Thank you for that information . According to your time/ temp table my cb is definately pasteurized. I hit 140° and was there forever. My question is pasteurization the same a fully cooked? Or is it safe for storage and need to be cooked.
It's fully cooked... All bacteria are killed and safe for human consumption...
Bacteria that are detrimental to us start dying at around 120F.. Time continues to kill them...
Higher temps kill them faster... at lower temps it just takes longer....
A Practical Guide to Sous Vide Cooking (douglasbaldwin.com)
Part I: Technique
1. Food Safety
Non-technical Summary
You cook food to make it safe and tasty. Sous vide cooking is no different: you just have more control over both taste and safety. In sous vide cooking, you pick the temperature that equals the doneness you want and then you cook it until it's safe and has the right texture.
Raw food often has millions of microorganisms on or in it; most of these microorganisms are spoilage or beneficial bacteria and won't make you sick. But some of these microorganisms are pathogens that can make you sick if you eat too many of them. Most food pathogens are bacteria, but some are viruses, funguses, and parasites. Your yogurt, aged cheese, and cured salami can have hundreds of millions of spoilage or beneficial bacteria in every serving; but they don't make you sick because spoilage and beneficial bacteria are distinct from pathogens. Since pathogens don't spoil food, you can't see, smell, or taste them.
While there are many ways to kill food pathogens, cooking is the easiest. Every food pathogen has a temperature that it can't grow above and a temperature it can't grow below. They start to die above the temperature that they stop growing at and the higher above this temperature you go, the faster they die. Most food pathogens grow fastest a few degrees below the temperature that they start to die. Most food pathogens stop growing by 122°F (50°C), but the common food pathogen
Clostridium perfringens can grow at up to 126.1°F (52.3°C). So in sous vide cooking, you usually cook at 130°F (54.4°C) or higher. (You could cook your food at slightly lower temperatures, but it would take you a lot longer to kill the food pathogens.)
While there are a lot of different food pathogens that can make you sick, you only need to worry about killing the toughest and most dangerous. The three food pathogens you should worry about when cooking sous vide are the
Salmonella species,
Listeria monocytogenes, and the pathogenic strains of
Escherichia coli.
Listeria is the hardest to kill but it takes fewer
Salmonella or
E. coli bacteria to make you sick. Since you don't know how many pathogens are in your food, most experts recommend that you cook your food to reduce:
Listeria by at least a million to one;
Salmonella by ten million to one; and
E. coli by a hundred thousand to one. You can easily do this when you cook sous vide: you just keep your food in a 130°F (54.4°C) or hotter water bath until enough bacteria have been killed.
How long does it take for you to reduce, say,
Listeria by a million to one? Your water bath temperature is very important: when cooking beef, it'll take you four times longer at 130°F (54.4°C) as it does at 140°F (60°C). What you are cooking is also important: at 140°F (60°C), it'll take you about 60% longer for chicken as it does for beef. Other things, like salt and fat content, also affect how long it takes; but these difference are small compared with temperature and species.
Since sous vide cooking in a water bath is very consistent, I've calculated the worst-case cooking times so you don't have to. My worst-case cooking times are based on the temperature, thickness, and type of the food and will give at least a million to one reduction in
Listeria, a ten million to one reduction in
Salmonella, and a hundred thousand to one reduction in
E. coli:
- Table 3.1 has the pasteurization times for fish;
- Table 4.1 has the pasteurization times for poultry; and
- Table 5.1 has the pasteurization times for meat (beef, pork, and lamb).
Thick pieces of food, like a rib-roast, take much longer to cook and cool than thin pieces of food: a steak that is twice as thick takes about four times longer to cook and cool! So unless you are cooking a rib-roast for a party, you should cut your food into individual portions that can be cooled quickly and easily. It's important that your pouches of food do not crowd or overlap each other in your water bath and are completely under the water; otherwise my tables will underestimate the cooking time.
If you're not going to eat all your food immediately, then you need to know that some bacteria are able to make spores. Spores themselves will not make you sick, but they can become active bacteria that could. Cooking to kill active bacteria like
Listeria,
Salmonella, and
E. coli will leave these spores unharmed. If you keep your food hot, then the spores will not become active bacteria. But when you cool your food, the spores can become active bacteria: if you cool your food too slowly or store it for too long, then these active bacteria can multiply and make you sick. To keep these spores from becoming active bacteria, you must quickly cool your food – still sealed in its pouch – in ice water that is at least half ice until it's cold all the way through. You can then store your food in your refrigerator for a few days or freeze it for up to a year.
