Pickling is the act of preserving food with acid.
You can do that as simply as submerging the food in vinegar, or lime juice, for a real
long time.
As long as you get the pH below the magic number of 4.6, you're going to have pickles.
But some people would argue that those are not true pickles, no, no, no.
They would say that true pickles are preserved by an acid created by the bacteria inside
the food itself: lactic acid.
That's what lacto-fermentation is.
It's a pretty magical process that yields some of the most delicious foods humans have
ever come up with.
It was one of the only ways people had to preserve vegetables until refrigeration.
And, when it comes to us modern people, there are scientists who believe we would be healthier,
our guts would be healthier, if we ate more of these lacto-fermented foods again, even
though we don't really have to anymore because, you know, we have the fridge.
That said, it can be a little scary eating a wet thing that you just left at room temperature
for a few weeks.
How do you pickle safely and how big are the risks?
Well, field trip to the University of Georgia Extension, where food microbiologist Dr. Carla
Schwan directs the National Center for Home Food Preservation.
"When you look at the microflora, the indigenous flora, in a cucumber, for example, or, you
know, a cabbage, if you're doing sauerkraut, there is around 10 million cells of indigenous
bacteria that are not lactic acid bacteria, so E. coli, coliforms, clostridium."
Yeah, you heard that right — lots of bad bugs inside vegetables, usually not enough
to make a healthy person sick, which is why we can eat raw vegetables.
Though, with these cucumbers, you got to make sure to knock off those little trichomes — very,
very sharp, those are.
And for pickling cucumbers, you want to cut off the flower end — not the stem end, but
the end where the flower used to be.
Why?
"Always remove the flower end because you could have certain fungi that are present
and they have enzymes that basically break down pectin."
Plus the flower itself makes some of these enzymes that could make the pickles kinda
soft and slimy, so that's not good.
That's why we cut off the flower end.
Anyway, there's not a ton of bad bacteria in most veggies, but what matters is the proportion.You
got millions of bad bacteria in contrast to maybe just 1,000 or a few thousand of the
good bacteria that we want — lactic acid producing bacteria.
There's only a few of them relative to the bad ones, so we got to give them an advantage.
"We select the good bacteria and we suppress the bad bacteria that are present there.
So how do we do that?
We utilize salt."
The trick is how much salt.
If you completely pack food in salt, you will kill everything.
Salt draws the water out of cells.
Bacteria shrivel up and die.
You preserve the food basically forever, which people have been doing for thousands of years.
That may be how some of them accidentally invented lacto-fermentation.
Maybe somebody was trying to salt cure their food, but they didn't have quite enough salt
that day and they did not put on enough salt to kill all microorganisms — it was just
enough salt to kill the bad ones.
Lactic acid producing bacteria are able to tolerate some salt.
How depends on the species, but here's one example.
Some lactic acid bacteria are able to absorb compounds from their environment that balance
out the osmotic pressure of the salt water around them.
Like the amino acid proline, for example — they suck it into their cytoplasm, it doesn't hurt
them in there the way that salt would and yet it is able to balance out the osmotic
pressure of the salt that's outside the cell.
It's like two people leaning on the same swinging door from both sides.
The door stays shut, and the water doesn't leak out of the cell.
So the sweet spot where bad bacteria die and good bacteria thrive is between 2 and 2.5%
salt by weight.
For pickled cabbage, that's really easy to figure.
You just weigh out your cut cabbage, figure out what 2.5% of that is, and sprinkle on
that much sodium chloride.
It's the weight of the salt, not the weight of sodium specifically.
In the case of European-style pickled cabbage, sauerkraut, this is basically it.
You let the cabbage sit for a while, maybe mash it up a little to draw out the natural
water inside the cabbage.
I love sauerkraut, and kimchi, but at this stage it really does smell like farts.
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Anyway, cabbage is really easy to ferment because enough water comes out of the cabbage
when you salt it that you can keep everything submerged below the salt water, the brine,
which you have to do.
You have to create an anaerobic environment for the food.
