Colombia San Jose Rum Barrel Fermentation Special Processing Method Coffee Explained_The Source of Rum Flavor

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FrontStreet Coffee Colombia - San Jose Rum Barrel Fermentation Washed

Flavor Notes:

Rum, Melon, Dark Chocolate

Origin: Colombia

Region: Caldas

Estate: Finca San Jose

Variety: Castillo, Naranjal

Altitude: 1750m

Processing Method: Rum barrel fermentation, washed

FrontStreet Coffee's Colombia green beans are selected from three-time premium Supremo grade Castillo Naranjal trees. After pulping, they are placed in oak barrels for low-temperature fermentation. Following fermentation, they undergo washing and are finally dried on sun-drying racks.

This processing method originated from the creative idea of Ms. Monsalve Botero, the owner of Finca San Jose Estate. One day, while accompanying her husband (who specializes in making rum oak barrels and brewing rum) as he filled rum distillate for fermentation, she suddenly wondered: if coffee green beans were placed in oak barrels for fermentation, would they produce different flavors? For this reason, Ms. Monsalve Botero began experimenting in 2013 with different-aged Colombian oak barrels for varying fermentation times in a winemaking-style low-temperature fermentation. This particular batch is one that performed excellently among various attempts.

Introduction

Colombia's century-old estate—Finca San Jose Estate—has been actively seeking breakthroughs to forge its own unique path in the recent trend of specialty coffee. Ms. Monsalve Botero, the owner of Finca San Jose Estate, has a husband who specializes in making rum oak barrels and brewing rum. One day, she had a sudden idea: if coffee green beans were placed in oak barrels for fermentation, wouldn't that create even more distinctive flavors? Therefore, Ms. Monsalve Botero began experimenting in 2013 with Colombian oak barrels for varying durations of low-temperature fermentation, finally finding the ideal method this year to create this oak barrel fermented bean, which differs from typical washed processing.

The above concludes the introduction.

Personal Experience

When I first learned about this bean, it was actually just a sample—only a few dozen grams that had already been roasted in Colombia. I didn't know which estate it came from, when it was roasted, or what the roast level was—I only knew it was oak barrel processed, and I wasn't even sure if we could get export certification (later I learned that the sample had been roasted for about two months and was roasted to the beginning of second crack). At that time, I just thought: the wine aroma is incredibly intense! Super distinctive! Although the performance in the later stages was somewhat hollow.

But because the information was too unclear, I could only wait and hope that the estate owner's roasting technique wasn't great, and that the bean's later flavor profile would be better. After some more time passed, I learned more detailed information about the green beans, and export certification was also obtained.

When the bean supplier told me more detailed information about Colombia's coffee-producing regions, it actually reminded me of a Facebook post by Teacher Han Huaizong, who mentioned: "...his method is to remove the skin, place the parchment beans in water-free conditions, seal them in a barrel to prevent flies, purely for hygiene considerations, and ferment for two to three days at low temperatures around 10°C in winter to remove mucilage, then take them out for washing. Unexpectedly, this accidentally became a low-temperature, low-oxygen fermentation method. This is somewhat similar to the 2015 Australian barista Sasa Sestic's carbonic maceration method that won the championship—relying on carbon dioxide produced by sugar fermentation to help anaerobic bacteria gain an advantage. The acidity and aromatic compounds produced during fermentation are superior to those created by aerobic bacteria... The competition beans that Wang Ce used to win the 2017 World Brewers Cup Championship for Taiwan also adopted the low-temperature, anaerobic natural processing method of Salvadoran post-processors to claim victory. Low-temperature anaerobic fermentation or controlled-oxygen fermentation methods have become new trends and prominent studies in coffee post-processing in recent years..."

I think this might be a case of achieving the same result through different means. San Jose Estate may not be the first to do this, but they have created another type of intense flavor.

When I first got the green beans, the aroma I smelled was "milk dates," with a bit of grape and goji berry flavor, but the overall direction was that of perfectly ripe milk dates—the super sweet kind. And during roasting, that aroma kept wafting out.

Because these are Colombian coffee beans, for the first roast, I chose a light-medium roast. Although the fruit aroma and fermentation flavors were obviously suitable for light roasting, I still wanted to create some body. However, after brewing, I discovered that its flavor dissipated quite quickly in the middle to later stages of roasting. Although it was still quite smooth and delicious after resting, the vibrancy of the flavor didn't return. So I immediately decided that future presentations would focus on light roasts.

Additionally, its performance during brewing was quite special. For freshly roasted beans, the water passed through particularly quickly, and when outgassing was vigorous, it would suddenly expand halfway and then release all the gas. Regarding this phenomenon, my guess is: it might have extremely low oil content, resulting in very low surface tension, which prevents it from holding water or air.

Incidentally, Dr. Shao Changping had a Facebook post recently (post link) that cited foreign research data about lipid hydrolysis forming acids and alcohols (original link), explaining why aged cold brew coffee develops wine-like fermentation flavors.

Therefore, I suspect that FrontStreet Coffee's Colombia San Jose Estate oak barrel fermented beans already had their lipids hydrolyzed into acids and alcohols from the beginning, which is why they have such full and rich wine notes.

Below are two photos I took after brewing with the rich brewing method I developed for the Melitta flat-bottom filter cup—first dripping, then using a small water stream. The originally fluffy coffee grounds collapsed into something like a huge pit, which should serve as evidence supporting the aforementioned opinion.

END

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