The first book I ever used to learn fermentation was a tome-like book called Nourishing Traditions. It's a famous book that some of you may have heard of or even read. The beginning of the book is about a hundred pages long including several pages talking about equipment and several more which is just citations.
So, naturally, I didn't read it. Too long, didn't read. But flipping through the recipes, my eyes repeatedly landed on a word that I didn't recognize: lacto-fermentation. It showed up in all the recipes I wanted to try including the pickle recipes. And although the first hundred pages surely thoroughly explained what that word meant, it was too much for me at the time. I just wanted to try making pickles.
The problem was that the pickle recipe called for whey as a preferred ingredient, and thus, I had to learn how to make whey, which means I had to have made either kefir or yogurt and preserved the whey. (Salt was listed as a second, lower-class option in the recipe.) That added yet another level of complexity to something I already didn't understand -- the idea of needing to make kefir to make whey to make pickles seemed like a lot of work, and although I may have tried once or twice (I don't remember to be honest) I figured pickling was just too complicated and not really for me. And that's where I left it off.
As I got gradually exposed to more pickling projects (olives in San Rafael, sauerkraut in Italy), I learned that it wasn't really so complicated. Let me tell you the whole story in a few words. There are only two ingredients needed to do lacto-fermentation. Those are:
- Salt
- Time
You do not really need whey -- using fermented liquid as a starter is known in the biz as "backslopping" and gives mixed results. That's not to say that whey and backslopping aren't useful but they aren't necessary either. So I recommend putting that stuff on the side for now but you can ask questions about it if you want.
A good rule of thumb is that whatever the stuff in your jar weighs -- all of it, together, including the water -- and the amount of salt you add should weigh about 2.5% of that. For that reason I recommend you buy exactly one piece of equipment before starting your fermentation journey. I recommend the Escali Primo as my old faithful. It's a kitchen workhorse and the price-point is right. But any scale that measures in grams will do. The procedure looks like this:
- Put the jar on the scale. Tare (zero) it.
- Add the things to the jar (including water)
- Take whatever that number is, multiply it by .025, and then add that amount of salt
You may be asking why we add salt at all? I promise we'll get to that.
[!TODO Bring Escale scale for demo]
Generally speaking if you follow this procedure, adding roughly right amount of salt and making sure whatever you're pickling is under the brine, you're going to make something safe and enjoyable to eat.
The basic principles
This is the kind of subject where you can get away with a lot by thinking at a pretty high level. You don't actually need to know the science to make pickles, and if you just follow the recipes you'll do fine -- but if you want to go off on your own path, you'll need a mental model of what you're doing. That's the purpose of learning the science. Knowledge is power. It'll also prevent you from falling prey to misleading things on the internet, which are really abundant. However, none of what I'm about to tell you is in any way controversial, and is more or less common knowledge.
There are two main players in fermentation: yeast and bacteria. Yeasts breathe like we do: when there is oxygen, they inhale it and exhale CO2. The lactic acid bacteria that we'll encounter are indifferent to oxygen and do perfectly well without it. They break down sugars into lactic acid. Yeast, it turns out, can also do perfectly well without oxygen. But they don't break down sugars into lactic acid -- instead they break it down into CO2 (again) and alcohol. This is why wine gets you drunk (alcohol) and champagne is fizzy (alcohol + CO2) and bread rises (CO2). Interestingly, if you've ever heard that lactic acid "builds up" in your muscles, it's through the same pathway that lactic acid bacteria use. Both human muscle cells and lacic acid bacteria break down sugars into energy, and release lactic acid as a side effect. [Note, you can ask me a little about this as it is not quite this simple!]
- yeast + oxygen + sugar --> carbon dioxide
- yeast - oxygen + sugar --> carbon dioxide and alcohol
- bacteria +- oxygen + sugar --> lactic acid
By the way when I say sugar, I don't mean honey or table sugar. I mean the things that chemists call sugars, which are anything like sucrose, cellulose, whatever. Not all bacteria break down all sugars and some sugars are easier or harder to break down. That's not detail we'll talk about unless it's really relevant.
Before we do anything else, let's open with a simple recipe. While I'm making this I'm going to pass it around for you guys to try. This is called sour cabbage, or sauerkraut in German.