If it's exposed to air, you're going to get some bad bugs, especially fungi.
On the other hand, you cannot seal this up tight either.
I know this looks and feels like we are canning, but we are not canning.
Canning is a totally different thing that requires using heat to sterilize everything,
among other steps, and you can't really do that with fermentation because you'd kill
the bacteria that you need to ferment your food and make lactic acid.
Canning also requires totally air-tight seals, but we can't do that in fermentation either.
"No, no.
Yeah, you're not going to seal it in a mason jar, because you have production of CO2 and
that could potentially explode, so you don't want that, right?"
So some people do ferment pickles in just a loose-fitting mason jar to let the gas escape,
but Dr. Schwan says that's not really a best practice.
Like here's my kraut after it's been fermenting about six weeks and you can see the dry cavities
that have developed.
Fungus and other bad stuff could grow in there where there's air, so what you really want
is a weight that will push all of the solids down below the brine as they shrivel.
There are pickling weights you can buy.
They're usually ceramic, which is both heavy and chemically nonreactive.
I should have done that.
This kraut smells great, but it's probably a little risky.
I don't think I'm going to eat it.
Let's do better with the cucumbers.
Whole cucumbers are a little bit trickier to pickle because not enough water is going
to come out of them to keep everything submerged, so you're going to have to use some water,
add some water, to get enough brine, and you're going to have to factor that water into your
calculations.
We need the total contents of this pot to be between 2 and 2.5% salt by weight, not
just the water.
So I either need to weigh the cucumbers with the water and then figure out 2.5% of that,
or I can just follow a time-tested volume-based recipe, like the ones provided by Dr. Schwan's
National Center for Home Food Preservation.
They have a book that you can buy, but they have tons of recipes for free on their website,
tested and trusted by scientists.
I'm following their recipe for dill pickles.
Fine sea salt — it dissolves readily and it has no additives like iodine or anti-caking
agents that could cloud the brine.
And then this is weird — a little bit of vinegar.
I thought the whole point of lacto pickles was no vinegar.
Well, Dr. Schwan says that commercial dill pickle makers usually use a lot more salt,
maybe up to 5% salt.
That's a little bit more reliable.
There's definitely no way that any bad bugs could survive in an environment that salty.
The problem is that the pickles are then inedibly salty.
So what they do after they ferment them is they put them into pure fresh water to purge
the salt out of them.
We're probably not going to do that at home, so, for us, that little bit of vinegar is
just an insurance policy.
It controls the bad bugs before the lactic acid bacteria can get established and start
making their own acid.
Dill pickles have dill (duh), maybe some spice and then a whole lot of garlic.
That's what makes a New York Jewish deli-style pickle to me.
Some people use food-grade lime — it gets you crispy pickles, but people say that tannins
in black tea leaves have a similar effect.
No idea if that's actually true.
Lay in the cucumbers.
They really can't be any bigger than that or they'll take too long to pickle.
And you can see that they're floating.
We need to weigh them down with something to keep them in that anaerobic environment.
Metal would react with the acid.
Glass is chemically inert and it'll provide a window through which we can watch.
Into the basement closet with you.
Normal room temperature is generally the best for lacto-fermentation, and we'll see you
in a few weeks.
Time lapse.
In the first week or so, enzymes break down the chlorophyll.
Anyone can see that, but a trained eye, like Dr. Schwan's, sees something else.
"Those small bubbles, I don't know if you can see here..."
Could be gas escaping from inside the cucumber cells, but it could also be CO2, which might
be created by our first-string good bacteria.
"Leuconostoc mesenteroides."
Yeah, what she said.
That species or a similar one will dominate for the first week, making CO2 and lactic
acid.
"When that is happening, you also see — let's say you have coliforms present, — you also
see the coliforms dying."
Coliforms would be bad things, like E. coli, bad soil bacteria.
Those first good ones can only handle a little acid, so once the environment gets to like
1% lactic acid, they shut down, and some more acid-tolerant species take over, like lactobacillus
brevis and lactobacillus plantarum.