Table 1.1 has approximate cooling times in ice water based on thickness and shape.
If you want to learn more about food safety, please continue reading below; see my book
Sous Vide for the Home Cook;
the excellent free guide by Dr. Snyder;
the FDA's food safety website; or your local health and human services department.
Cooling Time to 41°F (5°C) in Ice Water
| Thickness | Slab-like | Cylinder-like | Sphere-like |
| 5 mm | 5 min | 3 min | 3 min |
| 10 mm | 14 min | 8 min | 6 min |
| 15 mm | 25 min | 14 min | 10 min |
| 20 mm | 35 min | 20 min | 15 min |
| 25 mm | 50 min | 30 min | 20 min |
| 30 mm | 1¼ hr | 40 min | 30 min |
| 35 mm | 1½ hr | 50 min | 35 min |
| 40 mm | 1¾ hr | 1 hr | 45 min |
| 45 mm | 2¼ hr | 1¼ hr | 55 min |
| 50 mm | 2¾ hr | 1½ hr | 1 hr |
| 55 mm | 3¼ hr | 1¾ hr | 1¼ hr |
| 60 mm | 3¾ hr | 2 hr | 1½ hr |
| 65 mm | 4¼ hr | 2¼ hr | 1¾ hr |
| 70 mm | 4¾ hr | 2¾ hr | 2 hr |
| 75 mm | 5½ hr | 3 hr | 2¼ hr |
| 80 mm | — | 3½ hr | 2½ hr |
| 85 mm | — | 3¾ hr | 2¾ hr |
| 90 mm | — | 4¼ hr | 3 hr |
| 95 mm | — | 4¾ hr | 3½ hr |
| 100 mm | — | 5 hr | 3¾ hr |
| 105 mm | — | 5½ hr | 4 hr |
| 110 mm | — | 6 hr | 4½ hr |
| 115 mm | — | — | 4¾ hr |
Table 1.1: Approximate cooling time from 130–175°F (55–80°C) to 41°F (5°C) in an ice water bath that's at least half ice. (My calculations assume that the food's thermal diffusivity is 1.1×10-7m2/s and the ice water bath has a surface heat transfer coefficient of 100 W/m2-K. For more details, see
Appendix A.)
Technical Background
My goal is to maximizing taste and minimizing the risk from food pathogens. While pathogenic microorganisms can be controlled with acids, salts, and some spices, sous vide cooking relies heavily on temperature control (Rybka-Rodgers, 2001).
You were probably taught that there’s a “danger zone” between 40°F and 140°F (4.4°C and 60°C). These temperatures aren’t quite right: it’s well known that food pathogens can only multiply between 29.7°F (-1.3°C) and 126.1°F (52.3°C), while spoilage bacteria begin multiplying at 23°F (-5°C) (Snyder, 2006; Juneja et al., 1999; FDA, 2011). Moreover, contrary to popular belief, food pathogens and toxins cannot be seen, smelt, or tasted.
So why were you taught that food pathogens stop multiplying at 40°F (4.4°C) and grow all the way up to 140°F (60°C)? Because it takes days for food pathogens to grow to a dangerous level at 40°F (4.4°C) (FDA, 2011) and it takes many hours for food to be made safe at just above 126.1°F (52.3°C) – compared with only about 12 minutes (for meat) and 35 minutes (for poultry) to be made safe when the coldest part is 140°F (60°C) (FSIS, 2005; FDA, 2009, 3-401.11.B.2). Indeed, the food pathogens that can multiply down to 29.7°F (-1.3°C) –
Yersinia enterocolitica and
Listeria monocytogenes – can only multiply about once per day at 40°F (4.4°C) and so you can hold food below 40°F (4.4°C) for five to seven days (FDA, 2011). At 126.1°F (52.3°C), when the common food pathogen
Clostridium perfringens stops multiplying, it takes a very long time to reduce the food pathogens we’re worried about – namely the
Salmonella species,
Listeria monocytogenes, and the pathogenic strains of
Escherichia coli – to a safe level; in a 130°F (54.4°C) water bath (the lowest temperature I recommend for cooking sous vide) it’ll take you about 2½ hours to reduce
E. coli to a safe level in a 1 inch (25 mm) thick hamburger patty and holding a hamburger patty at 130°F (54.4°C) for 2½ hours is inconceivable with traditional cooking methods – which is why the “danger zone” conceived for traditional cooking methods doesn’t start at 130°F (54.4°C). [Note that 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.]
