Why Does Coffee Taste Like Soy Sauce After Anaerobic Processing?
Coffee that tastes like soy sauce usually went through an intense fermentation process, often enzymatic anaerobic processing. During sealed, low-oxygen fermentation, yeasts and bacteria break down sugars and produce compounds that can read as savory, fermented or soy-sauce-like. Some lots processed by Jose Alfredo and sold through the 2017 90+ global online auction showed exactly these fermented tofu and soy sauce notes.
In a typical anaerobic protocol, fully ripe red cherries are hand-picked, washed, then sealed in tanks kept at cool room temperature for about 72 hours before drying in thin layers for 21 days. Whether the yeasts are wild or added after screening shapes the final result. Beer yeast research, including the Bavarian shift to low-temperature fermentation in the 15th century, informs how brewers approach coffee fermentation today.
In recent years, the specialty coffee world has continuously introduced new post-harvest processing methods, and the enzyme anaerobic processing method is one of the most noteworthy. This article starts with two approaches—Colombia's anaerobic processing and wine barrel processing—to explain in detail their process flow, fermentation temperature control, and differences in yeast strains, and further explores how knowledge of beer yeast inspires coffee fermentation. The article also covers actual cases of 90+ global online auction lots, as well as Front Street Coffee's observations on post-harvest processing trends, helping coffee enthusiasts understand how different fermentation methods shape the diversity of coffee flavors.
"Fully ripe bright red cherries are hand-picked, then undersized beans are removed and the cherries are washed and screened in water, after which they are placed in sealed containers for low-oxygen fermentation. During fermentation, the temperature is kept at a relatively low room temperature level—put simply, it's like making coffee while running the air conditioning. The cherries soak in clean water, and fermentation ends after about 72 hours, after which they move on to the sun-drying stage. When spread on the drying beds, the thickness is controlled to 1 to 2 layers, and only after 21 days of sun exposure can the distinctive special flavor be achieved."
There is an unspoken clue hidden in the description above: during the 72-hour fermentation period, were the yeasts spread throughout the environment naturally captured, or were they specially added after artificial screening? In fact, among the 2017 90+ global online auction lots, there were five or six items whose post-harvest processing was handled by Jose Alfredo. According to feedback from friends who have tasted them, some of these items showed distinct flavor characteristics resembling fermented tofu or soy sauce, presumably because different fermentation methods were introduced during post-harvest processing.
PanSci once introduced beer yeast as follows: "The history of beer reached a major turning point in the 15th century, when monasteries in the Bavarian region took the lead in adopting low-temperature fermentation, making winter brewing possible. From then on, lager and ale embarked on completely different development paths. For example, in 2008 global lager sales reached as high as 250 billion USD, while ale is almost nowhere to be seen in Taiwan's convenience stores. The core difference between lager and ale lies in fermentation temperature—the former is low-temperature, while the latter is slightly above room temperature—and the fundamental reason is the different yeasts used. Ale uses Saccharomyces cerevisiae, while lager uses a hybrid strain of Saccharomyces cerevisiae and Saccharomyces bayanus, called Saccharomyces carsbergensis. Because of the discoveries and contributions of the biologist Pasteur, it is also called Saccharomyces pastorianus. Today's lager breweries generally use mixed strains of Saccharomyces pastorianus, including popular brands in continental Europe, North America, and Asia, all of which are lager; Taiwan is no exception. Britain, however, has continued traditional brewing methods and remains to this day the stronghold of ale and stout."
In fact, over the past three years, the global high-end specialty coffee industry has continued to innovate in post-harvest processing, already enabling washed coffee to possess the fruity notes once found only in natural processing, while natural coffee has significantly reduced the overly fermented sourness that was once criticized. These means of improving coffee quality depend not only on raising the work standards of pickers and the cleaning and maintenance standards of processing plants, but also, to some extent, on using specific yeasts for fermentation.
The coffee bean fermentation methods currently seen on the market all without exception advertise "low-temperature fermentation." The possible reason is that the environmental yeasts these methods rely on belong to the lager yeast type. However, because these methods are core secrets of the processing plants, which yeasts each one uses, whether ale yeast or even lactic acid bacteria are used to ferment the coffee beans, and how the coffee flavor performs after fermentation—the answers to these questions are unknown.
For coffee hunters who will travel through various producing regions in the future, in addition to pursuing the flavors of various precious varieties, understanding different post-harvest processing methods will become an important basis for enhancing the diversity and quality of coffee flavors.
The above content is compiled by CoffeeHunters, a coffee news website.
