DouglasBaldwin

I've recently become hooked on my variant of Heston's triple-cooked fries. Rather than directly follow the recipe in the Big Fat Duck Cookbook, I (of course) integrate sous vide for the first cooking. I cut Yukon gold potatoes into 1/2"x1/2" fries, rinse for a couple minutes under running water, vacuum seal in a pouch with a 1% brine, and cook sous vide at 185F/85C for 40 minutes. Now that the starches have gelated and the fries are almost falling apart, I drain the liquid from the bag and gently place on a couple paper towels in my vacuum chamber to boil off the surface moisture and rapidly cool the fries through evaporative cooling. I do my second cooking in vegetable oil which is above the boiling point of water but below the temperature at which the Maillard reaction occurs rapidly (so between 250--275F/120--130C). The fries again go in the vacuum chamber. Finally, since the Maillard reaction occurs rapidly between 300--350F/150--180C, the final cooking is done in oil at (or slightly above) 350F/180C until nicely browned. I think the fries are amazing tossed with just a little sea salt.

It is a matter of time. Chicken can be safely cooked at 131 or above IF IF IF you make sure to keep it at temperature for the correct amount of time. The time is very different at 131 than at 140. So, please see the tables that Doug Baldwin has on his site. Keep in mind that you need to add up two times to know the safe time: the time required to bring the food up to temperature plus the time at-temperature required to make it food safe. --E ← As a note, the pasteurization tables in my guide already include a safety margin --- they also assume the worst on how long it will take the food to heat. You can certainly pasteurize poultry at 136F/57.5C (see my guide for times), but a lot of people find the color and texture of poultry cooked at 136F/57.5C to be "disturbing." Part of the problem, is that many enzymes are still active at that temperature and can make significant changes in the texture of the flesh in the time it takes to pasteurize. That said, give it a try and tell us what you think.

There is absolutely no problem cooking meat at 55C/131F. Most food pathogens stop growing by 45C/113F (Listeria, Salmonella, etc.), almost all the rest stop growing by 50C/122F and only C. perfringens is able to grow up to 53C/127.5F (and only because of a Phoenix phenomenon that is occasionally observable in laboratories). Certainly pasteurization takes longer at 55C/131F than it does at 60C/140F, but this is easily achieved in a water bath; besides, even the conservative 2005 US Food Code gives pasteurization times at 54.4C/130F (in section 3-401.11.B.2). Furthermore, the interior of intact beef muscle is essentially sterile and doesn't even need to be pasteurized (see discussion up thread).

As with every food safety question, it is somewhat complicated. On the one hand, the interior of intact beef muscle is essentially sterile and so the roast can be as large as you want. On the other hand, if the interior is not sterile and contains (a high initial load of) C. perfringens, then the coldest part of the roast should reach 54.4C/130F within 6 hours. So, how big can a roast be if you want the center to reach 54.4C/130F within 6 hours? Well, it depends on how hot the water bath is, what the thermal dynamic properties of the meat are, the shape of the meat, and how "thick" the roast is (among other things). The higher the water bath temperature is above 54.4C/130F, the larger the roast can be. The more spherical the roast is, the larger it can be. If you want to cook in a 55C/131F water bath and the roast is approximately cylindrical then it can be up to 95--135mm/3.7--5.3in thick (depending on how close the roast is to a perfect cylinder and what the thermal diffusivity of the meat is (see Table A.9 of my guide)).

It all depends on what texture you want your ribs to be. When I think ribs, I don't picture medium-rare meat and so use a higher temperature. The amount of liquid in the bag does not just depend on temperature but also on time: at 140F/60C, beef cooked for 24 hours loses about 31% of its weight while beef cooked for only one hour loses only about 7% of its weight (Bouton and Harris, 1981). I rather doubt you will notice much of a difference between ribs cooked at 180F/82C for 6 hours and 155F/68C for 24 hours. When I cook pork spare ribs at 155F/68C for 24 hours or at 176F/80C for 8 hours they both come out moist and very tender (even when I skip brining).

