Alison Stewart: This is All of It on WNYC. I'm Alison Stewart. If you missed anything this week, like our What the Hack? call in about no-buy groups, or our conversation with writer Hanif Kureishi about his memoir Shattered, or our big picture conversations with Oscar nominees behind the scenes of this year's most acclaimed films. Check out our podcast feed and if you what you hear, leave us a nice rating. Now let's get this second hour started.

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Alison Stewart: As we put the lid on another week of great conversations, we're going to spend the hour talking about some other things you can put a lid on. We're talking about the strategies for preserving foods, namely canning, fermenting and pickling. We'll start with fermenting. It's a process that uses different bacteria and other microorganisms to help change the composition and flavors of food. Think of it as in enlisting and nurturing your own little tiny army of sous chefs to work some magic at the molecular level. The brines and acidity produced through the fermentation process can extend the shelf life of your base ingredients.

Ferments are a versatile kitchen strategy that can run the gamut from condiments and toppings sauces or miso. You can ferment starters sourdough or a ginger bug. You can ferment veggies, keeping a bit of crunch or bring on some complex flavors. Joining me now to talk about all things fermentation is Arielle Johnson, who joined us a while back to talk about her book Flavorama: A Guide to Unlocking the Art and Science of Flavor. She's also got a PhD in flavor science and appropriate to this conversation is a co-founder of Noma's Fermentation Lab. Hi Arielle.

Arielle Johnson: Hi there. Thanks for having me on.

Alison Stewart: We said, you are a co-founder of Noma's Fermentation Lab. Before all that, what was your introduction to fermenting in the kitchen?

Arielle Johnson: Some of it was actually my grandfather. My maternal grandparents lived just outside of Scranton, Pennsylvania and he was a county extension agent. They had a lot of tomatoes particularly around, but he would also buy in grapes to do a little semi-legal home winemaking in the basement. I think that was my first introduction to the delicious delights of fermentation.

Alison Stewart: It's a fairly broad category to process. What are the different kinds of fermentation and what do they have in common that they can all fit into this label of fermentation?

Arielle Johnson: I would-- If you're asking a microbiologist they might have a slightly more technical definition, but I would define fermentation for, normal people, as transforming food with microbes. The wine I was talking about, that is a yeast fermentation. In all fermentations, generally, you have bacteria, yeasts, technically fungi, some of these microbes. In all fermentations, they're eating something as food and fuel in whatever ingredient they're in. Then they are producing a new substance or molecule. Yeast eat sugar and produce alcohol. Lactic acid bacteria, which are in sourdough, lacto-fermented pickles, like sauerkraut and kimchee, as well as cultured dairy yogurt.

They're eating sugar and producing lactic acid. Then you have oddballs, like acidic bacteria. These make vinegar. They actually eat the alcohol produced by yeasts and then transform that into acetic acid, which is the vinegary acid in vinegar.

Alison Stewart: All right. You said fermentation relies on microorganisms to produce a chemical change, right?

Arielle Johnson: Yes.

Alison Stewart: When it's not something that you introduce, like yeast or a probiotic capsule, how do you know you're getting the right naturally occurring microorganisms?

Arielle Johnson: Generally, there are historically developed rules of thumb. Especially for lactic fermentation, this is probably the one that we do the least, intentional inoculation. There's lactic acid bacteria all over your skin, in your guts, all over the skins of microbes. It's a very prevalent and diverse naturally occurring realm of microbes. We know from historical tradition and now we know from chemistry and biochemistry that they are pretty tolerant to salts, whereas other spoilage microbes aren't. You'll see a lot of vegetable fermentations, like sauerkraut, kimchee, rely on a certain amount of salt.

You add a bit of salt at the beginning, that puts a damper on anything, possibly spoilage. Then the lactic acid bacteria gets to work and they produce acid pretty quickly, which is a double do along with the salt, hampering the growth of any other microbes. If you're doing electric fermentation and it turns sour, then you're generally in good territory.

Alison Stewart: Since these things are alive and they need to be kept alive and they need to be nourished through this process. Do you think of them ingredients or some pet?

Arielle Johnson: They're a bit more like pets. I sometimes feel a shepherd with a flock of sheep. I can't use the grass that they are eating directly, but if I treat them I'll have wool to shear and knit into a sweater at the end. In this case the grass is the sugars and the wool sweater is things lactic acid and other delicious flavors.

Alison Stewart: My guest is Arielle Johnson, food scientist and co-founder of Noma's Fermentation Lab and the author of Flavorama: A Guide to Unlocking the Art and Science of Flavor Listeners, if you have any questions or success stories about fermentation, maybe you have some failures, I don't know. You want to give us a call? 212-433-9692. 212-433-WNYC. Share your fermentation stories or any other fermenting or pickling questions you have for flavor scientist Arielle Johnson. Again, Our number is 212-433-9692. 212-433-WNYC.

