Happy Hour — Grow Weekly

Ah yes, happy hour… who doesn’t like a good deal? And while we’re on the topic of good deals, it would be silly not to talk about the amazing deal we have with yeast as an organism. We give yeast food, and they give us happy hour (well, they give us alcohol anyway) through the process of fermentation. The thing is, this process of fermentation does SO much more than make your local happy hour possible. Fermentation also gives us a whole bunch of foods such as bread, yogurt, and chocolate. It also happens in our own bodies to give us energy when we run out of oxygen, and in our gut when our digestive system absorbs nutrients. There are certainly other applications of fermentation, but we’ll hold off on those for now. This week, we’ll take a look at fermentation as a process, how it’s harnessed by us humans, and how you can set up your own fermentation at home. There’s no better way to enjoy happy hour than to indulge in a freshly posted Grow Weekly article… and a fermented beverage, too, of course.

What is Fermentation?

Fermentation can be broadly classified as the metabolism of carbohydrates in the absence of oxygen (also called anaerobic respiration). There seem to be some other definitions that float around, though, such as the metabolism of sugars into acids, alcohol, and/or gases, but I’m going to stick with the first definition. In a more basic sense, fermentation involves an organism eating sugar and directly converting it into energy and a few byproducts, such as alcohol. Now, there are a number of ways this process of fermentation can be carried out depending on what organism is doing the fermenting and what the exterior environment is like. As I alluded to before, we’re going to look at lactic acid and alcohol fermentation primarily, so the processes here are fairly well understood. This is not entirely surprising given that humans have been harnessing these processes of fermentation for literally a couple millenia.

Ancient Egyptian hieroglyphics depicting the wine-making process

In both cases of lactic acid and alcohol fermentation, we start with the modest sugar molecule. Once consumed, the bacteria/yeast/person takes the sugar molecule and converts it into pyruvic acid (or pyruvate) along with some energy. Here’s where things start to get interesting. In humans when we’re low on oxygen, we take the pyruvic acid and convert it directly into lactic acid (or lactate) in order to get just a bit more energy before basically being “finished” with the original sugar. This typically occurs in the muscles when expending quick bursts of energy (e.g., sprinting), which gives us the energy we need without much oxygen but also results in a buildup of lactic acid. Lactic acid allows us to “feel the burn” when we’re working out, and it eventually gets sent to your liver where it’s broken down. Lactic acid also gives yogurt its tangy flavor. So technically, yogurt lets you “taste the burn”... right? Notice that this is again used by humans when oxygen levels are in short supply because using oxygen helps generate even more energy from a single glucose molecule, which is much more efficient and preferred than undergoing fermentation.

In alcoholic fermentation, we jump back to our pyruvic acid that was formed from sugar. Instead of quickly converting it into lactic acid and dumping it, other organisms may convert the pyruvic acid into what’s called acetaldehyde as well as some carbon dioxide gas (which gives fermented beverages the lovely bubbly effervescence). A higher level of acetaldehyde can sometimes be present in fermented beverages due to incomplete fermentation, and it can actually give a hint of “green apple” flavor. Acetaldehyde is also a suspected carcinogen, though, so maybe lay off the green apple a little. This acetaldehyde is then converted further into ethanol (alcohol) in the final step. This process also aids in the overall energy generation process for organisms.

Now, both processes of lactic acid fermentation and alcoholic fermentation are NOT performed by all organisms. This is obvious for us as humans because it’s hard to imagine what would happen if our body generated a bunch of ethanol in our bloodstream instead of lactic acid whenever we were performing strenuous exercise (you’d just have to do a few sprints in order to feel a bit tipsy). Yeast is the real powerhouse of alcohol fermentation, and lactobacillus provides us with lactic acid-based foods. Lactobacillus produces lactic acid, duh. Both of these are microorganisms, with yeast being a type of fungus (check out a previous Grow Weekly!) and lactobacillus being a type of bacteria. These two microorganisms befriended the human race a while back when human civilizations began to ferment beverages and leaven bread. Perhaps even more interestingly, this use of fermentation developed independently all over the world. From beer made in Ancient Egypt to mead made in Asia during the Vedic period (~1500 BC) to Native Americans making octli (or pulque, which is an agave-based fermented beverage). It wasn’t necessarily difficult since literally you let some sugary water sit out, and it will likely start to ferment.