Brad: I'm afraid you are somewhat mistaken. Please see my guide for more information. Chris: I'm afraid I am a bit confused by the wording of your questions. Is the meat you are storing in your walk-in raw or cooked? I do not recommend storing raw meat in vacuum pouches --- many psychrophiles can grow at those temperature. Meat cooked sous vide and rapidly chilled can be stored for up to 10 days at 5C/41F (see my guide for more details). [Moderator's note: discussion continues in Sous Vide: Recipes, Techniques & Equipment (Part 5)]

My first concern is food safety. When home and professional chefs cook sous vide, they have completely control of the cold chain. It is highly likely that the food you sell will be temperature abused, and sous vide prepared foods do not spoil safe. At the very least, you should pasteurize the food for a 6D reduction in Listeria monocytogenes and have very short and prominent expiration dates. This of course limits what you can prepare --- most fish will taste overcooked if heated for the pasteurization times in Table 3.5 of my guide.

I happened to make butternut squash soup last night. 1-2 Butternut squash, peeled and cut Into 1/2" planks 2-3 Onions 3-6 Tablespoons butter Brown sugar to taste Sea salt to taste Lemon juice to taste Peel the squash, cut into planks and reserve the seeds. Steam the loosely stacked slices of squash for 20--25 minutes until tender and offers no resistance to a paring knife. Meanwhile, dice the onion and caramelize in butter over medium heat. Add a pinch of baking soda to speed browning. Place caramelized onion and steamed squash in blender and add water to half the height of squash. Blend in batches until smooth. Transfer to a large pot. Season soup with salt, brown sugar and lemon juice to taste. Enjoy!

Chuck, your times and temperatures are in the right ball park. I actually detailed how I was going to prepare my families turkey up thread in post #2129; since I picked up an organic free-range turkey, I skipped the brining steps; I also left the skin on the breast and crisped it (and the dark meat) in a pan with oil at 350F/180C; for the gravy, see post #2197. While it is true that you can pasteurize poultry at 136F/57.5C (see Tables 4.7 and C.11 in my guide), most people find the color and texture disturbing. Meat and poultry is the most tender around 140F/60C because that is when the sarcoplasmic proteins finish aggregating/gelling and before the muscle fibers have started to shrink longitudinally (and squeeze out the moisture). Sam is quite right that even 140F/60C is a bit low for dark meat --- I typically cook my legs and thighs at either 155F/68C for 24 hours or 176F/80C for 8--10 hours (often after brining and with a couple tablespoons of rendered fat in the bag).

I have never compared fresh-ground to pre-ground, but strongly feel that prime-grade dry-aged beef makes the best hamburgers. Like many serious about beef, we buy our beef by the half from a farmer we know --- without any overhead, it is surprisingly economical at only a couple dollars a pound. After aging, the locker packages the cuts we want and grinds the rest into hamburger; while not quite as good as hamburger made from grinding the entire steer (as hummingbirdkiss mentioned above), it is better than anything you can find at your local butcher and is a fraction of the price.

gregnz is quite right that the heat flow rate is just dQ/dt = hA(T1-T2), where T1 is the temperature of the food's surface, T2 is the temperature of the heat source, and A is the foods cross-sectional area. It is incorrect, however, to assume that h, the surface heat transfer coefficient, is the same in water below boil and boiling water. Indeed, h is about 5 times larger for boiling water as it is for simmering water. So, the initial heat transfer rate to the food's surface is about 1000 kW/m^2 for boiling water and 160 kW/m^2 for water at 90C/200F (where the food started at 10C) [McGee 1999]. (This is also the reason why forced convection is used in sous vide cooking.) Edit: Fixed Typo.

I agree with both Ruth's and Sam's comments above. Personally, I love making a quick sauce from the liquid in the bag. Even when just pasteurizing a chicken breast, I often strain the liquid, thicken it with a hydrocolloid, and season it to taste. That's not to say the liquid can always be made into a sauce; seasoning or brining the meat before cooking often results in liquid which is too salty to be made into a sauce. Thus, I often do not season the meat before cooking (except lard when cooking confit-style). [Although I stress brining pork and poultry in my guide, I typically do not brine natural or free-range meat.] To make a sauce from the liquid, I typically: (1) Heat the liquid in the microwave to aggregate and gel the (sarcoplasmic) proteins, (2) Strain the liquid through a chinoise, (3) If there is sufficient volume, I simmer the liquid in a shallow pan to reduce its volume and concentrate its flavors, (4) If necessary, I thicken the liquid with a hydrocolloid (such as xanthan gum), and (5) Season the sauce to taste before pouring it over the meat. For poultry, I crisp and brown the skin in a pan over medium heat with (nut or vegetable) oil between 300F/150C and 350F/180C for 30 seconds to a minute to prevent the skin from burning. For pork and beef, I typically sear the meat with my Iwatani butane blowtorch. If you make a sauce from the liquid in the bag, how do you make it?

