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Everything posted by DouglasBaldwin

  1. Since I don't see it mentioned above, you can also use my egg calculator (http://www.chefsteps.com/activities/the-egg-calculator) to compute the cooking time at different bath temperatures for different yolk viscosities. It solves a differential equation to compute the yolk viscosity based on Vega's paper and my own, extensive, experiments and measurements.
  2. I'm giving a free American Chemistry Society (ACS) Webinar entitled Sous Vide Cooking and Chemistry on 9 May 2013 at 2 p.m. EST. Registration is limited, so sign up now if you want to participate! (Coincidentally, I'm missing my doctoral hooding ceremony to give my webinar. But I can go to commencement the next day, so my friends and family still get to watch me graduate.)
  3. From a food safety perspective, there is nothing wrong with cooking from frozen. In fact, many food scientists recommend cooking from frozen; for example, O. Peter Snyder --- a food scientist I respect a lot --- recommends cooking your holiday turkey in the oven from frozen at http://www.hi-tm.com/Documents2005/turkey-cook-frozen.pdf . (Something most people are aghast to hear.) Some believe that the is a noticeable difference in texture, when cooking sous vide, between thawed and frozen; but I'm skeptical about this. Perhaps someone on here will do a blind taste test to find out. Either way, this is a taste and not a safety issue.
  4. Or, I could generate and post a new table . EggHeatingTimes80C.pdf
  5. Morkai: The most important part of the “cooling to 4.4°C/40°F within 11 hours” is the initial cooling from 52.3°C/126.1°F to 21°C/70°F (say, within about 2 hours). The lower the temperature, the longer it can safely be held there; cf. Table A-2 in (FDA, 2011). Edit: Linked to wrong edition.
  6. Hi Morkai, Since there seems to be quite a bit of confusion, I thought perhaps that I might chime in. This is mostly a review of the food safety section of my guide and of my IJGFS article. Let's go through things step-by-step: You buy meat from a trusted source that doesn't have a strong smell, isn't slimy, and is before the best-by or use-by date. We hope that this will keep the number of microorganisms low, say less than 10/g of each of the Salmonella species, Listeria monocytogenes, etc. and less than 100/g of Clostridium perfringens (cf. Snyder 1995). We want this because it takes from 104 to more than 1010 of the different Salmonella species to make a healthy person ill; an immune compromised person needs as few as one to ten infective, active pathogens to make them ill. You thoroughly wash your hands, using the double-wash method, before you start cooking or after you use the toilet. This is important because pasteurization for the Salmonella species, the pathogenic strains of E. coli, and Listeria monocytogenes does not reduce viruses like Hepatitis A or norovirus to a safe level. (The double-wash method first uses a brush with soap to clean under the fingernails, followed by a rinse, followed by more soap that's worked into a lather, another rinse, and drying with paper towels.) You seal the meat in pouches, using the water-displacement method or using a vacuum sealer. Both these methods make it so there is little or no air between the food and the pouch and so allows for the efficient transfer of heat from the water to the food. I always assume there's enough oxygen for the bacteria that need it and that there isn't any oxygen for the bacteria that need that, because I can imagine cases where either is true. You put the meat in the pre-heated water bath. If your not pasteurizing, you want to keep it above 27°C/80°F for less one hour (FDA, 2011). If you're pasteurizing, you want to limit the amount of toxins that are formed and aren't destroyed by heating: so you want to keep it above 21°C/70°F and below 48°C/118.4°F for less than 2 hours (FDA, 2011). This is equivalent to requiring that the core of the food reaches 54.4°C/130°F within six hours. Now you hold the food at or above 52.3°C/126.1°F until any active pathogens have been reduced to a safe level. For healthy people, a 3-log10 reduction of the Salmonella species is generally recommend; for immuno-compromised people, a 7-log10 reduction is generally recommended. You can hold it here indefinitely from a food safety perspective or an optimum amount of time (give or take 10%) for texture. You then serve the food or chill the food rapidly to limit sporulation of Clostridium perfringens (since it creates its toxins while sporulating); cooling to 4.4°C/40°F within 11 hours is generally recommended. Given the small size of your short-ribs, refrigerating them likely accomplished this. Now you can refrigerate or freeze the food. You can freeze indefinitely (though taste is usually degraded after 6 to 18 months). When refrigerating, you want to limit spore outgrowth and subsequent multiplying; the limiting pathogen is Clostridium botulinum and the recommended storage times are: below 2.5°C/36.5°F for up to 90 days; below 3.3°C/38°F for less than 31 days; below 5°C/41°F for less than 10 days; or below 7°C/44.5°F for less than 5 days. Now you reheat so that the food is above 21°C/70°F and below 48°C/118.4°F for less than 2 hours (FDA, 2011) to limit toxin formation by Clostridium botulinum, Bacillus cereus, and Clostridium perfringens.
