Leftovers Survival Guide

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Let’s cut to the chase: we look forward to Thanksgiving leftovers almost as much as the formal dinner itself. One of the most emblematic leftover preparations is undoubtedly the post-Thanksgiving turkey sandwich. A delicious amalgamation of last night’s meal, this sandwich is the essence of Thanksgiving between two slices of structurally sound bread. When it comes to handling leftovers, however, things can get a bit funky. Here’s what you need to know.

Danger, Danger

At the end of dinner, there’s a mad rush to clean the kitchen and pack leftovers so that loafing can begin. It’s usually an afterthought, but proper packaging is a crucial step for ensuring your leftovers survive.

Cooked food should be chilled quickly to inhibit bacterial growth. The “danger zone” range is 4–60°C / 40–140°F, encompassing temperatures between refrigeration and cooking temperature. This zone is notorious because it provides favorable conditions for bacteria to rapidly multiply. The longer food spends cooling in this zone, the more likely it is that your leftovers will harbor unwanted microbes. As a general guideline, food should not sit in the danger zone for more than four hours. The guideline also comes into play for thawing food. A whole turkey and similarly large foods thaw slowly and unevenly, so they should not be left to thaw at room temperature. As the bird slowly thaws, bacteria will develop on the outer tissue layers even though the inside remains frozen.

SV5_Frozen Turkey Thawing_MG_9930

It’s important to note that these guidelines, developed by the FDA, are an oversimplification of how bacteria behave. Multiplication rates vary according to many factors, such as temperature, moisture, and pathogen type. More conservative recommendations from other organizations, such as the USDA, suggest that two hours is a more suitable estimate, while others expand the window to six.

As you get ready to pack leftovers, do the math and toss anything that could have exceeded this threshold. If it’s particularly warm in your kitchen, dispose of leftovers well before the four-hour mark. Food should be disposed of after an hour if it held in a 32 °C / 90 °F environment.

Rapid cooling has another big benefit: it maintains juiciness and fresh-cooked flavors better than slow cooling can. Juices gel and thicken before they escape, and flavorful aromatics stay locked in your foods.

The obvious remedy to cooling hot food appears to be simply placing it in the refrigerator straight away. But this strategy happens to be the worst way to cool and store leftovers. Warm packages stay warm, well after an hour, and actually raise the temperature of surrounding foods, increasing the risk of spoilage as illustrated in the infrared images below. It’s an interesting problem: food should be chilled rapidly, but cooling via the refrigerator or freezer is problematic.

SV5_Fridge w hot food thermal
Top: Hot food immediately placed in a refrigerator. Bottom: One hour later, leftovers are still hot and neighboring food is now warmer.

The Art of Cooling and Reheating Leftovers

Putting warm leftovers away probably seemed like a mundane task a few paragraphs ago. Now it might feel more like a dilemma, but you have several options.

If you’re cooling lots of sauce, like warm gravy or stock, pour it into a shallow container to increase the surface area. The shallower the container, the faster your liquids will cool. You can also divide the sauce or stock among several smaller containers.

The best way to quickly cool food to refrigeration temperatures is to dunk your sealed foods in ice water, which can be as simple as a sink or bowl of cold water with lots of ice cubes. Once the food is chilled, it can then be stored, still sealed, in a freezer or in the enclosed drawers at the bottom of the fridge, which maintain the most stable temperatures. Avoid the shelves in the door, which are the warmest part of a refrigerator.

When you’re ready for reheating, simply put your bags of leftovers in a heated water bath, and let them warm gradually. Most foods should be reheated to 60 °C / 140 °F, though red meat should be reheated to its original cooking temperature. Avoid reheating any food to temperatures above 65 °C / 149 °F, and take care not to overcook food. Finally, allow reheated food to rest. The rationale is similar to why we let meat rest— resting allows the exterior to cool slightly while juices thicken. This final step will preserve the flavor and moistness of the food.