Maybe it doesn’t need to be said, but the humans back then didn’t have an understanding of the biological side of fermentation when they first witnessed its wonders. It actually wasn’t until the 18th and 19th centuries that chemists and scientists actually discovered yeast and how it played a role in fermentation. Much of this work proving that yeast was a living organism essential for fermentation was performed by Louis Pasteur, the man responsible for your pasteurized milk. Shortly after, another scientist named Edward Buchner came along and actually isolated the enzymes present in yeast that make alcohol fermentation possible, and he could carry out fermentation in the absence of the yeast cells. His concoction of enzymes is called “zymase”, and is pretty nifty in the study of fermentation.

So now that we have a very basic understanding of fermentation (carbohydrate is eaten for energy in the absence of oxygen and forms byproducts), let’s take a look at how us humans put it to use.

How do Humans Harness Fermentation?

I suppose we’ll start with a fermentation that’s pretty intimate since it’s one that happens to be going on right now in your own belly… in your intestines, to be exact. Yep, right now a multitude of bacteria are chowing down on the food moving through your digestive tract as it makes its way to, well, the toilet. You actually have about 10 times MORE bacterial cells in your gut than you do human cells that make up your entire body. Since your intestines don’t really have much oxygen present, the bacteria there break down your food (or what’s left of it after moving through your stomach) through fermentation processes. Though we only discussed two types of fermentation earlier in this article, the fermentation processes in your gut are a bit different and predominantly produce byproducts of short chain fatty acids and various gases, potentially including carbon dioxide. So yeah, you typically only have a TINY bit of bacteria and yeast in your intestines that produce alcohol for you through fermentation. Although… there IS a disease called Autobrewery Syndrome in which these particular yeast and bacteria actually do infect your intestines in such a way that they produce a significant amount of alcohol through fermentation. This then results in a buildup of alcohol in your intestines that gets directly absorbed into your body, and those with Autobrewery Syndrome present with symptoms of intoxication without ever having consumed any alcohol.

While the video below clearly is talking about cows (and I certainly don’t mean to call you a cow), the process of microorganisms fermenting in our intestines is actually quite similar to the process in cows’ digestive systems. Maintaining healthy microorganisms in your intestines is important to your own health and ability to extract nutrition from foods you eat. Also, I don’t endorse Purina cow feed, only the initial informational part of the video.

Now that we’ve seen a bit about the importance of fermentation in our intestines, we can also explore the importance of fermentation outside of our intestines. Fermenting foods results in a change of the nutritive properties of the food. Since microorganisms basically “pre-digest” the food or drink during fermentation, there’s bound to be some changes in what we end up consuming. For example, yogurt and fermented milks end up having a higher antioxidant activity as compared to normal milk, and certain fermented foods such as sourdough bread have been shown to have a lower glycemic index, which helps prevent adult-onset diabetes. The level of certain vitamins even changes with foods that get fermented, especially B vitamins. In addition to altered nutritive properties, fermented foods with active microbial cultures (so not baked to death in an oven) serve as probiotics that contribute to the health and diversity of the microorganisms in our own intestines.

Now, here’s a short list of foods and drinks that incorporate some form of fermentation:

Yogurt: Milk that has been fermented by lactobacillus and streptococcus bacteria resulting in a thick mixture with lactic acid and other fermentation byproducts. Lactose (a menace for people that are lactose intolerant) is a type of sugar that is present in milk, but these bacteria help break some of this lactose sugar down during fermentation, making yogurt more digestible than milk.

Cheese: ALSO fermented milk, except this time mixtures of enzymes, such as rennet, get thrown into the mix typically. Milk curdles through the fermentation and enzymes, and then curds (solid curdled bits of milk) get collected and separated from the whey (liquid remaining form the curdled milk). The curds are used to make the cheese. It’s hard to nail down a singular process for making cheese since there are SO many types of cheese with a slightly different process to make each. One interesting aspect of cheese-making is that the holes that you find in certain cheeses such as Swiss or Emmentaler are actually created when bacteria in the cheese culture produce carbon dioxide gas. It’s like carbonation for cheese.

Beer and wine: Here we deal almost exclusively with alcohol fermentation, although certain sour beers and natural wines likely have some wild bacteria and yeast that produce lactic acids in addition to ethanol. With beer, the sugar that we start with is from malted barley typically, although sometimes other grains such as oats are thrown in for flavor or textures. The sugars are extracted from the grains into water, and yeast is then added to the sugary water mixture to ferment. Once the yeast is done...voila! You have beer. Now, people certainly add other ingredients to beer as well, especially hops, but hops actually aren’t necessary to ferment grain into beer. Hops simply add flavor, modify pH, and actually act as a sort of antiseptic that fends off bad bacteria that could throw the yeast off their game. Wine is certainly similar, except instead of sugars extracted from grains, we ferment grape juice.You can get a more complete idea of the winemaking process (not just the fermentation part) in the video below.

