DouglasBaldwin

So long as the ribs are completely submerged and there is a reasonable amount of space between them, it doesn't matter where the immersion circulator (IC) is located. Since you are concerned, then connect a tube to the outtake of the pump so that the intake is on one side of the tank and the outtake is on the other side of the tank. (This of course assumes that your IC is fairly new, since the pumps on old ICs can be rather anemic.) Since that is a lot of meat, you may need to incorporate additional heating elements into your tank design (controlled with a bang-bang temperature controller set just below your desired water bath temperature). It is also very important that you use a lid (say Lexan or metal) to reduce the workload of the IC (since evaporation uses a lot of energy).

You are quite right that there is little risk in consuming unpasteurized fish, so long as you have a healthy immune system. The problem, is that many people reading these threads may think it is also safe to serve salmon mi cuit to highly susceptible or immune compromised individuals. Just because it has been safe for millennia, does not necessarily mean that it is still safe. Our oceans are not as healthy as they were then --- they are much more polluted and many areas have been severely over fished. They also knew the provenance of their fish --- something that we rarely are privy to now. Therefore, we can no longer assume that the interior flesh of our fish is sterile and parasite free (as we have been able to do for millennia).

There is no need to thaw before reheating --- you can always place the frozen food directly into the water bath. In the future, I would highly recommend packaging large cuts of meat into portions for 2-3 people. Then, you will only need to open as many portions as you need. The problem with repackaging leftovers, is that the pasteurized meat can easily be contaminated by food pathogens and spoilage microorganisms. This will severely reduce the storage life of your sous vide prepared foods. It also means that you should re-pasteurize the leftovers before eating them. On the other hand, food which is still in the vacuum pouches it was cooked in, do not need to be re-pasteurized and can even be eaten cold --- so long as they were stored for a time and temperature combination that prevented any spores from outgrowing and multiplying to dangerous levels (see my guide or post #1773 in this thread). I absolutely agree with Nathan. I think it is very important for practitioners of sous vide to understand all the food safety issues connected with the technique.

So, from a food safety perspective, it really isn't advisable to cook salmon `mi-cuit'. While it may not be as tasty, I would recommend pasteurizing all fish at the temperatures and times I posted up thread (in post #2011).

To quote my guide: So, if the bags were kept at `the cusp of freezing' then your duck confit should remain safe indefinitely. (Since if there was any non-proteolytic C. botulinum {which is unlikely, since it is usually only present in fish}, you reduced it to a safe level during cooking.) Traditionally prepared confits also have botulism concerns, but are also fine if they are stored at below 50F (10C) in a reduced oxygen environment (e.g., covered with fat).

Any difference in taste or texture? ... ← I didn't notice a significant difference between the two. But, that doesn't mean there might not be a significant difference in taste or texture in another recipe. Either way, it is certainly interesting and runs counter to one of our long held assumptions.

There is NO point to multi-stage cooling. If you are going to store the SV product after cooking, then you should cool it to storage temp (very cold - ideally just above freezing) as soon as possible. The best way to do this is to either immerse in ice water, or use a blast freezer (like a convection oven, but with cold air not hot). ... ← I know I'm quoting a rather old post, but I recently had an interesting discussion with a chef who uses the CS (Cuisine Solutions) system. It seems that the reason for cooling ``successively, at room temperature, in cold water, then in ice water'' is to allow the meat time to absorb some of the liquid in the bag. My initial tests seem to confirm this. I cooked a batch of pork confit (see my guide). Then I rapidly cooled half the batch in ice water. The other half I cooled for 15 minutes at room temperature, then 15 minutes in cool tap water, then in ice water until cold. After reheating one bag of each, the slowly cooled meat was 2.4%* heavier than the rapidly cooled meat. * [(MS+FS)/(MS+FS+LS)]/[(MR+FR)/(MR+FR+LR)] - 1 = 2.4%, where M is the weight of the meat, L is the weight of the liquid, F is the weight of the rendered fat, S is for slowly cooled, and R is for rapidly cooled.

