This bacteria oxidizes ethanol to acetic acid, and also further oxidizes the acetic acid to carbon dioxide and water. These organisms are metabolized due to the acidulation of cocoa beans at high temperatures, which causes diffusion and hydrolysis of proteins in the cotyledons. Acetic acid bacteria primarily form the precursors of chocolate flavor. These include members of the genus Acetobacter as well as Gluconobacter [2]. High temperatures and increase in pH along with increased aeration leads to the development of aeobic spore-forming bacteria of the genus Bacillus.
This includes B. The Bacillus spp. Aerobic spore-forming bacteria form chemical compounds that cause acidity and sometimes off-flavoring if fermentation continues for too long [2]. Filamentous fungi are also found in the well-aerated parts of the fermented mass. They may cause hydrolysis of some of the pulp and produce acids, but are not considered important in microbial succession. Of the filamentous fungi, Aspergillus fumigatus and Mucor racemous are the most present in the fungal population up to the end of fermentation.
The drying and roasting process contains a very small portion of microbes such as, lactic acid bacteria, acetic-acid bacteria, aerobic spore forming bacteria, and others.
The residual microbes will begin to form endospores as conditions such as levels of heat increase and the humidity decreases, in addition to that mold can begin to form if the drying conditions are not correct, but not much else is known.
In the past bean drying involved the use of sunlight and spreading out the beans over a wide area; these days bean drying has evolved to using large machines that regulate temperature and humidity [7] although there are that some may still dry their beans the traditional way. The rate at which the beans dry is also an important factor involved in the study of chocolate making if conditions are not right then microbes such as fungi may begin to form.
At this stage of chocolate production the maker would want to minimize the amount of microbes since they can alter the flavor of the chocolate.
Research has found that rapid drying at low humidity and slow drying at high humidity were more harmful to cocoa beans. They determined that this was due to a leakage of electrolytes and concluded that if one were to determine the optimal rate for drying, finding the point at which the least amount of damage done from mechanical and metabolic stresses would probably be the optimal point [10].
Another has found that conditions for getting good results were brought up by drying at low temperature or occasional breaks from drying if dried at high temperature [11]. If should be known that some companies have been advertising the fact that bacteria and fungus that are involved in developing chocolate have been branded as dangerous when in fact they are not.
After roasting the cacao beans are cleaned until there is just the nib portion of the bean left, and then they are grounded up and heated until the chocolate moves to a liquid state. The process ends in a step known as tempering where chocolate is given its shiny appearance [14]. There are several factors that appear to affect the flavor of chocolate, including the components that make up the bean pulp. One study has claimed that the concentration of free fatty acids increases with the fungal degradation of the lipid matter in the cocoa bean, thus affecting the chocolate flavor [1].
During the fermentation of the bean pulp, bacteria produce various products such as alcohols, acetic acid, and organic acids, all of which can contribute to bean death. The chemical changes that arise from the bean death add to the initial aroma, coloring, and flavor of the cocoa; all of which are finalized in the drying and roasting stages [15].
Acetic acids, such as A. They can produce various byproducts from metabolizing sugars and organic acids, and these byproducts can contribute to the aroma of cocoa beans during fermentation [1]. Yeast plays an important role in the fermentation of the cocoa bean by producing ethanol and ultimately acetic acid, which leads to bean death; thus setting off a series of biochemical changes that contribute to the flavor of the chocolate [1].
Following the drying process, the water content of the bean pod is greatly reduced, at which point the beans are roasted in order to create the characteristic flavoring and odor of chocolate. Yeast plays a vital role in the final chocolate flavors of the roasted beans.
It has also been found that the enzymes that the yeast releases are important for the chocolate precursor components. It is only when the cocoa beans have actually been roasted does the characteristic chocolate aroma occur [20]. Bacillus bacteria are also involved in the fermentation process of the cocoa beans, predominately in the end stages of fermentation when the environmental conditions of the process are more aerobic oxygen containing and less acidic.
Some of these Bacillus bacteria that have been identified include Bacillus subtilis , Bacillus stearothermophilus, Bacillus cereus , Bacillus licheniformis , Bacillus coagulans, and Bacillus pumilus. The production of organic acids and pyrazines by Bacillus bacteria has been shown to affect the flavor of cocoa by allowing the enzymes produced to enter the cocoa beans and alter the chemical quantities inside [1]. Climate conditions, harvesting seasons, the ripeness of the cocoa pod including the quality of the bean pulp all affect the fermentation of the cocoa bean.
