Jump to content


participating member
  • Posts

  • Joined

  • Last visited

Contact Methods

  • Website URL

Profile Information

  • Location
    Arvada, CO

Recent Profile Visitors

2,431 profile views
  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.
  • Create New...