They go about eating the sugar in the cucumbers.
Yes, there's a little bit of sugar in a cucumber.
They create lactic acid as a waste product, eventually driving the pH in there below 4.6,
which is crucial.
You might be wondering why Dr. Schwan is plotting a downward trajectory to describe rising acid
concentration.
It's because as acid goes up, pH goes down.
And we gotta get the pH below 4.6.
"Clostridium botulinum will not grow below 4.6 and so, if your pH is about 4.6, you have
to be worried about clostridium and you know that clostridium botulinum produces a neurotoxin
that causes botulism.
We definitely don't want to have that.
There's also other pathogens that will survive and will grow at higher pH, so you're talking
about listeria, you're talking about E. coli, salmonella.
So it's a whole gang of bacteria that could be present if you stop the fermentation too
early."
That said, for many years, New York Jewish delis have sold these things they call "half
sours," which is a pickle they take out before it's completed its fermentation process, so
it's not so sour and it's a little bit more crisp and green, and nobody's gotten botulism
from those as far as I can tell, no case reports that I can find.
Crucially though, those delis put them into the refrigerator, and the refrigerator would
also slow the growth of the botulism bacteria.
That's really, really important.
Back in the day, they didn't have refrigeration, so they had to keep fermenting until the pickles
were really sour.
Somewhere between a pH of three and four is where the good bacteria can't take it anymore.
They shut down and your pickles are done as they're ever going to be.
They should smell sour.
They should taste sour.
At this point, it's safest to either can them or transfer them to the fridge, because bad
things could happen.
Wait for it, wait for it, and ... mold.
Giant mold bloom about six weeks in.
Spores could've floated in on the air or they could've been on my spices.
Mold or other fungus can grow on any of the surface that's exposed to air.
You're supposed to skim it off as soon as you see it, but I didn't want to mess up the
time lapse, and, as a result, things got really out of hand.
Now, lots of the fungal growth is going to be harmless things, like yeast.
And Dr. Schwan says even dangerous fungi generally will not create mycotoxins in salty conditions,
but only if you skim frequently.
"You don't want to have that, different layers of mold, because that top layer of mold could
be producing mycotoxin and it's not in contact with the brine or anything.
And yeah, I would not eat that.
If you had removed it over time consistently, then yes.
But like this, after eight weeks, definitely not."
Yeah, I'm just going to have a teeny-tiny little bite.
Tastes great.
What a shame.
Here's what Dr. Schwan likes to use as a weight — a sealed plastic bag full of 2.5% brine.
It conforms to the bowl, fully covering the surface, though gas can still get out.
And if the bag leaks, no problem, because it's filled with brine and not plain water
that would dilute the brine.
If you do that and you follow a time-tested recipe, like the ones they have from the National
Center for Home Food Preservation, it's going to keep you out of trouble.
Dr. Schwan is aware of no documented case in which someone has gotten sick from properly
lacto-fermented vegetables.
Meat, sure — but not vegetables.
And I've been combing the literature, I can't find anything.
I've talked to other food microbiologists, they don't know of any cases.
It's just not a thing that seems to happen.
These pickles are really safe as long as you do everything basically right.
Use your senses though.
If the pickles smell like they're rotting, if they don't smell or taste sour, well, that's
an indication that your good bacteria lost the battle against the bad ones.
But follow the recipe and that just probably won't happen.
What's more likely to happen is that all of these live beneficial bacteria and their metabolites
will end up in your gut where they will improve your gut health, and that's a really complicated
topic that we'll talk about more another day, but that is real science.
"There has been some studies showing that, I think, if you consume 120 grams of kimchi
— I think it was, a study I saw — a day, you're going to have health benefits.
And I was trying to do that for a while, and it's a lot of kimchi.
I wasn't able to keep up.
But yeah, in South Korea, that's the average."
And, of course, kimchi is basically sauerkraut with a lot more interesting flavors.
Delicious, but it's all thanks to those lactic acid bacteria that have co-evolved with us
humans for millennia.
And long may we mutually benefit each other.