help- my beef is tough when reheated

There are a few exceptions, but as a general rule you can't cook meat twice. You can only cook it and reheat it because of changes at the cellular and molecular levels having to do with moisture crossing the cell membranes and protein denaturing, respectively.

Next time, whether you cook a tough cut low and slow to tenderize, or a tender cut hot and fast to get a nice, juicy medium rare -- cook it til it's done and stop.

Your largest mistake was to attempt to continue the cooking process -- rather than reheating it gently until it was just hot enough to eat.
You absolutely cannot dry roast, then pot roast. Under certain specific conditions you can go the other way 'round, but that's another post.

For what it's worth, the natural juices released by the meat when sliced are not properly speaking "au jus," whether in terms of American or French culinary terms. In French terms jus is usually the juices left in the pan after a roast cooked as a poele is removed. In classic American it's typically a light gravy made with the jus plus some aromatics -- poele or no poele. Most often though, an American au jus, as in prime ribs of beef or a beef dip is mostly beef broth and wine.

To get ahead of the obvious question, a poele is like a braise but with only a tiny bit of moisture added to the (covered) roasting pan. The method encourages the formation of pan juices without drying out the meat.

Just an educated guess here, but unless you actually meant what I just defined as jus, the meat gave liquid so copiously because you carved it before it had fully rested. That the meat likely started dry exacerbated the problem you caused by your over-reheating.

Bottom line: Beef reheats well in slices, and reheats well in gravy too. But as I said the reheating needs to be gentle. Heat only until warm, then stop.

BDL

A lot of places do not even reheat the meat. They have it at room temp and simply pour hot Au Jus over it. A French Dip sandwich would be an example of this. I reheat whole ribs of beef all the time and never have a problem. First time it is cooked real rare, on reheat I wrap in plastic wrap then foil and heat in 250 oven about 4 hours. I have yet to get a complaint in 2 years. You on the other hand are making potroast. Roasting dries out meat, and to roast it in its own juice is boiling it, it can only get tough specially since it, is as you said sliced thin. Also rounds of beef, both bottom and top tend to get fiberous when cooked second time. Also as BDL stated DO NOT slice it before reheating

Doodle! For the life of me I cannot see how you can get a decent roast beef dinner(Not Pot Roast) out of thinly sliced roastbeef that has been frozen then reheated in juice or gravy. If nothing else no guest can get a choice of temperature. If someone figures out how to do this, they will make a lot of money

If you wanted pot roast, you should have made it pot roast from the giddyup, yes.

I didn't suggest you should poele. I was talking about options. If you tell me what you want to do, I might be able to tell you how to do it -- from one of a number of perspectives -- home cook, "American Bistro," small catering, 'q, French, and "California Cuisine," to name several. Chef Ed and I have some overlap, but he knows a lot more than I do about serving big numbers. Other people here bring different perspectives.

I'm not really familiar with pressure-cooking. I know great things can be done, but I've never tried to do them.

Before I comment on this, I'd like to know what you mean by jus, what the sequences were, and some rough idea of quantities.

One of the problems we're having is the meaning of the term "roast beef." I see Chef Ed is trying to get some clarity on this, too.

When you say "roast beef," do you mean roasted uncovered like a rib roast? roasted covered like a poele; or braised like a pot roast?

Not necessaily. You've pre-sliced and packed in sauce. As long as the reheating process is relatively gentle, and the packets are not too thick, reheating from frozen shouldn't be a problem in microwave or in vacuum packs reheated in hot water.

Not much of an issue. All fond is good fond -- at least as long as it isn't carbonized.

Now that IS a problem.

Aha! I see. If you care (and you shouldn't), the proper name for it is a "stock-enriched jus lie."

Bottom line: If I had a better idea of what you're trying to do, in terms of the exact nature of the dish, the number of servings, the nature of the setting (retirement home, country-club, work-site, ...?), and so on, I can either do a better job of helping or letting you know you're outside my limited area of competence.

BDL

I frequently smoke top sirloin roasts to rare, slice thin and vacuum pack(no added liquid). Completely thaw, bring to room temp, a quick dip into some hot beef broth and onto a sandwich. Never had issues with it getting tough but the reheat is a minute at most in simmering broth.

Sounds like some Vietnamese pho techniques. Works well with decent cuts of thinly sliced raw beef as well.

In my not so competent opinion, part of the problem is freezing with liquid. That can lead to a lot more cell wall damage as ice crystals grow and puncture the cells. So when thawed all the moisture seeps out of the 'wounds' so to speak. Such a situation works to some extent with ground meats, like salisbury steak TV dinners and such, but when dealing with slices of roast you'll have issues with texture and toughness.

mjb.

But the explosion of cell walls due to freezing shouldn't result in toughness, in fact it should result in the meat being mushy and sludgy. I just think that the double cooking process is causing a lot of moisture to be lost from the meat, even if it is being cooked in juices (think of meat left over from making broth for 4 hours, it'll inevitably be drier than meat cooked from brothmaking for less time.