Jackal10, I just got the 2006 J. Food Science article by O'Bryan, et al. and found it very useful indeed. For those interested, I have updated my pasteurization tables (4.1--5.2) to reflect these more accurate D and z values. Since the review article had many D and z values at the temperatures we cook at, I took the arithmetic mean of the D and z values. Since I am no longer extrapolating from much higher temperatures, the 6D Listeria monocytogenes pasteurization times are now inline with the 6.5D (for beef) and 7D (for poultry) Salmonella pasteurization times. So, if you printed off my guide and use the tables frequently, I would recommend printing a new copy and throwing away the old copy. Edit: Typo

The thickness is the total thickness. As mentioned in my guide, I use thermal diffusivity of 0.956 mm^2/sec in all calculations. I chose this thermal diffusivity to assure (with 98% confidence) that I am not underestimating the temperature of the meat. However, except for thick pieces of meat, a higher thermal diffusivity will not substantially reduce the pasteurization time. The FDA article mentioned that ``as a general rule, the interior muscle tissue of a healthy live animal harvested from unpolluted waters is sterile'' [pp. 1291]. However, without knowing the provenance of the fish, we should not assume that it is sterile. Moreover, the FDA article states that ``bacterial and viral contamination in finfish is generally assumed to be present on the external surface, whereas in molluscan shellfish and crustaceans contamination may be internalized...'' [pp. 1293]. As for cold holding times, the 2005 Food Code states that food must be discarded if not served within four (4) hours of being removed from temperature control (3-501.19.B). As for cold storage, the 2005 Food Code (3-501.17.A) allows up to 7 days of storage at less than 41F (5C) or up to 4 days at less than 45F (7C). Since the food is being prepared sous vide, the 2005 Food Code (3-502.12.D.2.e) states that: All that being said, it would be much easier to hold it in the water bath until it is needed (which is also allowed by the 2005 Food Code {3-501.16.A.1}). While perfectly safe, have you found that the texture is adversely affected by holding in the water bath for that many hours?

nickrey, I do something very similar, except I remove the skin before bagging. I never preformed a double blind tasting, but always felt that cooking with the skin on caused too strong of a fish taste. Jackal10, The FDA paper was quite interesting. They also felt that a 6D reduction in Listeria would result in at least a 6D reduction in Salmonella, S. aureus, Campylobacter, and E. coli O157:H7 (see Appendix II). Based on Appendix II, they are using D[63C] = 2.8 min with z = 7.45C for Listeria monocytogenes. This results in the following pasteurization times for a 6D reduction of Listeria in a 131F (55C) water bath: mm -- HH:MM:SS 5 -- 02:24:50 10 -- 03:26:28 15 -- 03:33:14 20 -- 03:43:01 25 -- 03:54:15 30 -- 04:08:27 35 -- 04:25:43 40 -- 04:44:48 45 -- 05:06:36 50 -- 05:31:25 55 -- 05:58:24 60 -- 06:27:37 65 -- 06:59:08 70 -- 07:32:37 and in a 141F (60.5C) water bath: mm -- HH:MM:SS 5 -- 00:38:29 10 -- 00:42:27 15 -- 00:49:11 20 -- 00:58:35 25 -- 01:10:37 30 -- 01:24:50 35 -- 01:41:19 40 -- 01:59:40 45 -- 02:19:54 50 -- 02:41:48 55 -- 03:05:17 60 -- 03:30:12 65 -- 03:56:44 70 -- 04:24:51 However, the report felt that Salmonella should be the target organism for inactivation during cooking. They also recommended that the inactivation times provided in the 2005 FDA Food Code (D[140F] = 1.73 min with z = 10F) be used even though they are not based on data for seafood. Thus, the pasteurization times for a 6.5D reduction in Salmonella in a 131F (55C) water bath are: mm -- HH:MM:SS 5 -- 01:31:10 10 -- 01:34:57 15 -- 01:42:09 20 -- 01:52:24 25 -- 02:04:47 30 -- 02:20:06 35 -- 02:38:34 40 -- 02:59:06 45 -- 03:22:13 50 -- 03:47:59 55 -- 04:15:46 60 -- 04:45:29 65 -- 05:17:15 70 -- 05:50:44

First off, ``Calculating the Total Growth of Bacteria in Cooked Food Using the FDA Code Controls'' by O.P. Snyder discuss the cold holding of food. Snyder concluded that the FDA regulations seem to correspond to 10 generations of growth (or 2^10 ~ 10^3 increase in either Listeria or Salmonella). I assumed that the pasteurization temperatures and times you mentioned were from the 2005 US Food Code section 3-401.11.B.2, which does indeed correspond to a 6.5D reduction in Salmonella spp (in beef and pork where D[140°F (60°C)] = 1.73 minutes and z = 10 °F {5.5°C}). In contrast, for Listeria monocytogenes in beef, D[140°F (60°C)] = 8.32 minutes and z = 10.8°F (5.98°C) [J. E. Gaze, G. D. Brown, D. E. Gaskell, and J. G. Banks, ``Heat resistance of Listeria monocytogenes in homogenates of chicken, beef steak and carrot,'' Food Microbiology 6 (1989), 251--259]. I'm afraid I do have access to either the Journal of Food Science or the Journal of Food Protection. I will certainly request those specific articles from my university library though.