Sauerkraut
Recipe
- Weigh some cabbage. Write down the weight. Shred it.
- Add 1.5%-2.5% of that weight in salt. Your choice.
- Massage the salt into the cabbage until all the water comes out and the cabbage is under the brine.
- Store the cabbage in a vessel that keeps it submerged. Put it in the fridge when it's sour enough.
[[At this point, pass around samples of the simple sauerkraut, and say the rest while people are trying the sauerkraut.]]
This is the entire recipe for a generic sauerkraut. As you can see, it's basic. There isn't even a need for water. Green cabbage is, on a pound for pound basis, as watery as a watermelon. Most vegetables are, actually, and the wetness or juiciness has more to do with how freely the water comes out of the cells. Carrots are close at 87%, but that water is bound pretty tightly in the cells, so they don't seem as watery to the touch. A banana, surprisingly, is actually one of the drier fruits at around 75% water by weight. And a potato is slightly ahead, at 80%.
[This could be a quiz -- match the vegetable to its percent water... using velcro or something.]
https://npr.brightspotcdn.com/23/49/3a0dc4b94daa9ac22494e4708572/water-content-of-vegetables-and-fruit.pdf
For nearly all of our projects we're going to assume that the vegetables we use are 100% water. That's why we were able to say, "take everything in this jar and add up all the grams whether it's a vegetable or it's water or it's something else." This may result in us oversalting by 10-20%, but when you're talking about 2-3g of salt, a difference of a half a gram doesn't make much of a difference.
Once you've finished the fourth step of making the sauerkraut, the laws of microbiology begin to work, and microorganisms begin to digest the sugars. Microorganisms, like bacteria and yeast, reproduce according to how comfortable they are. If an organism doesn't like being cold (I do, and my girlfriend doesn't), and you put that organism in the fridge, it will decide that now isn't the right time to go about reproducing, and it will focus on other stuff, like surviving. Reproducing is something we only have the luxury of doing when all the circumstances are just right. (Just ask my girlfriend.)
Now we can come to why we add the salt. Just as lactic acid bacteria kind of like an oxygen-free environment, they also kind of like salt. This separates them from other bacteria which do not. The salt makes the lactic acid bacteria feel like it's a great time for reproducing, while the other bacteria somewhat hold back. As the lactic acid bacteria reproduce, they also let out a bunch of...
...yes, lactic acid. A side effect of the lactic acid is that this suppresses even more the growth on non-lactic acid bacteria. As it's a byproduct of their metabolism, lactic acid bacteria have gotten somewhat used to being around lactic acid. However they are not completely immune, and once the jar is totally full of lactic acid, the liquid becomes to acidic for even the lactic acid bacteria, and they die too. There's a lesson in that story.
Anyway, the point is that the salt helps our friends, the lactic acid bacteria, get a head start. This is why our friends who wrote Nourishing Traditions recommended using whey -- to give a head start (and lower the amount of salt needed the ferment.) But unless you're really sensitive to salt -- and most people aren't -- using the salt is just fine.
Sauerkraut was invented multiple times. In China, it's called Suan Cai (sour cabbage, again). This invention served a purpose. What was it?
A brief commercial break to talk about: Scurvy
https://www.unhcr.org/media/scurvy-and-its-control-major-emergencies
One of the deadliest occupational hazards in the world is... wait. What do you guys think I'm gonna say?
[Take questions]
It's a disease which affected infants in the early 1900s...
...the Americans during the gold rush, as they traveled six months by land from the East Coast of America to California...
...and millions sailors over the last thousand years.
That disease is scurvy. It causes your gums to bleed, your skin to ulcer, and then you painfully empty your bowels and then die. It caused extreme losses in the past. Sailors were more likely to die of scurvy in peacetime than in battle during war. Captains could lose 2/3 of their men on a voyage.
For the survival of soldiers and for a successful mission, it was necessary to treat scurvy somehow. Lots of people observations were made -- for example, Vasco de Gama noted that his sailors rapidly sprang to life when given oranges from a local tribe -- but other, seemingly contradictory observations were also made (raw meat seemed to prevent scurvy as well).
