What parasites are problematic in sous vide


Obviously, one should use only clean ingredients. However, especially with game and river/lake fish that's rather difficult.

  1. What are parasites that should be taken into account in sous vide cooking, or any other tightly controlled low-temperature cooking?
  2. What is the minimum core temperature and time to kill all parasites?

For sake of reality, "all parasites" should be limited to those in Europe and northern America.

I'm not looking for "just boil everything" or "only use inspected ingredients". Also, note that in sous vide, same temperature can be maintained for extended period of time. At least some temperature guidelines are higher than they have to be to account for quick, uneven cooking.

Best Answer

All information that gives safe cooking temperatures without reference to time at that temperature is wrong. The FDA guidelines, and state and local health dept. guidelines not only confict with each other, they are flat out wrong!

They all represent efforts to simplify molecular biology to two or three mindless rules. In the process, they guarantee that you will either overcook your food, or (if you care about good food) ignore the rules. Or possibly both.

For a summary of the actual bacteriocidal data, take a look at Douglas Baldwin's site: http://www.douglasbaldwin.com/sous-vide.html#Safety He has compiled information based on the actual growth and death curves for the pathogens that concern us most in the kitchen: salmonella, e.coli, lysteria, clostridium perfringes. Taking care of these will also get you out of the woods with protists, parasitic worms, norovirus, and everything else besides bacterial spores (another subject ... more relevant to canning).

For an even more thorough examination of the issue, take a look at the Microbiology for Cooks chapter in Vol. 1 of the Modernist Cuisine series. Both Baldwin and Myhrvold have arrived at the same conclusion by consulting the actual science. The official guidelines are irrelevant.

The original question is "what is the shortest temperature and time to kill all parasites." By "parasite" I'm assuming the OP means pathogen, since parasites are technically just one type, and not usually the most important.

There's no good answer if we take this question literally, because killing all of anything is almost impossible. Autoclaving in a pressure cooker at 250°F / 121°C for 30 minutes still leaves about one in a trillion botulinum spores alive. Pasteurization leaves about 1 in 300 million pathogens alive (by definition, actually).

Cooking guidelines aren't about trying to kill everything; we just try to bring pathogens down to a safe level. A safe level is one where if you eat the food that's been refrigerated properly, in a reasonable amount of time, and you have a reasonably good immune system, it will be very unlikely that you'll get sick. I know that's a lot of disclaimers, but it's a messy world.

Here are some basic guidelines. You'll get much more thorough versions looking at the above (or similar) sources. This stuff is best expressed as a graph. I'm padding it a bit for simplicity and safety:

126°F / 52°C for 6 hours

130°F / 54.5°C for 2 hours

135°F / 57°C for 40 minutes

140°F / 60°C for 12 minutes

150°F / 65.5°C for for 1 minute 15 seconds

160°F / 71°C for 8 seconds

This is the time for killing salmonella (the most heat resistant of the pathogens we care about) to pasteurization standards.

Please note that these are not cooking times: these are times the food needs to be held at the temperature after reaching it. Normal minimum cooking times just reflect how long it will take for the center of the food to reach a given temperature. The above times are additional.

You may have noticed that the first three temperatures above are well within the FDA's "danger zone." It's curious that the official guidelines consider your food in danger when it's actually in the process of being pasteurized.

But it's not necessarily that complicated. We don't really have to pasteurize food most of the time. If you eat conventionally cooked medium-rare steak, fish that doesn't taste like rubber, or chicken that still has some juice left in it, then you eat un-pasteurized food. It's not a problem, because with the exception of ground meat, virtually all pathogens reside on the outer surfaces of the food. And they get more than hot enough when you sear the food, whether the main part of the cooking was sous-vide or some other way.

Pasteurization is mostly an issue with cook-chill sous-vide, which is where you prepare food for reheating many days (even weeks) later.

Botulism is not a concern unless you're doing cook-chill and trying to keep the food for way, way too long (or in a much too warm fridge). The bacteria does indeed like the airtight bag, but it doesn't like the cold.