A Practical Guide to Sous Vide Cooking (2024)

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Sous Vide for the Home Cook

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Preface

Sous vide is French for “under vacuum” and describes a method of cooking in vacuum sealed plastic pouches at precisely controlled temperatures. With the proper equipment and some basic knowledge, you can prepare consistently delicious and safe food. With more advanced knowledge, you can safely create (or modify) recipes to realize your unique vision.

This guide attempts to distill the science of sous vide cooking to provide you with the tools you needed to safely realize your creative visions. PartI discusses the techniques and safety concerns of sous vide cooking. Some prototypical recipes are explored in PartII. The mathematics of sous vide cooking are detailed in AppendixA. Finally, AppendixB discusses the specialized equipment used in sous vide cooking.

Introduction

Sous vide is a method of cooking in vacuum sealed plastic pouches at relatively low temperatures for fairly long times. Sous vide differs from conventional cooking methods in two fundamental ways: (i)the raw food is vacuum sealed in heat-stable, food-grade plastic pouches and (ii)the food is cooked using precisely controlled heating.

Vacuum packaging prevents evaporative losses of flavor volatiles and moisture during cooking and inhibits off-flavors from oxidation (Church and Parsons, 2000). This results in especially flavorful and nutritious food (Church, 1998; Creed, 1998; García-Linares et al., 2004; Ghazala et al., 1996; Lassen et al., 2002; Schellekens, 1996; Stea et al., 2006). Vacuum sealing also reduces aerobic bacterial growth and allows for the efficient transfer of thermal energy from the water (or steam) to the food.

Precise temperature control is important when you cook fish, meat, or poultry. Suppose you want to cook a thick-cut steak medium rare. You could cook it on a grill at over 1,000°F (500°C) until the center hits 120°F (50°C) and then hope the center will come up to 130°F (55°C) after a short rest. You might sear one side of the steak in a pan, flip the steak over, put it in a 275°F (135°C) oven, and pull it out just before the center comes up to 130°F (55°C). Or you could vacuum seal the steak, drop it in a 130°F (55°C) water bath for a few hours, pull it out of your water bath just before you want to serve it, and sear the outside in either a smoking hot pan or with a blowtorch; what you'll get is a medium-rare steak with a great crust that is the same doneness at the edge as it is at the center. Moreover, you can cook the flavorful flat iron steak (very safely) in a 130°F (55°C) water bath for 12 hours and it'll be both medium-rare and as tender as filet mignon.

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.

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 1inch (25mm) thick hamburger patty and holding a hamburger patty at 130°F (54.4°C) for 2½hours 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 formspores 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 6hours 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 D₆₀^6.0 = 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, D₆₆^6.0 = 0.55 minutes and D₅₄^6.0 = 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 6.5decimal reduction of Salmonella in beef, so the coldest part should be at least 140°F (60°C) for at least 6.5D₆₀^6.0 = 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 5decimal 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 Table1.1.

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 6decimal 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

1. below 36.5°F (2.5°C) for up to 90 days,
2. below 38°F (3.3°C) for less than 31 days,
3. below 41°F (5°C) for less than 10 days, or
4. 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 6decimal reduction in non-proteolytic C. botulinum requires 520minutes (8hours 40minutes) at 167°F (75°C), 75minutes at 176°F (80°C), or 25minutes 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 eithera water bath or a convection steam oven. Convectionsteam ovens allow large quantities of food tobe prepared, but do not heat uniformly enough to usethe tables in this guide. Sheard and Rodger (1995)found that none of the convection steam ovens theytested heated sous vide pouches uniformly whenfully loaded. Indeed, it took the slowest heating(standardized) pouch 70%–200% longer than thefastest heating pouch to go from 68°F to 167°F (20°Cto 75°C) when set to an operating temperature of176°F (80°C). They believe this variation is a resultof the relatively poor distribution of steam at temperaturesbelow 212°F (100°C) and the ovens dependenceon condensing steam as the heat transfermedium.

In contrast, circulating water baths heat veryuniformly and typically have temperature swings ofless than 0.1°F (0.05°C). To prevent undercooking,it is very important that the pouches are completelysubmerged 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 rackor some other constraint.

Preparing for Packaging

Seasoning

Seasoning can be a little tricky when cooking sousvide: 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 thedish as they do in conventional cooking methodsbecause the temperature is too low to soften thestarches and cell walls. Indeed, most vegetables requiremuch higher temperatures than meats and somust be cooked separately. Finally, raw garlic producesvery pronounced and unpleasant results andpowdered garlic (in very small quantities) should besubstituted.

For long cooking times (of more than a couplehours), some people find that using extra virginolive oil results in an off, metallic, blood taste. (Sincethe extra virgin oil is unheated and unrefined duringproduction, it is reasonable that some of the oil willbreakdown even at a low temperature if give enoughtime.) A simple solution is to use grape seed or anyother processed oil for longer cooking times; extravirgin olive oil can then be used for seasoning aftercooking.

Marinating, Tenderizing and Brining

Since todays meat is younger and leaner than themeat of the past, many cooks marinate, tenderize orbrine the meat before vacuum packaging.

Most marinades are acidic and contain eithervinegar, wine, fruit juice, buttermilk or yogurt. Ofthese ingredients, only wine presents any significantproblems when cooking sous vide. If the alcoholis not cooked off before marinating, some ofit will change phase from liquid to vapor while inthe bag and cause the meat to cook unevenly. Simplycooking off the alcohol before marinating easilysolves this problem.

Mechanical tenderizing with a Jaccard has becomequite common. A Jaccard is a set of thin bladesthat poke through the meat and cut some of the internalfibers. The Jaccard does not typically leaveany obvious marks on the meat and is often usedin steak houses. By cutting many of the internalfibers that would typically contract with heat andsqueeze out the juices, it can slightly reduce theamount of moisture lost during cooking. For instance,when cooking a chuck steak for 24 hours at131°F (55°C) the Jaccarded steak lost 18.8% of itsweight compared to 19.9% for the non-Jaccardedsteak. In general, more liquid weight is lost thelonger a piece of meat is cooked at a given temperature–however, this additional weight loss is balancedby the increased tenderness from collagen dissolvinginto gelatin.

