THE SCIENCE OF FOOD: STEAKS, BUGS AND EXPIRATION DATES

J Kenji Alt: Well, I recently wrote this article for the New York Times about expiration dates. So I've been thinking about that, because expiration dates are one of those things, you know, I, you know, my mom largely ignored expiration dates when we were younger. So sometimes I would come in and find, you know, orange juice that had expired a month in the past, or certainly spices that that had been sitting there for 12 to 15 years. In fact, she probably still has some of the same spices she had when I was a kid. And then, you know, as I became sort of like a teenager, I started thinking and telling my mom, you know what, this is kind of gross, I'm going to go through your fridge and just start throwing these things away. And I did that. And now as a as a, as a father, myself, I mostly ignore the expiration dates again, because I had always thought they were about food safety, about whether the food was fit to be eaten or whether it would make you sick, right. But then it turns out that it's not, that's not what they're about at all. In fact, they have nothing to do with food safety, so that the only food that is required to have an expiration date on it is baby food, everything else is there voluntarily. And it's there as sort of a manufacturer's best guess, as to when the food is not going to be at peak quality anymore.

CK: Let me just stop you there. If they're not required to put an expiration date on, which means that a lot of foods would not be returned from the supermarket, because it's since no one knows what the expiration date is, aren't they losing millions of dollars for something that's not actually required by the federal government?

JKA: Well I mean, a food manufacturer, you know, if you're buying, you know, you see four different brands of milk, and one of them doesn't have an expiration date on it, and you buy it, and it turns faster than you expected, then I would just stop buying that brand of milk, you know, I think they, I think they do have something to gain by predicting when their food is going to actually taste good. But you know, the thing is that most foods will actually last well past their expiration date, because that expiration date is really just a guess about best quality. And of course, you know that that guess is really it's it, that's what it is, it's a guess, because they can't tell exactly how the food is going to be shipped, how it's going to be stored, whether someone carried it around the supermarket, and then decided to put it back on the shelf, you know, and then once you get it home, of course, they don't know how how you're storing it at home, you know, whether you're drinking the milk out of the carton, or whether you're, you're opening up the jars with dirty hands, etc. So, it's really, really difficult to actually predict how food is going to behave once it leaves the factory. So usually, those estimates are actually pretty conservative. So, if you're treating your food Well, it's probably going to last well beyond the expiration date does.

CK: So you mentioned something interesting. You said whether you drink out of the bottle or your head dirty hands when you open the jar. So, introducing bacteria into a container that you just opened that could have a substantial impact on the longevity of that food.

JKA: Oh, absolutely. Yeah. So let me give an example. I got my restaurant we go through a lot of cheese and we you know, we get giant blocks of it and then we grade it on So that's one of the things where we require gloves because we know that if you grate cheese with bare hands that you've just washed versus grated cheese with, with gloves on, it'll last for like, weeks longer, like you'll start to see, you'll start to see molds sooner. And I did this little experiment at home with my daughter, where we bought a package of grated cheese from the supermarket. One handful, we picked up with just her hands before we washed them. Another handful we picked up after carefully scrubbing her hands. And then the third one we picked up with gloves on our hands. And then we put them in containers and stored them in the fridge and the one that you that you touch without washing your hand obviously starts to mold weeks before the other two. And gloves is the longest but but yeah, absolutely. So, milk, for instance, especially if you get like the UHT milk, ultra-high temperature pasteurized milk that milk is is heated to 250 degrees Fahrenheit, which is hot enough not just to kill bacteria and viruses, but actually destroy spores as well. And then it's pumped aseptically into containers and sealed. So, it should be completely sterile in there, which is why it lasts for months and months. So, there's nothing really going on in there until you open it and then bacteria from your mouth from the air. That's when bacteria start to get in. And that's when the sort of the clock starts ticking on when it's going to go off.

CK: So what about eggs? You know, I've heard all these rumors about eggs being older than they say. I mean, what's the deal with eggs? The French used to keep eggs on the counter. They never refrigerated them, right?

JKA: Yeah, well, they still do that in lots of parts of Europe. You know, the reason they do that is because when the US eggs are washed, and that sort of removes is that waxy cuticle surrounding the egg. So, you then have to refrigerate them because it makes them more air permeable and makes them more permeable to bacteria and viruses. Whereas in Europe, they don't wash them before selling them. So, you know, it's sort of like in one case, they're dirtier or when you buy them, but you don't have to refrigerate them. Whereas in the US they're cleaner when you buy them, but it's then easier for them to get reinfected. So is this sort of a trade off? That's right, that's right, that trade off?