Anyway, it became necessary for anyone on the seas to have on hand a supply of so-called "anti-scorbutics" (anti-scurvy objects) and so a lot of trial and error and careful observation went into finding which foods had this mysterious antiscorbutic property which were also suitable for long-term voyages.
James Cook, the explorer, observed saurkraut to be a mild antis-corbutic and, unlike oranges, didn't spoil. He took thousands of pounds of sauerkraut with him when he sailed, along with other items like barley malt and bouillon and boiled orange juice. I bring this up to say that only the sauerkraut contained meaningful amounts of vitamin C. In one of his journals, he noted that, although he lose four men -- one from a fall, two from drowning, and one from a mysterious illness -- none died from scurvy. This, he regarded, as a great success. As wild as it sounds, the sauerkraut saved many lives.
This is another aside, but he could not convince his crew to eat the saurkraut initially:
The Sour Kroutt, the Men at first would not eat it, until I put it in practice—a method I never once Knew to fail with seamen—and this was to have some of it dressed every day for the Cabin Table, and permitted all the Officers, without exception, to make use of it, and left it to the Option of the men either to take as much as they pleased or none at all... whatever you give them out of the common way—altho' it be ever so much for their good—it will not go down, and you will hear nothing but murmurings against the Man that first invented it; but the moment they see their superiors set a value upon it, it becomes the finest stuff in the world and the inventor an honest fellow
https://gutenberg.net.au/ebooks/e00043.html
So if your kids won't eat sauerkraut, try the ol' Captain Cook method -- tell them they can't have it because they're not old enough, and see what happens.
Just for context about how recent all of this is: In 1930, my grandpa was born. He is still alive. 2 years later, in 1932, Albert Szent-Gyorgyi discovered that vitamin C deficiency caused scurvy in animals. Its anti-scorbutic nature resulted in its name: ascorbic acid.
The story of scurvy is more than I can share with you right now. I'd love to talk more about it after the class so ask me about it if you're interested.
The humble dill pickle
Go. Fie, fellow Quicksilver, what a pickle are you in!
Qu. Pickle? pickle in thy throat; zounds, pickle!
https://www.gutenberg.org/files/46312/46312-0.txt
We are ready to take the next step. It is time to talk about the cucumber pickle. If you understand a pickle, you already understand a lot about fermentation. There's a whole universe in a pickle.
[At this point, pass around the pickled cucumber for people to try.]
A cucumber has a story that stretches as far back as man's, and it has just as much of a claim to this earth as we do. We have no right to feel superior to a cucumber, and therefore we must give it the respect it deserves, and take it seriously.
Cucumbers grow, blossom, and in the process of blossoming, attract animals that need the water in the cucumber. Remember that cucumbers are almost entirely water. In the process of eating the cucumbers, animals eat the fruit and spread the seeds.
For some reason, cucumbers also have a dead-man's switch -- specific enzymes at the blossom end of the cucumber begin to dissolve the fruit from that end.
The point of telling this story is to say that the needs of the cucumber are very different from the needs of man. It is interested in propagating its seeds and destroying the fruit. Man is interested in preserving the fruit. So to make a good pickle we must figure out how we can arrest the process of decay, and make a cucumber pickle that we can eat with some crunch for the rest of the year.
In our last recipe we only added salt, and our logic was that the sauerkraut had plenty of water within it. Cucumbers have slightly more water than sauerkraut (around 95% water by weight) but the trick of shredding and salting won't work on a cucumber as the inner flesh is too mushy, very much like a watermelon. So instead, we add water to a brine.
Dill pickle recipe (crude and simple)
- Some cucumbers (say, 350g)
- Some garlic (10g)
- Some dill (add a bunch -- like 20-30g)
- Spices if you wish
- 2.5% salt
- Cut off both ends of the cucumbers, about 1/3 of an inch (or 1cm).
- Add everything to the jar. Shake the jar to dissolve the salt.
Once the water is in the brine the salt will dissolve. Salt dissolves perfectly fine in cold water, although it dissolves quicker in warm water, but some agitation can make up for the difference in temperature. Once the salt is added to the jar, firmly shake the jars for around 60 seconds to help dissolve the salt. It's good to leave a little room in the top of the jar to help with this -- try packing the cucumbers below the jar's "neck." You can also use a finer "pickling salt", as coarser salts take longer to dissolve. But they will all dissolve eventually, whether the water is warm or cold, and whether you shake or not. But I think it's helpful to get things saltier right away, and I don't mind the workout. It maintains my youthful vigor!