Brining has become increasingly popular inmodern cooking, especially when cooking pork andpoultry. Typically the meat is placed in a 3 to 10%(30 to 100 grams per liter) salt solution for a coupleof hours, then rinsed and cooked as usual. Brininghas two effects: it dissolves some of the supportstructure of the muscle fibers so they cannotcoagulate into dense aggregates and it allows themeat 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 themeat will still lose around 20% of its weight whencooked, the net effect will be a loss of only about0–12% of its original weight.

Cooking

There are two schools of thought when cooking sousvide: either the temperature of the water bath is(i) just above or (ii) significantly higher than the desiredfinal core temperature of the food. While (ii) iscloser to traditional cooking methods and is used extensivelyin (Roca and Brugués, 2005), (i) has severalsignificant advantages over (ii). Through out thisguide, I define just above as 1°F (0.5°C) higher thanthe desired final core temperature of the food.

When cooking in a water bath with a temperaturesignificantly higher than the desired final coretemperature of the food, the food must be removedfrom the bath once it has come up to temperature tokeep it from overcooking. This precludes pasteurizingin the same water bath that the food is cookedin. Since there is significant variation in the rateat which foods heat (see Appendix A), a needle temperatureprobe must be used to determine when thefood has come up to temperature. To prevent airor water from entering the punctured bag, the temperatureprobe must be inserted through closed cellfoam 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 oncethe temperature probe is removed.

In contrast, cooking in a water bath with a temperaturejust above the desired final core temperatureof the food means the food can remain in thewater bath (almost) indefinitely without being overcooked.Thus, food can be pasteurized in the samewater bath it is cooked in. While cooking times arelonger than traditional cooking methods, the meatcomes up to temperature surprisingly quickly becausethe thermal conductivity of water is 23 timesgreater than that of air. Moreover, temperatureprobes are not necessary because maximum cookingtimes can be tabulated (see Appendix A and Tables2.2 and 2.3).

Effects of Heat on Meat

Muscle meat is roughly 75% water, 20% proteinand 5% fat and other substances. The protein inmeat can be divided into three groups: myofibrillar(50–55%), sarcoplasmic (30–34%) and connectivetissue (10–15%). The myofibrillar proteins (mostlymyosin and actin) and the connective tissue proteins(mostly collagen) contract when heated, whilethe sarcoplasmic proteins expand when heated.These changes are usually called denaturation.

During heating, the muscle fibers shrink transverselyand longitudinally, the sarcoplasmic proteinsaggregate and gel, and connective tissuesshrink and solubilize. The muscle fibers beginto shrink at 95–105°F (35–40°C) and shrinkageincreases almost linearly with temperature up to175°F (80°C). The aggregation and gelation of sarcoplasmicproteins begins around 105°F (40°C) andfinishs around 140°F (60°C). Connective tissuesstart shrinking around 140°F (60°C) but contractmore intensely over 150°F (65°C).

The water-holding capacity of whole musclemeat is governed by the shrinking and swellingof myofibrils. Around 80% of the water in musclemeat is held within the myofibrils between thethick (myosin) and thin (actin) filaments. Between105°F and 140°F (40°C and 60°C), the muscle fibersshrink transversely and widen the gap betweenfibers. Then, above 140°F–150°F (60°C–65°C) themuscle fibers shrink longitudinally and cause substantialwater loss; the extent of this contraction increaseswith temperature.

For more information, see either the nontechnicaldescription in (McGee, 2004, Chap 3) or theexcellent review article by Tornberg (2005).

Tender Meat

When cooking tender meats, we just need to get thecenter up to temperature and, if pasteurizing, holdit there from some length of time. Cooking timesdepend critically on the thickness of the meat: doublingthe thickness of the meat increases the cookingtime four fold!

Table 2.1: Temperatures corresponding to rare, medium-rare and medium in meat and fish.

While there is no consensus as to what temperaturesrare, medium-rare and medium correspondto, I use the temperatures in Table 2.1. In general, the tenderness of meat increasesfrom 122°F to 150°F (50°C to 65°C) but thendecreases up to 175°F (80°C) (Powell et al., 2000;Tornberg, 2005). The approximate heating times forthawed and frozen meats are given in Tables 2.2 and 2.3. For acomplete discussion on how these times were computed,please see Appendix A.

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^-7m²/s and surface heat transfer coefficient of 95W/m²-K.) For thicker cuts and warmer water baths, heating time may (counter-intuitively) be longer than pasteurization time.

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^-7m²/s and surface heat transfer coefficient of 95W/m²-K.)

If the food is not being pasteurized (as is the casewith fish and rare meat), it is important that thefood come up to temperature and be served withinfour hours. Unlike conventional cooking methods,this is easily accomplished by cutting the food intoindividual portion sizes before cooking–which iswhy cooking times over four hours are not shownfor temperatures below 131°F (55°C). It is importantthat only immune-competent individuals consume unpasteurizedfood and that they understand the risks associatedwith eating unpasteurized food.

Tough Meat

Prolonged cooking (e.g., braising) has been usedto make tough cuts of meat more palatable sinceancient times. Indeed, prolonged cooking canmore than double the tenderness of the meat bydissolving all the collagen into gelatin and reducinginter-fiber adhesion to essentially nothing(Davey et al., 1976). At 176°F (80°C), Daveyet al. (1976) found that these effects occur withinabout 12–24 hours with tenderness increasing onlyslightly 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 toughcuts of beef (from animals 0–4 years old) werethe most tender when cooked to between 131°Fand 140°F (55°C and 60°C). Cooking the beef for24 hours at these temperatures significantly increasedits tenderness (with shear forces decreasing26%–72% compared to 1 hour of cooking). Thistenderizing is caused by weakening of connectivetissue and proteolytic enzymes decreasing myofibrillartensile strength. Indeed, collagen begins todissolve into gelatin above 122°F to 131°F (50°Cto 55°C) (Neklyudov, 2003; This, 2006). Moreover,the sarcoplasmic protein enzyme collagenaseremains active below 140°F (60°C) and can significantlytenderize the meat if held for more than6 hours (Tornberg, 2005). This is why beef chuckroast cooked in a 131°F–140°F (55°C–60°C) waterbath for 24–48 hours has the texture of filet mignon.

