BilboBaggins,
We normally do our primary Christmas dinner on Christmas Eve, and this year I’m doing two entrees, one of which is a prime grade prime rib roast, around 6 ½ lbs. I’m undecided about the cooking method at this point, but if I choose to cook it sous vide I’ll do it as I have many times in the past for around 6 hours at 130°F, which I consider medium rare.
When I see some of the very extended double-digit sous vide cooking times some people recommend for sous vide cooking of cuts like prime rib I’m a bit baffled and wonder what their source material is for they recommendations they make. The one thing that’s certain is that they don’t take into consideration the enzymatic action effects on the meat’s proteins, specifically, the enzyme known as cathepsin.
Cathepsins begin to break down proteins around 122°F. The breakdown is a long process, and cathepsin activity is still going on during a lengthy cook at 130°F, or higher. Therefore, you would not want to cook a cut like prime rib for a long period of time sous vide. These enzymes are active, and too much time in the presence of tenderizing enzymes can make meat’s protein, which is quite tender to start, mushy. Some of the extended cooking times recommended might be fine for a crappy and tough low grade cut of meat, but not prime rib.
Bear in mind that the temperature that you choose to cook your roast sous vide at is the target core temperature of the finished roast. How you start the cooking process can influence the overall length of time involved. If you start with a cold roast straight from the refrigerator in tepid water, it will take significantly longer to reach the core temperature than if you start with the roast at room temperature in water pre-heated to the core temperature.
Good luck.