In a
previous post, I had recommended the
4130 NIST-Traceable Temperature Controller to control the temperature in a slow cooker. Unfortunately, that particular controller has a range that tops out at 60 degrees C / 140 degrees F, which is enough for cooking beef for long periods of time, but not enough for say, cooking duck confit, which for which a sous vide temperature of 80 degrees C is recommended. In addition, the 4130 is pretty expensive; almost $150. It’s possible to add a resistor to change the range of the 4130, but the temperature displayed by the controller is no longer correct, and you have manually create a conversion table between true temperature and the temperature as seen by the controller.
I’ve recently come across a cheaper and better possibility, the
Ranco ETC-111000-000 Temperature Controller which is only half the price and comes with a much larger working range (-30 to 220 degrees F). The price with the AC cord already wired in is $75; and
the version which just has a 120VAC SPDT relay is only $60.
A bit more about food safety. There has always been a lot of concern about bacteria growth and botulism, for good reason — and so therefore the recommendations for cooking temperature have a lot of safety margin in them — to the point now that the USDA recommends that steaks be cooked to at least 145 degrees F, which is well within what had traditionally been called “medium”, and chicken to at least 165 degrees F, which is enough to really destroy taste and texture. Sous vide cooking, especially some of the more low temperature variants, have raised a lot of concerns, to the point where a few years ago New York City (temporarily) banned it, causing a great outcry in the foodie community, since many top restaurants use sous vide techniques.
First of all, any recommendation about internal temperatures and food safety that doesn’t also factor in time is massively oversimplifying the problem. Here is a table taken from “Food Safety Hazards and Controls for the Home Food Preparer”, published by the Hospitality Institute of Technology in 1994:
| Temperature, F |
Time, 5D kill |
Time, 6.5D kill |
| 130 |
86.42 minutes |
112.34 minutes |
| 135 |
27.33 minutes |
35.53 minutes |
| 140 |
8.64 minutes |
11.23 minutes |
| 145 |
2.73 minutes |
3.55 minutes |
| 150 |
51.85 seconds |
1.12 minutes |
| 155 |
16.40 seconds |
21.32 seconds |
| 160 |
5.19 seconds |
6.74 seconds |
| 165 |
1.64 seconds |
2.13 seconds |
This table lists the time to reduce bacteria concentrations of Salmonella and E. coli from 100,000 to 1 (5D) or 3,162,277 to 1 (6.5D). The FDA and USDA recommend cooking hamburger to 5D destruction. Since it is extremely unlikely for there to be more than 100 Salmonella organisms per gram of meat, a 5D kill will reduce Salmonella concentrations to no more than 1 organism per kilogram. So whether you cook a piece of meat to an internal temperature of 165 degrees for 1.64 seconds, or hold it at 130 degrees for 90 minutes, the effect on Salmonella and E. coli bacteria will be the same.Of course, one concern is that in many forms of cooking, particularly oven roasting and grilling, the temperature of the food as it heats up may not be even; so how do you guarantee that all parts of the food product has been brought up to the requisite 165 degrees? One way that recipe authors, fearful of liability concerns, have done so is to tell people to cook meat to much higher internal temperatures, to provide that extra safety margin at the expense of dessicated, horribly tasting turkey or chicken. But the advantage of sous vide cooking is by immersing the food in a water bath, the excellent heat conductivity of water helps guarantee that the entire body of meat will get raised to desired temperature relatively quickly. (How quickly depends on the thickness of the meat, obviously). So if you hold a roast beef that has been vacuum packed in a Foodsaver bag for five or six hours, there should be no question that all of the common bacteria has been inactivated, and that amount of time at 130 degrees F should be sufficient to inactivate 99.9 percent of all botulism toxin molecules (not there should be any in a fresh piece of meat, of course!)
However, sous vide temperatures are not enough to kill bacterial spores, in particular C. botulinum, which is responsible for botulism. This requires temperatures far in excess of boiling water at sea level. For example, home canning protocols recommend holding the food product at 250 degrees F for at least 15 minutes. This is an issue in the restaurant business because very often food would be cooked sous vide, and then stored in the vacuum sealed bags for potentially weeks (yes, you could be eating an extremely expensive meal at a top-end French restaurant that had been cooked several weeks ago, and reheated just before serving; yummy, no?). If the food packages aren’t cooled quickly enough, and then allowed to warm to the danger zone, it’s possible that in the anerobic environment the C. botulinum spores could germinate and then start producing toxin. But, if you are cooking home sous vide where you are serving the food right after it has been cooked, this shouldn’t be a concern.
We're heading off on a vacation, the first real "put our feet up" kind of
vacation since our belated honeymoon a couple of years ago.
Our ultimate destination is the Seychelles, a tiny set of islands off the
east coast of Africa, near Madagascar. Sarah's aunty and uncle live here.
Her uncle's the deputy commissioner for the United Nations Indian Ocean Tuna
Commission.
Getting there is pretty heinous. We're flying to Houston, then to Dubai,
then to the Seychelles. Originally we were leaving tomorrow, but Sarah
noticed that we only had an hour to transfer in Houston, and when she
checked with the airline, they agreed (despite them booking the entire trip
in the first place). So now we've changed to a flight today, with a night in
a hotel in Dubai. Emirates only fly to the Seychelles a couple of times a
week, so we really don't want to miss the Dubai-Seychelles leg. The flight
from Houston to Dubai is 15 hours. That's worse than San Francisco to
Sydney. Not looking forward to sitting on a plane for that long.
Flying on September 11 is an interesting experience so far. It seems that
the airlines are "randomly selecting" all passengers who aren't US citizens
for secondary inspections at the security checkpoints. I was vaguely aware,
but had largely forgotten, that if they print SSSS in the bottom corner of
your bording pass, then you've been randomly selected. The TSA guy was very
apologetic, as he proceeded to completely dismantle our carry-on luggage.
The other fun aspect is that hurricane Ike is busy making its way towards
Houston. It's not supposed to make landfall until Saturday, but since
they've already evacuated some cities south of Houston, I'm really hoping it
doesn't bugger up our flights.
We're in the Seychelles for 10 days, and then we're going to spend 3 days in
Dubai on the way back. It'll be during Ramadan, which is apparently an
unpopular time for Westerners, so all of the hotels are nice and cheap. It
looks like it's going to be pretty hot as well.
I need to learn about 