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Reading about fermentation
Aug. 1st, 2021 01:57 pmI brought _The Art of Fermentation_ by Sandor Katz with me on the Florida trip, and I've been reading it straight through (though I skipped the bits on alcohol fermentation, which I am largely disinterested in.) The book is somewhere between an encyclopedia, an ethnohistorical foods survey, and a how-to guide. It's very approachable.
The main takeaway on fermentations involving lactic acid bacteria (e.g. yogurt, sauerkraut, and to some extent salami) is that as long as there's an anaerobic environment and sufficient carbohydrates, environmental lactic-acid bacteria will pretty much just take over and acidify and make something safe to eat. They're salt-tolerant, so salt helps them get a leg up, but it's not necessary, and you can often replace it with "backslopping" some of the previous batch in as a starter. (Salt is important for culinary reasons, though, including not allowing sauerkraut to get mushy.) I was startled at how many traditional fermentations are just "put the raw milk in the gourd" and food comes out a few days later. Milk in particular is ideal for this, and you see that in traditions all through Europe and Africa. It turns out that "aging like milk" is a bit of a misnomer -- unless the milk is pasteurized, in which case there's a bit more of a gamble.
However, just because it's safe doesn't mean it's tasty (to you). I've long been suspicious of how the variety of smells of cheeses is widely tolerated in American cuisine, but milk is only supposed to smell one way (a single very mild smell). It sounds like many of the times I've had "spoiled" milk, it would have been recognizable to *someone* in the world as a perfectly good dairy ferment, but that my upbringing has taught me to be disgusted by it (or rather, hasn't taught me to like it). As Katz points out, fermentation is a large middle ground between fresh and rotten. Some things are unambiguously rotten, but many are culturally relative. You just have to take your own society's word for it sometimes!
I also feel a little more vindicated in my willingness to eat "old" food from the fridge, trusting my eyes and nose and tongue: Molds are bad, brightly colored ones more so, and bad smells and flavors mean bad food. As far as I'm aware, I've never gotten food poisoning (although I also hear that's mostly a result of people not washing their hands in food harvesting and prep after using the toilet!)
===
Industrialization of traditional fermentation processes produces more *uniform* products, but doesn't really increase safety, and the flavors tend to be of only middling quality. The nutrition can also be reduced relative to the traditional methods. Both of these are because the industrial process uses one or more pure cultures on sterilized ingredients, rather than high diversity of species and strains you'd get from indigenous bacteria (those found on hands and ingredients). This is also why you can't really culture yogurt from storebought yogurt for more than a couple of iterations; the theory is that bacteriophages eventually kill of your cultures. Traditional yogurts use traditional yogurts as starters, and the diverse ecosystem of bacteria is more resistant to infection. Unfortunately, food regulators often don't understand this, and sometimes crack down on traditional fermentation; one salami-maker had to pay $100,000 to commission a study proving to the USDA that his methods don't allow _E. coli_ to grow. If he had succumbed to pressure, he would have had to use methods that make the same homogeneous salami that everyone else makes, rather than the exceptional products he was known for. And the use of pure cultures also inhibits home production and experimentation; if commercial yogurts used the historical Bulgarian cultures, I'd be able to make my own yogurt at home just by taking a sample of storebought stuff.
===
Meat and fish fermentation is more difficult because of the lack of carbohydrates -- there's no food for the safe bacteria, so putrefying bacteria have free reign. That's why salami has sugar added, and why fish is so often fermented with rice. (This is also why curing flesh requires so much more salt than preserving vegetables.)
Botulism used to be primarily caused by improperly prepared sausages (hence the name, from the Latin "botulus", for "sausage"). In the anaerobic, high water-activity, low acidity interior of meat, _Clostridium botulinum_ can thrive; traditional meat fermentation uses a combination of drying, salting, and souring to protect against this. In modern times, however, we get to enjoy the risk of botulism from canned vegetables as well! These vegetables would historically have been fermented instead, with far safer results. A special case is garlic in olive oil, which is *too* anaerobic; the safe thing to do is to ferment the garlic first, *then* use it for infusion. There was also a depressing note on Alaskan fish preservation -- traditional fermentation was done in grass-lined pits, but some people are switching to plastic and are getting botulism as a result of the anaerobic environment. Be careful of messing with traditions that work.
===
Many fermentations (or foods in general) are best done in a specific geographic and cultural context. For example, fermentations involving mold (e.g. tempeh, soy sauce, miso) are harder to arrange in a low tech way unless you live in a climate that is conducive to them, since the molds want access to air but *also* humidity *and* warm temperatures. Fish are easier to dry in a cool, dry, sunny climate. Meat is best preserved in cool, humid conditions, so slaughter and hunting are preferentially done at certain times of year. Many fermentations rely on local ingredients that are hard to acquire elsewhere, where preservation would be required for shipping and would destroy the important microbes on their surfaces. I would *like* to make my own tempeh, and it wouldn't be too hard, but I can't just get it going based on local materials. On the other hand, sauerkraut is ridiculously easy to make in New England; all I need is a cabbage, salt, a scale, and a jar (and ideally also a basement.) Those are things I already have. I'll likely do some experimentation with millet and lentils in fermented batters, such as dosa.
===
A good many fermentations are about preserving an abundance of food for the scarce part of the year -- sauerkraut, rakfisk, umeboshi. But others are primarily about developing flavors (wine, chocolate, miso), making the indigestible or toxic into something edible (some seeds), or reducing cooking requirements (many vegetables and grains, tough meat). In a few cases you get new forms entirely, like sourdough bread and carbonated beverages. These aren't exclusive, of course; soybeans in particular show up in almost all of these categories. Cheese certainly spans many of them.