MCAH_SV_Slow Cooker Sous Vide Cutaway

If dunking your foods in ice water isn’t an option, let them cool on your counter (if time allows), or, if the weather is cold, place covered leftovers outdoors until they’ve cooled enough for safe storage.

Warmed-over Flavors

Turkey and ham come with an additional challenge: the slightly stale, somewhat-rancid aroma that develops after being reheated. It’s an aroma that can put a considerable damper on daydreams of savoring a delicious turkey sandwich.

The underlying cause of rancidity is the oxidation of unsaturated fats found in muscle-cell membranes. When first cooked, these unsaturated fats remain reasonably stable. Once the meat cools, however, the cell membranes readily break down, exposing fat molecules to oxidation. The greater quantity of unsaturated fats, the more likely warmed-over flavors will arise after reheating cooked meat, which is why such aromas are commonly found in seafood, poultry, and pork.

Iron, abundant in meat and myoglobin filaments in muscle, catalyzes these oxidation reactions after food has been heated, cooled, and then reheated. Brines with curing salts can be used as preventative measures against the reaction, but salt alone can do more harm than good. The best way to buy more time for your leftover turkey is to keep it tightly packaged in a sous vide bag after cooking. The air-free environment therein will help slow the process of oxidation.

Now back to that sandwich. There’s a lot to be said for one perfect bite of thanksgiving—getting all of those flavors in a single bite. When it comes to sandwiches, be strategic. First, if you don’t use a water bath to warm your turkey, try reheating it in extra gravy to restore flavors and lost moisture. As you begin construction, use cranberry sauce as a spread, and then add your gravy-soaked turkey. Next comes a rather difficult decision: whether to finish your sandwich with stuffing or potatoes, but not both. Too many carbohydrates will upset the delicate ratio of proteins and condiments.

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Cooking with Syllables: Carrageenan

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What is Carrageenan?

History

From eggnog and soy milk to infant formulas and toothpaste, carrageenan is found everywhere. The word carrageenan may sound foreign and vaguely exotic, but it’s simply a generic term for a type of sugar extracted from various species of red seaweed. In Modernist cooking, it’s classified as an emulsifier, stabilizer, hydrocolloid (hydrophilic colloid), or gum, all of which function in some way to thicken or clarify ingredients, or to bind moisture. The term carrageenan has been around since at least 1889 and is derived from carrageen, circa 1829, which is a purplish, cartilaginous seaweed colloquially known as “Irish moss,” found off the coasts of North America and Europe. In fact, the seaweed gets its moniker from a small Irish fishing village, Carragheen, where it’s plentiful. Traditionally, the seaweed was boiled in sweetened milk to create a pudding. Simmering the seaweed unlocks the ingredient’s gelling properties. Its use, however, can be traced back even further to at least 400 CE, where it was used as a gelling agent and as an ingredient in homemade cold-and-flu remedies. Industrially, carrageenan is extracted chiefly from the red algae Chondrus crispus (class Rhodophyceae), but it can also be extracted from various species of Gigartina and Eucheuma.