My goal is to maximizing taste and minimizing the risk from food pathogens. While pathogenic microorganisms can be controlled with acids, salts, and some spices, sous vide cooking relies heavily on temperature control (Rybka-Rodgers, 2001).
You were probably taught that there's a “danger zone” between 40°F and 140°F (4.4°C and 60°C). These temperatures aren't quite right: it's well known that food pathogens can only multiply between 29.7°F (-1.3°C) and 126.1°F (52.3°C), while spoilage bacteria begin multiplying at 23°F (-5°C) (Snyder, 2006; Juneja et al., 1999; FDA, 2011). Moreover, contrary to popular belief, food pathogens and toxins cannot be seen, smelt, or tasted.
So why were you taught that food pathogens stop multiplying at 40°F (4.4°C) and grow all the way up to 140°F (60°C)? Because it takes days for food pathogens to grow to a dangerous level at 40°F (4.4°C) (FDA, 2011) and it takes many hours for food to be made safe at just above 126.1°F (52.3°C) – compared with only about 12 minutes (for meat) and 35 minutes (for poultry) to be made safe when the coldest part is 140°F (60°C) (FSIS, 2005; FDA, 2009, 3-401.11.B.2). Indeed, the food pathogens that can multiply down to 29.7°F (-1.3°C) –
Yersinia enterocolitica and
Listeria monocytogenes – can only multiply about once per day at 40°F (4.4°C) and so you can hold food below 40°F (4.4°C) for five to seven days (FDA, 2011). At 126.1°F (52.3°C), when the common food pathogen
Clostridium perfringens stops multiplying, it takes a very long time to reduce the food pathogens we're worried about – namely the
Salmonella species,
Listeria monocytogenes, and the pathogenic strains of
Escherichia coli – to a safe level; in a 130°F (54.4°C) water bath (the lowest temperature I recommend for cooking sous vide) it'll take you about 2½ hours to reduce
E. coli to a safe level in a 1 inch (25 mm) thick hamburger patty and holding a hamburger patty at 130°F (54.4°C) for 2½ hours is inconceivable with traditional cooking methods – which is why the “danger zone” conceived for traditional cooking methods doesn't start at 130°F (54.4°C). [Note that 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.]
We can divide sous vide prepared foods into three categories: (i) raw or unpasteurized, (ii) pasteurized, and (iii) sterilized. Most people cook food to make it more palatable and to kill most the pathogenic microorganisms on or in it. Killing enough active, multiplying food pathogens to make your food safe is called pasteurization. Some bacteria are also able to form spores that are very resistant to heat and chemicals; heat the food to kill both the active microorganisms and the spores is called sterilization. [Sterilization is typically achieved by using a pressure cooker to heat the center of the food to 250°F (121°C) for 2.4 minutes (Snyder, 2006). To sterilize food sous vide, you'll need special retort plastic bags that can be used in a pressure cooker or an autoclave.]
Foods you've pasteurized must either be eaten immediately or rapidly chilled and refrigerated to prevent the outgrowth and multiplication of spores. Moreover, the center of the food should reach 130°F (54.4°C) within 6 hours to prevent the toxin producing pathogen
Clostridium perfringens from multiplying to dangerous levels (Willardsen et al., 1977).
Raw or unpasteurized food must never be served to highly susceptible or immune compromised people. Even for immune competent individuals, it's important that raw and unpasteurized foods are consumed before food pathogens have had time to multiply to harmful levels. With this in mind, the US Food Code requires that such food can only be between 41°F (5°C) and 130°F (54.4°C) for less than 4 hours (FDA, 2009, 3-501.19.B).
Pasteurization is a combination of both temperature and time. Consider the common food pathogen
Salmonella species. At 140°F (60°C), all the
Salmonella in a piece of ground beef doesn't instantly die – it is reduced by a factor ten every 5.48 minutes (Juneja et al., 2001). This is often referred as a one decimal reduction and is written D606.0 = 5.48 minutes, where the subscript specifies the temperature (in °C) that the D-value refers to and the superscript is the z-value (in °C). The z-value specifies how the D-value changes with temperature; increasing the temperature by the z-value decreases the time needed for a one decimal reduction by a factor ten. So, D666.0 = 0.55 minutes and D546.0 = 54.8 minutes. How many decimal reductions are necessary depends on how contaminated the beef is and how susceptible you are to
Salmonella species – neither of which you're likely to know. FSIS (2005) recommends a 6.5 decimal reduction of
Salmonella in beef, so the coldest part should be at least 140°F (60°C) for at least 6.5D606.0 = 35.6 minutes.