Bread: Another yeast fermentation that results in alcohol and carbon dioxide gas. The sugars here are from the flour which is typically from some form of wheat (although other bread can be made from other grains, too!). While the alcohol evaporates off when bread is baked, the carbon dioxide that was generated via fermentation gets trapped in the dough to create little air pockets responsible for bread’s nice airy texture. With sourdough bread, lactobacillus and other wild yeasts and bacteria join the party and ferment the flour. Because of the diversity of microorganisms used to ferment sourdough bread instead of just commercial yeast, other forms of fermentation, such as lactic acid fermentation, also take place. The presence of other fermentation byproducts such as lactic acid is what gives sourdough bread that slight characteristic tanginess.
Chocolate: Chocolate originates from cacao beans that grow in pods on tropical cacao trees. After the pods of beans have been harvested from the tree, the beans and pulp from the pod are laid out for close to a week to ferment with natural yeast and bacteria. During this period of fermentation, different chemicals are produced by the microorganisms (including lactic acid and ethanol) which contribute to the final flavor and aroma profile of chocolate. After fermentation, the pulp is removed and the beans are dried, roasted, and further processed to get cocoa products such as cocoa butter and cocoa powder (and the classic Hershey’s bar).

The inside of a cacao pod showing the beans and pulp. Certainly doesn’t look anything like a Hershey’s chocolate bar yet.

Parts of a coffee fruit with the bean inside.

Coffee: The process of coffee production also harnesses the power of fermentation along its supply chain. Roasted coffee beans that we use to make coffee with start out as coffee cherries, These cherries are picked from coffee plants before being depulped and fermented. During fermentation, the outer “mucilage” layer of the coffee fruit consisting of complex carbohydrates is broken down by natural yeasts and bacteria. This process also decreases the water content in the coffee fruit before further processing steps. This fermentation is an essential step in bringing you your morning cup of joe, and can even impact the final flavor profile.

Pickles (and some other pickled things): It’s important to make the distinction that pickling and fermentation are not exactly the same process. Both can be used to preserve foods, and many things are both pickled AND fermented, such as sauerkraut. Pickling is preservation in brine and/or acid, but certain types of bacteria (ahem, lactobacillus) can tolerate this type of environment and produce lactic acid necessary for that acidic component. You can think of “quick pickles” as those made by soaking cucumbers in salt and vinegar, and old-fashioned pickles are those that are slowly fermented using natural bacteria.

How-to Guides

Basically all of these fermentation techniques have been around for a long, long time (because bacteria and yeast have been around for a long, long time). So honestly, how hard can it be? Well, I’m going to focus on a few specific home fermentations in particular, mostly because I’m pretty sure most of us don’t have a coffee plant or cacao tree hanging out in our backyard to ferment with. It’s pretty easy to obtain dairy products, flour, grains, and cucumbers, though.

Yogurt. Perhaps one of the easiest methods of starting a homemade yogurt is just using milk and a bit of yogurt with live “probiotic” bacterial cultures purchased from the store. Heat the milk to 180°F or until boiling without scalding the milk in order to kill off any residual bad bacteria and microorganisms. Then, cool the milk down to about 105-110°F. Add a bit of the store-bought yogurt that has a live bacterial culture to the milk and stir to combine. Put a lid or cover on the container and store at a temperature of around 100°F, although this can probably range anywhere from 85°F to 110°F. This can be a weird temperature but one way to deal with this is to store the container on some warm electrical device or in your oven with just the light turned on. Some pressure cookers or slow cookers even have a “yogurt” setting that you could use. Check the container every few hours, and the milk should thicken to a yogurt within about a day! The cool thing is, now you can use some of your own homemade yogurt to start the next batch instead of purchasing store-bought yogurt.
Alcohol. Now, there exists an incredible number of different alcohols out there that I won’t even attempt to cover. So I’ll stick with generic beer and wine, and you can figure out the rest. Note that drinks with higher alcohol contents must be distilled since the yeast performing the fermentation can’t live in conditions with alcohols levels reaching above around 10-20% or so by volume (which is good for our hand sanitizer).
For beer, you can start with malted barley or even “malt extracts” which you can buy online or at specialty brewing stores. I’m not going to cover the malting process here because that’s a bit more difficult to control at home. The whole brewing process is covered pretty briefly and thoroughly in this video here:

Note that it’s important to keep things clean and sanitary since introducing too many bad bacteria or other microorganisms can crowd out the yeast that you add. This might result in different forms of fermentation that produce things other than alcohol that might not be so desirable. The one-hour boil helps kill any of these residual microorganisms during the brewing process.