Sam is quite right about collagen. Part of the confusion is that while collagen begins to contract between 140F/60C and 150F/65C, the soluble collagen begins to unfold/dissolve into gelatin above about 122F/50C to 131F/55C. As for the sarcoplasmic protein enzyme collagenase, it remains active below 140F/60C and can significantly tenderize the meat if held for more than 6 hours. [see sections "Effects of Heat on Meat" and "Tough Meat" in my guide for references.] I have a great affinity towards pulled pork and make it frequently. I agree with the above comments --- cook it until it feels right. For me (cooking sous vide), that tends to be around 20 hours at 155F/68C or 10 hours at 176F/80C. [both combinations achieve the same effect and were indistinguishable in a blind taste test at a recent dinner party.] Although it probably is not necessary, I usually brine my pork in a flavored 7--10% salt solution for 6--12 hours before cooking --- the 7--10% salt solution allows the pork to absorb up to 20--25% of its weight in brine (Graiver et al., 2006) and produces a very moist pulled pork. I also render my own lard and put a couple tables spoons in the plastic pouch, but that is a discussion for another thread :-). Edit: Fixed typo.

Actually, his description of cook-chill is quite reasonable. He stresses rapidly chilling the bags of cooked food in ice water baths --- rapid chilling reduces sporulation of C. perfringens. He recommends storing food at below 38°F/3.3°C --- this will prevent spores of non-proteolytic C. botulinum spores from outgrowing and producing dangerous levels of neurotoxin (within four weeks). Since some of his recipes do not achieve a 6D reduction of Listeria, he recommends freezing the food if you do not plan on using it within 3 days --- Listeria can grow at temperatures down to 29.3°F (-1.6°C).

I'm really not that surprised. While food scientists have no problem cooking at 130F/54.4C indefinitely, the safety section sticks to the "danger zone" dogma of the FDA. What I am surprised at, is that all the tough cuts of meat are cooked well done at over 158F/70C for 8--24 hours. Even sticking to the dogma of the "danger zone", tough cuts could be cooked at 140F/60C for 8--24 hours (which has been shown to produce especially tender meat).

Despite pre-ordering "Under Pressure" ages ago, I finally got it in the mail this afternoon. My first impressions are below. Once I have had time to carefully study the book, I will try and cobble together a proper review. I am generally impressed by the depth and scope of Thomas Keller's "Under Pressure". The 79 pages of recipes for fruits, vegetables and desserts are especially interesting since they have only been touched on in the "Sous Vide: Recipes, Techniques & Equipment" thread. The recipes for fish and meat do not differ significantly in temperature or time from those discussed in the sous vide thread or in my "A Practical Guide to Sous Vide Cooking". Being written by chefs, it is not surprising that "Under Pressure" lacks the scientific rigor of Nathan or my writings. This is especially true when it comes to cooking times, which are independent of thickness. [Recall that heating times increase four fold when the thickness is doubled.] The discussion of safety is mostly correct, but propagates the myth of the "danger zone" being between 40F/4.4C and 140F/60C. [it also misstates that "Salmonella is the most heat-resistant bacteria" when it is well known that Listeria is the most heat resistant bacteria.] While I certainly commend them on stressing the importance of storing food at below 38F/3.3C (to prevent the outgrowth of C. botulinum), the discussion on pasteurization is very limited. That said, most people probably feel that my guide excessively dwells on food safety and pasteurization times.

Nathan is of course absolutely correct that the grey (or even greenish) surface color of the meat is caused by a lack of oxygen. This lack of oxygen, is also the reason why beef cooked sous vide often looks pale when first cut but then becomes a bright red after being exposed to oxygen for a few minutes. According to Lawrie's Meat Science, 6e, pp. 212--216: The color of the meat depends on the quantity and type of myoglobin present. In general, the amount of myoglobin reflects the level of muscle activity. However, the concentration of myoglobin in a muscle can occasionally be several hundred-fold different over distances of 1 cm. When (fresh) meat is cooked, the purplish-red myoglobin, bright red oxymyoglobin and brown metmyoglobin denature into brown globin haemichromogen. The extent of this denaturation depends strongly on temperature and weakly on time (the amount of denaturation increases slowly with time). Indeed, beef cooked to an internal temperature of below 140F/60C has a bright red interior; between 140F/60C--160F/70C a pink interior; and, to 160F/70C--175F/80C or higher a greyish brown. Below 150F/65C, myoglobin denaturation may be caused by enzymic action or co-precipitation rather than from temperature.