FH4_Modernist Food Shelf_MG_6695

Function

Inherently vegetarian with no nutritional value, seaweed-based thickeners like carrageenan have new, modern applications. Most commonly, carrageenan can adjust the viscosity of dairy products like cheese, or it can serve as an emulsion stabilizer in salad dressings by keeping your oil and vinegar mixed. In more advanced applications, it will glue meat together, allowing for the creation of hot aspics and other seemingly contradictory foundations. Chemically, carrageenan is classified as a polysaccharide, a type of sugar. Its properties are varied and complex, but its basic function is to thicken and stabilize. It does this by forming large yet flexible matrices that curl around and immobilize molecules. Because of its inherent flexibility, carrageenans can form a variety of gels under a wide range of temperatures, but each type of carrageenan only becomes fully hydrated at a characteristic temperature. Some carrageenans can be hydrated without adding heat, while others must be brought to 85°C / 185°F or higher before saturation occurs, and a few have a hydration temperature that depends on the presence of other ions, the most common of which is calcium. Carrageenan actually comes in five varieties, classified by how much sulfate (SO4) it contains and its solubility in potassium chloride. Named after Greek letters, they are ι (iota), κ (kappa), λ (lambda), ε (epsilon), and μ (mu), however, only the forms iota, kappa, and lambda are used in Modernist cooking. All forms contain roughly 20–40% sulphate, which dictates how firmly (and whether) a gel will set, how the gel freezes and thaws, and how syneresis (the separation of water from its gel, also known as weeping) is affected. As the amount of sulfate increases, the strength of a gel decreases.

Safety

Recently, there has been some speculation over the safety of carrageenan. Carrageenan has been a focus for many mammal studies because of its potential to cause inflammation, ulceration, colitis, polyps, and colorectal tumors. Although such maladies are reported in animal studies, at the time of writing this connection has not been validated in humans because carrageenan’s molecular size and accompanying bonds prevent it from being digested naturally. To understand why carrageenan does not cause morbidity in humans, it’s important to differentiate between carrageenan and its degraded form, poligeenan. Poligeenan is the digested form of carrageenan and consists of molecular fragments small enough to pass from the digestive tract to the circulatory system. It is poligeenan that causes the many illnesses researchers describe in mammals, but current research has shown that the human digestive tract is limited in its ability to break down carrageenan into poligeenan. The primary pathway of human digestion, the alimentary canal, is, despite its placement, considered to be outside the body; a compound is not considered to be in the body until it moves from the digestive tract to the circulatory system. And, in order for any compound to affect human organs, such as the brain, liver, or heart, it must be small enough to cross the intestinal walls. Carrageenan is too large to do so, but poligeenan’s small size can. Not surprisingly, it has been postulated that carrageenan can be fragmented by natural digestive processes, but, to date, this has yet to be demonstrated in humans. In addition to carrageenan’s large size, its inherent bonds pose another challenge to the human digestive tract. Carrageenan is held together by β-glycosidic bonds, which are ubiquitous in the plant world, but most mammals, including humans, lack the proper enzymes to break them.

Recipes and Sourcing

Because of its utility, carrageenan is an ingredient that we use frequently, appearing in many recipes throughout Modernist Cuisine and Modernist Cuisine at Home. Carrageenan is used to create the creamy texture of our Pistachio Gelato and to stabilize our American Cheese Slices. Although you may not be able to find carrageenan on the shelves of neighborhood grocery stores, it’s easy to source online. If you’re ready to start testing this ingredient, try out our Pistachio Gelato recipe or Raspberry Panna Cotta in Modernist Cuisine at Home.

EMUL6_Pistachio Gelato_MG_8551

The Microbiology of Raw Cookie Dough

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In May 2009, an outbreak of foodborne illness sickened at least 80 people across 30 states; it put 35 people in the hospital. The source of that outbreak was raw, store-bought cookie dough.

To better understand the risk of getting sick from undercooked foods, it’s important to know a little about the mechanics of foodborne illnesses. They almost always fall into one of three categories:

  • The first category is a non-invasive infection. This is when pathogens from the food get into your gut and continue living there, but without penetrating the lining. Tapeworms are typically non-invasive, as are certain kinds of bacteria, which may nevertheless secrete toxins that make you ill.
  • The second variety of foodborne illness is an invasive infection. This occurs when pathogens migrate from the gut into the blood or other organs where they can wreak havoc and secrete toxins. Some delightful examples include the parasitic trichinella worm and many strains of bacteria including Salmonella enterica and Escherichia coli.
  • The third category is food poisoning. People sometimes apply this term broadly to any kind of foodborne illness, but food poisoning actually refers specifically to the poisoning of the body by toxins that bacteria have released inside the food before you eat it. Because these toxins are already present before you start cooking, food poisoning typically sets in quickly following a contaminated meal, whereas foodborne infections take a bit of time for bacteria to reproduce inside your body. Botulism, the biggest fear of home-canners everywhere, is one well-known example of food poisoning.