Chilling for Later Use

In the food industry, sous vide is used to extend theshelf life of cooked foods. After pasteurizing, thefood is rapidly chilled in its vacuum sealed pouch andrefrigerated (or frozen) until needed. Before finishingfor service, the food is then reheated in a waterbath at or below the temperature it was cooked in.Typically, meat is reheated in a 131°F (55°C) waterbath for the times listed in Tables 2.2 or 2.3 since the optimal serving temperature formeat is between 120°F–130°F (50°C–55°C).

The danger with cook-chill is that pasteurizingdoes not reduce pathogenic spores to a safe level. Ifthe food is not chilled rapidly enough or is refrigeratedfor too long, then pathogenic spores can outgrowand multiply to dangerous levels. For coolingand 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 complexreaction between amino acids and reducing sugars.After the initial reaction, an unstable intermediatestructure is formed which undergoes further changesand produces hundreds of reaction by-products. SeeMcGee (2004) for a nontechnical description or Belitzet al. (2004) for a technical description.

The flavor of cooked meat comes from the Maillardreaction and the thermal (and oxidative) degradationof lipids (fats); the species characteristics aremainly due to the fatty tissues, while the Maillard reactionin the lean tissues provides the savoury, roastand boiled flavors (Mottram, 1998). The Maillardreaction 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 thetemperature. Even small increases in pH, greatly increasesthe Maillard reaction and results in sweeter,nuttier and more roasted-meat-like aromas (Meynierand Mottram, 1995). The addition of a little glucose(e.g., corn syrup) has been shown to increasethe Maillard reaction and improve the flavor profile(Meinert et al., 2009). The Maillard reaction occursnoticeably around 265°F (130°C), but producesa boiled rather than a roasted aroma; good browningand a roasted flavor can be achieved at temperaturesaround 300°F (150°C) with the addition of glucose(Skog, 1993). Although higher temperatures significantlyincrease the rate of the Maillard reaction,prolonged heating at over 350°F (175°C) can significantlyincrease the production of mutagens.

Mutagens formed in the Maillard reaction (heterocyclicamines) have been shown to be carcinogenicin mice, rats and non-human primates; however,while some epidemiological studies have shown a relationwith cancer development, others have shownno significant relation in humans (Arvidsson et al.,1997). These mutagens depend strongly on bothtemperature and time: they increase almost linearlyin 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°Cto 390°F/200°C) roughly doubles the quantity of mutagens(Jägerstad et al., 1998). While adding glucoseincreases browning, it can decreases the productionof mutagens (Skog, 1993; Skog et al., 1992). Thetype of fat used to sear the meat in a pan has onlyminor effects on the formation of mutagens, but thepan residue using butter was significantly higher inmutagens than when using vegetable oil (Johanssonet al., 1995).

In order to limit overcooking of the meat's interior,very high temperatures are often used to brownmeat cooked sous vide. Typically, this means eitherusing a blowtorch or a heavy skillet with just smokingvegetable oil. Butane and propane blowtorchescan burn at over 3 500°F (1 900°C) in air, and producea particularly nice crust on beef; while many usea hardware propane blowtorch, I highly recommendusing an Iwatani butane blowtorch since propane canleave an off-flavor. I prefer the lower temperature of askillet with just smoking vegetable or nut oil (400°F/200°C to 500°F/250°C) when searing fish, poultryand pork. Since the searing time at these high temperaturesis very short (5–30 seconds), mutagens formationis unlikely to be significant (Skog, 2009).

3. Fish and Shellfish

Fish lends itself particularly well to being cookedsous vide. Since sous vide brings out the natural flavorsof the fish, it is important that only very freshfish which still smells of the sea be used. When purchasingfish, the flesh should be shiny, moist andfirm to the touch; have your fishmonger package thefish with ice and store the fish on ice in your refrigerator.Just before cooking, always check for and removeany scales or pin bones (with needle-nose pliersor tweezers).

Most fin and shellfish are best cooked medium(140°F/60°C) to medium-rare (120°F/49°C). The exceptionsbeing arctic char and salmon which are bestcooked medium-rare (120°F/49°C) to rare (110°F/43°C) and tuna which is best cooked rare (110°F/43.5°C) to very rare (100°F/38°C).

Fish intended for immune compromised individualsor for cold holding (i.e., cook-chill) shouldbe pasteurized for at least the times in Table 3.1 (to achieve 6D reduction of Listeriamonocytogenes). While such a pasteurization willreduce all non-spore forming pathogens and parasitesto a safe level, it will not reduce the risk ofHAV or norovirus infection from shellfish. Since a4D reduction of HAV in molluscan shellfish requiresholding at an internal temperature of 194°F (90°C)for 1.5 minutes, the risk of viral contamination isbest controlled through proper sanitation and hygiene(National Advisory Committee on MicrobiologicalCriteria for Food, 2008). Since the spores ofnon-proteolytic C. botulinum are not inactivated bypasteurization, the fish should be stored at below38°F (3.3°C) for no more than three to four weeks.

Table 3.1: Pasteurization times for a one million to one reduction of Listeria in fin-fish. I used D₆₀^5.59 = 2.88 minutes for lean fish (such as cod) and D₆₀^5.68 = 5.13 minutes for fatty fish (such as salmon) from Embarek and Huss (1993). For my calculations I used a thermal diffusivity of 0.995×10^-7m²/s, a surface heat transfer coefficient of 95W/m²-K, and took β = 0.28 (to simulate the heating speed of a 2:3:5 box).

Poached Fish

• Fish Fillets (Cod, Snapper, Monkfish,Sea Bass, Mahi-Mahi, etc.)
• Salt and Pepper
• Garlic Powder (Optional)
• Olive Oil

Remove the skin from the fillets. Season the fillets withKosher/sea salt, black pepper, and a little garlic powder.Then individually vacuum seal the fillets with 1–2 tablespoonsof olive oil or butter.

After determining the thickness of the thickest fish fillet,cook the fillets in a 131°F (55°C) to 141°F (60.5°C)water bath for at least the times listed in Table 3.1.

After removing the fillets from the water bath, the fishmay either be served immediately (perhaps after quicklysearing in a hot skillet with just smoking oil) or rapidlychilled in an ice water bath (see Table 1.1) andeither frozen or stored at below 38°F (3.3°C) for three tofour weeks. Note that fa*gan and Gormley (2005) foundthat freezing did not reduce the quality of fish which wascooked sous vide.