The rate at which the bacteria die depends on many factors, including temperature, meat species, muscle type, fat content, acidity, salt content, certain spices, and water content. The addition of acids, salts, or spices can all decrease the number of active pathogens – this is why mayonnaise (with a pH less than 4.1) does not need to be cooked. Chemical additives like sodium lactate and calcium lactate are often used in the food industry to reduce the risk of spore forming pathogens like
Clostridium species and
Bacillus cereus (Aran, 2001; Rybka-Rodgers, 2001).
Pathogens of Interest
Sous vide processing is used in the food industry to extend the shelf-life of food products; when pasteurized sous vide pouches are held at below 38°F (3.3°C), they remain safe and palatable for three to four weeks (Armstrong and McIlveen, 2000; Betts and Gaze, 1995; Church, 1998; Creed, 1995; González-Fandos et al., 2004, 2005; Hansen et al., 1995; Mossel and Struijk, 1991; Nyati, 2000a; Peck, 1997; Peck and Stringer, 2005; Rybka-Rodgers, 2001; Simpson et al., 1994; Vaudagna et al., 2002).
The simplest and safest method of sous vide cooking is cook-hold: the raw (or partially cooked) ingredients are vacuum sealed, pasteurized, and then held at 130°F (54.4°C) or above until served. While hot holding the food will prevent any food pathogens from growing, meat and vegetables will continue to soften and may become mushy if held for too long. How long is too long depends on both the holding temperature and what is being cooked. Most foods have an optimal holding time at a given temperature; adding or subtracting 10% to this time won't change the taste or texture noticeably; holding for up to twice this time is usually acceptable.
For cook-hold sous vide, the main pathogens of interest are the
Salmonella species and the pathogenic strains of
Escherichia coli. There are, of course, many other food pathogens but these two species are relatively heat resistant and require very few active bacteria (measured in colony forming units, CFU, per gram) to make you sick. Since you're unlikely to know how contaminated your food is or how many of these bacteria your (or your guests) immune system can handle, most experts recommend a 6.5 to 7 decimal reductions of all
Salmonella species and a 5 decimal reduction of pathogenic
E. coli.
The most popular methods of sous vide cooking are cook-chill and cook-freeze – raw (or partially cooked) ingredients are vacuum sealed, pasteurized, rapidly chilled (to avoid sporulation of
C. perfringens (Andersson et al., 1995)), and either refrigerated or frozen until reheating for service. Typically, the pasteurized food pouches are rapidly chilled by placing them in an ice water bath for at least the time listed in Table 1.1.
For cook-chill sous vide,
Listeria monocytogenes and the spore forming pathogenic bacteria are our pathogens of interest. That's because
Listeria is the most heat resistant non-spore forming pathogen and can grow at refrigerator temperatures (Nyati, 2000b; Rybka-Rodgers, 2001), but appears to require more bacteria to make you sick than
Salmonella or
E. coli. Most experts recommend a 6 decimal reduction in
Listeria if you don't know the contamination level of your food.
While keeping your food sealed in plastic pouches prevents recontamination after cooking, spores of
Clostridium botulinum,
C. perfringens, and
B. cereus can all survive the mild heat treatment of pasteurization. Therefore, after rapid chilling, the food must either be frozen or held at
- below 36.5°F (2.5°C) for up to 90 days,
- below 38°F (3.3°C) for less than 31 days,
- below 41°F (5°C) for less than 10 days, or
- below 44.5°F (7°C) for less than 5 days
to prevent spores of non-proteolytic
C. botulinum from outgrowing and producing deadly neurotoxin (Gould, 1999; Peck, 1997).
A few sous vide recipes use temperature and time combinations which can reduce non-proteolytic
C. botulinum to a safe level; specifically, a 6 decimal reduction in non-proteolytic
C. botulinum requires 520 minutes (8 hours 40 minutes) at 167°F (75°C), 75 minutes at 176°F (80°C), or 25 minutes at 185°F (85°C) (Fernández and Peck, 1999). The food may then be stored at below 39°F (4°C) indefinitely, the minimum temperature at which
B. cereus can grow (Andersson et al., 1995). While O'Mahony et al. (2004) found that the majority of pouches after vacuum packaging had high levels of residual oxygen, this doesn't imply that the
Clostridium species – which require the absence of oxygen to grow – aren't a problem since the interior of the food often has an absence of oxygen. Most other food pathogens are able to grow with or without oxygen.
2. Basic Technique
Sous vide typically consists of three stages: preparing for packaging, cooking and finishing.