I'm afraid you are mistaken, those pasteurization times correspond to 6.5D reduction in Salmonella but not Listeria monocytogenes. A similar decimal reduction in Listeria at 131F (55C) would take quite a bit longer.

I frequently brine both pork and poultry when cooking sous vide (see my guide for details). That said, pork chops cooked at 131F (55C) for 12 hours and poultry breasts cooked at 140F (60C) until pasteurized are perfectly acceptable without brining. I feel that brining is important when cooking pork shoulders and poultry legs confit style (8--12 hours at 176F {80C}). Additionally, the meat can also be mechanically tenderized using a Jaccard. There is indeed a search function at the bottom left-hand side of this page. If you had noticed the search, you would have discovered that brining has been discussed at some length up thread. (But, there is always room for additional discussing ).

For the Mahi-Mahi, I used thermal diffusivity as a fitting parameter (that is, I calculated it from the measured data). Even if had found the thermal diffusivity in the literature, I would expect it to vary from fish to fish and species to species; much of this variation comes from differences in fat and water content. This variation in thermal diffusivity is the reason why I tabulate the `worst case' cooking time in my tables instead of trying to predict the actual cooking time (as Nathan does). That is, if the water bath is just above the desired final core temperature, I am assuming it is much less of a sin to cook the meat longer than needed than to not cook it long enough*. While this assumption seems reasonable for most meat, I have begun questioning its validity for fish --- often when I cook fish based on my cooking tables, I find that they come out mushy because the fiber-weakening enzymes are still very active at my desired final core temperature (~120F/50C). Without a good source for the thermal diffusivity of fish in the literature, it will take me quite awhile to determine the range of thermal diffusivities in fish experimentally. * This is especially true if the meat is being pasteurized, since underestimating the temperature of the meat would result in food which hasn't actually been pasteurized.

Yep, even the linear heat equation does a surprisingly good job. Just for fun, I measured the core temperature of a 27mm thick piece of Mahi-Mahi (in a 131F {55C} water bath) every 20 seconds and compared it with my numeric calculations. In the plot, I used a thermal diffusivity of 1.24 mm^2/sec and a heat transfer coefficient of 1000 W/m^2-K (since I used a circulating water bath). The blue line is the surface temperature of the Mahi-Mahi, the red line is the predicted core temperature and the blue dots are the core temperature as measured by a ThermoWorks MicroTherma2T with a needle probe. In my guide I use a thermal diffusivity of 0.956 mm^2/sec so that I am 97.7% confident that my predicted temperature will be lower than the measured temperature. I also use a heat transfer coefficient of 100 W/m^2-K since many people use naturally (rather than forced) convection water baths.

The danger zone is between 29.3°F and 127.5°F (-1.6°C and 53°C). Different microorganisms grow at different temperatures; for instance Salmonella can grows between 41.5°F--114°F (5.5°C--45.5°C) while Listeria monocytogenes can grow at temperatures down to 29.3°F (-1.6°C) and Clostridium perfringens can grow at temperatures up to 127.5°F (53°C). The pathogens can be inactivated with cooking (that is, we can pasteurize the food). This is typically achieved by heating the food to above 130°F (54.4°C) and holding it there for some length of time (please see my web page for more information). The problem, is that some pathogens produce toxins and/or spores which are not destroyed when cooking. For instance, C. perfringens produces both a toxin and spores (which is very resistant to heat).

(1) You are quite right, if you want a `steakier' short rib then you would use a lower temperature for a longer time (say 131F/55C for 24 hours) and if you want a `braised' short rib then you would use a higher temperature for a shorter time (say 176F/80C for 8-12 hours). (2) The air pump may not be necessary, but it certainly doesn't hurt anything. If you have a good (thermocouple) digital thermometer, you can measure the water temperature at multiple points and see if the water temperature is uniform without the air pump. (3) Everyone probably has their favorite `blow 'em away' sous-vide recipe. I usually show off the power of sous-vide by making roast beef: chuck roast seasoned with salt and pepper and cooked for 24 hours at 131F/55C. I use chuck roast because it has great flavor, is extremely tender after the collagen has dissolved into gelatin, and is inexpensive (only about $3/lb at Costco). Some of my friends absolutely love sous-vide salmon, while others don't care for it at all. Many of my friends like sous-vide chicken breasts, but I think that is just because conventionally prepared chicken is grossly overcooked. If you do go for chicken, I would recommend removing the skin first and preparing it separately and then brining the chicken breasts.

