewery, which he founded together with his brother in 2013. As the brewery grew their production facility was relocated Kwai Hing on the Kowloon mainland, however they have always maintained their presence on Lamma Island, with their locally renowned and recently upgraded Beer Shack.

Specializing in mixed cultured wild ales and barrel aged sours, Christmas 2020 brought to their brewery a 100L coolship.

For months now I have been bugging Luke, no pun intended, to conduct an experiment to capture wild yeast on Lamma Island.

Despite Hong Kong’s sub-tropical climate, there is a small window of opportunity between December and January when the temperature can drop low enough to support inoculation. Furthermore, to my pleasant surprise, reports of Hong Kong having the “coldest” New Years Day in twenty years gave us the first opportunity to have a try.

After discussions on recipe formulation and brewing methods we set a date for our experiment, the evening of Friday January 1, 2021.

To help us with this experiment, we were lucky to get assistance from the President of the Lamma Homebrew Club, Scott Taylor who kindly allowed us to utilize his impressive homebrew system, along with his beautiful property, to park the Yardley Brothers coolship for the evening in his yard surrounded by a plethora of indigenous flora such as eucalyptus tress and bouganvillea.

(i) A homebrew system was used to prepare the wort (ii) The coolship was left out overnight among indigenous flora (iii) The inoculated wort was collected and sent to the brewery for fermentation

The recipe

Brewing in the traditional sense along with the brew set-up size would have proven to be difficult to fill the coolship so we decided on two separate mashes with each recipe being made up of the following ingredients:

FIRST MASH: Maris Otter 14.2kg (70%)  & Oats 6kg (30%)

SECOND MASH: Maris Otter 7.1kg & Oats 3kg

9g of calcium chloride and 6g of gypsum was also added to both mashes for water corrections.

For the first mash in, we did a short protein rest and collected 50% of the turbid mash into the kettle and boiled it to extract tannins, starches, and polyphenols.

Next, we continued to heat 30L of strike water to 73c to top off mash with a target temperature of 66c. In reality, it was actually 68c. After a ten minute rest, we stepped up the temperature to 76c and 78c for ten minutes each, respectively.

Aged hops were added to the boil for their anti-microbial properties

With another short mash time, the wort was run off into the kettle with a PH check of 5.5 before boil, with us hitting our target pre-boil gravity of 1.043 and post boil of 1.048.

The second batch was a single infusion mash at 69c for 40 minutes with a pre-boil of 1.043 and post boil of 1.048, hitting our target gravities for both mashes.

Before we added 167g of ten year old aged hops, we did a PH adjustment with 100ml of phosphoric acid to prevent mold growth and inhibit any possibility for botulism with a final PH of 4.54.

At cast out, we added the aged hops to the combined mashes into the coolship. We cast out with the wort at 92c and the stainless steel of the coolship at 10c, with all the wort into the vessel at 9:20 PM at a temperature of 71c.

With a midnight temperature check at 46.6c, we came back at 6:45 AM the next morning to find the wort sitting comfortably at 17.5c.

The inoculated wort is transferred to barrels for fermentation at the Yardley Brothers brewery

After a final PH reading of 4.54 and an original gravity of 1.048, we emptied the coolship into twice cleaned kegs, to be sent over to the barrel room at the production facility of Yardley Brothers in Kwai Hing. As a test sample, we filled a growler with a sample of wort as to monitor the fermentation process without disturbing the barrel.

So let’s get something out of the way. Just like this article because there is no en

ding to this story yet, you probably shouldn’t bother with spontaneous fermentation if you’re impatient or if you fear uncertainty. You must let go to be in total control, be willing to except unknowable outcomes and take things like they come.

Spontaneous fermentation gives you the opportunity to create something truly, uniquely yours.

I hope this article has enlightened a few and spark some ideas on the endless of creating new and unique beers – we’ll let you know how ours turned out.

Cheers!

James.