In almost all cases, the cooking medium is either a water bath or a convection steam oven. Convection steam ovens allow large quantities of food to be prepared, but do not heat uniformly enough to use the tables in this guide. Sheard and Rodger (1995) found that none of the convection steam ovens they tested heated sous vide pouches uniformly when fully loaded. Indeed, it took the slowest heating (standardized) pouch 70%–200% longer than the fastest heating pouch to go from 68°F to 167°F (20°C to 75°C) when set to an operating temperature of 176°F (80°C). They believe this variation is a result of the relatively poor distribution of steam at temperatures below 212°F (100°C) and the ovens dependence on condensing steam as the heat transfer medium.
In contrast, circulating water baths heat very uniformly and typically have temperature swings of less than 0.1°F (0.05°C). To prevent undercooking, it is very important that the pouches are completely submerged and are not tightly arranged or overlapping (Rybka-Rodgers, 1999). At higher cooking temperatures, the pouches often balloon (with water vapor) and must be held under water with a wire rack or some other constraint.
Preparing for Packaging
Seasoning
Seasoning can be a little tricky when cooking sous vide: while many herbs and spices act as expected, others are amplified and can easily overpower a dish. Additionally, aromatics (such as carrots, onions, celery, bell peppers, etc.) will not soften or flavor the dish as they do in conventional cooking methods because the temperature is too low to soften the starches and cell walls. Indeed, most vegetables require much higher temperatures than meats and so must be cooked separately. Finally, raw garlic produces very pronounced and unpleasant results and powdered garlic (in very small quantities) should be substituted.
For long cooking times (of more than a couple hours), some people find that using extra virgin olive oil results in an off, metallic, blood taste. (Since the extra virgin oil is unheated and unrefined during production, it is reasonable that some of the oil will breakdown even at a low temperature if give enough time.) A simple solution is to use grape seed or any other processed oil for longer cooking times; extra virgin olive oil can then be used for seasoning after cooking.
Marinating, Tenderizing and Brining
Since todays meat is younger and leaner than the meat of the past, many cooks marinate, tenderize or brine the meat before vacuum packaging.
Most marinades are acidic and contain either vinegar, wine, fruit juice, buttermilk or yogurt. Of these ingredients, only wine presents any significant problems when cooking sous vide. If the alcohol is not cooked off before marinating, some of it will change phase from liquid to vapor while in the bag and cause the meat to cook unevenly. Simply cooking off the alcohol before marinating easily solves this problem.
Mechanical tenderizing with a Jaccard has become quite common. A Jaccard is a set of thin blades that poke through the meat and cut some of the internal fibers. The Jaccard does not typically leave any obvious marks on the meat and is often used in steak houses. By cutting many of the internal fibers that would typically contract with heat and squeeze out the juices, it can slightly reduce the amount of moisture lost during cooking. For instance, when cooking a chuck steak for 24 hours at 131°F (55°C) the Jaccarded steak lost 18.8% of its weight compared to 19.9% for the non-Jaccarded steak. In general, more liquid weight is lost the longer a piece of meat is cooked at a given temperature– however, this additional weight loss is balanced by the increased tenderness from collagen dissolving into gelatin.
Brining has become increasingly popular in modern cooking, especially when cooking pork and poultry. Typically the meat is placed in a 3 to 10% (30 to 100 grams per liter) salt solution for a couple of hours, then rinsed and cooked as usual. Brining has two effects: it dissolves some of the support structure of the muscle fibers so they cannot coagulate into dense aggregates and it allows the meat to absorb between 10–25% of its weight in water (which may include aromatics from herbs and spices) (Graiver et al., 2006; McGee, 2004). While the meat will still lose around 20% of its weight when cooked, the net effect will be a loss of only about 0–12% of its original weight.
Cooking
There are two schools of thought when cooking sous vide: either the temperature of the water bath is (i) just above or (ii) significantly higher than the desired final core temperature of the food. While (ii) is closer to traditional cooking methods and is used extensively in (Roca and Brugués, 2005), (i) has several significant advantages over (ii). Through out this guide, I define just above as 1°F (0.5°C) higher than the desired final core temperature of the food.
When cooking in a water bath with a temperature significantly higher than the desired final core temperature of the food, the food must be removed from the bath once it has come up to temperature to keep it from overcooking. This precludes pasteurizing in the same water bath that the food is cooked in. Since there is significant variation in the rate at which foods heat (see
Appendix A), a needle temperature probe must be used to determine when the food has come up to temperature. To prevent air or water from entering the punctured bag, the temperature probe must be inserted through closed cell foam tape. Even when using closed cell foam tape (which is similar to high density foam weather stripping), air will be able to enter the plastic pouch once the temperature probe is removed.
