Moisture Bulbs Maurice

The question frequently asked is; do I sear before, or after I sous vides my T-bone steak, and the answer is either works but it all depends on process.

In the kitchen it’s all about process, and without understanding process we are no better than monkeys. I always try to encourage chefs to study more science, nonetheless most chefs are instinctive, intuitive and ignore science in the kitchen, unless it has to do with molecular recipes.

Recently I cooked two T-bones for my friend Maurice, a detailed orientated personality, obsessed with getting it right. The one T-bone I seared and cooled and vacuumed, and the other I cooked sous vides and seared after the water bath. The main difference is mostly in the moisture content, which seemed higher in the pre-seared T-bone. While I didn’t measure the moisture, or follow it scientifically, the surface of the pre-seared steak definitely was more moist.

The main issue you’ll face with the pre-seared steak is rendering the fat, which is best done in the oven after cooking. But it isn’t as easy as it looks. The T-bone’s surface of the pre-seared T-bone took too much time to sear, and it was difficult due to the evaporation – let me elaborate.

As hot dry air flows over cool and moist foods, the temperature at the surface of the food begins to rise steadily. The moisture is constantly evaporating from the surface, and the evaporation accelerates as the dry-bulb temperature rises. The dry-bulb temperature is the temperature is usually thought of the temperature setting you select on your oven’s dial, dry heat.

Because it takes energy to change water from liquid to vapor, the evaporation of the H20 cools the surface and dries it out. That cooling effect slows the rise in the surface temperature of the food, and at the same time hot air in the oven is adding heat to the food and evaporation cooling is sucking heat out of the food.

Surprisingly, until the surface of the food is almost completely dried, evaporation holds the exterior temperature of the food below the boiling point of water. The boiling point of water is 100°C at sea level. If you set the oven at 250°C, the foods temperature at the surface is at least 150°C cooler.What essentially happens is, all of the additional heat energy at the surface of the food is being used to vaporize water and the heat does not invert into the meat.

Ultimately to understand and control the cooking of the T-bone, the end result depends on three important stages in cooking. As the surface of the steak dries you have; settling period, constant rate, and falling rate.

In the first, settling period, the temperature at the surface of the food quickly rises from its starting point up to the wet-bulb temperature but then stalls and remains there until the surface dries substantially.

After the settling period, the wet-bulb temperature increases again but more slowly than before when enough water evaporates from the food. The humidity in the oven increases, and this jump in humidity retards further evaporation, and the wet-bulb temperature goes up. So basically you have two water vapor forces, the force from the T-bone and the oven’s force and more moisture in the oven from the surface evaporation.

But as the water evaporates is just as quickly replenished, which drives juices to the surface from deeper within the moist interior. During this period (constant-rate period), the steak spatters water from its capillary channels from within the steaks intricate channels into the oven. The core gradually begins to dry, and its temperature rises to equal the wet-bulb temperature in the oven.

The dilemma is when we cook a steak, we want it cooked and juicy, so we want the constant-rate period to be as brief as possible. Cooking with a high dry-bulb temperature, with high humidity or, even better, with both-helps curtail this stage.

The third and final stage of drying, called the falling-rate period, begins once the surface of the food becomes dried out and the T-bones’s juices from the center no longer reach the surface to keep it wet. A crust forms and beneath the crust, the food is still moist, and evaporation continues. What happens next depends on whether the dry-bulb temperature is above or below the boiling point of water.

At dry-bulb temperatures below 100°C, the real baking temperature of the dry crust, as well as a narrow layer of still-moist food just beneath it, shoots up quickly to nearly match the oven temperature. The sudden rise occurs because evaporation slows. The dry crust thickens and traps water below it. Much of that confined water is tightly bound to the molecules of the food, so it cannot evaporate readily. As evaporation dwindles, so does its cooling effect.

Things work a little differently when the dry- bulb temperature in the oven is above 100°C, as is typical for baking. Once a dry crust appears on the food, a boiling zone forms beneath that crust. The food in that region cannot get any hotter than the boiling point of water until nearly all the water there evaporates.

On the other hand, the same hot oven does wonders for the crust. As the crust heats up to the dry-bulb temperature of the oven air, it undergoes a cascade of complex chemical reactions that usually include the Maillard reaction. The resulting pigments paint a golden color over the crust of everything from baking bread to “roasting” meat or simply grilling.

These chemical changes occur at temperatures above 130°C a typical temperatures would burn the crust were it not for wafts of steam and a trickle of juices continually percolating up from the boiling zone. Together, they provide just enough moisture to cool the browning surface long enough for baking to finish. They also provide a steady supply of chemical ingredients dissolved sugars, proteins, oils, and other reactive molecules for the flavorful reactions occurring at the crust that make baking, well, baking.

In the end, its your choice, and it is dependent on what you temperature you use in your water bath, and the searing process, and when and how you spice the surface of the meat, and most importantly how you sear the steak, and critically the finishing of the T-bone in the oven, with or without oven moisture. Of course if you brine the meat, it will have another effect. To make the perfect T-bone it takes some science and practice to get it right, and as they say, “practice makes it perfect”.

sources: modernist cuisine and Wikipedia.


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