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Old 10-17-2005, 08:29 AM   #1
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Question Sous Vide (sp?). Is it safe?

In another thread, Jennyema pointed out that the USDA says cooking foods at low temps is not always safe. Here is the quote...

Quote:
Originally Posted by jennyema

Here's what the USDA says: "(O)vernight cooking of meat at a low temperature isn't a safe method .... so. It's not safe to cook any meat or poultry in an oven set lower than 325°F. At 200° F, meat remains in the "Danger Zone" (between 40 and 140° F) where bacteria multiply rapidly and can form toxins."
My question is, what about sous vide cooking where the food is vacuum packed and cooked at very low temps. Chicken, for instance, could be cooked at 170 degrees for a very long time. This is well below the 325 degrees that the USDA mentions. I see that the USDA talks about this with "oven" cooking. Since sous vide would be done on a stove top (I would assume), would that make a difference?

Discuss.

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Old 10-17-2005, 10:17 AM   #2
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Sous vide is a cooking method that shouldn't be confused
with other slow cooking methods.

For example fish is cooked from as low as 104 for salmon
up to about 114.Chicken about 140 and beef around 130.
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Old 10-17-2005, 10:19 AM   #3
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Yes foodaholic that is correct, but based on the USDA statement that Jenny provided us, how is this method considered safe? Cooking chicken at 140 is much lower than the 325 that the USDA talks about. How is this method safe?
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Old 10-17-2005, 10:32 AM   #4
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Because it combines low temperatures and an anaerobic environment, sous-vide cooking has long given health officials the heebie-jeebies. Local restaurant inspectors, who take their cues from the USDA, have been taught to cite restaurants for food kept in the "danger zone for bacterial growth," between 40 and 140 degrees Fahrenheit. Even now, many would be inclined to red-flag chefs who cook their beef cheeks at 130 degrees. But more recently, the USDA has published complex charts showing that as long as meats are held at lower temperatures for the proper period of time, pathogens should be killed as conclusively as if the meat were cooked to higher temperatures. These new findings, along with the fact that Europeans have safely cooked this way for years, suggest that properly executed sous vide is a safe way to prepare food.And I would think if
Thomas Keller and Ducasse think it's OK then I would certainly take that as prove positive.


This is not the same thing as boiling food in a bag.Sous vide is a vacuum enviroment nitrogen cooled and then cooked.To attempt sous vide at home would be impossible,unless of course you have the equipment and experitise.
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Old 10-17-2005, 12:50 PM   #5
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Quote:
Originally Posted by GB
Yes foodaholic that is correct, but based on the USDA statement that Jenny provided us, how is this method considered safe? Cooking chicken at 140 is much lower than the 325 that the USDA talks about. How is this method safe?
Keep in mind GB that cooking at an oven temp of 325 can and will continue to cook something until no moisture is left and can be ground into powder.Cooking sous vide maintains that low temp indefinately without any noticable deteriation of the food.For example,sous vide spare ribs probably have a total of 40 hours of preliminary sous vide cooking and then at serving time is brought upto a contant temp.

I think if anyone was to investigate sous vide cooking you would find it very involved,and when world class chefs are doing this with great success I believe any issues regarding doneness and food safety have been taken into account.

I believe the USDA has one thing in mind.Make sure there's nothing that we recommend that we won't get sued for...
so cook the living daylights out of everything,including milk and cheese.
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Old 10-17-2005, 01:11 PM   #6
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And about the Anerobic reference, the organizm that exrcetes the botulizm toxin requires an anerobic state to survive. It is because of this fact that sodium nitrite was added to encased sausages, and many canned foods. The sodium nitrite (or is that nitrate, I always get those two confused. ) inhibits the botulism critter from groing, and in fact, destroys the little pest.So, the vacuum seal doesn't garuntee safety from micro-organism growth, unless the food was iradiated with gamma particles, or sterilized in some other way while sealed in the bag.

The nasties start dying at around 150 degrees, give or take a few. They are all dead by the time the food reaches 165. The problem is that they can and do multiply readily as the food is comming up to temperature. And depending on the organizm, they may release dangerous substances into the food.

Salmonella and E-Coli aren't a problem as they are the pathogens that make us sick. But with some organizms, such as botulism, it isn't the bug that's dangerous, but the poison they secrete into the food as they metabolize what they eat.

So, if the food takes a long time to come up to temperature, as is the case with very low/slow cooking, the organizm will do its thing until it's dead.

