Classy Microorganisms by Angelica Y. Yang


What's a classy dinner without some fine wine and cheese? Unlike produce such as fruits and vegetables, these types of food are made and processed with microorganisms like bacteria and fungi. 

Image credit: Shutterstock website

But there's no need to panic! Biology tells us that there are many types of bacteria and fungi, both harmless and harmful to humans. 

Some are even beneficial, and have been used throughout history to make a variety of food: from bread and yogurt, to beer and kimchi.


Before we discuss how these microbes help in food production, we have to learn more about these organisms.

What are Bacteria and Fungi? 

Bacteria are prokaryotes (organisms that have no true nucleus) that can thrive in many different environments. Bacterial cells have two protective coverings: an inner cell membrane, and an outer cell wall. These layers help protect the cells from being easily lysed, or destroyed. 

Some kinds of bacteria can cause disease: these include the bacteria that can give us strep throat, pneumonia, or tuberculosis. These are what our parents and teachers often refer to as "bad" bacteria.

However, only a few kinds of bacteria are "bad"! Many are harmless, and some are even "good", such as the probiotic bacteria that you can find in yogurt and Yakult. 

These kinds of bacteria not only provide yogurt with its characteristic tanginess, but can also aid our digestive and immune systems in fighting off intestinal infections. 

The different types of bacteria in yogurt.
Image credit: MedIndia website

On the other hand, fungi are eukaryotes (organisms with cells that contain a true nucleus). Like bacteria, they can also thrive in a variety of environments. They were formerly classified as part of the plant kingdom, but were eventually placed into a category of their own (Kingdom Fungi) because of how different from the plants they actually were!

Fungi also have cell walls, but these are made of chitin. They also cannot produce their own food. Instead, fungi get nourishment from decomposing matter, or from their hosts (they can be parasitic).

As with bacteria, some fungal species can cause us to get sick. For instance, fungi like Trichophyton can infect your skin and nails and give you ringworm. If ringworm affects the skin on your feet, this is better known as athlete's foot. 

However, our collective ingenuity has also led us to use these organisms for food: the mushrooms in your mushroom soup, the yeast that makes your bread rise, and the molds that refine cheese into Roquefort and Cashel blue are all fungi. 

Of course, one must take caution when picking random mushrooms from your garden, as they may be poisonous.

Don't eat this fungus! The Amanita muscaria (common name: fly amanita) is a
poisonous mushroom that is known for its hallucinogenic properties.
Image credit: University of Connecticut website

Microorganisms in Cheese

The cheese industry is growing bigger and bigger each year, and it's all thanks to bacteria and fungi. The LiveScience website describes the cheese-making process as comprising eight crucial steps. 

Be it  for Gruyere, Cheddar, or Parmesan, the cheese-making processes involved aim to expel water, de-mineralize the casein protein with bacterial acids, and to add salt for intensified flavor.

The process begins with fresh milk. Milk contains two types of proteins: casein, and whey. Casein, along with fat, makes up the bulk of the solid part of the cheese. Whey is the liquid that remains after the milk curdles. 

To separate casein and whey, starter bacteria have to be added to the milk. Starter bacteria, such as the lactic acid bacteria, kick-start the demineralization process of casein. The chosen bacterial cultures are mixed with rennet, an enzyme that removes the hydrophilic (water-loving) layer of the casein. 

The end stage of this step is the coagulation of the casein into curd - a soft, white solid that is also formed when milk sours. 

The rest of the steps include tedious processes of expelling (or, squeezing out) excess water or whey from the cheese block. Each type of cheese needs varying conditions, such as accurate moisture levels, or precise amounts of salt. 

                         This interesting video shows the painstaking process behind making Swiss cheese.

Yeast in Wine-making

Great wine starts with high quality grapes. But without the help of science, the fruits would remain in their original form. 

Bunches of grapes are handpicked by the farmers, and carefully sheared from their vines. They are then crushed and pressed, before being placed into large steel vats. The freshly squeezed juices are then mixed with yeast. 

The addition of yeast is a very important step in the process of fermentation, which converts sugars into alcohol. The two ingredients needed to kick-start the fermentation are sugar and yeast. 

We can find a lot of natural sugar in grapes.
Image credit: Shutterstock website

When mixed with the Saccharomyces yeast, the natural sugars will turn the grape juice into alcohol and carbon dioxide. Usually, this fermentation process generates a lot of heat - which is not suitable for wine making. To remedy this, winemakers have started using stainless steel vats to keep the temperature cool. 

The fermentation process is over when all the sugar has been turned into alcohol, or when the alcohol level reaches 15%. At this level, the yeast will die naturally, while the left-over sugars will remain. 

                                                                                  The wine-making process in detail. 

Food Microbiology

The study of microorganisms in food is part of the exciting world of Food Microbiology. This expanding field of science explores the beneficial and harmful effects of microbes in food production, and how they interact with the food we consume. 

By using scientific principles from food microbiology, inventors, researchers, chefs, and farmers can explore new ways in creating healthier and more interesting food options for everyone. 

So the next time you order a slab of cheese or a glass of wine, think about the microbes (the good kind!) that helped in making your restaurant experience classier, and more delicious. After all, not all microorganisms are "bad". 

REFERENCES: 

1. Biology for Kids. (2016). Retrieved from http://www.ducksters.com/science/biology/fungi.php
2. Fermentation and wine making. (n.d.). Retrieved from http://www.morethanorganic.com/fermentation
3. HOW WINE IS MADE: Turning Grape Juice into Alcohol. (n.d.). Retrieved from http://www.winetrail.com/juiceintoalcohol.html
4. Lahne, J. (2010, February 09). Serious Cheese: Know Your Microbes. Retrieved from http://www.seriouseats.com/2010/02/what-microbes-make-cheese.html
5. Overview of Food Microbiology (July 8, 2011). Retrieved from: https://www.fsis.usda.gov/wps/wcm/connct/dcbfde80-3d65-4b21-9685-9d6676367aac/PHVt-Food_Microbiology.pdf?MOD=AJPERES
6. Vidyasagar, A. (2015, July 23). What Are Bacteria? Retrieved from: http://www.livescience.com/51641-bacteria.html

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