Patrick Oconnell
The smell of cheese is produced by microorganisms, which are so small that they cannot be seen without a microscope. As the bacteria eat to get energy, they produce a stinky gas made up of molecules, including ammonia or sulfur compounds, which are responsible for the smell of many cheeses. The composition of the cheese microbiome, which includes bacteria, yeast, and fungi, is critical to the flavor and quality of the cheese. Researchers have found that bacteria essential to ripening cheese can sense and respond to compounds produced by fungi in the rind, enhancing the growth of some species of bacteria over others. This process of bacteria and fungi communicating with each other through volatile organic compounds (VOCs) can be manipulated to improve the quality and variety of flavors in cheese production.
| Characteristics | Values |
|---|---|
| Bacteria | Brevibacterium linens, Psychrobacter, Vibrio casei |
| Fungi | Galactomyces |
| Volatile Organic Compounds (VOCs) | Geosmin |
| Gases | Ammonia, Sulfur compounds |
| Cheese | Limburger, Époisses, Roquefort, Blue cheese, Camembert |
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What You'll Learn
- Human bacteria can be used to make cheese
- Bacteria and fungi communicate with each other
- Bacteria and fungi work together to create the flavour and aroma of cheese
- Bacteria and fungi can be manipulated to improve the quality and variety of flavours
- Some of the molecules that create the smell of cheese include ammonia or sulphur compounds
Human bacteria can be used to make cheese
UCLA postdoctoral fellow Christina Agapakis produced cheese using bacteria from human body parts, including belly buttons and tongues. She collected bacteria from donors, including a New York Times food-and-culture writer and an artisan cheesemaker. Through her work, Agapakis highlights the disconnect between our culture's disdain for human bacteria and our appetite for foods with roots in bacteria, like cheese.
Cheese is a traditional food that has been made since the late Stone Age. It is created through microbial fermentation, where protein catalysts made by microbes break down the proteins and sugars in milk. This process results in simpler products that can be stored for longer periods than fresh milk. Cheese contains high numbers of living, metabolizing microbes, with over 100 different microbial species found in a single type of cheese.
The microbes in cheese include bacteria, yeast, and filamentous fungi (molds). These microorganisms interact with each other and the environment to create the distinctive flavor, smell, and texture of each cheese variety. The starter culture of bacteria is particularly important in defining the final composition of the cheese. However, as the cheese ages, the microbial mixes can change, and bacteria not present in the starter culture may become dominant.
While human bacteria can be used to make cheese, it is important to note that the resulting cheese may not be suitable for consumption. Agapakis's human bacteria cheeses were intended for smelling and contemplating our connection to the microbial world. Additionally, the process of making cheese from human bacteria can provide insights into the intricate biological interrelationships between humans and other living organisms.
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Bacteria and fungi communicate with each other
The bacteria that are responsible for the characteristic smells of human armpits or feet are also closely related to those involved in the cheese-making process. For instance, Limburger cheese, one of the most popular stinky cheeses in the world, is often compared to body odour.
Interestingly, bacteria are not the only organisms that play a role in the cheese-making process. Fungi, too, are crucial in this transformation. Fungi, including the diverse range of yeasts, moulds, and mushrooms, form their own kingdom, distinct from plants, animals, and bacteria.
Fungi have evolved various methods of communication, including with bacteria, to coordinate their growth and behaviours. They communicate through a network of chemical and electrical signals. They release chemical signals called pheromones and extracellular signalling molecules to communicate with other fungi and organisms in their environment. In response to these signals, fungi can change their growth patterns, initiate sexual reproduction, or activate defence mechanisms.
Fungi also communicate within their own species and with other organisms. Each growing tip has a degree of autonomy and is accountable to the whole organism, similar to the relationship of social insects to their hive. Between the cells within every mycelium, there is a constant flow of chemicals, nutrients, and electrical impulses that keep the whole network informed and coordinated.
Furthermore, mathematical analysis has revealed that the electrical signals fungi send to one another exhibit patterns that bear a striking structural similarity to human speech. These signals have been found to cluster into trains of activity, resembling vocabularies of up to 50 "words". While the interpretation of these signals as a language is still a subject of debate, they undoubtedly play a crucial role in the communication and coordination of fungi, including their interactions with bacteria, in various ecosystems.
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Bacteria and fungi work together to create the flavour and aroma of cheese
The aroma of cheese is created by bacteria and fungi working together. When cheese ages, the bacteria and fungi on the rind release volatile organic compounds (VOCs) into the air, which our noses detect as distinct cheese smells. These VOCs are also chemical signals that the fungi use to communicate with the bacteria, stimulating their growth and metabolism.
The bacteria and fungi also secrete enzymes that break down amino acids and fatty acids, producing acids, alcohols, aldehydes, amines, methyl ketones, and various sulfur compounds. These biological products are what give cheeses like Camembert, Blue Cheese, and Limburger their signature smells.
For example, the bacteria Brevibacterium linens is responsible for the smell of human body odor and is also found in some of the smelliest cheeses, such as Époisses and other blue cheeses. Similarly, the bacteria Psychrobacter is stimulated by VOCs produced by the fungus Galactomyces, which is found on cheese rinds.