  7. I strongly recommend cooking directly after rapid aging and not refrigerating. Rapid aging without additional hurdles (as they're called in the food safety biz) is already pushing the boundary of what's considered safe. I'd suggest using an additional hurdle like an acidic marinade (with pH less than 4) as Pedro does and never using mechanically tenderized meat when rapidly aging.
  8. DouglasBaldwin : Is that really 45 '°C' - so not aging as people would think, but actually cooking at a low temperature? Yes, I did mean 45 °C / 113 °F. When I think ‘cooking’ I think about proteins denaturing and foodborne pathogens being reduced to a safe level. In that sense, rapid aging is closer to traditional aging than cooking. Even at 45 °C / 113 °F, many of the enzymes that affect the muscle fibers are active and can significantly increase tenderness — just as they do in traditional aging.
  9. Hi. Earlier this week, someone emailed me asking me why I talk about collagenase increasing tenderness below 60 °C after about six hours but that Heston in “In Search for Perfection” ages his steak at 50 °C and McGee says that fiber weakening enzymes “denature, become inactive, coagulate” at about 55 °C. I thought some of you might have the same question, so I've pasted my answer below: There are a lot of different enzymes in meat. We're mainly interested in proteolytic enzymes that split proteins or peptides (which are chains of amino acids) and these enzymes are called proteases. Enzymes are named by adding an -ase onto what they act on; so any enzyme that breaks up collagen is called a collagenase. The enzymes that are important in aging or conditioning can be divided into calpains and lysosomal enzymes (including cathepsins): • Calpains need calcium ions to be activated and act on muscle fibers (but not myosin or actin, which make up 65–70% of the myofibrillar proteins). • Lysosomal enzymes act on muscle fibers (both myosin and actin) and (some) collagen. See Lawrie's Meat Science for more details. When meat is aged, typically at 1–3 °C for 1–4 weeks, it's mainly changes to the muscle fibers that increase tenderness. This is surprising because the break down of connective tissue (collagen and elastin) would seem to be the most likely cause of increased tenderness. Nonetheless, a famous experiment (Sharp, 1957) showed that almost no collagen is broken down during aging — even when he aged sterile meat for one year at 37 °C! Since there is a great number of enzymes, there isn't a single temperature that they stop working at. Recall (from page 17 of my IJGFS article) that the sarcoplasmic proteins (which are mostly enzymes and myoglobin) start to denature around 40 °C and finishes around 60 °C. So, in other words, some enzymes stop working around 40 °C and most have stopped working around 60 °C. The rapid aging that Heston — well, actually, Chris Young who was working for Heston at the time and told me that he based that recipe on what he'd been reading in Lawrie's Meat Science — is interested in is the break down of muscle fibers that occur in normal aging. Indeed, in another experiment that compared aging at 2 °C with 38, 43, and 49 °C found that the rate of aging was about 7 times faster at 38 °C and about 18 times faster at 49 °C than at 2 °C. This is what Myhrvold et al. (2011) is after when they suggest aging meat for even 4 hours at 45 °C can significantly increase tenderness. While my recipes at above 55 °C and below 60 °C get some mild rapid aging while it heats up, I don't believe that this significantly increases the tenderness. What I'm after was first reported in Laakkonen et al. (1970), where they found that collagenase was active below about 60 °C and could significantly increase tenderness if held there for about six hours. Now, it seems that this collagenase only acts on some of the collagen and most of the collagen that's broken down at these temperatures (especially on the long, 1–3 day cooks) is a continuous nonenzymic breakdown. In another interesting experiment by Sharp (1964), he again held beef at 37 °C for 97 days but only after first heating to 70 °C for 15 minutes or 100 °C for 45 minutes; after heating to 70 °C, soluble hydroxyproline was 2% and raised to 23% after aging and after heating to 100 °C it raised from 12% to 55% — but certainly the enzymes are no longer active after heating so it'd seem that these changes are nonenzymic changes in the connective tissue. I don't know what exactly this implies, but it's certainly interesting.