You can join us on the air or you can text to us at that number as well. When you're not adding microorganisms, like yeast, you're relying on things found on skins and bacteria. You're looking for good bacteria.

Arielle Johnson: Exactly.

Alison Stewart: How can I make sure I'm finding good bacteria?

Arielle Johnson: Generally, the USDA gives a lot of recommendations around canning, preserving fermentation. They're a naturally pretty cautious group of people. One of their microbiology experts has come out and said that he can think of new no example in recorded history where someone has gotten sick from lacto fermented vegetables. If you want to be very, very careful relying on some of these more acidic fermentations like a lactic acid fermented vegetable or a vinegar, generally if you have acid and it doesn't smell a dead animal- sorry for the [crosstalk] knows- then you're in generally good territory. With more complex fermentations making miso, often you start with very pure cultures or rely on a home maintained culture that has historically not made anyone ill.

Alison Stewart: Let's talk about that maintenance because you have to feed your fermentation, sometimes they need to be burped through the process.

Arielle Johnson: That's true.

Alison Stewart: Can you walk us through some of the maintenance that folks should expect to do if they plan on making fermentation a part of their cooking life?

Arielle Johnson: Yes. Probably the most famous high-maintenance fermentation starter would be a sourdough starter. This is, instead adding dried yeast to make a 11 delicious bubbly bread, you have a basically wild ongoing culture of a mixture of yeasts and bacteria. To keep that going and keep them all in balance with breaking larger components down to feed to the others and then swapping various other things you need to keep adding flour and water to a sourdough starter. There's definitely ways to put it into longer term storage if you're not baking every day.

Often you see people bring the water right down and keep it in the fridge so that the fermentation proceeds very, very slowly. Another, simple fermentation starter, if you like crème fraîche, which is that nice, tangy, cultured cream. The easiest way to make crème fraîche is to take a small amount of existing crème fraîche and add it to heavy cream. You could also use buttermilk or a kefir starter or even yogurt sometimes will work. In that case, if you're eating these products regularly, we call that back slopping, taking a little bit of the existing fermentation that you've done and adding it to kick off the new one.

Alison Stewart: I believe we have a question for you. This is Sanich. She was calling in from Newark. Hi, Sanich, thanks for calling All of It.

Sanich: Hi. Actually, I thought of many more questions, but I'm going to start. Okay. First of all, I'm making yogurt. Okay. I started with a yogurt machine, a regular yogurt bacteria. Then I found something called Matsoni and that doesn't require all this special preparation with milk. Just put cold milk, put Matsoni and it works. My question is I also sometimes make a Russian yogurt, called Ryazhenka, and it's made from baked milk. The first question is, what's the difference? Do you know? Taste is different. Many people ask me if I put more sugar in it, but of course I don't.

Another thing I do, I also do sauerkraut, my own sauerkraut. I only use cabbage, carrots and salt. My main question, that's the one I was calling about, I started to make sausages. I buy cheap meat. For the sausages, some people say that I have to use nitrate salt. Some people say it's not required. The second question is, what's the use for the nitrate? Do I have to use it?

Alison Stewart: Let's start with that one. Does he have to use nitrate salt for sausages?

Arielle Johnson: Yes. Fermenting meat is something I don't to mess around with. I mean, I do on occasion, but it is one of the cases where you do have to be careful about things botulism, especially if you're using a ground meat, because then any stuff on the outside of the meat gets to the inside. There are absolutely traditions around the world where you have aged and fermented charcuterie and meat that doesn't use nitrates. Generally, nitrates are, you can think of them as an insurance policy. They act almost as an antibiotic. They're not literally an antibiotic, but they are quite good at hampering the growth of pretty much any microbe that could hurt you. I would say, unless you have a time proven recipe that you' confident about, I would tread on the side of caution and use more nitrates when you're starting out.

Alison Stewart: Let's go to Orla in upstate. Hi, Orla, thanks so much for calling All of It.

Orla: Hi. My question please, what tips would you have for someone who wants to make sourdough bread for the first time, including where to obtain the starter culture? Thanks.

Arielle Johnson: If you have a friend that is a very passionate sourdough baker and maintains their own starter, that's the easiest place to, and lowest maintenance place to get a starter. It's actually possible to start your own starter. I have a lot of baker friends who do this. They'll end up at a new bakery or they'll be doing a pop up at a restaurant and a mixture of flour and water left out on the counter for a few days and fed in intervals will actually grow its own sourdough starter. There are some books I would probably go with either Chad Robertson's or Richard Hart's books about baking will definitely guide you through the finer steps of creating and maintaining a sourdough starter. It is much less mystical and difficult than some people make it out to be.