You should drop it in after it has come up to temperature. Dropping it in a water bath while it is still heating up might allow toxin producing bacteria to multiply to dangerous levels. For instance, the toxin forming C. perfringens can multiply to dangerous levels if a center temperature of 127.5F (53C) is not reached in less than 6 hours. Moreover, even in a water bath that has already come up to temperature, the meat must be cut so that it is -- less than 85mm thick when placed in a 131F (55C) water bath, -- less than 105mm thick when placed in a 141F (60C) water bath, -- less than 115mm thick when placed in a 147F (64C) water bath, or -- less than 140mm thick when placed in a 176F (80C) water bath, to assure that it will reach at 127.5F (53C) in 6 hours.

While I have collected some experimental data, I base my calculations on the results of various academic journals articles (from Journal of Food Engineering, Meat Science, Food Research International, Lebensmittel-Wissenschaft und Technologie,...). While the mathematics of computing heating/cooling times is straightforward (for a mathematician ), it requires numerous assumptions that cannot be true in all (or even any) cases. My first assumption is that there is no harm in cooking a piece of meat longer than it needs to come up to temperature, but not cooking a piece of meat long enough could be very dangerous. Thus, my goal is to compute cooking/cooling times that assure (with 98% confidence*) that any meat you cook/cool will reach the desired temperature within the computed time. Therefore, I am not at all surprised that your sausage cooked a good deal faster than my tables predicted. The problem, is that there is no way to determine a priori if the sausage will be done in the time listed or in half the time listed. Even for the same type and cut of meat, one piece could take more than 60% longer than another**. There is a measurable difference between circulating and non-circulating water baths, but it is less than you might expect. How quickly the surface temperature changes depends on the heat transfer coefficient of the cooking medium. For instance, (very roughly speaking) the heat transfer coefficient of naturally convected air is about 10 W/m^2-C, about 100 W/m^2-C for naturally convected water, 1,000 W/m^2-C for circulated water, and 10,000 W/m^2-C for steam. Using a thermal diffusivity of 0.956 mm^2/sec, a 20mm thick piece of meat takes: -- 42:37 in naturally convected air, -- 25:32 in naturally convected water, and -- 24:51 in forced convection (circulated) water, to come up to 64C in a 65C cooking medium (with a starting temperature of 4C). The problem, is that a crock-pot has little or no natural convection and the meat could take much longer than calculated. Moreover, the times assume that the average temperature of the cooking medium does not drop substantially when the meat is inserted. * I am (perhaps fallaciously) assuming that thermal diffusivity is normally distributed. ** For similar pieces of pork, the thermal diffusivity ranged for 1.12 to 1.83 mm^2/sec in [J Food Eng 77 (2006) 731--738]. Edit: Fixed formating.

Well, it of course depends on what you are cooking. If you are cooking at below 131F (55C), then you shouldn't hold it at all. If you are cooking at or above 131F (55C) and only want to hold it for a couple hours, then I would recommend holding it in the water bath. If you want to hold it longer than a couple hours, then you should rapidly cool it in a ice water bath (see my tables above) and then refrigerate it at a) below 36.5F (2.5C) for up to 90 days, b) below 38F (3.3C) for less than 31 days, c) below 41F (5C) for less than 10 days, or d) below 50F (10C) for less than 5 days. This will prevent the outgrowth of non-proteolytic C. botulinum. If you are doing a confit (or similar recipe) with the center temperature at 176F (80C) for longer than 6 hours (or 185F {85C} for longer than 36 minutes), then it just needs to be stored at below 50F (10C). Unless there is sufficient air left in the package to allow B. cereus to grow (i.e., you used a clamp style vacuum sealer rather than a chamber style vacuum sealer), in which case it must be stored at below 39F (4C). Edit: Fixed formating.

