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In these troubling times we tend to use secondary cuts even more. Last week we had a fund raiser group for lunch, thier budget was relatively decent though a beef option was requested and we had done already a braised short rib the prior year. This yeas we chose a flank steak cooked sous vide. A couple of weeks ago we had a tasting where we cooked the herb oil marinated flanks at 55C for 18hours in the circulator, seared them before serving. The client enjoyed the tender flanks so much it was a “go”.  Once the event came closer the size of the event outgrew our circulator capacity and we had no other choice than to cook them in the RATIONAL combi ovens. In various forums there have been concerns that combi ovens could not keep the temperature constant enough to cook sous vide. Left with no other choice we put it to the test again. This time with temperature loggers planted all over. When we cook sous vide in our combi ovens we usually place the bags in hotels pans filled with water to ensure a more constant cooking environment.

First we cleaned the 4C cold meat and placed it immediately into the vacuum bag. Into one bag we placed also a Temp1000P submersible probe, at which point the first set of data recording started. The bag were placed back into a freezer for a few minutes cool down quicker. Once below 2-3C we added the oil-herb mixture and sealed the bags. Since we were cooking little over 160lbs and only one vacuum sealer we placed the sealed bags back into the freezer. Into one of the bags we inserted a hypodermic probe and attached an Extech EA15 logger. The logging started right before the bags went into the freezer the second time.

In the mean while we had the combi oven heating up to 60C, full steam, and added the water filled the 4″ GN hotel pans. By the time the water in the pans reached 60C the meat went down to 1,at which point added the vacuum bags. In our case two 12×18″ bags per pan. Each bag had 3 flanks. A 4″ hotel pan has an approximate volume of 10 liters. The two bags have a volume of 3 liters. We want to make sure not to overfill each pan to ensure a constant cooking.

By the time the 20 pans were filled the water temperature of each pan fell to approximately 54C, when the cooking cycle started. We reduced the temperature to 57C, to achieve a internal temperature of the meat between 55C-56C. The two loggers were in different pans and locations of the oven to ensure a better reading. In the first 50 minutes the internal temperature of the meat went from 1C to 50C incerasing almost 1 degree per minute. It took another 2.5 hours to reach 55C. At least from a food afety stand point we were safe and reached 55C/131F within 4 hours. We continued to cooking cycle for another 18hours, or a total cooking time of 22 hours.

Analyzing the resulting four temperature logs, one from the Temp1000P, one from the EA15, and the two of the RATIONAL oven itself, where one is the actual cabin temperature the other one the temperature of the water bath where we placed the C/T probe we see that: The temperature variation of the combi oven itself can vary +/- 5C because of the low heat steam generated.  For the most time the cabin temperature was +/- 2C within the 57C, the water bath temp was 1-2C below the 57C, so at any time it was at or over 55C, the both temp loggers recorded the meat anywhere between 55.2C and 55.9C, for the last couple hours the temperature variance was eve smaller between 55.3C and 55.4C.

Conclusion, batch cooking sous vide in a water bath is doable and very close to the preciseness of the cirulator when the bags are placed into a water bath. As we continue to cook sous vide in the Rationals we will keep more log and share our findings. One thought we had during the proces was that dry heat is more constant in the combi ovens than steam heat.  Since we place the bags already into water baths would we achieve a more constant heating curve if we cooked in dry heat. We will certainly find out.

To finish the flanks itself we took them out of the bags, seared them ala plancha and placed them on racks back into the combioven Cooking program Roasts -> Overnight Roasts -> Skip Searing-> 55C/131F, until serving which was less than 30 minutes away.

If the flanks were cooked on a prior day we would have of course chilled them down immediately after the cooking cycle in the blast chiller.