Sous Vide Prime Rib: Temperature, Time and Roast Width

Sous vide prime rib cooks at 131°F (55°C) for medium-rare. A roast that measures 2.75 in (7 cm) straight through its center needs at least 3 hr 30 min in the bath, is at its best between 3 hr 30 min and 4 hr 30 min, and can stay in for up to 10 hr.

The time depends on that width, not on the weight. The width also sets a limit: the calculator covers roasts from 2 to 3.75 in (5.1 to 9.5 cm), and a wider roast has to be cut down first. Every time on this page comes from the calculator.

What prime rib is

Prime rib is another name for the standing rib roast, a cut from the rib primal. Wikipedia's entry says the whole rib section runs from rib six through rib twelve, and that a roast may hold anywhere from two to seven ribs. The name does not require USDA Prime grade beef.

Jason Logsdon's prime rib guide at Amazing Food Made Easy explains the relation to steak: prime rib and ribeye are the same cut, and ribeye is cut before cooking while prime rib is left whole.

Measure the roast: the width limit

Measure straight through the center of the roast at its thickest point, including the bone on a bone-in roast.

If the roast is oval, wider than it is tall, enter the smaller dimension only if the other is no more than one and a half times as large. Otherwise treat it as a flat piece and use the ribeye setting with its thickness.

The same measurement through the center is used for the other roasts the calculator times as cylinders, including a whole beef tenderloin and a rolled, tied turkey breast.

A roast wider than 3.75 in (9.5 cm) is outside the range of the published tables. Cutting it into two shorter roasts does not change the width. Cut it between the bones into pieces no more than 2.5 in (6.4 cm) thick and use the ribeye setting. That setting measures through the thickest part, including the bone if there is one.

The reason is heating time. Douglas Baldwin's guide to sous vide cooking notes that thick pieces of food, like a rib roast, take much longer to cook and cool than thin ones, and that the center of the food should reach 130°F (54.4°C) within 6 hours.

The guide has no rib roast recipe. Its roast beef recipe, written for top blade, chuck or top round in a 131°F (55°C) bath, says to cut the roast so that it is no more than 2.75 in (7 cm) thick, and its pulled pork recipe gives the same figure. The calculator uses that thickness as its default width for prime rib.

On the ribeye setting at 131°F (55°C), a piece 2 in thick needs 3 hr 45 min and a piece 2.5 in thick needs 6 hr. Those times are longer than for a round roast of the same measurement, because the heating tables treat a flat slab and a cylinder differently. A 2.5 in piece is close to the 6 hour heating limit at that temperature and carries a warning, so a thinner piece or a higher temperature is the more cautious choice. The ribeye guide has the full table.

Logsdon prefers slabs in any case, because they cook faster and each one can be cooked to a different doneness.

Prime rib temperature options

131°F (55°C), medium-rare. The default: warm red to pink throughout, tender and juicy. Logsdon cooks his prime rib almost exclusively at 131°F (55°C) or 135°F (57.2°C). This setting is recommended up to a 3 in (7.6 cm) roast.

140°F (60°C), medium. Pink throughout, firmer and still juicy. This is the setting for a roast wider than 3 in, up to the 3.75 in limit.

150°F (65.6°C), medium-well. Faint pink, firm and drying out, with a grainy texture. The maximum drops to 4 hr for a roast up to 2.5 in.

125°F (51.7°C), rare. Rare is not practical for a thick roast, because the center cannot warm through inside the time limit for temperatures of 130°F (54.4°C) and below. Only a roast up to 2.25 in (5.7 cm) fits inside that limit, and rare is not recommended at 2.5 in or wider.

The steak temperature chart compares these levels across beef cuts.

How long to sous vide prime rib, by width

At 131°F (55°C) the minimum for roasts up to 3 in is the heat-through time, which is the time for the center to come within 1°F (0.5°C) of the bath. A 2 in roast needs 2 hr, a 2.5 in roast needs 3 hr and a 3 in roast needs 4 hr. All of them have a 10 hr maximum.