The composition of the cheese microbiome, including the types and amounts of bacteria, yeast, and fungi, is critical to the flavor and quality of the cheese. By understanding and manipulating this process, cheese producers can potentially improve the quality and variety of cheese flavors.
Interestingly, the perception of cheese aromas as "good" or "bad" is highly subjective. In one experiment, researchers presented a molecule commonly found in cheese to subjects, telling some that it smelled like cheese and others that it smelled like vomit. The responses varied greatly, highlighting the subjectivity of smell perception.
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Bacteria and fungi can be manipulated to improve the quality and variety of flavours
Fermentation is a process that has been used for over 7000 years to preserve and enhance the flavour of various foods and drinks. It involves the use of microbes such as bacteria, yeasts, and moulds to transform carbohydrates into different substances. For instance, the yeast strain Saccharomyces cerevisiae is used to produce alcoholic beverages like beer, wine, and cider, while Lactobacillus is commonly used in dairy and vegetable fermentation.
Bacteria and fungi play a crucial role in the fermentation process, and their manipulation can indeed improve the quality and variety of flavours in food products. For example, in cheese-making, the bacteria and moulds used can significantly impact the final product's flavour and texture. Penicillium camemberti, for instance, is a type of mould used to produce soft, creamy cheeses like Camembert and Brie. On the other hand, Limburger cheese, known for its strong, pungent aroma, is made using bacteria closely related to those responsible for body odour. In an experiment by researcher Christina Agapakis, she produced cheese using human bacteria from belly buttons and tongues, resulting in cheese with a strong odour. This demonstrates the intricate connection between human bacteria and the bacteria used in food production, particularly in the creation of unique flavours and aromas.
Fungi, such as yeasts and moulds, are also widely used in food processing. They aid in the cultivation of food by helping to break down organic matter and promote plant growth. Additionally, they are essential in fermentation processes, contributing to the development of distinct flavours and textures in foods like bread, wine, and soy sauce. For instance, Aspergillus oryzae is used in the production of soy sauce, miso, and sake, while Candida milleri is used to produce kombucha, sourdough, and kefir.
Furthermore, enzymes derived from fungi are employed in the food industry to improve taste and nutritional value. Fungal lipases, for example, are used to enhance the flavour of dairy products and remove excess fat from meat and fish. Pectinase, derived from Aspergillus niger, is used in the extraction of fruit juices. Additionally, proteases obtained from fungal sources are valuable in brewing and baking.
The use of bacteria and fungi in food production offers numerous benefits, including enhanced flavour, improved nutritional value, and extended shelf life. However, it is important to implement stringent quality control measures to prevent contamination by undesirable microorganisms and mycotoxin-producing fungi, which can pose risks to human health and result in economic losses.
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Some of the molecules that create the smell of cheese include ammonia or sulphur compounds
The human body is host to a variety of bacteria, some of which are responsible for body odour. Interestingly, certain bacteria on the human body are closely related to those involved in the cheese-making process, resulting in similar odours. For instance, the bacteria responsible for the characteristic smells of human armpits or feet are also commonly found in some of the stinkiest cheeses, such as Limburger cheese.
The molecules that contribute to the smell of cheese can vary, but they often include ammonia or sulphur compounds. These compounds are produced by bacteria and can be influenced by factors such as diet, the composition of the bacteria, and the metabolic activity of the bacteria. For example, the presence of direct or indirect odorants in the diet can impact the types of odorant compounds produced by the bacteria.
In the case of Limburger cheese, the bacteria Brevibacterium linens is responsible for its distinctive smell. This bacterium is also found on human skin and is a significant contributor to body odour, particularly foot odour. The bacteria break down the amino acids present in the cheese, releasing volatile sulphur compounds that contribute to the strong smell.
While the smell of cheese is often associated with ammonia or sulphur compounds, it is important to note that other molecules can also play a role. For example, esters and fatty acids can contribute to the overall aroma profile of cheese. Additionally, the perception of smell is highly subjective, and what one person may perceive as a pleasant aroma may be unpleasant to another.
The study of the bacteria-derived products that contribute to body odour and cheese odour can provide valuable insights into the intricate biological interrelationships that exist between human beings and other living organisms. It also highlights the subjective nature of our perception of smells and how it can be influenced by our expectations and cultural context.
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Frequently asked questions
As cheese ages, bacteria eat to get energy and produce a stinky gas made up of molecules, including ammonia or sulfur compounds, which are responsible for the smell in a lot of stinky cheese.
Limburger, Roquefort, and Époisses are some of the smelliest cheeses in the world.
The odor in blue cheese comes from a mold named Penicillium roqueforti.
Tufts University researchers found that the funky smells from cheese are a way for fungi to communicate with bacteria. The composition of the cheese microbiome is critical to the flavor and quality of the cheese.
Researchers at UCLA produced cheese using human bacteria collected from belly buttons and tongues. The bacteria in cheese are closely related to the bacteria responsible for body odor.
