What Science Says About Food Poisoning And The Slow Cooker

We have all heard the battle cry on the Internet of those that are thumping their chest and waving their hands  about food poisoning, especially when it comes to using the humble slow cooker.

Here are a few of their statements on the matter:

"Food doesn't get hot enough 2 kill bacteria if reheated in a slow cooker"

"(Slow) Cooking with frozen food significantly increases the amount of time it takes for your food to reach this safe temperature and thus significantly increases the chances of you and your family getting food poisoning :(  I for one WILL NOT take that risk with my loved ones.  But you are free to weigh up this risk for you and your family."

"Jane, you mentioned turkey - do you do a whole turkey in the sc? I've googled and some articles say yes and others say it's a food poisoning risk. I'd love to know for next Christmas!."

"you could go high and then after two hours before going to low. This is so meat reaches correct temp quicker so you don't get food poisoning."

These people are so busy being 'right' and insisting that others follow their teaching that they haven't done the homework to get the facts.

Read on to have your paradigm shifted.

Is Foodborne Illness a Real Concern With Slow Cookers?

The short answer, NO. There is no more danger of foodborne illness using a slow cooker than any other type of heat source. More foodborne illness is caused by food being left out after it’s cooked than before or during the real cooking process.

"The concern is unfounded and is perpetuated ignorance."

The US Department of Agriculture states that the slow cooking method is a safe method of preparation because the steam created within the tightly covered pot combined with the lengthy cooking time destroys the bacteria that might be present in the food. For the slow cooker to produce enough steam to kill the bacteria, it must be at least ½ full.

How do slow cookers work?

A slow cooker is a covered ceramic crock set into a double-walled outer aluminum container. Electric coils in the walls of the outer container slowly heat the inner crock, which holds the heat exceptionally well, maintaining a consistent temperature with little energy use (200 to 300 watts of electricity per hour). The low and high settings the low setting for most slow cookers is about 200°F for the high setting is about 300°F.

Slow cookers are closed systems like an oven and can be used for most things that you use an oven for. The lid design creates a tight seal, trapping heat and moisture within the crock and allows little evaporation. The condensation of cooking liquid drips back down  the crock keeping the food moist allowing the meal to be left unattended for several hours without having to worry about your meal burning or drying. The lids are clear so that you can see what is going on inside without lifting the lid and dropping the inside temperature. If there is condensation on the inside of your lid just to give it, a little jiggle and the moisture will roll off, and you will be able to see inside your pot. If you do need to lift the lid, know that you also increase the cooking time by letting the steam escape and bringing down the temperature; adding 15 minutes for low and 10 minutes on high to your cooking time.

The food poisoning concerns debunked by science.

According to the Mayo Clinic, there are more than 2,000 strains of salmonella bacteria, but only a dozen or so make people sick. Most often, salmonella poisoning results in gastroenteritis, a severe stomach illness. Salmonella is most often contracted by eating raw or undercooked meat, poultry, or eggs.

If you think you might have salmonella poisoning, consult your doctor. The illness typically runs its course in a matter of days even without treatment, though doctors urge patients to drink plenty of fluids to prevent the dehydration that sometimes results from vomiting and diarrhea.

According to CDC.gov (the Center for Disease Control),” Many cases of botulism are preventable. Foodborne botulism has often been from home-canned foods with low acid content, such as asparagus, green beans, beets and corn and is caused by failure to follow proper canning methods. However, seemingly unlikely or unusual sources are found every decade, with the common problem of improper handling during manufacture, at retail, or by consumers; some examples are chopped garlic in oil, canned cheese sauce, chile peppers, tomatoes, carrot juice, and baked potatoes wrapped in foil.

Because the botulinum toxin is destroyed by high temperatures, persons who eat home-canned foods should consider boiling the food for 10 minutes before eating it to ensure safety. “This is why foods of this nature are brought to above 140°F.

Notice that there was no mention of cooking with a slow cooker.