Remember, the greater the difference in temperature, the faster the energy transfer. That is, if you place 85 degree food in a 165 degree oven, it will take much longer for the food temperature to rise to a safe level than if you took that same 85 degree food and placed it into a 325 degree oven.

Some people don't understand the implications of this. I've even heard it stated that if you use place hot water into a freezer, it will turn to ice faster. Of course this is false logic. At first, the temperature change is dramatically faster due to the great difference in temperatuer. But there is no momentum effect. As the water cools toward freezing, the temperature change slows in direct relation to the temperature difference between the air and the water. Therefore, it can be seen that the hot water will actually take longer to freeze than will water that is colder. It makes sense from a scientific standpoint. The same is true for all energy transfer between differing energy levels (heat differences in this case).

So I too would caution on the side of safety. Low and slow may make the food tender, and keep it juicy, but too low and slow invites trouble.

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Old 10-17-2005, 07:40 PM   #7
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Found this,a good read.

The Slowest Food
Why American chefs have taken up sous-vide cooking.
By Sara Dickerman
Posted Wednesday, July 20, 2005, at 11:35 AM PT




Chefs are always looking for extreme ways to cook. Some espouse extreme labor intensiveness: "Dude, you have to remove the pods, skins, and sprouts on every one of those fava beans." Others seek out extreme ingredients: "Our chickens are milk-fed, then finished on figs." There's even extreme rusticity: "Don't use a brush to baste that spit roast; use these rosemary branches instead." And now, it seems, there is extreme slowpokery. Elite restaurants are proudly selling beef cheeks and short ribs cooked for 30 or 40 hours, or fish slow-roasted at 160 degrees. The most popular and fascinating of these superslow techniques is sous-vide cooking.

Sous vide is the practice of cooking food at low temperatures in vacuum-packed plastic bags. (The term is essentially French for "vacuum-packed.") Once you get beyond the cosmic ick of cooking in plastic, the sous-vide effect—something I have experienced in a few European restaurants and some ragtag home experiments—is uncannily tender. Food looks firm and neat but collapses quite willingly in your mouth. And since no juices or vapors escape from those little plastic parcels, food cooked sous vide is full of flavor—a little garlic goes a long way.

Cooking in sealed packets is nothing new. For centuries, people encased food in something more or less waterproof, like a pig's bladder, and heated it in a water bath. Food cooked this way was steamy, moist, and perfumed with any herbs or spices sealed inside the bundle. Then, in 1974, a French chef named Georges Pralus learned that he could prevent the shrinkage of foie gras during cooking if he sealed it in plastic and poached it slowly. Pralus went on to teach the great chefs of the era, including Paul Bocuse, Alain Ducasse, and Michel Bras, about his method, and the technique became fairly common in Europe. (For an interview with Pralus in French, click here.)





The technique remains essentially unchanged. Ingredients are packed in heat-safe plastic bags, and air is sucked out of the package. (Believe it or not, the FoodSaver seen on late night infomercials is the machine of choice for amateurs.) The packets are then cooked in steam or water that is heated to the desired final temperature of the bag's contents. To keep food safe while cooking at extremely low heats, restaurants use scientific-grade immersion baths and steam ovens, which maintain temperatures impeccably. The method can be approximated at home with a closely observed pot of water on the stove, but the temperature will not be as stable. (Sous-vide curious? Click here for advice on trying it yourself.)

In the early days, many European chefs adopted sous vide less for the astonishing textures it produced than for the fact that—once you get beyond the equipment—it's a really economical way to cook. Sous vide produces almost no waste, and it's hard to screw up. For one thing, you can't overcook the food. If you roast your meat in a 350-degree oven, you must pull it out once the internal temperature reaches, say, 130 degrees for medium-rare beef. If you don't reach the oven in time, your dinner will be ruined. With sous vide, you're cooking in water that is the temperature you'd like your meat to end up, in this case 130 degrees. Once the beef reaches that temperature, you can hold it there indefinitely while you fix an elaborate plateful of garnishes. Or, if you cool it briskly, you can keep it in the refrigerator much longer than food that is not vacuum packed (and thus exposed to aerobic bacteria), so restaurant kitchens can prepare meals for reheating days in advance. Paula Wolfert, the globetrotting cookbook author, says the French chefs she encountered in the 1970s used the technique to make a little money on the side: They had their cooks package sous-vide stews and braises in between services and then sold the results to local bars.

