Coffee Fermentation: Controlling the fermentation process is essential for harnessing the power of Fermentation to produce beneficial flavor characteristics in coffees. It is a chance to impact flavor through a biological mechanism occurring naturally in all coffee processing forms.
Producers and roasters can ensure taste diversity while enhancing coffee uniformity and quality by recognizing the power of Fermentation and processing.
Coffee Fermentation, in general
Before dissecting the challenges in the relationship between Fermentation and – coffee processing, we must first become familiar with the term “fermentation” (Latin for “severe,” which means “to ripen”).
In microbiology, Fermentation is the metabolic process through which bacteria transform carbohydrates into energy molecules and release other organic chemicals.
In the coffee business, however, Fermentation is defined as “the stage in which the coffee, after being peeled, is steeped in a bath of water until the mucilage is entirely dissolved whole.”
As you might expect, Fermentation begins as soon as the coffee is plucked (or even before, depending on humidity). The idea is that Fermentation can either improve or degrade its taste. It’s just a question of how you handle it.
Coffee fermentation dynamics
Fermentation has become an essential aspect of post-harvest coffee processing, whether you like it or not, and it can happen in one of two ways:
- This is called Aerobic Fermentation, when oxygen is present in the air. Microorganisms grow and release secondary organic materials using oxygen and substrates (organic substances found in coffee pods).
- The coffee cherries are immersed in the bath during Anaerobic Fermentation (after peeling). This enables many microbes to function in the absence of oxygen. Both of these processes can co-occur during the preparation of coffees, but Anaerobic Microbial Fermentation is easier to manage and more homogenous.
Enzymes catalyze every reaction that occurs during the Fermentation of coffee. More than 50 yeast and bacterial species have been found in coffee fermenting coffee in previous investigations.
Pectin lyase, polygalacturonase, and pectin methylesterase are the three most essential enzymes produced by microorganisms that degrade pectin properties during Fermentation. Polygalacturonase is the most critical enzyme in Fermentation.
The Effect of Fermentation on the coffee-making process
To allow spontaneous Fermentation, coffee cherries are processed using one of three ways immediately after harvest (dry, wet, and semi-wet processing). The time required for Fermentation varies depending on the processing method.
However, the fundamental goal of all fermentation techniques is to remove the mucilage layer, which is high in polysaccharides (pectin), and reduce the water content of the coffee beans. On the other hand, Fermentation positively impacts coffee quality if it is correctly regulated.
Fermentation is necessary to eliminate the mucilage from a technical standpoint. The three main categories of elements that make up the mucilage surrounding the coffee beans are pectin, cellulose, and starch – this “mucus” prolongs the time it takes to dry the beans and, in turn, turn, in some cases, to dry.
It also leads to mold growth, which lowers the product’s quality. As a result, we make every effort to encourage Fermentation, aided by natural enzymes found in coffee cherries and microorganisms in the environment. Microorganisms (yeast, bacteria) contribute to weight loss by creating various enzymes.
Even though we know that mucilage fermentation takes 8 to 72 hours in wet processing, coffee brewed for 8 hours will taste different from coffee brewed for 8 hours.
However, fermenting at an altitude of 700m at 25°C will produce a different flavor than coffee fermented at 1500m at 12°C, or fermenting in wooden barrels with porcelain, ceramic, and cement tanks will have completely different results.
As a result, the fermentation process introduces many new variables that influence the final quality of the coffees we drink.
Coffee fermentation’s opportunities and challenges
According to several studies, maintaining control over the process is the most challenging aspect. The first issue is to avoid over-fermenting the coffee since this would result in spoilage bacteria, negatively affecting the coffee’s taste and flavor.
Coffee beans that have been over-fermented are known as ‘Stinkers.’ These particles contain unacceptable chemical components, particularly propionic and butyric acids, which have a strong (onion-like) odor and should not be present in high concentrations under ideal conditions greater than one milligram per milliliter.
The fermented coffee that occurs on its own
You’d be correct if you assumed that the flavor faults develop when the coffee cherries are in the wet processing tank. Of course, this is insufficient.
Ferment coffee happens in wet coffee tanks and honey and dry coffee processing.
Natural Fermentation takes place regardless of further processing; as soon as the coffee fruit leaves the branch, the microorganisms available on the surface of the coffee fruit are everywhere, at all times.
There is an “entry” to “cup” the fruit pulp rich in sugar, protein, and water.
In other words, the following are some of the possible patterns that can emerge when Fermentation occurs spontaneously:
- Overripe coffee cherries are left on the tree to ferment naturally.
Fermentation/contamination: Overripe fruit left on the ground for an extended period.
- Overfermentation: As previously indicated, poor management control during wet processing results in a wide range of disagreeable flavors – connected with putrefaction, generally known as Stinker.
- Because the fermentation process is so complicated, there are numerous possible results. Poor, uncontrolled Fermentation can result in mold or even artificial flavors, so producers must understand, monitor, and implement the process. Attempt to achieve “sufficient fermentation.”
Regulate the fermented process in a proactive manner
In the food business, manufacturers have purposefully chosen spontaneous Fermentation or added commercial yeast strains to the processing process for items such as bread, wine, beer, etc.
To assist in developing suitable taste alterations, this is highly uncommon in the coffee market since most producers regard Fermentation as a dangerous factor that degrades quality rather than considering the benefits of flavor; microbial strains are responsible for this.
From a different perspective, the intricate coffee husk serves as a protective barrier for the seed, and once it is removed, the green coffee bean is highly vulnerable to injury.
As a result, most modern coffee processing literature emphasizes the significance of speedy processing and marketing to minimize the risk of coffee quality degradation. More extended processing periods imply a higher chance of poor quality.
Developing high-potential individuals’ ferment coffee
During the fermentation process in the coffee tanks, the yeast only does one thing: devour the sugars in the rind and make enzymes that aid in the breakdown of pectin (the main ingredient in mucilage).
However, the yeast creates secondary metabolites known as taste precursors and their core activity (reabsorbed into the coffee bean). As a result, adequately fermented coffee is a more sophisticated and valuable product than organically treated coffee.
The ratio of sugar and nutrients in the skin of the coffee bean impacts the fermentation process differently in different varieties of it.
With different coffee varieties, the proportion of sugar and nutrients in the coffee pod affects the fermentation process differently. Not to mention the structure of the fermentation tank, the ambient temperature, the water quality, and countless other factors that also create different fermentation results; this means that we are fully capable of maintaining the variety of flavors – while reducing the appearance of undesirable flavors.
And, after all, Fermentation is inevitable. It is simply a matter of choosing between limiting or developing its potential.
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