  10. I actually do have a recipe for braised oxtail on page 62 of my book; I recommend 175F/80C for 12–18 hours.
  11. Thank you Shalmanese for your quick response to Tatoosh's question. To add a little detail, let me quote the food safety section of my web guide:
  12. I just wanted to let you know that the first issue of the International Journal of Gastronomy and Food Science is finally out. It seems that all 10 articles (including my review article on sous vide cooking) are available for free download.
  13. It's normal for the liquid in the bag to look unappetizing, especially for the long, low-temperature recipes. If you drain the liquid into a microwave-safe bowl and microwave it until it boils, it'll look more like what you're used to; many then filter out the precipitated (sarcoplasmic) proteins and brown them in a pan (with some fat) (add some flour to the fat to make a roux,) and then add the filtered liquid to make a simple sauce. That said, this method doesn't make a lot of sauce and the protein you just cooked is likely to get too cold while you prepare it.
  14. Hello Elsie, Let me see if I can unpack some of the comments made in this thread for you. When cooking, some thing happen quickly and other things happen slowly. In traditional cooking, few recipes take advantage of these slow processes. Sous vide cooking makes controlling these slow processes practical. The slow processes, like the enzymatic break down of collagen, mostly increase tenderness. If what you want to cook is tender, such as fish, then you want to limit the slow processes by not keeping the food in the water bath for too long. So if you are cooking tender pork chops, then you'll probably just want to bring them up to temperature and then hold them at that temperature until they're pasteurized. If your pork chops aren't very tender — as I find most of today's lean pork — then using these slow processes to increase tenderness is useful. Cooking for a long time at 130°F has the added benefit of making the color of the meat paler. This is why my cooking times are much longer for some cuts of pork chops than those recommended by Chris. Obviously, I recommend reading my free web guide and my new review article (which discusses fast and slow processes in more detail).
  15. It's very hard to accurately predict heating times in a dry oven because the surface heat transfer coefficient, h, is too low (say 15–30 W/m2-K). For example, let's look at a variety of h values and see how it changes the heating time of a 50 mm cylinder to 54°C in a 55°C medium: h HH:MM 10 07:10 15 04:57 20 03:58 25 03:24 30 02:59 40 02:32 50 02:15 65 02:00 80 01:50 100 01:42 150 01:32 200 01:27 250 01:24 300 01:22 400 01:20 500 01:18 650 01:17 800 01:16 1000 01:15 As for food safety, I just don't have enough data on how sterile the interior of intact muscle meat really is. Obviously there's a huge problem with mechanically tenderized meat. There are other reasons why the meat's interior might not be sterile, such as a dirty knife being used to exsanguinate the animal. The meat could always be pasteurized using ionizing radiation before rapid-aging (or rapid-conditioning) but the general-population's fear of radiation precludes this option. High-pressure probably can't be used because it'd denature many of the enzymes need in the aging process. I'm sorry I don't have a better answer for you. There may be research out there, but I don't currently have the time to look for it. I don't do rapid-aging myself but I'm a very risk-adverse person. Edit: Fixed a typo and added more h values.
  16. That was my experience as well when testing recipes for my cookbook. A family friend gave many several cuts from deer (and elk and antelope) that he'd bow-hunted and I didn't have any problem with gaminess or mushiness. I haven't read that section of MC so I can't comment on their results, just that I didn't have a problem with the meat I was given.
  17. Hi Bob, I'm not sure when the first issue will be out. The emails I've gotten from Elsevier with the proofs to my article seem to indicate that it is for real and will be published very soon. I promise that I'll post more information as it becomes available.
  18. Some of you may be interested in the review article, Sous Vide Cooking: A Review, that I wrote for the first issue of the International Journal of Gastronomy and Food Science — a new peer-reviewed Elsevier journal. I'm not sure when the first issue of the journal will be out, but I'm guessing it'll come out later this month or next. Being a review article, it only has a few new things and mostly draws from my guide and a few of my ‘review’ posts in this topic.
