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sous vide cooking.. Safe Times-Temps from Doug Baldwins tutorial

daveomak

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If you need help understanding this "somewhat" confusing stuff, I'm here somewhere...
PM is probably the best route.. Dave
I think I did my best at transferring this data... If I screwed up, let me know... I tried to arrange it in a step by step format for easier understanding....


When using sous vide, I have noticed some sites have incorrect or incomplete information about times and temps, in their recipes, for safe food... Doug Baldwin has created cook books and this tutorial on the "why's" things are the way they are, based on scientific data... He has a Doctorate in Mathematics...
I recommend you use Baldwin's data for creating safe sous vide food... Read his tutorial, skip the mathematics, and try to understand the reasoning for things...
http://www.douglasbaldwin.com/sous-vide.html

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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.

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johnmeyer

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That is a lot of data, but much of it doesn't seem like it could be true. Why do I say this?

Well, if I cook a 1" (25 mm) steak to medium-rare (135 F), then the tables say it has to stay at this temperature for two hours to be safe. However, when a steak is cooked conventionally to this same internal temperature, that cooking is finished in about 10-12 minutes, from the time it is put on the grill until it is pulled and served. The little nasty critters in the inside of the meat don't know whether the heat is coming from a water bath or a charcoal grill: they only know how hot it is around them in the inside of the meat, and for how long.

Therefore, according to these tables, every medium-rare one inch thick steak ever cooked over a fire should be unsafe. But, if this were true, we'd have a massive number of steak-related food poisoning cases each year.

So, I feel like I am missing something.

I say this despite the fact that I too have quoted quite a few of these time/temperature pasteurization charts, but the more I see them, the more I begin to question whether they provide the whole story about how to prepare safe food. There has to be some other factor that has kept billions of people from getting sick when consuming medium rare steaks cooked to 135 degrees in only ten minutes. Yes, I understand that the outside, when cooked conventionally, gets ripping hot and is safe, but the microbes in the inside only experience 135 for a minute or two before the steak is served and therefore, according to these tables, should still be quite alive and still able to make us sick.
 

daveomak

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Geeez John, You are mixing apples and oranges.... Your logic sucks, and you noted it...
Don't use the tables.... Make up your own....
I'm posting this stuff for folks that want to learn to use a sous vide and make perfectly safe food to eat....
 

johnmeyer

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Geeez John, You are mixing apples and oranges.... Your logic sucks, and you noted it...
Don't use the tables.... Make up your own....
I'm posting this stuff for folks that want to learn to use a sous vide and make perfectly safe food to eat....
Why do you have to be so snippy ("your logic sucks"). I don't deserve that. I was quite respectful in my reply, without a hint of snarkiness. I totally respect your posts.

I am simply trying to understand why ... well, I already stated it above. There is something about the time/temperature tables that seems to not make sense: why isn't the center of a medium-rare steak teaming with still-alive pathogens when it has only been at 135 for 1-2 minutes?
 

daveomak

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You know whole muscle meats are considered sterile... That's why a prime rib can be cooked to 120F... Rare.... And that's why you can cook a steak to rare no problems....
 

daveomak

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This segment of Baldwin's tutorial goes a long way in explaining stuff....

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.
 

johnmeyer

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Thanks Dave! Your explanation, along with the extensive quote from his book, helps me understand.
 

daveomak

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As an example.. A frozen 1" thick steak pasteurized at 140....

Thickness.... Time to reheat, from frozen to 1deg. F below set temp... say it's 140... (table 2.3)
25 mm........1¾ 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.)

Then to pasteurize .. (table 5.1)
Thickness.....Time to pasteurize, at 140...
25 mm .......1½ hr

Total time from frozen to pasteurized, 1" thick steak or chop .... 1.75 + 1.5 = 3 hours and 15 minutes at 140 F....


Anyhow, that's how I read this....
 

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