In trying to verify or dispel the myths and mysteries of the use of slow cookers, in this day and age, I set about doing my research. The research in and of itself was enough to write volumes.

For the sake of brevity, I’ll keep this section matter-of-fact… or I may get a little snarky, and we don’t want that.

My first stop for researching the safety of the slow cooker method of food preparation was the government food safety sites. I don’t know if you ever subjected yourselves to these sites, but they are quite interesting. My questions and answers are as follows:

  1. At what temperature does bacteria grow on food and how long must food stay at that temperature for the bacteria to be a health issue?

Most foodborne bacteria grow between 40°F and 140°F. That is to say, that the temperature of the food itself must be between 40°F and 140°F for bacteria to grow and it must stay between 40°F and 140°F for one to two hours minimum for bacteria to START to grow. The fluctuation in times depends on the temperature of the food according to the USDA website. Food temperatures closer to 40°F can be left at that temperature for two hours while foods that are closer to 90°F bacteria may well have started growing after an hour.

As an interesting aside the USDA went on to say that most of this foodborne bacteria dies at 165°F.  I think that perhaps that’s why so many of their suggested food doneness temperatures are 165°F.

  1. Is it safe to cook frozen meat and poultry without thawing it first?

According to food safety.gov, “if you don’t have enough time to thaw meat or poultry, remember it is safe to cook from a frozen state. Your cooking time will be about 50% longer than cooking fully thawed meat or poultry.” But according to the USDA, “you should always thaw meat or poultry before putting it into a slow cooker. If using commercially frozen slow cooker meals, prepare according to manufacturer’s directions.”

The government has contradicted itself.

I went to the government’s chat function named, Ask Karen, to ask about the discrepancy in these two web pages. I copied and pasted the above and then ask ‘her’ what the difference was between my freezing meals and meals commercially frozen when putting them into a slow cooker. Her reply, “I see no difference as long as the meat and produce are cut into similar size pieces as a commercial product.”

If you have an interest in such products, the Crock-Pot website sells and ships frozen meals to be taken from the freezer to your slow cooker which should ease any concerns about the validity of the method.

  1. The next thing I noticed on the USDA website was that it stated “that when roasting meat and poultry to use the oven temperature no less than 325°F.” The low setting on slow cookers is 200°F so again I went to Ask Karen to see if this meant that roast beef, pork, and poultry should not be cooked in a slow cooker at all.

I was relieved when she replied “If you are cooking food in the oven they recommend 325 °F or higher. The slow cooker doesn’t have temperature settings, but ‘low’ for a slow cooker is safe because with the heating element surrounding the food causes it to heat up quickly.” You just got to love Mr. Naxon!

The government guidelines on food safety are ‘guidelines’ meant for our well-being and are written to best protect the least intelligent of us; they are written at different times by different people with different mindsets and backgrounds for different purposes. Application of common sense needs to be applied. Often when the government gives a guideline, it is because they have not had the time, funds or desire to test the item in question, so the answer is always ‘don’t do it.’

So what have we learned from asking the government and looking at the practices of the major corporations, with major legal staffs, recommendations for use of their slow cookers?

  1. The temperature of the actual food must stay for 1 – 2 hours between 40°F and 140°F for foodborne bacteria to start to grow. Frozen food that is not to 40°F is not a factor and once the food reaches 40°F it will heat just the same as food that started at 40°F.
  2. A lot of foodborne bacteria die at 140°F and even more at 165°F.
  3. You may cook frozen food cut in chunks in the slow cooker, noting that it will add about 50% to your cook time. The transference of heat will not keep the food between 40°F – 140°F for an extended period because “the heating element surrounding the food causes it to heat up quickly.”
  4. You can prepare roasts in the slow cooker because of “the heating element surrounding the food causes it to heat up quickly.”

Now that you have some science-based information you can speak with  authority and perhaps your science - based information will out weigh the wives' tales of food poisoning relating to slow cookers.

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