  19. Doing calculations from frozen is much more complicated. I'm the first to admit that my heating-from-frozen tables aren't what I'd like them to be; that's why I don't have pasteurization-from-frozen tables! I coded up some numerical methods back in 2009 and they seemed like they worked great until I actually compared them with experiments. I think if I had about a hundred hours I could improve my numerics to a point that I'd trust them for pasteurization, but don't count on me having that kind of time anytime in 2012.
  20. vengroff is doing what I do. We compute the destruction of pathogens based on the temperature throughout the heating process. Indeed, this is why some of the heating times in Table 2.2 are longer than the pasteurization times in Table 4.1. (Though, my tables always assume that the core is being pasteurized.) For healthy people, a 3D reduction of the Salmonella species is generally considered sufficient and that might be a nice option. MC takes the simpler approach that you just mentioned. The tables from the 2009 Food Code also don't take this into account except at the highest temperatures. Nonetheless, what we do is science-based and well justified in the literature.
  21. I discussed this in some detail upthread. The 4-hour rule doesn't assume that you'll be pasteurizing the food and so vegetative (or active) pathogens are the main concern. Suppose you're heating a piece of fish to a rare-doneness (e.g., 42°C/108°F) then any pathogenic microorganisms in or on the fish will multiply rapidly at this temperature and you have to limit the time to keep these pathogens from reaching a level that'll make a healthy person ill. Indeed, FDA (2011) Table A-2 recommends less than 2 hours above 21°C/70°F and 1 hour above 30°C/86°F to keep these vegetative pathogens from reaching dangerous levels. [Most healthy people have an estimated illness dose of more than 105 microorganisms of the Salmonella species and the pathogenic strains of E. coli; most purchasers require that the raw ingredients have less than 10 Salmonella or E. coli per gram; these times correspond to less than five to ten generations (25=32 and 210=1,024) generations (depending on the pathogen) so a 100 g serving would have less than 102+1.5+1 = 104.5 to 102+3+1 = 106 vegetative pathogens.] Limiting heating time from fridge to 54.4°C/130°F to less than six hours and then pasteurizing is mainly concerned with toxin formation. The main toxin-forming pathogens are Bacillus cereus, the Clostridium species, and Staphylococcus aureus; FDA (2011) Table A-2 gives a maximum exposure time of 2 hours above 21°C/70°F for the Clostridium species and 3 hours above 21°C/70°F for Bacillus cereus and Staphylococcus aureus. From my mathematical models, this corresponds to a maximum heating time of six hours from fridge to 54.4°C/130°F.
  22. Note: I made a small typo in Step 7: It should say “repeat steps 5 & 6”.
  23. Since you asked me to chime in, I will. Mikels did everything right. The rapid chilling reduces the risk of sporulation and freezing prevents any pathogens that are present from growing. As Bob pointed out, Mikels did not need to repasteurize but just reheat (or rethermalize, as some like to call it). When might you have problems with heating-and-cooling repeatedly? The biggest problem is texture degradation, partly from longer cooking times and partly from ice-crystals formation. Neither of these is a big concern with brisket but are an issue with tender meat such as steaks, chicken breasts, fish, etc. The food safety question is more complicated, but just because it hasn't been very well studied and so I can only give you my (expert) opinion. Let's look at the risks at each step: You buy your raw food and it usually has millions of microorganisms on and in it — most of which are spoilage bacteria. To reduce the risk of the harmful pathogens from multiplying rapidly, you store your meat, fish, and poultry in a refrigerator (or in a freezer) and use it before its “best by” date. You vacuum-seal your raw food. Vacuum packaging doesn't reduce any of the microorganisms, so you must either return it to the refrigerator or freezer or (in most cases) begin cooking immediately in a temperature controlled water bath. You heat your vacuumized raw food in a temperature controlled water bath or steam oven. This stage is known as a “critical control point” in the food safety biz. As the food heats, microorganisms begin to multiply rapidly with most of them growing fastest between 30°C (85°F) and 50°C (120°F). If you're not heating to pasteurize, then minimizing the growth of these pathogens is a critical step. For example, fish cooked rare or medium-rare shouldn't spend more than about an hour between fridge and table. Once the temperature of the food exceeds about 52.3°C (126.1°F), then all the known food pathogens stop growing and begin to die. (Johnson et al. (1983) reported that Bacillus cereus could multiply at 