Figuring Out Correct Cook Times

Let's say you're cooking a 3 pound roast Sous Vide @ 135°F for 24 hours. If you cut that roast - in half - would you get the same results by cooking it for 12 hours at 135°F?

I ask because I know that when you cook in a pressure cooker the amount of food doesn't matter as much, it's always the same length of time and temp and I just wondered which way to manually figure out the correct cook times. Thanks

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Comments

brian_martin2001

Times are rarely calculated by weight. It usually depends on the thickness and the cut of meat (tough/tender). When I cook a chuck pot roast at 130°F, it doesn't matter much if I leave it whole, or if i slice it down into steaks. If I don't cook it for at least 36 hours, it's still going to be pretty tough. What type of roast are you cooking?

AngelArs_240456

Right now I'm cooking a eye of round. It was 1.5 pounds which I cut in half (two 3/4 pound). Hoping that 135°F for 14 hours will be enough to cook them.

Brandon_Byrd_40557

No. When you're cooking for extended time periods, what matters isn't so much the size of the meat but how long it's held at a particular temperature. The holding step is what breaks down tough connective tissue, and that's not going to be accelerated by making the meat smaller.

AngelArs_240456

If size isn't a factor, then why would a steak take an hour to cook and a roast 24?

Is it the part of the cow that's being cooked that determines the length of time?

JasonWirth_68226

Surface area to volume determines how quickly your food comes to temp. After that it's simply time and temp that determine the breakdown. The center of two 1.5 pound steaks will come to temperature faster than a whole 3 pound roast because you increased the surface area. In the case of long cooks where you're dealing with connective tissue the difference is washed away by the total length of time cooking. Also with a steak vs a roast the difference is usually between bringing it to temp. to cook it through, vs breaking down connective tissue and collagen.

Brandon_Byrd_40557

Size does matter if you're cooking to core temperature. You don't cook top round to core temperature; you cook it for much longer than that. A 1.5lb round roast doesn't take 24 hours to reach a core temperature of 135F. In any event, the meat will be fully cooked after 14 hours. Whether it will be as tender as you were hoping is another matter.

Brandon_Byrd_40557

Yeah, what he said.

Brandon_Byrd_40557

Just saw your second question. Yes, the part of the cow matters. That's why it takes 72 hours to cook medium rare short ribs or beef cheeks, but only an hour or so to cook a tenderloin filet or strip steak of the same thickness. These latter cuts are tender enough that they only need to be brought to temperature and then they're ready to be seared and served. Cheeks and short ribs,y contrast, are shot through with connective tissue that needs to be broken down and made tender by long exposure to low heat. Top round is somewhere in the middle. It is a relatively lean cut of meat (which means that it can dry out) and it tends to be on the tough side, which is why people usually slice it thin and use it as "roast beef." It's not a good cut to carve a big steak from. To help it out, you need to let it hang out in the bath for longer than you'd need to if you were cooking a more tender (and more expensive) cut.

AngelArs_240456

THANKS Brandon. That makes perfect sense. A muscle on the cow that was used a lot would need more cooking time to break it down, but a part of the cow that isn't used a lot wouldn't need as much time. I'll increase the cook time from 14 hours to around 21 and check it then.

AngelArs_240456

THANKS Jason.

AngelArs_240456

Just an update: at 136 for 21 hours it turned out incredibly well. Can't wait to try the Joule for Thanksgiving Turkey.

fisher23

For your roast the time would remain the same for the 3 pound or the 1.5 pound. The thing here is that you are cooking for texture. You need the time for the connective tissue break down and no matter the size it will take about the same amount of time. Tender cuts are totally different the time will vary by thickness but the idea is just to bring the tender cut upto core temperature all the way through. Dr. Baldwin recommends 24-48 hours for eye of round, 130°F for medium rare and 140°F for medium. ("SOUS VIDE FOR THE HOME" by Douglas E. Baldwin, pg 46) I highly recommend his book. You can also get, "A Practical Guide to Sous Vide" for free on his website, which has a lot of sous vide information.

AngelArs_240456

Excellent Book. THANKS!