Now this recipe is fine as far as it goes, but you may have picked up on something unusual. Why did we cut the ends off of the pickles?
Pickles are good when they are crunchy, and if you just blindly throw pickles in a jar, they will not be. Here we have our first nontrivial fermentation problem, and again, we learn that a solution was found by trial and error, before the exact cause was proven by scientists.
Cucumber pickles had a problem. They were meant to last the winter, but after months in storage, they got soft and soggy. If you like a mushy pickle you are in the minority and probably have other unpleasant opinions as well.
It was known by housewives for some time that removing the blossom end of the pickle resulted in a firmer cucumber. This was a bit hard to accomplish on an industrial scale at the time, and it was also not exactly proven that it was important, before scientists figured out that indeed, the blossom end of the cucumber contains a large amount of pectinase. And here we have our first enzyme. Enzyme names end in -ase and the thing before the -ase usually says what they do. In this case, pectinase breaks down pectin.
What is pectin? It's a protein that maintains the rigidity of the cell wall of the cucumber. It keeps the cucumber crunchy, in other words. Removing the blossom ends of the cucumbers allowed them to stay crunchy for longer.
Many industrial pickles will have both ends removed, because I think that's easier than trying to find which end is the blossom end (sometimes it's hard to tell.) That's why I tell you guys to remove both ends. But if you can tell which one is the blossom end, you only need to remove that one.
There is some pectinase activity in the entire cucumber, but there is more pectin-dissolving stuff in the flower than in the entire rest of the cucumber combined. The pectinase seems to come not from the cucumber itself but from fungi that live on the cucumber flower.
There is another problem. Man enjoys eating cucumbers for most of the year. But cucumbers ripen during a fairly short span of the year -- perhaps a few weeks. Again, this is no problem for the cucumber. But for man, he has a glut of cucumbers for a few weeks in summer, where he cannot possibly eat them all, and then none for the remaining 50 weeks of the year.
Thus, a man's priorities and a cucumber's priorities have been at odds for a long time.
We don't quite know how it happened, but man at some point figured out that by putting cucumbers in salty water, the cucumbers transformed into pickles. Until around a hundred years ago (I'm rounding) no one would have had a clue exactly what was happening when a cucumber became a pickle. What was the story of what was happening inside those jars? That story, it turns out, is a story of a miraculous coincidence. It is such a miraculous coincidence, that my belief is that it cannot possibly be a coincidence, because it is simply too coincidental! Let me explain.
What happens when you put salt and water and a cucumber inside a jar is this. First, it does not matter where you get the salt, nor does it matter where you get the water or cucumbers -- the process is always the same. The salt rapidly suppresses the growth of most bacteria except for a few, Lactobacillus predominantly. They are called Lacto-bacillus because they are bacteria ("bacillus") that produce lactic acid. We will talk more about that in a second, but now you know where the name comes from. It just so happens that Lactobacillus generally don't mind salt at all, whereas many other bacteria find the environment unhospitable, and don't do much multiplying.
Then something else happens. The Lactobacillus, free as they are to multiply, produce their lactic acid. Just so you have a picture in your head, lactic acid is a three carbon molecule. You can think about it like C-C-C (with little hydrogens and oxygens around the three carbons). And when lactobacillus "eat", this is what they give off as waste. What do they eat? They eat the sugars in the food.
As you can imagine, lactobacillus have some tolerance for being around lactic acid. And so this salty water, which so many bacteria already don't like, is now quickly becoming more and more acidic as the lactobacillus shoot out C-C-C constantly. The cucumber brine is now full of C-C-C. The other bacteria hate it. Many of them die. It's devastating. It's chaos. It's a wasteland.
Except not for the lactobacillus, who are happily just doing their thing. The lactobacillus which, by coincidence, are not only safe, but healthy to eat! And this is the miraculous coincidence. You take this whole process involving billions of uncontrolled organisms, add a little of this and a little of that, wait a while, and you can predictably turn an ordinary food into an extaordinary one.
