Is there a "rule of thumb"to follow for pasteurizing food?
Asked by ElsieD on Wednesday, January 04
Should certain foods be pasteurized? How do you know when to pasteurize something? I've been trying to find the answer to this without success. Should ground meat always be pasteurized? If pasteurizing to the core of food, eg loin lamb chaos which we are having tonight, will this change the texture of the food? When do you pasteurize only the surface and when do you pasteurize to the core? I THINK I remember seeing somewhere that if meat is cooked sous vide with the intention of quick chilling it for eating a few days later or frozen, it should be pasteurized to the core. But, I've been reading so much I'm getting confused. Help!!! And, thank you.
5 Answers to This Question
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It's really quite scientific, by which I mean that it is precise and measurable.
<br />Take a moment to understand this chart:
<br /><a href="http://www.cookingissues.com/wp-content/uploads/2010/02/bacteria_time_temperature2.jpg">http://www.cookingissues.com/wp-content/uploads/2010/02/bacteria_time_temperature2.jpg</a>
<br />And follow the links at the bottom of the graph for detailed temperatures for various meats.
<br />Killing of harmful microorganisms is a function of time and temperature, the higher the temperature the less time is needed to kill the bugs, different bugs survive and thrive at different temperatures as well.
Answered by Roberto Leibman on Wednesday, January 04
Sous vide techniques allow a cook to pasteurize foods more completely than traditional cooking methods alone. This is because: (1) temperature control is more precise and receives more attention and (2) pasteurization is a product of both time and temperature, and sous vide allows a cook to slow cook the food long enough to pasteurize it without overcooking. That said, there are foods that are not pasteurized unless overcooked. These are primarily seafoods.
<br />When the meat is not ground or jaccarded, the majority of bacteria will be on the outside surfaces. Pre-searing, which I usually dismiss as a non-productive complication, can be a useful tool if the level of pasteurization is important. It should also be noted that freshness and proper food handling are more important.
<br />My own habit is to cook everything beef to medium rare at 131 degrees for a long time, long enough to pasteurize better than traditional cooking at even that low temperature (24 hours for all but the most tender cuts). Foul is cooked to medium (140 F) for white meat and medium well for dark meat (148-156F). Cooking times should be kept under 6 hours for foul to keep them from getting mushy, but 2 hours with the core temperature at 140 or higher is plenty to pasteurize more effectively than can be achieved by traditional cooking methods. Pork can be handled like white meat chicken to be served.
<br />Which leaves us to ponder how to prepare some foods for "susceptible'" people such as expectant mothers. Clearly, chose "medium" for ground beef (140 for two hours or more), but for fish avoid sous vide unless "pre-seared". For tenderloin and other tender cuts of beef, pre-sear and/or raise the temperature to near "medium" done temperatures in the core for two hours.
Answered by Leigh Jones on Sunday, June 16
Roberto, thank you for your response, but it doesn't really answer the questions I asked. If someone has the answer, I would appreciate hearing from them.
Answered by ElsieD on Thursday, January 05
My answer was that in general you should use the science and existing data to figure out what you need to do. The chart (and the USDA data) can help you answer your questions:
<br />- Should certain foods be pasteurized (by which I assume you mean the bugs in it killed to a given percentage)
<br />It depends if you're concerned about bugs, who you're feeding the food to and what the source of the food is, certain foods are more likely to have patogens than others.
<br />- Should ground meat be pasteurized?
<br />Same answer, ground meat's issue is that when you grind meat the surface (which is most likely to be contaminated) gets spread throughout the mass of meat, all things being equal you should be more careful with ground meat (or sear before grinding)
<br />- Will it change the texture of the food?
<br />Yes. Heat cooks food, time changes food, your end result will vary with heat and time.
<br />- When do you pasteurize only the surface and when do you pasteurize the core?
<br />What do you understand by pasteurization? I'm not sure I understand the question.
Answered by Roberto Leibman on Friday, January 06
Pasteurisation is the process of killing the vast majority of bacteria present, it is a form of preservation. You can't really pasteurise "just the surface", because any bacteria in the centre of your food can move to the surface afterwards.
<br />Anyway, so long as you are cooking your food above 55 deg C ( I think that's about 130 F) you only need to pasteurise food if you are planning on keeping it unfrozen for longer than you could keep it unfrozen raw. You certainly don't need to pasteurise anything you're planning on eating immediately, no matter what it is. You also don't need to pasteurise anything you are going to freeze, freezing and pasteurisation are two different types of preservation. Freezing stops any existing bacteria from multiplying, pasteurisation reduces the number of bacteria present.
<br />Be aware though, that pasteurisation doesn't kill ALL bacteria, and the food will go off eventually. Frozen food does not go off at all so long as it stays frozen, but the taste and texture can change over time.
<br />I think what you're getting mixed up about is very low temperature cooking. If you cook a piece of meat at a low temperature (below 55C or so) for a very long time, you will most likely grow bugs in it. Best thing to do is cook it hotter or shorter. I wouldn't trust any "surface pasteurisation" to keep my food safe.
Answered by Bronwyn on Saturday, April 14
You can also find a lot of sous vide information, as well as over 100 recipes, in our book Beginning Sous Vide
which you can get at Amazon.com or as a pdf download