In contrast, cooking in a water bath with a temperature just above the desired final core temperature of the food means the food can remain in the water bath (almost) indefinitely without being overcooked. Thus, food can be pasteurized in the same water bath it is cooked in. While cooking times are longer than traditional cooking methods, the meat comes up to temperature surprisingly quickly because the thermal conductivity of water is 23 times greater than that of air. Moreover, temperature probes are not necessary because maximum cooking times can be tabulated (see
Appendix A and Tables 2.2 and 2.3).
Effects of Heat on Meat
Muscle meat is roughly 75% water, 20% protein and 5% fat and other substances. The protein in meat can be divided into three groups: myofibrillar (50–55%), sarcoplasmic (30–34%) and connective tissue (10–15%). The myofibrillar proteins (mostly myosin and actin) and the connective tissue proteins (mostly collagen) contract when heated, while the sarcoplasmic proteins expand when heated. These changes are usually called denaturation.
During heating, the muscle fibers shrink transversely and longitudinally, the sarcoplasmic proteins aggregate and gel, and connective tissues shrink and solubilize. The muscle fibers begin to shrink at 95–105°F (35–40°C) and shrinkage increases almost linearly with temperature up to 175°F (80°C). The aggregation and gelation of sarcoplasmic proteins begins around 105°F (40°C) and finishs around 140°F (60°C). Connective tissues start shrinking around 140°F (60°C) but contract more intensely over 150°F (65°C).
The water-holding capacity of whole muscle meat is governed by the shrinking and swelling of myofibrils. Around 80% of the water in muscle meat is held within the myofibrils between the thick (myosin) and thin (actin) filaments. Between 105°F and 140°F (40°C and 60°C), the muscle fibers shrink transversely and widen the gap between fibers. Then, above 140°F–150°F (60°C–65°C) the muscle fibers shrink longitudinally and cause substantial water loss; the extent of this contraction increases with temperature.
For more information, see either the nontechnical description in (McGee, 2004, Chap 3) or the excellent review article by Tornberg (2005).
Tender Meat
When cooking tender meats, we just need to get the center up to temperature and, if pasteurizing, hold it there from some length of time. Cooking times depend critically on the thickness of the meat: doubling the thickness of the meat increases the cooking time four fold!
| Rare | Medium-Rare | Medium | | | |
| Meat | 125°F | (50°C) | 130°F | (55°C) | 140°F | (60°C) |
| Fish | 108°F | (42°C) | 122°F | (50°C) | 140°F | (60°C) |
Table 2.1: Temperatures corresponding to rare, medium-rare and medium in meat and fish.
While there is no consensus as to what temperatures rare, medium-rare and medium correspond to, I use the temperatures in Table 2.1. In general, the tenderness of meat increases from 122°F to 150°F (50°C to 65°C) but then decreases up to 175°F (80°C) (Powell et al., 2000; Tornberg, 2005). The approximate heating times for thawed and frozen meats are given in Tables 2.2 and 2.3. For a complete discussion on how these times were computed, please see
Appendix A.
Heating Time from 41°F (5°C) to 1°F (0.5°C) Less Than the Water Bath's Temperature
| Thickness | Slab-like | Cylinder-like | Sphere-like |
| 5 mm | 5 min | 5 min | 4 min |
| 10 mm | 19 min | 11 min | 8 min |
| 15 mm | 35 min | 18 min | 13 min |
| 20 mm | 50 min | 30 min | 20 min |
| 25 mm | 1¼ hr | 40 min | 25 min |
| 30 mm | 1½ hr | 50 min | 35 min |
| 35 mm | 2 hr | 1 hr | 45 min |
| 40 mm | 2½ hr | 1¼ hr | 55 min |
| 45 mm | 3 hr | 1½ hr | 1¼ hr |
| 50 mm | 3½ hr | 2 hr | 1½ hr |
| 55 mm | 4 hr | 2¼ hr | 1½ hr |
| 60 mm | 4¾ hr | 2½ hr | 2 hr |
| 65 mm | 5½ hr | 3 hr | 2¼ hr |
| 70 mm | — | 3½ hr | 2½ hr |
| 75 mm | — | 3¾ hr | 2¾ hr |
| 80 mm | — | 4¼ hr | 3 hr |
| 85 mm | — | 4¾ hr | 3½ hr |
| 90 mm | — | 5¼ hr | 3¾ hr |
| 95 mm | — | 6 hr | 4¼ hr |
| 100 mm | — | — | 4¾ hr |
| 105 mm | — | — | 5 hr |
| 110 mm | — | — | 5½ hr |
| 115 mm | — | — | 6 hr |
Table 2.2: Approximate heating times for thawed meat to 1°F (0.5°C) less than the water bath's temperature. You can decrease the time by about 13% if you only want to heat the meat to within 2°F (1°C) of the water bath's temperature.