Salmon 'Mi-Cuit'

While salmon mi-cuit is a popular among sous videenthusiast, it should never be served to immunecompromised individuals. The low cooking temperaturesin this recipe are not sufficient to reduce thenumber of foodborne pathogens or parasites. Sincethe prevalence of the parasite Anisakids simplex mayexceed 75% in various types of fresh U.S. commercialwild salmon (National Advisory Committee onMicrobiological Criteria for Food, 2008), I recommendeither freezing the fish (below –4°F/–20°C forat least 24 hours) to kill the parasites or pasteurizingthe fish using the times and temperatures in Table 3.1.

The texture of sous vide prepared salmon is verymoist and tender. To contrast this texture, theskin should be removed before vacuum packaging,crisped, and served as garnish.

A common problem when cooking salmon, isthat the protein albumin leaches out of the fish andcoagulates unattractively on the surface. This can belessened by brining the fish in a 10% salt watersolution for 10 minutes.

• Salmon (Coho, Sockeye, Chinook, or Steelhead)
• Olive Oil
• Salt and Pepper
• Garlic Powder (Optional)

Set the temperature of the water bath to 108°F (42°C)for rare salmon, 122°F (50°C) for medium--raresalmon, or 140°F (60°C) for mediumsalmon. Then prepare a 10% salt water solution(100 grams salt per 1 liter cold water).

For crisp salmon skin to contrast the very moist andtender texture of the salmon, remove the skin from thesalmon and then brine the salmon in the refrigerator for10 minutes.

If cooking the salmon medium, the easiestway to crisp the skin and remove it from the salmonis to quickly sear the salmon (skin side only) in a panover high heat with just smoking oil. The skin will theneasily peel off the flesh. The skin can then be finishedwith a blowtorch or simply placed in a warm oven untilneeded. If cooking the salmon rare or medium-rare, cut the skin off the fish and then crisp it between cooking sheets in the oven.

After the salmon has finished brining, rinse and patdry with paper towels. Then season with salt, pepperand a hint of garlic powder. Vacuum seal the seasonedsalmon in a plastic pouch with 1–2 tablespoons extravirgin olive oil (frozen overnight if using a clamp stylevacuum sealer).

Cut the salmon into individual servings and vacuum seal. For rare and medium-rare salmon, cook the salmon for 15–20 minutes. For medium salmon, pasteurize it for the time listed in Table 3.1. Then remove the salmon from its pouch,garnish with crisped salmon skin, and serveimmediately.

4. Poultry and Eggs

Chicken or Turkey Breast

Traditionally, light poultry meat is cooked well-done(160°F/70°C to 175°F/80°C) for "food safety" reasons.When cooking chicken and turkey breastssous vide, they can be cooked to a medium doneness(140°F/60°C to 150°F/65°C) while still beingpasteurized for safety.

• Boneless Chicken or Turkey Breast
• Salt and Pepper

Remove any skin from the breast and reserve for garnishor discard. Reserved skin can easily be crisped using eithera salamander/broiler or with a blowtorch.

If brining, place the poultry meat in a 5% salt watersolution (50 grams per 1 liter) in the refrigerator for30 minutes to 1 hour. (If tenderizing with a Jaccard,do so before brining.)

Rinse and dry with paper towels. Then season withKosher/sea salt and coarse ground pepper. Vacuum sealbreasts (one per bag). The breasts may be frozen at thispoint until needed.

To cook and pasteurize, place (thawed) breast in a 146°F(63.5°C) water bath for the times listed in Table 4.1. [After cooking, the breasts may be rapidlycooled in ice water (see Table 1.1) and frozenor refrigerated at below 38°F (3.3°C) for up to three tofour weeks until needed.]

Remove breast from plastic pouch and dry with a papertowel. The meat can then be served as is or brownedslightly by using either a very hot pan (with just smokingoil) or a blowtorch. Serve immediately (garnished withcrisped skin).

Table 4.1: Time required for at least a one million to one reduction in Listeria and a ten million to one reduction in Salmonella in poultry starting at 41°F (5°C). I calculated the D- and z-values using linear regression from (O'Bryan et al., 2006): for Salmonella I used D₆₀^6.45 = 4.68 minutes and for Listeria I used D₆₀^5.66 = 5.94 minutes. For my calculations I used a thermal diffusivity of 1.08×10^-7m²/s, a surface heat transfer coefficient of 95W/m²-K, and took β=0.28 (to simulate the heating speed of a 2:3:5 box). For more information on calculating log reductions, see Appendix A.

Turkey, Duck or Goose Leg Confit

• Duck, Goose or Turkey Legs
• Rendered Duck or Goose Fat (or Lard)
• Salt and Pepper

Place legs in a 5–10% brine (50–100 grams salt per1 liter) for three to six hours. The brine may be flavoredwith sprigs of thyme, bay leaves, garlic, and orange/lemon slices.

After brining, rinse legs and pat dry with paper towels.Season with Kosher/sea salt and coarse ground pepper.Individually vacuum seal the legs with 2–4 tablespoonsof rendered fat.

Place the vacuum sealed legs in a 176°F (80°C) waterbath for 8 to 12 hours. Since some of the liquid in thebag will change phase (to gas), the bag will puff and mayfloat to the surface. To prevent uneven cooking, the bagsshould be held under water using a wire rack or someother restraint. [After cooking, the legs may be rapidlycooled in ice water (see Table 1.1) and frozenor refrigerated at below 39°F (4°C) indefinitely.]

To serve, (reheat and) sear until skin is crispy. May alsobe served without skin and torn into pieces.

Perfect Egg

The custardy texture of the white and yolk of theso called "perfect egg" is caused by the denaturingof the egg protein conalbumin at 148°F (64.5°C). InFigure 4.1, we observe that thedenaturing of the protein ovotransferrin at 144°F(62°C) causes the egg white to coagulate (This, 2006, Chap 3).

Place egg in a 148°F (64.5°C) water bath for 45 minutesto 1 hour. Crack egg and serve immediately.