131°F/55°C, but no one else has demonstrated growth at this temperature and so Clostridium perfringens is used instead.) Many recommend that the core of the food reach 54.4°C (130°F) within 6 hours (even me) to keep C. perfringens to less then 10 generations (or less than 2 hr 10 min between 35°C and 52°C as per Willardsen et al. (1977)), but this is not a critical control point: While C. perfringens does produce toxins, it only produces them while sporulating (and so isn't a concern when heating) and the toxin is easily destroyed by heating (since it's destroyed in only 10 min at 60°C); see, for instance, Chap. 24 of James M. Jay's Modern Food Microbiology, 6th ed. (2000). So, it's only the vegetative form of C. perfringens that's a hazard when heating and they're easily reduced to safe level when pasteurizing for Salmonella, Listeria, or E. coli. Therefore, heating to 54.4°C (130°F) within six hours is only a critical control point if the food isn't then being pasteurized and the growth of other pathogens is often a greater concern. However, at some point the growth and toxin formation of S. aureus, C. botulinum, and B. cereus does become a critical control point since these toxins aren't destroyed when pasteurizing for active (vegetative) pathogens. If pasteurizing, then you hold the food at 52.3°C (126.1°F) or above until any active (or vegetative) pathogens have been reduced to a safe level. What's a safe level? That's a surprisingly tricky question. First, we don't really know how many vegetative pathogens will make you sick; about 15–20% of the US and UK population is more susceptible to foodborne disease (Lund and O'Brien 2011). Moreover, without knowing how many pathogens are present in the raw food or after heating, then we don't know how many we need to reduce even if we knew what a safe level is. (For an interesting discussion on this, I highly recommend “Scientific Criteria to Ensure Safe Food” from the National Academies Press (2003).) Therefore, we make an informed guess that a million to one reduction in Listeria monocytogenes, a ten million to one reduction in the Salmonella species, and a hundred thousand to one reduction in E. coli will be sufficient. You can, of course, see my guide for computed times for different thicknesses of food and for different cooking temperatures. If you eat the cooked food immediately, you don't have to worry about any additional pathogens growing. If you chill the food for later use — as I frequently do — then it's important to follow a few simple steps: You have to chill the food rapidly to limit sporulation of C. perfringens (since it creates its toxins while sporulating); we usually do this in an ice-water bath (see my guide for cooling times). You must leave it in its vacuumized pouch to prevent recontamination. You need to properly store the food in either a refrigerator (see my guide for times at different temperatures) or in a freezer: proper storage is critical in preventing spores of C. botulinum and B. cereus from outgrowing and producing toxins, which aren't destroyed when reheating (neither S. aureus nor B. cereus toxins are destroyed by heating and C. botulinum toxins need either a high temperature or a very long time). [*]When you reheat (or rethermalize) your chilled food, your main concerns are the toxin formation of C. botulinum and B. cereus since you should have already reduced the non-spore forming pathogens in step 3. Reheating to a core temperature of 54.4°C (130°F) within 6 hours should be sufficient. [*]Now, suppose you want to repeat steps 3 & 5. If you germinate and then kill C. perfringens, C. botulinum, and B. cereus over and over, you'll eventually destroy all the spore-forming bacteria (see sauce sterilization using Tyndallization for more information), but I don't know if you'll destroy all of them before a dangerous level of toxins has accumulated. I think you'd be safe if you cook-chill-reheat-chill-reheat-serve but I'm not comfortable recommending more than two reheat-chill cycles before serving. Further research is clearly required for a definitive answer.
  24. That's excellent advice dougal. I don't use a reducing sugar (glucose, fructose, or lactose) wash when searing with a blowtorch either but I find it useful when pan searing (since even a smoking hot pan isn't nearly as hot as a blowtorch's flame). You need very little reducing sugar to enhance the Maillard reaction, I recommend using a 3–4% corn syrup or glucose solution or about ½ teaspoon syrup in a ¼ cup water — at this concentration, you're unlikely to taste any added sweetness but should taste an improved flavor profile. As always, see the Maillard section of my guide for more information.
  25. I'd try 2–4 days at 130˚F (55˚C) for the lamb neck; give it a squeeze (through the pouch) once a day to judge if it's tender enough yet; I'm guessing that 3 days will give you what you want.
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