Now I mentioned earlier that there is a coincidence here. What is it? Well you would think that perhaps this slapdash process of salting the water and letting the bacteria run out of control might produce an unstable, unpredictable, and perhaps even unhealthy thing. But it basically never does. I'm not saying never never, because the odds are never zero, and there are ways that ferments can go wrong, though these are usually due to user error. As long as you follow the basic rules laid out -- the same rules that have been followed since the beginning of time -- you will not only find that your concoctions are safe, but that they are healthy. And this is the strange thing to me. Why should lactofermented foods be healthy at all. How come it is that lactobacillus make us healthier? How come it is that bad bacteria -- pathogenic bacteria -- don't take over?
Apart from sauerkraut being one of the nicer ways to eat cabbage (from my point of view, anyway), to reduce sauerkraut to a source of a single vitamin would be to commit one of the great scientific sins: to mistake knowing something from knowing everything. Clinical trials in the short term show effects on the gut microbiome from eating sauerkraut but the exact results and their downstream effects aren't conclusive. It is difficult to take two identical groups and tell one to eat sauerkraut and the other not to. We mostly rely on retrospective studies, and these are less conclusive than randomized, controlled, trials.
https://idlewords.com/2010/03/scott_and_scurvy.htm
Sauerkraut is arguably the simplest form of fermented cabbage. But it is far from the only one. You may be familiar with another popular form of fermented cabbage from Korea. [Take time for questions here.]
Safety
You should follow some basic rules.
- Trust your senses
- Follow the directions
Basically, it's hard to mess up, and if you check the CDC website for example of botulism, they are almost entirely from canned foods. Botulism bacteria don't like acid, salt, or other bacteria. The reason why botulism can be such a risk in canned food is because they are NOT acidic, sometimes NOT salty, and often are pasteurized to kill bacteria (pasteurization does not kill botulism spores.) But for all our ferments, if you use enough salt, and your ferment gets sour enough, and you trust your senses, you have nothing to worry about.
The difference between store-bought and homemade stuff
Commercially produced products
Lactic acid bacteria
Lactic acid bacteria are called so because they take sugars in the media and break it down for energy, producing lactic acid as a waste product. (There is energy in lactic acid, but they lack the complex machinery to break it down.) The scientific word for this process is called "fermentation."
You may have heard that when you work out, your muscles produce lactic acid too. Is this a coincidence? It is not. It might surprise you to learn that when muscle cells break down sugars to produce lactic acid it is also called fermentation, because it is, more or less, the same as what the bacteria are doing. When one solution appears in biology, you tend to see it elsewhere.
With this little bit we now know about lactic acid bacteria, we can now imagine a picture of how the process goes. The bacteria are like little cars that run on sugars (glucose, fructose, lactose -- depending on the species) and emit lactic acid as exhaust.
There is a lot we don't know about these bacteria and every day we learn new and surprising things. The goal here is to get you to a practical point where you have a mental model of what's going on inside your jars, even if some of the details of that model turn out to be oversimplified.
The essential tools
For lactofermentation there are only two things you need to buy: some form of closed container, and a scale. In today's world, the scale is not optional. If you don't already have one, I recommend the Escali Primo kitchen scale, which is about $25, but any kitchen scale which measures in grams is good enough.
[[Hold up Escali scale]]
Let's talk about the simplest ferment in the world. Sauerkraut needs only two ingredients: cabbage and salt. No water is needed to make the brine for saurkraut -- the salt can pull out all the water it needs from the cabbage itself.
[This could be a quiz]
As a dry vegetable it may surprise you to learn that its weight is mostly water. Cabbage, by weight, is as wet as a watermelon -- about 92% water by weight, according to UCLA. Most of the weight in fruits and vegetables -- 90-95% of it -- is water. Root vegetables, like potatoes and carrots, can be reluctant to give up their water in the presence of salt (the water is more tightly bound within the plant cells) which can make them harder to shred and salt. But cabbage works fine.