Figure 4.1: Pictures of intact eggs cooked in a water bath for 75 minutes at temperatures ranging from136°F (57.8°C) to 152°F (66.7°C). From left-to-right and top-to-bottom, the water bath temperature was136.0°F (57.8°C), 138.0°F (58.9°C), 140.0°F (60.0°C), 142.0°F (61.1°C), 144.0°F (62.2°C), 146.0°F (63.3°C), 148.0°F (64.4°C), 150.0°F (65.6°C), 152°F (66.7°C).

In 2014, I developed the patented Egg Calculator at ChefSteps to allow you to pick the yolk's and white's texture independently.

Pasteurized in Shell Egg

While only 1 in 10,000–20,000 intact shell eggscontain hazardous levels of Salmonella enteritidis(McGee, 2004; Snyder, 2006), Grade A eggs wereimplicated in 82% of outbreaks between 1985and 1991 (Mishu et al., 1994). Therefore, whenworking with highly susceptible or immune compromisedpopulations, pasteurized eggs should alwaysbe used in dishes which call for raw eggs (e.g., chocolatemousses).

Place egg in a 135°F (57°C) water bath for at least1 hour and 15 minutes (Schuman et al., 1997).

Pasteurized intact eggs can be stored and usedjust like raw eggs. While the properties of the eggyolk are unaffected, the egg white is milky comparedto a raw egg. Whipping time is significantly longerfor pasteurized eggs, but the final whip volume isnearly the same (Schuman et al., 1997).

5. Beef

For tender cuts of beef–such as tenderloin, sirloinand rib-eye–season, vacuum seal in heat stableplastic pouches, and cook either very-rare (120°F/49°C), rare (125°F/51.5°C), medium-rare (130°F/54.5°C), or medium (140°F/60°C) for the time listedin Table 2.2. For extended shelf-life (i.e.,cook-chill or cook-freeze) or when serving immunecompromised individuals, the beef must be pasteurizedfor at least the times in Table 5.1. After heating, sear the beef using either ablowtorch, a very hot grill, or a pan with just smokingoil.

As the cooking temperature increases from120°F to 150°F (50°C to 65°C), Vaudagna et al.(2002) found that cooking weight loss increased andshear force decreased. They also found that holdingthe beef in the water bath for 90–360 minutes didnot have a significant effect on the cooking weightor the shear force. Above 160°F (70°C), tendernessdecreases and cooking weight loss continuesto increase because of myofibrillar hardening (Powellet al., 2000). When compared to other cookingmethods, beef cooked sous vide to the same temperaturehas a more intense reddish color (García-Segovia et al., 2007).

Table 5.1: Time required to reduce Listeria by at least a million to one, Salmonella by at least three million to one, and E. coli by at least a hundred thousand to one in thawed meat starting at 41°F (5°C). I calculated the D- and z-values using linear regression from O'Bryan et al. (2006), Bolton et al. (2000), and Hansen and Knøchel (1996): for E. coli I use D₅₅^4.87 = 19.35 min; for Salmonella I use D₅₅^7.58 = 13.18 min; and for Listeria I use D₅₅^9.22 = 12.66 min. For my calculations I used a thermal diffusivity of 1.11×10^-7m²/s, a surface heat transfer coefficient of 95W/m²-K, and took β=0 up to 30mm and β=0.28 above 30mm (to simulate the heating speed of a 2:3:5 box).For more information on calculating log reductions, see Appendix A. [Note that if the beef is seasoned using a sauce or marinate which will acidify the beef, then the pasteurizing times may need to be doubled to accommodate the increased thermal tolerance of Listeria (Hansen and Knøchel, 1996).]

For tough but flavorful cuts of beef–such as topblade, chuck, and top round–season the meat andcook in a 131°F (55°C) water bath for 24–48 hours.This is the lowest temperature at which (insoluble)collagen denatures (dissolves) into gelatin, at highertemperatures the denaturing occurs more quickly(Powell et al., 2000; This, 2006).

Flat Iron Steak

Beef cooked in a vacuum will look paler thanmedium-rare when first cut, but will get redder onceexposed to oxygen.

• Flat Iron (Paleron or Top Blade) Steak
• Salt and Pepper

Rinse and dry steak with a paper towel. Jaccard steak,then season with salt and pepper. Vacuum seal (andfreeze until needed).

Place vacuum sealed steak in a 131°F (55°C) water bathfor about 12 hours. The meat will have a greenish-browncolor after cooking which will disappear after searing.[The steak may be rapidly cooled in ice water (see Table 1.1) and frozen or refrigerated at below38°F (3.3°C) for up to three to four weeks until needed.]

Remove steak from vacuum bag, pat dry with a papertowel, and sear quickly with a blowtorch or in a pan withsmoking vegetable or nut oil.

Roast Beef

• Top Blade, Chuck, or Top Round Roast
• Salt and Pepper

Dry roast with a paper towel. Then cut the roast sothat it is no more than 70 mm (2.75 in) thick; or, slicethe roast into individual servings and follow the recipeabove for flat iron steaks.

Season the roast with Kosher/sea salt and coarseground pepper. Then vacuum seal and place the roastin a 131°F (55°C) water bath for about 24 hours. [Aftercooking, the roast may be rapidly cooled in ice water (seeTable 1.1) and frozen or refrigerated at below38°F (3.3°C) for up to three to four weeks until needed.]

After removing the roast from its vacuum pouch, pat theroast dry with paper towels. Then sear the roast to adeep mahogany color using a blowtorch. Then slice andserve immediately.

Brisket

• Beef Brisket
• Sugar, Salt and Pepper

Cut slits in the fat cap in a crosshatch patter. Brine thebrisket in a 4% salt, 3% sugar solution (40 grams saltand 30 grams sugar per liter of water) in the refrigeratorfor 2–3 hours. Rinse and dry brisket with paper towels.

Flavor the brisket either by smoking it for 30–60 minutesor by searing the fat cap with a blowtorch. Thenvacuum seal the brisket either whole or cut into two tofour pieces.