For wine, it’s somewhat similar. Certain grape varieties are more suited for winemaking, so using grapes purchased at the grocery store for eating might not give you very high quality wine. Once you get your wine grapes, you simply have to squeeze the juices out of them into a clean container. This can be done using your hands, a fancy grape press, or the old-fashioned way with your feet. Once you have the grape juices, there are several things you COULD add, but aren’t especially necessary. Certain enzymes, nutrients, Campden tablets, and sulfites can be added to control the fermentation, but they don’t actually perform the fermentation. That duty does to the yeast, which you can again purchase, with certain yeasts better suited to wine production (so, again, best not to use bread yeast). After adding yeast to the juice, cover the container and add an air-lock or one-way valve to allow gases to release from the container. After 1-2 weeks, pour the fermenting liquid through a filter (like a cheesecloth) into a second container. If you don’t have a filter, you can just decant to remove any solids that fell to the bottom. In this second container, cover again with an air-lock or one-way valve and allow it to ferment for another few weeks. Repeat this last step of transferring the liquid to a clean container every few weeks until the wine is relatively clear and free of sediments or solids.

This is low-key just a plug for my own sourdough starter that I prepared. You can see a few bubbles from the carbon dioxide.

Sourdough bread. I’ll be honest on this one, the folks over at King Arthur Flour are certainly more knowledgeable than I am regarding sourdough bread. To make sourdough bread at home, you need to begin by making a sourdough starter, which you can find direction on here: https://www.kingarthurbaking.com/recipes/sourdough-starter-recipe
Essentially, this sourdough starter is a mini environment where you cultivate your own wild yeasts and bacteria that can then be used to ferment, or leaven, dough. The flour provides the sugars and nutrients, nature provides the microorganisms that ferment, and just like that you can add “microbiologist” to your résumé.

Pickles. Classic pickles (technically pickled cucumbers) can be made at home fairly easily without all the bells and whistles. Use freshly-picked, unwaxed, washed cucumbers of a variety that is suited for pickling. Yes, that means the cucumbers you use for slicing and eating in salads may not be the best type for pickling. Using a container made of glass or food-grade plastic, add your whole cucumbers along with water, kosher or sea salt, and any spices you deem worthy or your pickles (hint: dill seems to work well). The water should cover the cucumbers completely to form an anaerobic environment and should fill at least 75% of the container’s volume. Then, place a coffee filter or other porous material over the opening of your container so that gases can escape during the fermentation but bugs and other annoying things can’t get into your prized pickles in the making.

Store the container in an area that maintains a constant temperature close to 70°F for about four weeks. Check the container regularly to make sure it’s progressing and you don’t have any mold contamination. Feel free to skim off any scum layer that forms on top of the liquid. Natural lactic acid bacteria present on the cucumbers will get to work fermenting the vegetables, and fermentation is complete when any bubbling in the container fully stops

So… we can see that fermentation is a pretty neat natural process both inside and outside of our own bodies. It allows us to do some incredible things, such as preserve foods and make tasty new creations such as cheese. It allows us to digest foods… which is kind of essential to our survival. Perhaps most importantly, though, it allows us to enjoy happy hour to its fullest. Cheers to that!!

to think about…

Microorganisms pretty much only need water, sugar (or any carbohydrate), and the absence of oxygen in order to ferment. Where else do you think fermentation occurs in the world around us?
Take a moment to reflect on how what you eat might affect the microorganisms fermenting foods in your intestine.
Given that antibiotics and cleaning chemicals are available and used much more widely today, how do you think that affects the microbes that perform fermentation for our foods?

Sources

https://www.nature.com/scitable/topicpage/yeast-fermentation-and-the-making-of-beer-14372813/

https://pubmed.ncbi.nlm.nih.gov/19335652/

https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook-2.0/section/2.29/primary/lesson/fermentation-bio

https://www.thinglink.com/scene/935938879154814978

https://sciencing.com/alcoholic-lactic-acid-fermentation-5635612.html

https://www.thoughtco.com/what-is-fermentation-608199

https://www.cookinglight.com/cooking-101/techniques/difference-between-fermenting-and-pickling

https://www.hindawi.com/journals/jfq/2019/4836709/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6567126/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7466055/

https://www.culturesforhealth.com/learn/yogurt/what-is-yogurt-history/