For years, the technique stayed in Europe, but recently it's made advances here. Charlie Trotter, Thomas Keller, and Wylie Dufresne are among the American sous-vide avant garde and have been exploring its possibilities for several years. But this year, Food and Wine's roundup of the best new chefs was saturated with references to sous vide and other superslow techniques. Sous vide, it seems, has arrived. Why has it taken so long?

Initially, American chefs may have avoided sous vide because they had concerns about food safety, but I suspect a more significant reason for this delay was aesthetic. For a couple of decades now, we have been carrying on a romance with the fire-bitten flavors and textures produced by high-heat roasting, pan-searing, and grilling. Because we Americans are so closely associated with the bad aspects of the food industry—mushy white breads, microwaveable pap, skinless boneless chicken breasts—high-minded American chefs have felt more of a need to distance themselves from the food industry than Europeans. Burnished, crackly food was the obvious alternative. In the late '80s and '90s, restaurant menus were rife with crusts, be they horseradish, potato, cornmeal, or just the dark amber veneer of a well-seared piece of meat. Barbara Kafka, who had written the definitive microwave cookbook, wrote a very popular book on roasting that advocated daringly high oven temperatures. Photographs in magazines like Saveur further fetishized the crust, lingering on the caramelized pan juices, for example, pooled beneath a glorious roast. And we shouldn't overlook dentistry: Food scientist and texture specialist Malcolm Bourne also argues that as more Americans kept their teeth longer in life, they chose to eat more challenging foods: "A lot of [the] crunchier, tougher food on the marketplace has been a result of a revolution in the dental industry."

But too much of any one texture becomes tiresome. Tenderness is ready for its comeback, particularly as the experimental superstars of international cuisine (including Ferran Adria and Heston Blumenthal, both sous-vide enthusiasts) have inspired young American chefs to use their kitchens as laboratories and seek out new textures. To explore the softer side of cooking, they are trying sous vide and also low-tech options like slow-oven roasting, olive-oil poaching, and even steaming. Crispiness still has a role at avant-garde restaurants, but it is often evident in particularly delicate, highly processed forms: translucent caramel fans; fish skin isolated from its flesh, then crisped in the fryer; or crunchy crumbs of freeze-dried olives.

As for that crackly crust, it may be slipping out of vogue for a moment, but it has its permanent place in our kitchens. The notion of a sous-vide turkey may excite a hard-core experimentalist, but you can be sure that any bird on the cover of a cooking magazine this November will have a gleaming mahogany sheen.



Sara Dickerman is a cook and food writer living in Seattle. She'd like to thank Bruce Cole, Harold McGee, Nathan Myhrvold, and Paula Wolfert for sharing their sous-vide expertise.
Illustration by Mark Alan Stamaty.
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Old 10-17-2005, 09:17 PM   #8
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Wow!
Extremely interesting, but still scary (imho). I can still picture the "wee beasties" crawling over the meats - regardless of the assurances of the experts who are obviously correct (they're still alive).

Unless a huge amount of meat is being prepared in this manner I think it would be terribly inefficient because of the long periods of energy consumption, albeit low.

By way of explanation, consider a chuck steak stew cooked in the conventional manner - low to medium energy input for 2 hours. In a pressure cooker the same ingredients would have a similar energy input for say 30 - 45 mins (a bit long, but...). Now under sous vide energy input would be low for hours & hours maybe 6 - 12 or 20 maybe and energy input would be possibly double or more.

I would be really interested to actually see a course on this sous vide, but in today's energy environment, for the family, I think it would be too inefficient to persue in the home cooking environment.

I must say though - how incredibly interesting.
Thanks for bringing this to our attention.
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Old 10-17-2005, 10:33 PM   #9
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I just had a thought come to mind. If slow cooking is bad....why is it ok to use a crockpot? Anyone?
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Old 10-17-2005, 11:08 PM   #10
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The crock pots/slow cooker I have owned have always brought food temperatures above170 degrees, and in a fairly short time. Usually, the foods cooked in a slow cooker are swimming in liquid. This regulates the temperature do to the nature of water. It can't rise above 212' or so. It boils to rid itself of energy that would raise the temperature further. But I can attest that I have recently prepared a meal of baby-back pork ribs in my slow cooker, on its lowest setting, and the liquid biled away for about 7 hours. The meat was badly overcooked, though immersed in simmering liquid, and was as dry and tough as any pork I've ever eaten.

Slow cookers are definately cooler than a 400 degree oven, but they produce temperatures high enough to boil water, and in the absence of liquid, to brown the meat surface through radient and convective heat.

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