If you are cooking the meat to sell, then the meat should be pasteurized, quickly cooled and stored below 38F (3C) or below 41F (5C) for less than 10 days (to prevent the growth of C. botulinum, C. perfringens, and B. cereus). There are two standards for pasteurization (i) Salmonella spp. and (ii) Listeria monocytogenes -- which one you need to use depends on which country you live in. As stated many times up thread, the cooking time depends on thickness and not weight. For poultry cooked in a 141F (60.5C) water bath to a center temperature of 140F (60C), I calculate the following times: Salmonella (7D reduction): 5mm......00:26:12 10mm....00:30:22 15mm....00:37:25 20mm....00:47:11 25mm....00:59:32 30mm....01:13:57 35mm....01:30:29 40mm....01:55:26 45mm....02:25:48 50mm....02:59:40 55mm....03:37:12 60mm....04:18:35 65mm....05:02:50 70mm....05:51:02 L. monocytogenes (6D reduction): 5mm......00:28:26 10mm....00:32:32 15mm....00:39:28 20mm....00:49:05 25mm....01:01:17 30mm....01:15:34 35mm....01:31:58 40mm....01:55:26 45mm....02:25:48 50mm....02:59:40 55mm....03:37:12 60mm....04:18:35 65mm....05:02:50 70mm....05:51:02 Cooling Time in Ice Water to 41F (5C): 5mm......00:01:14 10mm....00:04:20 15mm....00:09:23 20mm....00:16:23 25mm....00:25:20 30mm....00:36:12 35mm....00:49:03 40mm....01:03:50 45mm....01:20:35 50mm....01:39:15 55mm....01:59:54 60mm....02:22:28 65mm....02:47:01 70mm....03:13:28 Being cooked at a lower temperature, the pasteurization times are much longer for beef cooked in a 131F (55C) water bath to a center temperature of 130F (54.5C): Salmonella (6.5D reduction): 5mm......01:31:10 10mm....01:34:57 15mm....01:42:09 20mm....01:52:24 25mm....02:04:47 30mm....02:20:06 35mm....02:38:34 40mm....02:59:06 45mm....03:22:13 50mm....03:47:59 55mm....04:15:46 60mm....04:45:29 65mm....05:17:15 70mm....05:50:44 L. monocytogenes (6D reduction): 5mm......02:24:50 10mm....04:49:54 15mm....05:54:17 20mm....06:05:21 25mm....06:16:42 30mm....06:31:47 35mm....06:50:30 40mm....07:10:23 45mm....07:33:32 50mm....08:00:15 55mm....08:29:10 60mm....09:00:26 65mm....09:34:27 70mm....10:10:41 Cooling Time in Ice Water to 41F (5C): 5mm......00:01:12 10mm....00:04:12 15mm....00:09:05 20mm....00:15:51 25mm....00:24:29 30mm....00:34:59 35mm....00:47:23 40mm....01:01:40 45mm....01:17:49 50mm....01:35:52 55mm....01:55:47 60mm....02:17:34 65mm....02:41:16 70mm....03:06:48 I use my immersion circulator in a counter-top food warmer/steam table so that the water bath is insulated (as per Pounce's suggestion up thread). Moreover, it is important to use a lid to limit evaporation; either make a Lexan lid or you can use steam table pan lids (say a 2/3 in the front and cut up a 1/3 for the back). [You can find a discussion on how I computed the above times on my sous vide page.]

You may also find my short guide to sous vide useful. It is still a work in progress, but it can be found here. I keep working on it whenever I have a chance. For instance, last week I included photographs illustrating eggs cooked for 75 minutes at 136F, 138F, ..., 152F. Today, I posted an updated and expanded section on food safety. It is my hope that my little guide can act as a stopgap until Nathan's book is released.

Cooking shellfish at only 113F (45C) for 12-24 hours is really dangerous! At that temperature, the common shellfish pathogens Salmonella spp., Staphylococcus aureus, and Clostridium botulinum can all grow and multiply. The heat resistant Clostridium perfringens (which grows at up to 127.5F {52.3C}) is not typically found in fin fish and shell fish; so it should be safe to sous vide fish at 125F (52C). At that temperature, it will take 383 minutes to pasteurize the fish (where Salmonella spp. is being used as the time-temperature standard for pasteurization). While the fiber-weakening enzymes may still be active at that temperature, collagen does not begin to dissolve into gelatin until 131F (55C).

You are quite right, according to the research papers I found, collagen begins dissolving into gelatin at 131°F (55°C). While I could be wrong, I suspect the reason Keller chooses 147°F is because the saturated fatty acid palmitic melts at 145°F (62.8°C). In beef and pork, roughly 60% of the saturated fat is palmitic. It takes higher temperatures (above 157°F {69.6°C}) to melt the saturated fatty acid stearic, which makes up 30-35% of the saturated fat in beef and pork. (The rest of the saturated fat, 5-10%, melts below 131°F {55°C}.)

While I certainly agree that it is far wiser to throw them out, doesn't it really depend on how long the temperature of the meat was between 120F and 55F (49C to 13C). According to Steele and Wright (2001), so long as the meat is cooled from 120F to 55F within 8.9 hours then (to 95% confidence) there would be less than a 10 fold increase in clostridium perfringens (which is what the FDA requires). Moreover, wouldn't the second cooking destroy the clostridium perfringens that had outgrown and multiplied? Anyway, I'm a mathematician and not a food scientist -- so I would listen to Nathan and throw them out.