Do not use these times to compute pasteurization times: use the pasteurization tables below. (My calculations assume that the water bath's temperature is between 110°F (45°C) and 175°F (80°C). I use a typical thermal diffusivity of 1.4×10-7 m2/s and surface heat transfer coefficient of 95 W/m2-K.) For thicker cuts and warmer water baths, heating time may (counter-intuitively) be
longer than pasteurization time.
Heating Time from Frozen to 1°F (0.5°C) Less Than the Water Bath's Temperature
| Thickness | Slab-like | Cylinder-like | Sphere-like |
| 5 mm | 7 min | 7 min | 6 min |
| 10 mm | 30 min | 17 min | 12 min |
| 15 mm | 50 min | 30 min | 20 min |
| 20 mm | 1¼ hr | 40 min | 30 min |
| 25 mm | 1¾ hr | 55 min | 40 min |
| 30 mm | 2¼ hr | 1¼ hr | 55 min |
| 35 mm | 3 hr | 1½ hr | 1¼ hr |
| 40 mm | 3½ hr | 2 hr | 1½ hr |
| 45 mm | 4½ hr | 2½ hr | 1¾ hr |
| 50 mm | 5¼ hr | 2¾ hr | 2 hr |
| 55 mm | 6¼ hr | 3¼ hr | 2½ hr |
| 60 mm | 7¼ hr | 4 hr | 2¾ hr |
| 65 mm | 8¼ hr | 4½ hr | 3¼ hr |
| 70 mm | — | 5 hr | 3¾ hr |
| 75 mm | — | 5¾ hr | 4¼ hr |
| 80 mm | — | 6½ hr | 4¾ hr |
| 85 mm | — | 7¼ hr | 5¼ hr |
| 90 mm | — | 8 hr | 5¾ hr |
| 95 mm | — | 8¾ hr | 6¼ hr |
| 100 mm | — | — | 7 hr |
| 105 mm | — | — | 7½ hr |
| 110 mm | — | — | 8¼ hr |
| 115 mm | — | — | 9 hr |
Table 2.3: Approximate heating times for frozen meat to 1°F (0.5°C) less than the water bath's temperature. You can decrease the time by about 13% if you only want to heat the meat to within 2°F (1°C) of the water bath's temperature.
Do not use these times to compute pasteurization times: use the pasteurization tables below. (My calculations assume that the water bath's temperature is between 110°F (45°C) and 175°F (80°C). I use a typical thermal diffusivity of 1.4×10-7 m2/s and surface heat transfer coefficient of 95 W/m2-K.)
If the food is not being pasteurized (as is the case with fish and rare meat), it is important that the food come up to temperature and be served within four hours. Unlike conventional cooking methods, this is easily accomplished by cutting the food into individual portion sizes before cooking–which is why cooking times over four hours are not shown for temperatures below 131°F (55°C). It is important that only immune-competent individuals consume unpasteurized food and that they understand the risks associated with eating unpasteurized food.
Tough Meat
Prolonged cooking (e.g., braising) has been used to make tough cuts of meat more palatable since ancient times. Indeed, prolonged cooking can more than double the tenderness of the meat by dissolving all the collagen into gelatin and reducing inter-fiber adhesion to essentially nothing (Davey et al., 1976). At 176°F (80°C), Davey et al. (1976) found that these effects occur within about 12–24 hours with tenderness increasing only slightly when cooked for 50 to 100 hours.
At lower temperatures (120°F/50°C to 150°F/ 65°C), Bouton and Harris (1981) found that tough cuts of beef (from animals 0–4 years old) were the most tender when cooked to between 131°F and 140°F (55°C and 60°C). Cooking the beef for 24 hours at these temperatures significantly increased its tenderness (with shear forces decreasing 26%–72% compared to 1 hour of cooking). This tenderizing is caused by weakening of connective tissue and proteolytic enzymes decreasing myofibrillar tensile strength. Indeed, collagen begins to dissolve into gelatin above 122°F to 131°F (50°C to 55°C) (Neklyudov, 2003; This, 2006). Moreover, the sarcoplasmic protein enzyme collagenase remains active below 140°F (60°C) and can significantly tenderize the meat if held for more than 6 hours (Tornberg, 2005). This is why beef chuck roast cooked in a 131°F–140°F (55°C–60°C) water bath for 24–48 hours has the texture of filet mignon.