E. coli, the invasive infection responsible for the May 2009 outbreak, lives in the intestinal tracts of humans and other warm-blooded animals. Like other bacteria, E. coli are tiny, being about one-thousandth of a millimeter across and only two to three times that in length. It would take 1.5 trillion of these germs to balance a small paperclip. But what E. coli lacks in size, it makes up for in notoriety. Most E. coli strains are harmless, but one in particular, E. coli O157:H7, has become infamous for its role in foodborne outbreaks, including contaminated milk, ground beef, spinach, and alfalfa.

Another common source of invasive infection is salmonella, which, although it wasn’t to blame in the 2009 cookie-dough outbreak, really is as dangerous as most people imagine. But here, too, confusion reigns over the true source of contamination. Salmonella bacteria do not live in chicken meat (muscle tissue), the source most commonly fingered as the culprit. Instead, the bacteria normally live in the intestinal tracts and feces of chickens and can contaminate the meat during slaughter and processing (except S. enterica, which can infect hen ovaries and contaminate intact eggs regardless of fecal contact). The poultry industry has made enormous strides in containing contamination, and chickens are far from alone in spreading the disease. In 2008, for instance, U.S. investigators traced a major outbreak of salmonella to tainted peanut butter and other peanut-containing foods.

Certain brands of raw cookie dough, which are labeled for raw consumption, such as cookie dough chunks in store-bought ice creams, are safe to eat raw. But even when safe handling practices are followed, eating homemade raw cookie dough, or store-bought cookie dough that is intended to be baked, will always carry some risk.

If you want to avoid a stomach ache—or worse—muster all your willpower… and wait for those cookies to emerge from the oven.

For more on the microbiology of food and food-related illness, check out our tips on Food52.com.

For a Great Summer Feast, Cook Ahead, and Bring Extra Fat

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Holding time is the key to pasteurization and safe eating.

Summer feasting can be great fun, but it poses a number of challenges for the cook. You may find yourself in an unfamiliar kitchen or even cooking at a park, on the beach, at a campsite in the woods, or in a friend’s backyard. The grill at hand may lack some of the features of your own, and you may have to share it with other cooks. Cookouts often involve making lots of portions and feeding impatient children.

The best way to ensure fast, delicious results despite all these hurdles is to prep and precook your food at home so that all you have to do at your destination is to warm it up and put on the final touches.

Cook chicken, steak, and other proteins sous vide before you leave the house. Allow the bags of food to cool while still sealed, and then pack them into your cooler with ice. To reheat the food, simply unbag it onto a hot grill and sear it quickly. (Our new book, Modernist Cuisine at Home, also reveals some tricks for improvising sous vide setups while tailgating or picnicking.)

Precooking the food sous vide is convenient, and it shortens the wait for those kiddies. More important, the precision of temperature that sous vide cooking offers allows you to safely cook every portion safely and to exactly the degree of doneness you want. Never again will you have to serve rubbery chicken or tough steak just to be certain it is safe to eat.

Eating Safely in the Great Outdoors

The key to safety is knowing how long to cook at a given temperature to achieve full pasteurization. If you are cooking chicken breasts, for example, you can heat them to a core temperature of as little as 55 °C / 131 °F. Once the center of the thickest part hits that target temperature, hold the chicken at that temperature for 40 minutes to pasteurize the meat. That temperature is not as high as many people are used to, and some prefer their chicken closer to medium-well than medium-rare. That’s easy to accommodate: just choose a higher cooking temperature. The greater the core temperature, the shorter the pasteurization time; see the table for some suggested holding times for chicken breasts and thighs.