I can tell you how I plan to prepare our turkey this Thanksgiving. [Although I am a huge fan of the molecular gastronomy movement, I stick to familiar flavors and seasonings for Thanksgiving.] If frozen, thaw your turkey completely before proceeding. If the bird was injected with brine before purchase, skip all the brining steps below. Thanksgiving Eve: Heat the water bath to 176F/80C. Carefully remove the turkey breasts and gently remove the skin. Brine the breasts in a 3--5% salt solution (30--50 grams salt per liter water) for 3--4 hours. Salt and pepper the skin and place flat on a wire rack in the refrigerator until Thanksgiving day. Remove the legs and wings and brine in a 7--10% salt solution (70--100 grams salt per liter water) for 3--4 hours. Vacuum seal the neck, back and any remaining dark meat in a heat stable plastic pouch. Place the bag in the water bath. After brining, rinse the turkey breasts, lightly season (with whichever spices you traditionally use), and individually vacuum seal each breast. Place the vacuum sealed breasts in the fridge overnight. [if you have two water baths, then cook the breasts for the time listed in Table 4.7 of my guide, rapidly chill in ice water for the listed in Table 1.1, and refrigerate until needed.] Once the legs and wings have finished brining, rinse, season, and vacuum seal with a couple tablespoons of fat (duck, goose, lard). Then cook in the 176F/80C water bath for 8--12 hours. Thanksgiving Day: Remove the legs, wings and spine from the water bath (if cooked overnight). Rapidly chill the legs & wings in an ice water bath for the times listed in Table 1.1 in my guide. Use the liquid and meat in the bag with the spine to flavor your gravy. In a 141F/60.5C (or 146F/63.5C) water bath, pasteurize the breasts for the time listed in Table 4.7 of my guide. After pasteurizing, reduce the temperature of the water bath to 131F/55C and place the pouches with the legs and wings in the water bath to warm. Just before serving, shred the dark meat from the thigh and wings. Either serve the shredded meat as is or place in a just smoking pan and brown one side. Using a Iwatani butane (or a propane hardware) blowtorch, crisp the skin on drumsticks. Crisp the skin from the breast either between parchment paper sandwiched between sheet pans in a hot oven or using either a blowtorch or a smoking hot pan. Then, serve the breast garnished with the crisped skin.

I actually do have a chamber vacuum sealer, and I can assure that the liquid almost always boils --- even olive oil. A couple tablespoons of liquid in the bag isn't a problem --- even at a hard boil, the liquid does not expand enough to reach the seal bar. Vacuum packaging high water content foods (for freezing) is more problematic; when the liquid boils, its effective volume increases rapidly and will pour out the top if you are not careful. Typically, I set my chamber vacuum to pull as strong of a vacuum as it can. Most chamber vacuum sealers use rotary vane vacuum pumps which can pull a medium vacuum* of 1 to 0.001 torr/mmHg (100 Pa to 100 mPa). If the food is moist, some of the liquid will change phase and displace the air in the bag with vapor. How much vapor depends on the temperature of the food; for water, the saturated vapor pressure is about 24 torr at 25C and 6.5 torr at 5C --- that means water at 25C boils around 24 torr and water at 5C boils around 6.5 torr. Assuming all the liquid doesn't boil away (a very safe assumption), then the strength of the vacuum pulled depends on the temperature of the food and how fast the gas in the chamber is removed --- that is, a steady-state is often reached where the amount of gas removed by the pump equals the amount of vapor generated by the liquid. So a particular chamber vacuum sealer can pull a much stronger vacuum on meat and marinade at 5C (with a vapor pressure of about 6.5 torr) than on hot soup at 80C (with vapor pressure of about 355 torr). Vacuum sealing food with a high liquid content is tricky. If you want to vacuum seal a lot of liquid, it is often convenient to freeze it in metered portions and then vacuum seal the individual portions. If you insist on keeping things liquid, cool the liquid as much as is feasible to increase the strength of the vacuum you can pull. Then place the liquid filled bag on a sloped board inside the chamber vacuum sealer so the liquid is as far away from the seal bar as possible. Then either fill the bag with just enough liquid so it does not exceed the volume of the bag when it rapidly boils or watch the vacuum sealing very closely with a finger on the stop/seal button and try to catch it before it boils out of the bag and makes a mess. * A medium vacuum is defined to be 25--0.001 torr. Edit: Edited for clarity.