Chilling for Later Use
In the food industry, sous vide is used to extend the shelf life of cooked foods. After pasteurizing, the food is rapidly chilled in its vacuum sealed pouch and refrigerated (or frozen) until needed. Before finishing for service, the food is then reheated in a water bath at or below the temperature it was cooked in. Typically, meat is reheated in a 131°F (55°C) water bath for the times listed in Tables 2.2 or 2.3 since the optimal serving temperature for meat is between 120°F–130°F (50°C–55°C).
The danger with cook-chill is that pasteurizing does not reduce pathogenic spores to a safe level. If the food is not chilled rapidly enough or is refrigerated for too long, then pathogenic spores can outgrow and multiply to dangerous levels. For cooling and refrigeration guidelines, see Chapter 1.
Finishing for Service
Since sous vide is essentially a very controlled and precise poach, most food cooked sous vide has the appearance of being poached. So foods like fish, shellfish, eggs, and skinless poultry can be served as is. However, steaks and pork chops are not traditionally poached and usually require searing or saucing. Searing the meat is particularly popular because the Maillard reaction (the browning) adds considerable flavor.
Maillard Reaction
The Maillard or browning reaction is a very complex reaction between amino acids and reducing sugars. After the initial reaction, an unstable intermediate structure is formed which undergoes further changes and produces hundreds of reaction by-products. See McGee (2004) for a nontechnical description or Belitz et al. (2004) for a technical description.
The flavor of cooked meat comes from the Maillard reaction and the thermal (and oxidative) degradation of lipids (fats); the species characteristics are mainly due to the fatty tissues, while the Maillard reaction in the lean tissues provides the savoury, roast and boiled flavors (Mottram, 1998). The Maillard reaction can be increased by adding a reducing sugar (glucose, fructose or lactose), increasing the pH (e.g., adding a pinch of baking soda), or increasing the temperature. Even small increases in pH, greatly increases the Maillard reaction and results in sweeter, nuttier and more roasted-meat-like aromas (Meynier and Mottram, 1995). The addition of a little glucose (e.g., corn syrup) has been shown to increase the Maillard reaction and improve the flavor profile (Meinert et al., 2009). The Maillard reaction occurs noticeably around 265°F (130°C), but produces a boiled rather than a roasted aroma; good browning and a roasted flavor can be achieved at temperatures around 300°F (150°C) with the addition of glucose (Skog, 1993). Although higher temperatures significantly increase the rate of the Maillard reaction, prolonged heating at over 350°F (175°C) can significantly increase the production of mutagens.
Mutagens formed in the Maillard reaction (heterocyclic amines) have been shown to be carcinogenic in mice, rats and non-human primates; however, while some epidemiological studies have shown a relation with cancer development, others have shown no significant relation in humans (Arvidsson et al., 1997). These mutagens depend strongly on both temperature and time: they increase almost linearly in time before leveling off (after 5–10 minutes); an increase in temperature of 45°F (25°C) (from 300°F/150°C to 350°F/175°C or 350°F/175°C to 390°F/200°C) roughly doubles the quantity of mutagens (Jägerstad et al., 1998). While adding glucose increases browning, it can decreases the production of mutagens (Skog, 1993; Skog et al., 1992). The type of fat used to sear the meat in a pan has only minor effects on the formation of mutagens, but the pan residue using butter was significantly higher in mutagens than when using vegetable oil (Johansson et al., 1995).
In order to limit overcooking of the meat's interior, very high temperatures are often used to brown meat cooked sous vide. Typically, this means either using a blowtorch or a heavy skillet with just smoking vegetable oil. Butane and propane blowtorches can burn at over 3 500°F (1 900°C) in air, and produce a particularly nice crust on beef; while many use a hardware propane blowtorch, I highly recommend using an Iwatani butane blowtorch since propane can leave an off-flavor. I prefer the lower temperature of a skillet with just smoking vegetable or nut oil (400°F/200°C to 500°F/250°C) when searing fish, poultry and pork. Since the searing time at these high temperatures is very short (5–30 seconds), mutagens formation is unlikely to be significant (Skog, 2009).
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