Whenever you cook food sous vide in advance, it is crucial to chill it soon after cooking and to keep it chilled until you reheat and serve it. The food should never spend more than four hours total in the “danger zone” of 4 °C to 60 °C / 40 °F to 140 °F. So bring plenty of ice if you are going on a long car ride, or if you won’t be grilling for a while. And don’t forget to bring a bottle of hand sanitizer along; even pasteurized food can become unsafe if you touch it with dirty hands.

Capture That Grilled Goodness

Generations of grillers have been trained to fear flare-ups, but that is misplaced. Certainly you don’t want flames charring your food, but most of the flavor from grilling actually comes from fat drippings, which ignite into flames and then travel back to the food as smoke. If you are quickly reheating precooked food, slow-cooking over coals in tin foil packets, or grilling veggies or other low-fat foods, it’s hard to capture much of this characteristic grilled flavor. An easy work-around is to season your meat and veggies with pressure-rendered fat. You can find a recipe at the bottom of the page.

Pressure-rendered chicken fat adds flavor as it drips into your heat source and rises back up as smoke.

You can use pressure-rendered fat when cooking on gas or charcoal grills, grill pans, or even in tinfoil packets. Just remove the food from the sous vide bag and brush it generously with the fat. Grill meats first, typically for about one minute per side. Then add vegetables and fruit as desired. Leave fruits, such as peaches or pineapple, on the heat long enough that the sugars in them caramelize. Remember, don’t panick when you see small flames flare-up and lick at the food: you want the smoke they generate to carry its flavor onto the food. But do keep a spray bottle on hand in case the flames get too high.

Leave Only Your Footprints…

Remember to never leave a grill, fire, or coals unattended. Spread the coals out and cover them with sand if necessary before leaving. Gather up all the plastic bags and other waste from your meal, and take it with you.

New Recipe: Garlic Confit

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We love pressure cookers for making garlic confit, stocks, and grains, too!

You can find our recipe for garlic confit along with tips on pressure cooker safety in our Recipe Library! We’ve also included a step-by-step video on how to safely use a pressure cooker and a helpful table on the boiling point of liquids at different gauges of pressure.

Is Liquid Nitrogen Safe?

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At the beginning of the MC project, Nathan set out to dispel many of the myths surrounding cooking, yet some common misconceptions about liquid nitrogen still persist. Sometimes we get questions like Is liquid nitrogen dangerous? Will it hurt you? Or, You can’t cook with liquid nitrogen! It’s poisonous!

The truth is, liquid nitrogen is completely inert except for its extreme temperature. It will cause any metal it comes in contact with to become freezing cold, but wearing dry gloves is enough to protect your hands from creating a “tongue stuck to the flagpole” scenario. The liquid nitrogen itself will evaporate before it contacts your skin due to the Leidenfrost effect (see video below).

Actually, liquid nitrogen pales in comparison to the dangers involved in most applications of fryer oil or even sugar. Fryer oil is extremely hot; it spills, it splatters, it splashes. Any cook who works frequently with deep fat fryers gets burned all the time. You get little blisters on your arms and hands when heating oil. The day we shot our wok cutaway photo, Max got all sorts of burns on his arms from tossing the phad Thai and oil so many times.

By the end of this shoot, Max’s arms were full of tiny burns from the hot oil.

When it comes to kitchen burns, sugar is enemy number one. Anyone who has had a close encounter with hot caramel knows that you really don’t want this stuff on your skin. If a little bit of the hot caramelized sugar lands on your hand, your first reaction is to rub it, which leads you to smear it onto your other hand. It just sticks everywhere, and you end up burned all over.