When we ferment vegetables we typically take whatever the total water weight is in the jar and add 1-5% of that weight in salt. I tend to use around 2.5%. Since vegetables tend to be around 90+% water, for the purposes of our calculations we will assume they're 100% water. Worst case, we're off by 10%, at worst case we'll be oversalting my 10%, and you won't be able to tell.
Kimchi
[[Play the Kimchi theme song -- if there weren't any kimchi]]
https://www.youtube.com/watch?v=7RxJhAW5YLs
Kimchi is profoundly special to South Koreans.
The Korean War created thousands of Korean orphans that were adopted by the international community. In the process of repatriating them, in bringing them back to Korea, the government created a program that included teaching them to make kimchi. My oldest friend (by time, not age) is Korean and the last time I was at his house I ate three different kinds of kimchi and that was my whole meal. Some monks in korea make kimchi. I'm not saying everyone in Korea likes kimchi, but a lot of them are probably
Kimchi is really a variation of sauerkraut. There have been more studies on kimchi and, perhaps the presence of contains onions and garlic make it more healthy overall. It's tough to say, though there is a lot of science on kimchi and it seems like the overall evidence points to it being healthy.
Kimchi recipe
[Too long to list here, but should bring ingredients to show what goes in the kimchi]
The 20,000 foot view of this class: you'll lear
Milk kefir
The process that happens in the jar isn't so different from what happens in your own gut. But generally the bacteria in the jar are different from those in your gut, so things which would ordinarily be indigestible can suddenly become nutritious.
A good example of this is kefir. Recall that the majority of the adults in the world are lactose intolerant. These people do not produce enzyme, lactase, which breaks down lactose into glucose + galactose, making it indigestible to them and causing problems as a result of that. These days you don't have to drink milk if you don't want to, and many people don't, but our ancestors couldn't afford to be as picky, and not being able to drink milk would have been a real disadvantage. So funny thing -- it turns out that many people in Asia, from the Caucasus, to Tibet, to China, can drink some form of fermented milk even if they're lactose intolerant. You might think that fermented milk just doesn't contain lactose, but this isn't true. Kefir contains around 50-80% of the lactose the equivalent volume of milk. One guess for why kefir is drinkable is that the bacteria get digested, which then release their own lactase enzymes into the small intestine, and breaking down the lactose.
https://www.sciencedirect.com/science/article/abs/pii/S0308814604003723 https://pubmed.ncbi.nlm.nih.gov/12728216/
Kefir is probably the most complex of all the fermented foods to understand from a scientific point of view. For example, kefir cannot be, today, created in a lab. No one knows where the first kefir, or kefirs, came from. It's a mixture of fungi and bacteria. For a reason that you can ask me about later, it forms in little pearls. Understanding where this magical substance comes from will be beyond the scope of this class, but to use it is pretty simple. You simply put the little pearls in milk, and the milk becomes kefir. And the kefir becomes even more kefir. You strain the pearls out and that is it. And you repeat the process forever whenever you want more kefir.
[Show an example here of kefir. Get little ketchup cups for this.]
Kefir, at its best, is a sparkly, sour, yogurt. At its worst, it can be a yeasty, musty, milk... wine. Not all kefirs are the same and depending on everything from the container you use to the temperature of fermentation will affect the result. For most of you, trial and error will be needed to get exactly the right result. But thankfully, the cycle of fermentation lasts about a day, which means you get nearly 400 tries a year. Take good notes and see what you can figure out about your kefir.
The uses of kefir do not stop with making drinkable yogurt. If you overferment kefir it will separate into two layers, like oil and water. In fact the upper layer is mostly fat, like oil, so it floats. The lower layer is whey. That upper layer can be skimmed off and run through a cheesecloth to make kefir cheese, which is like a cream cheese. Maybe a bit sparkly.
[Show example of kefir cream cheese.]
More interestingly, the whey can be used for all sorts of projects.
You can take the whey, for example, add it to a little bit of sugary water, to make a sparkly drink. This is an alternative for people who like to make kombucha, but find it hard. Using the whey from kefir makes the process much simpler, but its probiotic power is comparable.
[Show an example of the sparkly drink.]
And biology is complex. But if you're just interested in knowing how to make things ferment, and to understand the general principles behind it to allow yourself to do your own experiments, then you should be able to take most of that away from this class. And there is a single main principle.