In addition, the different flavors produced have been linked to the presence of esters in the chemical composition of the cocoa bean. These esters have been linked to the existence of yeasts and acetic acid bacteria such as Acetobacter and Gluconobacter.
However, not all the chocolate odors are due to the presence of microbes. Some of the odors were due to the thermal conditions of the fermentation process.
Some of these off-flavorings could have been the result of contamination in the drying process [19]. It has been studied that the regular consumption of foods high in flavonoids can decrease the risk of cardiovascular disease [17].
Specific to cardiovascular health, a specific sub-group of flavonoids known as flavanols falvanols , are found in cocoa products such as chocolate [16].
Various studies have shown improvements in blood pressure, and the functioning of endothelial cells and platelets due to the consumption of cocoa products that contain flavanols [17]. Dark chocolate also has greater concentrations of phenols and catechins than milk chocolate [18].
There are several various fungal diseases that have had detrimental effects on Theobroma cacao plant. These fungi infect Theobroma L. This infection causes hypertrophy and hyperplasia in the cacao, ultimately resulting in tissue damage.
Fermentation methods vary depending on regional preferences and availability of resources. Individual producers will make different choices in the type and size of the fermentation vessel they use, the number of days they ferment cacao for, how often they turn the cacao, pulp preconditioning pod storage prior to fermentation , and other factors.
But generally speaking, all cacao fermentation follows a similar process including an anaerobic phase and an aerobic phase. The specific details of each stage are influenced by a multitude of factors , not limited to pod ripeness, climactic and ambient weather conditions, pod quality, and batch size.
Fermenting cacao beans in the Philippines. Anaerobic conditions are simply environments that lack oxygen. In cacao, the pulp surrounding snugly packed beans creates a juicy barrier that blocks air from entering the system. The pulp is composed of water, high levels of sugars sucrose, glucose, fructose , and various acids. T hese sugars and the high acidity in the pulp create ideal conditions for microorganisms.
The main players during this phase are yeasts, lactic-acid-producing bacteria, and pulp enzymes. Using anaerobic respiration, yeasts quickly consume simple sugars and produce carbon dioxide, ethanol, and low amounts of energy.
Lactic acid producing bacteria convert citric acid, glucose, and other carbohydrates in the pulp into lactic acid. Microbes are working around the clock to produce ethanol and lactic acid. You can see tiny bubbles of carbon dioxide gurgle up to the surface of the cacao in this stage. In the early stages of fermentation, active yeast breaks down sugar found in the cacao pulp and produce bubbles of carbon dioxide.
Enzymes also help to break down the pulp, transforming it into a liquid that runs off and is known as sweatings. As the mass is broken down, there is more space for air to enter the process. Citric acid is also broken down and runs off with the sweatings, helping to increase the overall pH of the fermentation.
The combination of rising pH and increased airflow marks the beginning of the aerobic phase of fermentation. Workers in the Philippines turn fermentation boxes to introduce more air. This process generates fruity-tasting molecules called esters and floral-tasting fusel alcohols. These compounds soak into the beans and are later present in the finished chocolate.
As the pulp breaks down, oxygen enters the fermenting mass and the yeast population declines as oxygen-loving bacteria take over. These bacteria are known as acetic acid bacteria because they convert the alcohol generated by the yeast into acetic acid. The acid soaks into the beans, causing biochemical changes. The sprouting plant dies. Fats agglomerate. Other enzymes break apart the antioxidant polyphenol molecules , for which chocolate has gained renown as a superfood.
As a result, contrary to its reputation, most chocolate contains very few polyphenols, or even none at all. All the reactions kicked off by acetic acid bacteria have a major impact on flavor. These acids encourage the degradation of heavily astringent, deep purple polyphenol molecules into milder-tasting, brown-colored chemicals called o-quinones. Here is where cacao beans turn from bitter-tasting to rich and nutty. Finally, as acid slowly evaporates and sugars are used up, other species—including filamentous fungi and spore-forming Bacillus bacteria — take over.
As vital as microbes are to the chocolate-making process, sometimes organisms can ruin a fermentation. An overgrowth of the spore-forming Bacillus bacteria is associated with compounds that lead to rancid, cheesy flavors. Cacao is a wild fermentation—farmers rely on natural microbes in the environment to create unique, local flavors.
Market demand for these fine, high-quality beans is growing. Makers of gourmet, small-batch chocolate hand-select beans based on their distinctive terroir in order to produce chocolate with an impressive range of flavor nuances. Yet in both cases, the bars contain nothing except cacao beans and some sugar.
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