While it is absolutely true that pure palmitic acid melts at 145F/62.8C and pure stearic acid melts at 157F/69.6C, the saturated fat in meat is not pure and melts at significantly higher temperatures. I do not know exactly how much higher the melting point is though. If I get a chance, I'll try and find it in the academic literature.

The FSA does have guidance on the cold storage of vacuum packaged food, and they can be found at: http://www.food.gov.uk/foodindustry/guidan...oodguid/vpguide However, their guidance only relates to the prevention of C. botulinum and cook-chill style sous vide cooking.

I don't think you can buy it from the website I linked to. I bought mine through my local restaurant supply store ( http://www.etundra.com ), but the one you linked to looks to be the exact same. As for the butane canisters, the only place I could find which shipped them for a reasonable cost was Very Asia ( http://veryasia.com/bu-6.html ). The canisters last quite a long time (about 20 hours of use), so you probably don't need more than a dozen to start with. Edit: Fixed links.

I would highly recommend the Iwatani butane blowtorch ( http://www.iwatani.com/asp/w_product/Produ...p?ProductID=133 ), it is half the price of the Bernzomatic mentioned up thread without any of the drawbacks. I find that hardware propane blowtorches leave an off flavor and cannot be held pointing down for the time necessary to sear the surface of more than one or two steaks. The Iwatani has neither of these problems and actually produces a larger and more consistent flame than the Bernzomatic I used to use.

You are both quite right. My comment assumed that joesan wanted to cook the meat for a long time at below 130F/54.4C to allow enzymatic tendering of the meat (since this thread has long assumed that these enzymes are only active below 130F/55C). If joesan simply likes rare beef, than he should absolutely follow Nathan's recommendations above. Moreover, unless you want spoon tender meat, I would not recommend cooking tender (or very well aged) cuts of meat at 130F--140F (55C--60C) for more than 6 hours. At least to my palate, well aged (4 wk) tender cuts of grass fed beef are unacceptably tender when cooked for more than 6 hours at 131F/55C. Minimally aged supermarket beef, however, may well need 24 hours at 140F/60C to be acceptably tender.

There is little evidence that cooking at less than 55C/131F has any advantages. I recently came across a journal article [J Food Sci 46 (1981) 475--478] which compared the tenderness of beef cooked at 50C, 55C, ..., 65C for up to 24 hours. For steers and cows less than four years old, the meat was most tender when cooked at between 55C/131F and 60C/140F for 24 hours. This was true of both freshly slaughtered and aged (up to 7 weeks) beef. Indeed, they found that beef cooked at 50C/122F was up to 6.1 times tougher than beef cooked at 60C/140F. This tenderizing is a result of a reduction in connective tissue strength and proteolytic enzymes which are active at temperatures below 65C/150F and decrease the myofibrillar tensile strength. Just to be clear, my calculations do not assume that the interior muscle is sterile. When doing cook-chill sous vide, it is typically assumed that there is high bacterial load of 10^4 vegetative cells of Listeria monocytogenes per gram and that pasteurizing will reduce the number of vegetative cells to less than one cell per 100 grams. (Note: Listeria is used because it is the most heat resistant non-spore forming pathogen and because it can grow at refrigerator temperatures.) While it is possible to reduce such a bacterial load of Listeria at 50C/122F, the common spore forming pathogen Clostridium perfringens can grow at up to 53C/127.5F. Therefore, the lowest typical temperature for pasteurization is 54.4C/130F. While it may be reasonable to assume that the interior muscle of meat and fish is essentially sterile (as Nathan and many food scientists do), I have never been comfortable with this assumption --- especially when the provenance of the meat or fish is unknown. In any case, I would recommend pasteurizing at 54.5C/130F and above if you are serving high risk individuals.