Erika,

First, my qualifications: I was trained as a microbiologist in college,
though I never worked in the field. I am now a chef, and just passed a
few weeks ago my recurrent food sanitation course and test.

I looked up Listeria Monocytogenes (the only infectious member of the
Listerosis genus) and found the following in my Basic Medical
Microbiology book.
"L. Monocytogones is a diptheriod-like bacillus (motile, gram positive)
found primarily in the intestinal tract of birds and mammals. It
sometimes infests humans and the disease is called listerosis.
Infections are more common in neonates, the microorganism being
transferred from other to fetus. The microorganisms have been associated
with still birth and meningitis."

Next, I looked it up in my Essentials of food safety and sanitation
manual, second edition. This is the 'standard' book on food safety
classes in Florida.

Without copying a lot of material, it says that L. Monocytogones is
particularly nasty, in apart because it is one of the few bacteria that
can grow at refrigerator temperatures (41 F/5C). It is most often
associated with raw milk, dairy items, raw meats, ready-to-eat foods,
meats such as hot dogs (i.e. sausages to non-North Americans), raw
vegetables, and seafood. In other words, a LOT of things can carry L.
Monocytogones.

Now, starting with this information, let's proceed logically.

It is a potentially fatal bug.

However, except for the warning that it can grow at 41F/5C), there are
no special warning/precautions noted that you should take.

So, what should you do? What I would do is:

Don't store potentially dangerous foods along time, because of the low
temperature growth 'problem'. Buy small quantities, eat what you want,
and discard the rest. Food can be dangerous and not smell/taste bad.
This is called a potentially dangerous food. L. Monocytogones can easily
create potentially dangerous food, because of it's cold temperature
growth abilities.

Monitor the temperature of your refrigerator. Buy and check a
refrigerator thermometer.

Avoid the foods above, unless properly cooked.

And what is properly cooked? Well, beef is properly cooked (rare) at
130F/54C, if held for 121 minutes (I know, bizarre times...)
Or, it is properly cooked (medium) at 145F/63C, if heated to this
internal temperature for 3 minutes.



Keep in mind the following:

The inside of a piece of meat is pretty close to sterile. I mean, the
outside may be very contaminated, but a piece of meat is pretty hard for
a bacteria to invade internally.

The outside temperature of a piece of meat will be at the temperature of
the oven after a few minutes. All, and I mean all, bacteria are killed
at 350F/177C, the most commonly used cooking temperature.

This means that hamburger, which is essentially all 'outside' meat (the
outsides are now inside, because of the grinding), and thus considered
contaminated. Hamburger and other ground meats (not poultry) must be
cooked to 155F/68C for 15 seconds to be safe. This is medium, bordering
on medium well.

All poultry must be cooked to 165F/74C to be safe.

By the way, I would avoid cooking using a microwave if you are worried
about food safety. Since they heat food unevenly, it is very possible to
get cool spots in food cooked in a microwave.

Given all the above information, I would think that medium roast beef
would be one of the safest foods around!

I hope this helps.

Colin
Clearwater, FL, USA







Erika wrote:
> I have a two pound roast beef that I was going to cook for tea
> tonight. (with roast potatoes, gravy, yorkshirepuds and veg)
> Normally I cook it in the oven and have it slightly pink in the
> middle.
>
> Now the trouble is since I am pregnant I am not allowed to eat meat
> that is not properly cooked through.
>
> Shall I then make a pot roast of it or is there any good way of
> cooking it in the oven withyout it getting dry?
>
>
>
> /Erika
>
> The first ten years of your life you try to be just like your parents.
> Then for then years you try to be as little as your parents as possible.
> Then you gradually change in to them.