Alison Stewart: Let's talk to Patricia from Manhattan. Hi, Patricia.

Patricia: Hi. I've got some leftover red wine from a dinner party and it's about two weeks old. I'd love to add it to my big bottle of red wine vinegar. Can I do that? Will it turn into vinegar?

Arielle Johnson: The key ingredient in making vinegar, in addition to a vinegar starter, you can just actually use old vinegar for that is oxygen. A lot of fermentations don't like air. That's why we have things like sauerkraut crocs and things that to keep things away from air. Acetic acid bacteria, which is the only bacteria that makes vinegar, absolutely needs oxygen to ferment and to live. If you wanted to up your stash of red wine vinegar, I'd take a big glass jar with quite a bit of headspace, dump your leftover wine in there and add, maybe 10% existing red wine vinegar. You can of that with a cloth napkin that's tied off, and it will basically turn itself into vinegar within a couple months.

Alison Stewart: Dan calling in from Bed Stuy. Hi, Dan, thanks so much for calling All of It.

Dan: I had a question about keeping pickles crispy. I have a lot of cucumbers around August, and last year when I tried doing a half sour, it just got soggy after a couple days.

Alison Stewart: Soggy cucumbers. Any advice, Arielle?

Arielle Johnson: Yes, it's a bit perverse that the first thing we think of when we say pickles is cucumber pickles. Cucumber pickles are some of the most finicky in terms of texture. One thing besides choosing often different varieties, smaller varieties of cucumber can help or varieties bred for pickling. Another thing that you can do is add a little bit of calcium in the form of-- I believe they sell it as a type of pickling salt. If you can also add even calcium hydroxide, CAL from an Asian grocery store or a Mexican store. Calcium essentially acts as a glue to firm up the molecules called pectin that hold the cells together.

If the pectin is firmed up and glued together, the pickle will taste a little less mushy. Yes, generally, especially on the pickling salts packaging, it'll give you an idea of the amount to add.

Alison Stewart: My guest is Arielle Johnson. She is a flavor scientist. She's helping us out with fermentation. If you have any questions, success story or abject fermentation failures and you want to learn more, we want to hear from you. 212-433-9692. 212-433-WNYC. Our screeners are standing by to take your calls. We'll have more after a quick break.

This is All of It.

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Alison Stewart: You are listening to All of It on WNYC. I'm Alison Stewart. My guest is Arielle Johnson, food scientist and co-founder of Noma's Fermentation Lab. She is also the author of Flavorama: A Guide to Unlocking the Art and Science of Flavor. Today we are talking about fermentation. I was in Alaska and it was the summertime, and the indigenous people there were harvesting giant vegetables. Cabbages the size of a little red wagon, huge carrots. They were fermenting. That's all they were doing was fermenting all summer long. It made me wonder, what's the history of fermentation?

Arielle Johnson: The very long term history of fermentation. A lot of biologists now think that, before we were even humans, when we were much earlier primates, we were eating, lacto fermented food. In terms of fermentation as a presence in human culture, human cuisine, I don't know that we have evidence of the very first fermentations. These things goes back thousands of years. Definitely, to the beginning of organized settlement. In a lot of these places, you'll find traces of wine or of beer, both fermented foods. Almost certainly a long time before that.

I guess there's two reasons for that. One is that fermentation is an excellent preservation method. A jar of sauerkraut or a properly fermented leg of ham will still be delicious and whole and safe to eat many months on from when you started it. Whereas the cabbage or the raw pork leg would be absolutely, a disgusting pile of mush. It's very handy for getting through the winter. Also with a lot of fermentations, they're very easy to do. A lot of fermentations actually basically start themselves like electric fermentation. Going back, probably there were early humans making a choice of like, "I'm going to eat food that has microbes in it anyway. Let's figure out a way and keep a tradition to make the most delicious ones."

Alison Stewart: Let's talk about safety. What parts of the process are risky in terms of introducing harmful bacteria and how do if something's not safe?

Arielle Johnson: The harmful microbes you'd want to look out for-- One of them is botulism, which is probably the scariest. It is also the rarest. Most modern cases of botulism that I've seen come from improperly canned meats. Botulism is a bacteria that comes from the soil. It is completely anaerobic, so it can't grow in the presence of oxygen and it likes protein and dislikes salts and acid. Fermentations to produce acid and use salts are a good way to guard against that. On the more prosaic side, you have molds. Molds like to grow on the surface of fermentations.