While the famed French Laundry is said to cook theirbrisket in a 147°F (64°C) water bath for 48 hours, I preferto cook brisket at 176°F (80°C) for 24–36 hours. Alternatively,some like to cook brisket at 135°F (57°C)for 36–48 hours. Since some of the liquid in the bag willchange phase (to gas), the bag will puff and may float tothe surface. To prevent uneven cooking, the bags shouldbe held under water using a wire rack or some otherrestraint. [After cooking, the brisket may be rapidlycooled in ice water (see Table 1.1) and frozenor refrigerated at below 38°F (3.3°C) for up to three tofour weeks until needed.]

Remove the brisket from the vacuum sealed pouch anduse the liquid from the bag to create a quick sauce (byreducing in a pan over medium-high heat and addinga corn starch slurry to thicken). Slice the meat acrossgrain into long, thin slices and serve with beef glace.

6. Pork

Traditional Style Pork Chops

While pork can be safely cooked at 130°F (54.4°C),many people find the slightly pink color of porkcooked at this temperature to be unsettling. To compensatefor cooking to medium (instead of mediumrare),I highly recommend brining the pork chopsto break down some of the support structure of themuscle fibers and to increase the water holding capacityof the meat; the maximum water uptake occurswhen brining in a 7–10% salt solution, with thechop absorbing 20–25% of its weight (Graiver et al.,2006).

Brine in a 7% salt, 3% sugar water solution (70 gramssalt and 30 grams sugar per 1 liter) in the refrigeratorfor one to two hour. (If tenderizing with a Jaccard, doso before brining.)

Rinse, dry with paper towels and season with Kosher/sea salt and coarse ground pepper. Vacuum seal porkchops (one per bag).

To cook, place in a 141°F (61°C) water bath for the cookingtimes in the Table 5.1. [The chopmay be rapidly cooled in ice water (see Table 1.1) and frozen or refrigerated at below 38°F (3.3°C)for up to three to four weeks until needed.]

Remove chop from vacuum bag, pat dry with a papertowel, then sear quickly with a blowtorch or in a panwith smoking vegetable or nut oil.

Slow Cooked Pork Chops

Season thick-cut pork chops with Kosher/sea salt andcoarse ground pepper. Then vacuum seal pork chops (oneper bag) and place in a 131°F (55°C) water bath for12 hours. [The chop may be rapidly cooled in ice water(see Table 1.1) and frozen or refrigerated atbelow 38°F (3.3°C) for up to three to four weeks untilneeded.]

Remove chop from vacuum bag, pat dry with a papertowel, then sear quickly with a blowtorch or in a panwith smoking vegetable or nut oil.

Pulled Pork

• Pork Roast (Boston Butt Roast or Picnic Roast)
• Lard
• Salt and Pepper

If bone-in, remove the bone from the pork roast witha boning knife. Either cut roast into steaks which areroughly 7 ounces each, or cut the roast so that it is nomore than 70 mm (2.75 in) thick. Then brine roast in a7–10% salt, 0–3% sugar water solution (70–100 gramssalt and 0–30 grams sugar per 1 liter) in the refrigeratorfor six to twelve hours.

Drain, rinse and pat dry with paper towels. Season thepork with Kosher/sea salt and coarse ground pepper.Place each piece of pork in a vacuum bag with 1–2 tablespoonsof lard (preferably non-hydrogenated) and seal.

Place the pork either in a 176°F (80°C) water bath for8–12 hours or in 155°F (68°C) water bath for 24 hours.When cooking at 176°F (80°C), the bag will puff (fromwater vapor) and may float to the surface. To preventuneven cooking, the bags should be held under waterusing a wire rack or some other restraint. [After cooking,the pork may be rapidly cooled in ice water (see Table1.1) and frozen or refrigerated at below38°F (3.3°C) for three to four weeks.]

Remove the pork from the bag and reserve the liquidfrom the bag. (Place the liquid in a container in thefridge overnight, skim the fat off and reserve the jelliedstock for future use.) Dry the surface of the meat with apaper towel.

For American style pulled pork, shred and serve withyour favorite barbecue sauce. For Mexican style pulledpork, sear the surface with a blowtorch (or in a pan withjust smoking vegetable or nut oil) before shredding.

Barbecue Ribs

• Pork Spare Ribs
• Barbecue Dry Rub
• Salt and Pepper

Cut the ribs into portions which will fit in the vacuumpouches (say 3–4 ribs per piece). Then brine roast in a7–10% salt, 0–3% sugar water solution (70–100 gramssalt and 0–30 grams sugar per 1 liter) in the refrigeratorfor 12–24 hours.

Drain, rinse and pat dry with paper towels. Generouslyseason the top of each rib with a barbecue spicerub (say 2T paprika, 1.5T celery salt, 1.5T garlic powder,1T black pepper, 1T chili powder, 1T ground cumin,1T brown sugar, 1T table salt, 1t white sugar, 1t driedoregano, and 1t cayenne pepper). Place each piece ofpork in a vacuum pouch and seal.

Place the pork either in a 176°F (80°C) water bath for8–12 hours or in 155°F (68°C) water bath for 24 hours.When cooking at 176°F (80°C), the bag will puff (fromwater vapor) and may float to the surface. To preventuneven cooking, the bags should be held under waterusing a wire rack or some other restraint. [After cooking,the pork may be rapidly cooled in ice water (see Table1.1) and frozen or refrigerated at below38°F (3.3°C) for three to four weeks.]

After removing the ribs from the bag, sear the top witha blowtorch. Then, serve immediately with barbecuesauce.

A. The Mathematics of Sous Vide

This guide is primarily interested in modellinghow long it takes the food to come up to temperatureand how long it takes to pasteurize the food. Theseare non-trivial tasks. Many simplifications and assumptionsare necessary.

