Delta-T cooking

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Delta-T cooking (ΔT-cooking) is either a cooking method in which the oven temperature increases according to the core temperature of the food, or a sous vide cooking method in which the water bath temperature is higher than the desired final core temperature.

Variable cooking medium temperature
Oven manufacturers and scientific research articles define Delta-T (ΔT ) as the difference between the food’s actual core temperature and the actual temperature of the cooking medium (air in the oven).

So ΔT-cooking is a cooking program in which the oven temperature increases according to the core temperature, in contrast to the traditionally constant oven temperature. Especially in larger roasts, this slows cooking, allowing more time for enzymes to tenderize meat (calpaines up to 39°C/102°F, cathepsines up to 49°C/120°F, collagenases up to 60°C/140°F).

Constant cooking medium temperature
The French Culinary Institute define Delta-T (ΔT ) as the difference between the food’s desired final core temperature and the constant temperature of the cooking medium (water bath). This definition also holds true in Nathan Myhrvold’s cooking time tables published in the eGullet Forums.

So in sous vide cooking, ΔT-cooking is a time-critical cooking method in which the water bath temperature is higher than the desired final core temperature, in contrast to the usual sous vide cooking method in which the water bath temperature is equal to (or minimally above) the desired final core temperature, allowing actual cooking time to exceed the minimal necessary cooking time without overdoing the meat. Cooking sous vide with a ΔT reduces cooking time which may be desirable for logistic reasons or for very thick cuts that would require cooking times that exceed safety limits.