They also, on the flip side, need oxygen to grow. Molds won't grow without oxygen. The traditional way to protect against mold growth is to use something like a double lid or an airlock or something to protect the surface of the fermentation from mold. Generally, if you find your fermentation going moldy and you're a beginner with fermentation, I would recommend just throwing it out and starting over. If you're more experienced, you don't actually need my advice for that. If you're wondering, then when in doubt, throw it out. Another thing to watch out for, especially if you're doing stuff-- This is more longer term dairy or meat or protein fermentations.

You can get not so much a dangerous bacteria, but a conversion of amino acids into biogenic amines. The most famous of which is histamine. Histamine is what causes the general allergy immunoresponse in our body. Think things like low salts, high water cheeses, or some other protein related fermentations can create these histamines. Those aren't poisonous in the same way, but they can trigger discomfort or even an allergic reaction in some people. Again that's more if you get into higher protein fermentations like mushroom soy sauce and things like that.

Again, the ways to protect against these things, wash your hands, wash your equipment, remove any visible dirt from anything that you're working with and make sure that you're using enough salt. Basically if it's a salted fermentation.

Alison Stewart: Let's talk to Eric, who's calling from the Bronx. Eric, you're on the air.

Eric: Hello, can I use the pickling juice that comes with regular pickles you get at the supermarket?

Arielle Johnson: Oh, to start a new fermentation?

Alison Stewart: Yes.

Arielle Johnson: Yes, I would say if it's a kosher dill pickle, then yes. Confusingly, if we're talking about pickling, some pickles are fermented. Some pickles we preserve by adding vinegar. I guess the vinegar was originally fermented, so there's technically fermentation involved. A vinegar pickle, if you will, if you use that brine in the can to preserve something, you will not get any fermentation or flavor creation that way. If it's the unpasteurized kosher dill pickles that are kept in the refrigerated section, that will definitely help kick start the new fermentation. Generally, lactic fermentations that are pretty good at starting themselves. If there's a flavor profile you particularly love, it can't hurt to back slop that in.

Alison Stewart: Let's talk to Philip, who's calling from Hawaii. Honolulu, actually. Hi, Philip, thank you so much for calling. You're on the air.

Philip: Hi. I have a couple of quick questions. One is the sauerkraut and yogurt and so on that you buy in the store in containers, are they not already pasteurized and therefore lacking in the health benefits that you would get from fermented food?

Arielle Johnson: It would depend on the brand. Many yogurts are unpasteurized, which is why they're sold under refrigeration. With sauerkraut-- I would have to personally check what different brands do to give you a better answer for that. Yes, there's definitely brands that you can find that don't pass pasteurize. Those, of course, tend to have a slightly shorter shelf life or they will continue to transform as you store them in your fridge. It's definitely possible to find beneficial bacteria in store bought fermentations.

Alison Stewart: Deanna, who is calling us from Houston, Texas. Hi, Deanna.

Deanna: Yes, hello. I used to live in New York and I'm still listening to New York radio every day. My question to your guest, I find it highly interesting topic for me because I have just started brand new trying to do kefir. I learned that the kefir has more fermentation and more good bacillus. while the yogurt gives you more calcium. Plus when you do yogurt, I used to do that in the past. Your former caller said, that you have to have those equipment to always keep it at a certain temperature. Now I'm into kefir. I like that very much. I tried my first batch, and it didn't work very well.

Alison Stewart: What can she do if her kefir didn't work the first time?

Arielle Johnson: yes. I would check the starter that you're using. I'm not sure if you're using a commercial kefir starter or a bottle of existing kefir. That's also a way to start it off. You also might want to up the ratio. If you're just starting out maintaining your own kefir starter-- For those who don't know what kefir is, it is a lacto fermented dairy product. It's cultured dairy, similar to yogurt, except yogurt is heated while it's fermenting, so you get both slightly different lactic acid bacteria and a thickening gelled text the proteins. So kefir is not heated when it's fermented, so you get a much looser texture and different populations of lactic acid bacteria. I would, if I were troubleshooting this, either get a new starter, try out a couple of different starters, and then try adding more starter at the beginning.

Alison Stewart: All right, we have. Our final question is coming from the control room. Our control room. Any favorite fermented dessert recipes?

Arielle Johnson: Oh, a little bit of miso and caramel can be delicious. Yes. It adds some saltiness, a lot of umami, both of which go well with that sugary, roasty flavor caramel.

Alison Stewart: I tell you, you just got a big nod from our next guests who are like, "Yes, that sounds good."

Arielle Johnson: Fantastic.

Alison Stewart: My guest is Arielle Johnson. She's a food scientist, co-founder of Noma's Fermentation Lab, author of Flavorama: A Guide to Unlocking the Art and Science of Flavor. Thanks, Arielle.

Arielle Johnson: Thank you so much.