Heating and Cooling Food

The transfer of heat (by conduction) is described bythe partial differential equation,

Tt=∇⋅(α∇T),$$T_t=\mathrm{\nabla }\cdot (\alpha \mathrm{\nabla }T),$$

Since we are only interested in the temperatureat the slowest heating point of the food (typically thegeometric center of the food), we can approximatethe three dimensional heat equation by the one dimensionalheat equation

⎧⎩⎨⎪⎪⎪⎪⎪⎪ρCp(T)Tt=k(T)[∂2T∂r2+βr∂T∂r],T(r,0)=T0,∂T∂r(0,t)=0,k(T)∂T∂r(R,t)=h[TWater−T(R,t)],(∗)$$\{\begin{array}{l}\rho C_p(T)T_t=k(T)\left[\frac{{\mathrm{\partial }}^{2}T}{\mathrm{\partial }{r}^2}+\frac{\beta }{r}\frac{\mathrm{\partial }T}{\mathrm{\partial }r}\right],\\ T(r,0)=T_0,\frac{\mathrm{\partial }T}{\mathrm{\partial }r}(0,t)=0,& (\ast )\\ k(T)\frac{\mathrm{\partial }T}{\mathrm{\partial }r}(R,t)=h[T_{Water}-T(R,t)],\end{array}$$

The geometric factor in (*) allows us to approximateany shape from a large slab (β = 0) to a longcylinder (b = 1) to a sphere (β = 2). Indeed, a cubeis well approximated by taking β = 1.25, a squarecylinder by β = 0.70, and a 2:3:5 brick by β = 0.28.

Figure A.1: Plot of temperature (°C) verse time (minutes) of a 27 mm thick piece of Mahi-Mahi cooked in a 131°F (55°C) water bath. The blue dots are the core temperature measured using a ThermoWorks MicroTherma2T with a needle probe. The blue line is the calculated core temperature of the Mahi-Mahi (where I used a thermal diffusivity of 1.71×10^-7 m²/secand a heat transfer coefficient of 155 W/m²-K).

Heating Thawed Food

For thawed foods, k, ρ and C_p are essentially constant.Sanz et al. (1987) reported that beef withabove average fatness had: a thermal conductivity of0.48 W/m-K at 32°F (0°C) and 0.49 W/m-K at 86°F(30°C); a specific heat of 3.81 kJ/kg-K at both 32°F(0°C) and 86°F (30°C); and, a density of 1077 kg/m³at 41°F (5°C) and 1067 kg/m³ at 86°F (30°C). This is much less than the difference between beef sirloin(α = 1.24×10^-7 m²/sec) and beef round (α = 1.11×10^-7 m²/sec) (Sanz et al., 1987). Therefore, wecan model the temperature of thawed foods by

⎧⎩⎨⎪⎪⎪⎪⎪⎪Tt=α[∂2T∂r2+βr∂T∂r],T(r,0)=T0,∂T∂r(0,t)=0,∂T∂r=hk[TWater−T(R,t)],$$\{\begin{array}{l}{T}_t=\alpha \left[\frac{{\mathrm{\partial }}^{2}T}{\mathrm{\partial }{r}^2}+\frac{\beta }{r}\frac{\mathrm{\partial }T}{\mathrm{\partial }r}\right],\\ T(r,0)=T_0,\frac{\mathrm{\partial }T}{\mathrm{\partial }r}(0,t)=0,\\ \frac{\mathrm{\partial }T}{\mathrm{\partial }r}=\frac{h}{k}[T_{Water}-T(R,t)],\end{array}$$

Most foods have a thermal diffusivity between1.2 and 1.6×10^-7 m²/s (Baerdemaeker and Nicolaï,1995). Thermal diffusivity depends on manythings, including meat species, muscle type, temperature,and water content. Despite these variationsin thermal diffusivity, we can always choose a (minimum)thermal diffusivity which will underestimatethe temperature of the meat as it cooks (and overestimatethe temperature as it cools). Thus, I usethe lowest thermal diffusivities reported in the literature (see Table A.1) in my pasteurization tables.Moreover, the food cannot overcook if it is placed ina water bath just above its desired final core temperature.Therefore, so long as the pouches do not floatto the surface or are packed too tightly in the waterbath, we can generate cooking tables which willassure perfectly cooked and sufficiently pasteurizedmeat.

Table A.1: The thermal diffusivity (at 0°C to 65°C) of various types of food reported in the literature.

Computing the Destruction of Pathogens

Using the above models for the temperature at theslowest heating point of the meat, the classicalmodel for the log reduction in pathogens is

LR=1DRef∫t010[T(t′)−TRef]/zdt′,$$LR=\frac{1}{D_{Ref}}{\int }_0^t{10}^{[T(t^{\prime })-T_{Ref}]/z}d{t}^{\prime },$$

B. Equipment

When I first posted this guide in 2008, there were few options for home cooks interested in cooking sous vide. After finishing my Ph.D., I joined ChefSteps and worked with them to develop the Joule. Then after joining Breville, I worked with them on PolyScience's HydroPro series. While these are the immersion circulators that I use, Anova also makes great immersion circulators and any of the International Sous Vide Association's approved devices will allow you to make safe and delicious food.

Water Baths and Steam Ovens

For short cooking times (such as when cooking fish), a pan of water on the stove can be used if you're willing to watch it closely and adjust the temperature by hand. However, this becomes increasingly tedious for longer cooking times and most cooks use an immersion circulator to regulate the temperature.

The most popular immersion circulator for home cooks come from Anova and ChefSteps. Restaurant chefs tend to use heavy-duty immersion circulators from PolyScience. Large hotel and school kitchens tend to use Winston CVap and similar humidity ovens.

All immersion circulators need to do three things: accurately measure the temperature of the water, heat the water, and mix the water.

The immersion circulators from Anova, ChefSteps, PolyScience, and other respected brands use a proportional-integral-derivative (PID) controller and an accurate thermometer to regulate their heaters. A well-tuned PID controller can keep the water's temperature within ½°F (¼°C) of your desired temperature throughout the cook. In almost all applications, it doesn't matter if the temperature varies 1 °F (0.5°C) over the cooking time; even a variation of a few degrees doesn't matter for most foods if the average temperature is within 1 °F (0.5°C).Because of their precision, most immersion circulators use a negative-temperature-coefficient thermistor to measure the water's temperature. A few use thermocouples or positive-temperature-coefficient thermistors, which can be just as accurate but tend to have more measurement noise that make tuning the PID controller more difficult.

Immersion circulators use a motor to move water either across heating elements suspended in the water or through a heated tube. Both methods work well, but tube heaters tend to be more powerful. Powerful heaters are important for restaurant chefs preparing many servings, which is why heavier-duty immersion circulators are usually 1,200 to 1,450 W; units intended for home cooks are usually 750 to 1,150 W. For most cooks, the average power usage is much lower than this after the water bath reaches its target temperature. So a powerful heater is mostly important for shortening the time until the water bath is heated and when cooking large amounts of food – such as a whole brisket – in a large water bath. Moreover, large amounts of food and large water baths require more powerful motors to pump enough water to prevent cold spots and ensure even heating.