CK: So so how old are eggs when you buy them? And how long do they last, you know,

JKA: In most parts of the country eggs, the expiration date that they get on them is 30 days after they were packed. And usually, they can be packed up to 30 days after they were laid, although in most cases, they're probably getting packed actually, like the day off or the day after they're they're laid, which means that, you know, if you add those numbers together, you get about 60 days as your lifespan for for an egg in refrigeration. And that's of course, just the sort of, you know, the peak quality level there in reality, they're probably going to last a month longer than that, you know, 90 days is not unreasonable for an egg to last.

CK: Are there any foods other than dairy products where you should be really concerned about expiration date versus other foods?

JKA: Well, there's there's none that I would really look exactly at the label, you know, other than just as a loose guideline, you know, I think using your nose and your your senses is the best way to tell if something's off. And of course, you know, when in doubt, throw it out, you know, things where you should be worried where that that can actually get you legitimately sick are canned goods and jarred goods where you know, if it can is bulging, or if it shows any rust is that's an indication that there might be bacterial action going on inside or that the seal has been contaminated so liquid is coming out and rusting the exterior, or with a with a with a glass jar with a screw top, if the buttons popped up, that means that there's probably some kind of bacterial activity going on inside and that's the kind of stuff you want to really be careful with. But you know, other than that, things tend to last a long time you know, spices for instance, you know, I said I went to my mom's house and I'm sure she has spices that are 35 years old from when I was a kid. Those spices are probably not going to kill you they most likely they're not going to taste like anything, but they're probably also not going to really harm you to eat it

CK: But I've had I'm going to push back so sure my mother you know, had the same spices she bought I think when she first got married after the Second World War and those were tasteless but I got some spices from what trip once North Africa and three or four years later some of that stuff was still really pungent so he is the six month rule or one year rule really a good rule of do a well preserved you know fennel seeds or something like that actually last and are fresh a long time

JKA: Oh yeah I mean it all has to do with how you store it and the state at which you buy the spices so you know it's a whole spices will last a lot longer than ground spices just as ground spices have more surface area for you know the aromatics to jump off from but yeah it i mean if you seal it you know if you especially if you like vacuum seal your spices or you put them into jars with really tight screw tops and you keep it in a in a pantry. You know, it's the same basic rules that I think most of us know which is like you know, light, heat and air are the enemies of freshness for pantry ingredients. One thing to note in your pantry though, is that with grains whole grains don't last quite as long as more refined grains so whole wheat flour will go off right before white flour does and this because of the fat that those contain, that tends to go rancid. So yeah, and but you know it's something that you'll smell before that you should be able to pretty easily smell it. It gets like a kind of soapy metallic smell to it, you know

CK: And cooking oils also. I know get very fishy. If there's any odor coming off of your cooking oil, then you've got a problem, right?

JKA: Yeah, if it smells fishy, or smells soapy, then for sure. And also touch wise, like if you if you put a little drop of it on your finger, it should feel slick. If it starts to feel sort of tacky or sticky, then that's an indication that also that is probably gone rancid. And you know, and again, that's probably not going to kill you to eat it. It's just not going to taste very good. And it's not going to behave in the way that you expect it to.

CK: So, expiration dates are not about food expiring they're about when food is at its peak, which is a very different thing. So next time I get a bottle half and a half. I'm still going to look at the expiration date. Because that yeah, I find that stuff really does go bad. But a chocolate bar, maybe not. Yeah, thank you, Kenji.

JKA: Thank you.

CK: That was j Kenji Lopez alt. He's the chief culinary consultant for Serious Eats. A food columnist for The Times also author of the Food Lab. The fact that expiration dates are relatively meaningless makes me think of some other perfectly useless product labels. Here are some of my favorites: on peanuts may contain nuts, on a shoe box average contents two, on a superman outfit does not enable where to fly. And in a car manual, it says in order to get out of car, open door, get out and then close doors. So, what's next? usage labels on bananas. That's it for today. If you tuned in to later, just want to listen again. You can download and subscribe to mostly radio on Apple podcast, Spotify, or wherever you find your podcast. To learn more about Milk Street please go to 177 Milk Street com there you can download each week's recipe. Watch the latest season of our television show or order our new cookbook, Milk Street Fast and Slow, Instant Pot Cooking at the Speed You Need. You can also find us on Facebook at Christopher Kimball's Milk Street now on Instagram and Twitter at 177 Milk Street. We'll be back next week and thanks as always for listening.

Christopher Kimball's Milk Street Radio is produced by Milk Street in association with GBH executive producer Melissa Baldino, senior audio editor Melissa Allison, co-executive producer Annie Sensibaugh. Associate Producer Jackie Novak, production assistant Sarah Clapp and production help from Debby Paddock. Senior audio engineer David Goodman, additional editing from Vicki Merrick Sidney Lewis and Samantha Brown. And audio mixing from Jay Allison at Atlantic Public Media in Woods Hole, Massachusetts. The music by Toubab Krewe. Additional music by George Bernard Egloff Christopher Kimball's Milk Street Radio is distributed by PRX