I’ve been working with liquid nitrogen in the kitchen for about five years now. I’ve dipped my bare hands in it, spilled it, splashed it, but never been hurt by it. I’m not saying you should go ahead and goof around with it, but you should give it a chance without fear. Go ahead and try it! It’s great for all sorts of applications. Just put on gloves, wear long pants so that it can’t drip into your shoes if you spill any, and don’t eat food until you’re sure the nitrogen has boiled off of it. (For a more complete discussion, see “Safe Handling of Cryogens,” page 2·464-466 in Modernist Cuisine.)

A number of recipes in Modernist Cuisine use liquid nitrogen to achieve special effects, from firm coating gels to foie gras torchon, from shrimp and grits to buttermilk biscuits. And, of course, we love Nathan’s method of cryofrying meat, which is to cook meat sous vide, then dip it in liquid nitrogen, and finally deep-fry it quickly to get a really nice, Maillardized outer crust with a rare or medium-rare interior. We use this technique in our mushroom cheeseburger recipe. And again, it’s really the hot oil from the deep fryer that you have to watch out for in that recipe.

Wearing gloves when handling liquid nitrogen protects your hands from the cold temperature of the metal container.

Although it’s not hard to handle liquid nitrogen safely, it is also not completely without risk. In fact, I just happen to be one of the few people in the world who have actually had a traumatic experience with the substance. I once used liquid nitrogen at a dinner for some guests and afterward was transporting a Dewar of the stuff in the back of my SUV. Although the Dewar was in perfect condition, some of the dinner guests had been playing with it and hadn’t refastened the lid. I didn’t realize that, and as I was heading up a hill, the Dewar fell over. Liquid nitrogen has a very low viscosity, so it is thinner than water and flows like crazy. It quickly spread all over the bottom of the car, and as it boiled off furiously, the car rapidly filled with vapor. It also got really cold, and I couldn’t see out of my rear view mirror or rear window. It was like driving through the densest fog–but the fog was inside the car!

The correct way to transport liquid nitrogen.

I pulled over and got out of the car as fast as I could. As the nitrogen evaporates into gas, it displaces oxygen in the air, so if a lot of it spills in an enclosed space it can create a suffocation risk. Emerging from the car, I looked back and saw white fog pouring out from every opening. Luckily, our photographer, Ryan Matthew Smith, was behind me and also pulled over. We opened the hatch of the SUV to get the Dewar out, in case it was still leaking. I heard the plastic in the car crackling as it warped from the intense cold.

When it was all over, I was surprised to find that despite the large size of the spill, it didn’t cause any permanent damage. If the Dewar had been filled with super-hot fryer oil instead of ultra-cold liquid nitrogen, it would have been a different story.

Thinking About Chemicals in Food

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Many people say they are uncomfortable with chemicals in their food. And Modernist chefs have been criticized occasionally for using some of the same modern ingredients that can be found in low-quality processed foods—even though the chefs use them for different reasons and in combination with ingredients of the highest quality. In a recent interview for Big Think, Modernist Cuisine coauthor Nathan Myhrvold explains why it’s important to avoid an overly simplistic view. All food consists of chemicals: they are the building blocks of life. But not all chemicals are equally good or bad for you. Check out the Big Think article and the video interview below.

Yes, You Are Overcooking Your Food

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Scientific American

Scientific American magazine has published a lengthy excerpt of from the Food Safety Rules chapter of Modernist Cuisine. Ever wonder where all those official guidelines for cooking pork, chicken, and other foods came from? Do they reflect rigorous scientific research, or just the codification of cultural preferences? Get the full scoop here, and learn why you really don’t need to cook your chicken breasts and pork chops to oblivion in order to make them safe to eat.

Scientific American also has created a fascinating slideshow of some of the more amazing photos in the book. It’s titled “A New View of Food and Cooking.”

Chicken breasts cooked to (L to R) 52 C, 55 C, 60 C, and 80 CChicken breasts cooked(left to right) to 52 C / 126 F, 55 C / 131 F, 60 C / 140 F,
and 80 C / 176 F. Notice how the meat shrinks and dries out at higher cooking temperatures.