Most home cooks use a stock pot with 3 to 5 Qt (3 to 5 L) of water with their immersion circulator. Restaurants tend to use polycarbonate food boxes and coolers with 20 to 40 Qt (20 to 40 L) of water. Pick a vessel a bit larger than the food you're heating, so 1½ to 2½ Qt/lb (3 to 5 L/kg) water to food will fully cover the food. This will reduce the amount of energy wasted heating extra water and the environment compared with more water and a larger bath. While a metal pot will lose a bit more energy to radiation and conduction, the biggest loss of energy to your kitchen is from evaporation. So if you're cooking for more than a few hours above about 150°F (65°C), covering the bath with plastic wrap will significantly cut the power used to maintain the water's temperature.

Other home cooks prefer the SousVide Supreme introduced back in 2009, which combines a PID-controller and a water bath into a single appliance. Unlike an immersion circulator, it comes with a tight-fitting lid and insulated walls that reduce electricity usage during long cooks. While it does not circulate the water within the bath, I didn't measure a difference in how long it takes to heat food.

If cooking for hundreds of people, large ovens that use humidity to efficiently heat food are a better choice than immersion circulators. When steam condenses onto the food, a lot of energy is transferred from the steam to the food. For example, just ¾ oz (20 g) of steam condensing on an 8 oz (225 g) steak would transfer enough energy to heat it from 40°F (5°C) to 130°F (55°C). This is also why steam can badly burn skin. For fish and medium-rare meat, the Winston CVap cook and hold ovens are a popular choice – they also allow you to get sous-vide-like results without using bags. For more information, see Chapter 8, Volume 2 of Myhrvold, Young, and Bilet's Modernist Cuisine (2011) to learn all about Rational combi and Winston CVap ovens.

While ovens that can control humidity can cook a lot of food at once, each serving takes longer than in a water bath. 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 oven's dependence on condensing steam as the heat transfer medium. Therefore, the tables in this guide cannot be used and needle temperatures probes must be used to determine cooking and pasteurization times.

Vacuum Sealers

Resealable pouches, such as Ziploc heavy-duty freezer bags, work very well for sous vide cooking below about 195°F (90°C) – above that temperature, the plastic softens and the bag might fail. When using a resealable pouch, it's important to remove as much air as possible so it doesn't insulate the food from the water (since air is a very poor conductor of heat). I do this by adding liquid to the pouch with the raw food and then submerging the pouch in cool water to displace the air; for detailed instructions see pages 250–251 in Sous Vide for the Home Cook or watch my chicken breasts video.

Many cooks just drop the bottom of the pouch, with the food and liquid inside, into the hot water bath, leave the top open, and clamp the open top to the side of the water bath. This also works well, but you must make sure the part of the bag above the water has no food pathogens on it. For example, you can roll the top of the bag down that will be above the water. If you're preparing food for anyone who is immune compromised, it's better to seal the bag and make sure every part of the bag is submerged under the water.

Some home cooks use clamp-style vacuum sealers, such as a FoodSaver vacuum sealer. The problem with clamp- or edge-style vacuum sealers is that it is difficult to get a strong vacuum, the bags are expensive (compared to those used in chamber machines), and liquids tend to get sucked into the machine. If your recipe calls for liquid to be in the pouch, I'd recommend using a resealable pouch instead of your clamp-style vacuum sealer. If you do want to use your clamp-style vacuum sealer, you can either

• freeze the liquid before putting it into the pouch; for instance, freezing a small ice cube tray filled with extra virgin olive oil is quite convenient.
• cut the pouch long, hang the edge over the counter (so the liquid is below the level of the vacuum channel), and push the “seal” or “stop and seal” button just before the liquid reaches the vacuum sealer.

Some advanced home and many professional cooks use a chamber-style vacuum sealers (such as those from PolyScience and Minipack). These machines are able to pull a much stronger vacuum than clamp-style vacuum sealers, use less expensive bags ($0.12 per square foot verse $0.42 per square foot), and are able to package liquids without freezing. However, chamber vacuum sealers are much larger and heavier than clamp style vacuum sealers and cost more than ten times as much.

Regardless of how you vacuum seal your food, I recommend adding liquid to keep the food's edges from getting crimped while cooking. The more delicate the food, the more liquid you should add; for example, you might put the same weight of oil as scallops in the bag to keep them from getting deformed.

If you plan on freezing your cooked food in its bag, I strongly recommend labeling it. It's often difficult to tell if the food is cooked or raw or if it's beef or pork after spending a few months in the freezer.

Digital Thermometers

Accurate temperature control is important for safe sous vide cooking: pasteurization times depend critically on temperature. I recommended that anyone interested in precision cooking – sous vide or traditional – invest in a good digital thermometer. For everyday cooking, the Comark PDQ400 is a great entry-level thermocouple thermometer. If you have the money, ThermoWorks' Thermapen is much faster than the PDQ400 and even easier to use.

If you like doing science experiments, you might consider getting several interchangeable probes and a thermometer that can read them. I have several K- and T-type probes from ThermoWorks and I'm very happy with them, especially the needle probes from TheromWorks that respond very quickly.

Basic Equipment Suggestions

$25–100

Heavy-duty Ziploc freezer bags and a large pot on a stove using a good digital thermometer.

$100–300

Heavy-duty Ziploc freezer bags and a consumer immersion circulator or SousVide Supreme.

$400–600

Heavy-duty Ziploc freezer bags and a heavy-duty immersion circulators.

$4,000–10,000

Large chamber vacuum sealer and several heavy-duty immersion circulators.

$10,000+

Large chamber vacuum sealer and several Winston CVap ovens.

C. Government Pasteurization Tables

The pasteurization times for beef, lamb and pork are listed in Table C.1. Table C.2 lists the pasteurization times for chicken and turkey.

Table C.1: Pasteurization times for beef, corned beef, lamb, pork and cured pork (FDA, 2009, 3-401.11.B.2).

Table C.2: Pasteurization times for a 7D reduction in Salmonella for chicken and turkey (FSIS, 2005).

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