Precision-cooked, Fried Hamburgers - Modernist Cryo-fried Burgers

This is my take on Modernist cryo-fried burgers as described in Modernist Cuisine. They are a perfect medium rare throughout the inside with a thin, crispy outer crust. This is achieved by cryo-frying the burgers: cooking them sous vide, briefly freezing them in liquid nitrogen to keep the inside from overcooking, and then frying them in hot oil.

The burgers were juicy and tender with an extremely satisfying crunch through the browned surface. The actual work making the burgers was minimal, but the setup complicated. I cooked these as part of Fried Day at the Instructables lab when we already had both liquid nitrogen and pots of hot oil ready to go.

Here are the abbreviated instructions; go through each step for pictures and more information:

Mix ground beef with salt to achieve a 0.8% salt concentration, refrigerate for an hour
Cook beef sous vide to an internal temperature of 131°F
Freeze the outside of the burgers in liquid nitrogen for 30 seconds
Fry the burgers in oil at approximately 425°F for 30 seconds

Many thanks to ReneediCherri for photography.

Step 1: Ground Beef, Salt, Make Patties

Modernist Cuisine recommends grinding your own meat to make the best burgers. They are undoubtably right, but knowing the amount of effort that goes into grinding meat from making sausage, I opted to skip this step, and instead started with 100% grass-finished ground beef.

Add salt to make a 0.8% concentration. Fold the salt into the ground beef, form patties with a mass of approximately 180 - 200 g, put them into plastic bags, and add 5 g of a neutral oil.

Step 2: Refrigerate

Refrigerate the patties for an hour. If you let them sit longer, the salt will start to make the meat rubbery, like sausage.

Step 3: Cook Sous Vide

Displace the air in the plastic bags by dunking them in water (the water displacement method). Do not vacuum seal the bags as it will deform the patties. Cook until the burgers have reached 131°F. I set my water bath to 133°F, and cooking took about an hour.

Step 4: Freeze With Liquid Nitrogen

Fill a bowl with enough liquid nitrogen to cover a burger. Immerse one patty at a time in the nitrogen for 30 seconds. The objective is to freeze just the outside of the burger and to keep the inside at medium rare during both the freezing and the frying steps.

Leave your utensils (in the images, either the strainer or the tongs) in the liquid nitrogen between freezing burgers to keep them cold which will help prevent the burgers from sticking to them.

Step 5: Fry in Hot Oil

Immediately after freezing, fry the burgers in hot oil for 30 seconds, then remove and drain them.

Make sure the oil is hot enough. On the stove top shown in the images, I could only achieve around 425°F by keeping the burner at high and covering the pot.

The objective of frying is to brown the entire surface of the burger through the Maillard reaction. Hand-wavingly, the liquid nitrogen is at approximately -200°C and the oil is at approximately 200°C, so equal time in each leaves the center of the burger just slightly colder than it started and doesn't overcook it.