I think my main interests are in "putting food up" during the harvest season with reducing cooking requirements a second, but I also delight in the wide variety of flavors. However, the latter more applies to fermentations I'm unlikely to do myself, such as cheese and mold/soy processes.
Some general notes so far:
The main takeaway on fermentations involving lactic acid bacteria (e.g. yogurt, sauerkraut, and to some extent salami) is that as long as there's an anaerobic environment and sufficient carbohydrates, environmental lactic-acid bacteria will pretty much just take over and acidify and make something safe to eat. They're salt-tolerant, so salt helps them get a leg up, but it's not necessary, and you can often replace it with "backslopping" some of the previous batch in as a starter. (Salt is important for culinary reasons, though, including not allowing sauerkraut to get mushy.) I was startled at how many traditional fermentations are just "put the raw milk in the gourd" and food comes out a few days later. Milk in particular is ideal for this, and you see that in traditions all through Europe and Africa. It turns out that "aging like milk" is a bit of a misnomer -- unless the milk is pasteurized, in which case there's a bit more of a gamble.
However, just because it's safe doesn't mean it's tasty (to you). I've long been suspicious of how the variety of smells of cheeses is widely tolerated in American cuisine, but milk is only supposed to smell one way (a single very mild smell). It sounds like many of the times I've had "spoiled" milk, it would have been recognizable to *someone* in the world as a perfectly good dairy ferment, but that my upbringing has taught me to be disgusted by it (or rather, hasn't taught me to like it). As Katz points out, fermentation is a large middle ground between fresh and rotten. Some things are unambiguously rotten, but many are culturally relative. You just have to take your own society's word for it sometimes!
I also feel a little more vindicated in my willingness to eat "old" food from the fridge, trusting my eyes and nose and tongue: Molds are bad, brightly colored ones more so, and bad smells and flavors mean bad food. As far as I'm aware, I've never gotten food poisoning (although I also hear that's mostly a result of people not washing their hands in food harvesting and prep after using the toilet!)
===
Industrialization of traditional fermentation processes produces more *uniform* products, but doesn't really increase safety, and the flavors tend to be of only middling quality. The nutrition can also be reduced relative to the traditional methods. Both of these are because the industrial process uses one or more pure cultures on sterilized ingredients, rather than high diversity of species and strains you'd get from indigenous bacteria (those found on hands and ingredients). This is also why you can't really culture yogurt from storebought yogurt for more than a couple of iterations; the theory is that bacteriophages eventually kill of your cultures. Traditional yogurts use traditional yogurts as starters, and the diverse ecosystem of bacteria is more resistant to infection. Unfortunately, food regulators often don't understand this, and sometimes crack down on traditional fermentation; one salami-maker had to pay $100,000 to commission a study proving to the USDA that his methods don't allow _E. coli_ to grow. If he had succumbed to pressure, he would have had to use methods that make the same homogeneous salami that everyone else makes, rather than the exceptional products he was known for. And the use of pure cultures also inhibits home production and experimentation; if commercial yogurts used the historical Bulgarian cultures, I'd be able to make my own yogurt at home just by taking a sample of storebought stuff.
===
Meat and fish fermentation is more difficult because of the lack of carbohydrates -- there's no food for the safe bacteria, so putrefying bacteria have free reign. That's why salami has sugar added, and why fish is so often fermented with rice. (This is also why curing flesh requires so much more salt than preserving vegetables.)
Botulism used to be primarily caused by improperly prepared sausages (hence the name, from the Latin "botulus", for "sausage"). In the anaerobic, high water-activity, low acidity interior of meat, _Clostridium botulinum_ can thrive; traditional meat fermentation uses a combination of drying, salting, and souring to protect against this. In modern times, however, we get to enjoy the risk of botulism from canned vegetables as well! These vegetables would historically have been fermented instead, with far safer results. A special case is garlic in olive oil, which is *too* anaerobic; the safe thing to do is to ferment the garlic first, *then* use it for infusion. There was also a depressing note on Alaskan fish preservation -- traditional fermentation was done in grass-lined pits, but some people are switching to plastic and are getting botulism as a result of the anaerobic environment. Be careful of messing with traditions that work.
===
Many fermentations (or foods in general) are best done in a specific geographic and cultural context. For example, fermentations involving mold (e.g. tempeh, soy sauce, miso) are harder to arrange in a low tech way unless you live in a climate that is conducive to them, since the molds want access to air but *also* humidity *and* warm temperatures. Fish are easier to dry in a cool, dry, sunny climate. Meat is best preserved in cool, humid conditions, so slaughter and hunting are preferentially done at certain times of year. Many fermentations rely on local ingredients that are hard to acquire elsewhere, where preservation would be required for shipping and would destroy the important microbes on their surfaces. I would *like* to make my own tempeh, and it wouldn't be too hard, but I can't just get it going based on local materials. On the other hand, sauerkraut is ridiculously easy to make in New England; all I need is a cabbage, salt, a scale, and a jar (and ideally also a basement.) Those are things I already have. I'll likely do some experimentation with millet and lentils in fermented batters, such as dosa.
===
A good many fermentations are about preserving an abundance of food for the scarce part of the year -- sauerkraut, rakfisk, umeboshi. But others are primarily about developing flavors (wine, chocolate, miso), making the indigestible or toxic into something edible (some seeds), or reducing cooking requirements (many vegetables and grains, tough meat). In a few cases you get new forms entirely, like sourdough bread and carbonated beverages. These aren't exclusive, of course; soybeans in particular show up in almost all of these categories. Cheese certainly spans many of them.
I think my main interests are in "putting food up" during the harvest season with reducing cooking requirements a second, but I also delight in the wide variety of flavors. However, the latter more applies to fermentations I'm unlikely to do myself, such as cheese and mold/soy processes.