Recipes give longer single times, and they fit inside that window. Jeff Akin's prime rib recipe for Anova cooks a 3 pound bone-in roast at 132°F (55.6°C) for 6 hours, and Logsdon cooks his for 4 to 8 hours. The calculator's minimum is the point at which the center is hot, and any time from there to the maximum works.

Medium prime rib

At 140°F (60°C) a 2.75 in roast needs 3 hr 30 min, the same as at 131°F (55°C), and is pasteurized after 4 hr 15 min. From 3 in up, the center takes more than 4 hr to heat through, so the minimum shown is the pasteurization time: 4 hr 45 min at 3 in, 6 hr at 3.5 in and 6 hr 45 min at 3.75 in. Do not shorten those times. The maximum is 10 hr.

How to sous vide prime rib

1. Measure the roast. If it is wider than the limit for your temperature, cut it between the bones first.
2. Heat the bath. Set it to 131°F (55°C), or to 140°F (60°C) for a wider roast.
3. Season. Akin salts the roast generously and refrigerates it for 1 to 12 hours before cooking. Logsdon salts lightly, adds dry spices, and saves fresh garlic and onion for the finish.
4. Bag it. Use a vacuum sealer, or a large zipper-lock bag sealed with the water displacement method.
5. Cook for the time that matches the width. Keep the bags in a single layer, fully under the water, and not overlapping. Crowded or overlapping bags heat more slowly, and the times shown will be too short for them.
6. Dry the roast and brown the outside.

Finishing the crust

The bath cannot brown the roast. Baldwin's guide puts good browning and a roasted flavor at surface temperatures around 300°F (149°C). Finish in a very hot oven or under a broiler to brown the outside.

Hot oven. Logsdon puts the roast in an oven preheated to 450 to 500°F (232 to 260°C) for 10 to 30 minutes. Akin brushes the dried roast with egg white, coats it with coarsely ground peppercorns, celery seeds, garlic powder and rosemary, and roasts it on a rack at 425°F (218°C) for 10 to 15 minutes, until the crust is dark golden brown.

Broiler, pan or torch. Logsdon lists the broiler as an alternative for a whole roast. For slabs cut between the bones, he sears each one in a hot pan or with a torch.

Akin rests the roast for 10 to 15 minutes before carving. To carve a bone-in roast, the beef industry's prime rib guide turns it on its side, cuts along the curve of the ribs to remove them, then turns the roast fat side up and slices.

Cooking prime rib from frozen

Inside the limits, a frozen 2 in roast needs 3 hr 15 min at 131°F (55°C). At 140°F (60°C) a frozen 2.5 in roast needs 6 hr 45 min, a 2.75 in roast needs 7 hr 45 min and a 3 in roast needs 9 hr. Those three are pasteurization times, so do not shorten them. The guide to cooking from frozen explains the method.

Safety

The USDA safe minimum internal temperature for beef roasts is 145°F (62.8°C) followed by a 3 minute rest, as listed on FoodSafety.gov. The rare, medium-rare and medium settings are below that.

At 131°F (55°C) a 2.75 in roast is heated through at the minimum time but not pasteurized. That is normal for a whole, intact cut of beef cooked to this doneness. To pasteurize it, cook it for at least 6 hr 45 min. A 2.5 in roast needs 6 hr.

Use that longer time, or a higher temperature, when cooking for pregnant women, children under 5, adults 65 and older, or anyone with a weakened immune system. If the label says mechanically tenderized or blade tenderized, or the meat has been injected, use the longer time as well.

An acidic sauce or marinade can make beef take up to twice as long to pasteurize. If the beef is in one, do not rely on the pasteurization time shown.

The sous vide safety guide explains why the limits change at 131°F (55°C).

Common problems

The crust is pale. Pat the roast dry before it goes into the oven, and use the top of Logsdon's 450 to 500°F (232 to 260°C) range or the broiler.

The meat is softer than expected. It was held toward the 10 hr maximum. That limit is about texture, and Baldwin's guide notes that meat continues to soften in the bath. Take the roast out closer to the minimum.