Kitchen Safety and Avoiding Food Poisoning
Myth: You want to kill all those bugs!
Reality: No, let’s not. First, it is probably impossible to do that. Second, the longer you cook something or the higher temperature you cook it, the more the heat will affect the flavor of the food. There are no guarantees that overcooking food will make it safe, or that undercooking food puts you in danger
Because it is an average, the standards are much higher than commonly needed. Even if you were to kill 99.9999% and someone’s thermometer was off, or the oven was not heating properly, then overcooking provides some safety but at the expense of flavor.
Within the U.S. Department of Agriculture (USDA), the entity responsible for this is the Food Safety and Inspection Service (FSIS). As with most government bodies, it has a scientific advisory panel that makes recommendations. The advisory panel found that the FSIS figures for poultry were way too high. The FSIS recommends temperature and time enough to kill 99.99999 percent of the bacteria but the panel recommended enough to kill 99.995 percent of the bacteria.
At 122°F there are no bacteria that are pathogenic (cause illness) to humans that survive. There are, in some hot springs, certain bacteria that thrive at these higher temperatures. These bacteria are not harmful to humans, and would not find the human host hospitable. Ironically, for them the human body is too cool, and they prefer temperatures much higher.
But on Chopped, they reject undercooked food!
I’m a huge fan of the Food Network. On the show Chopped you will see the judges reject food that they consider “undercooked” or “raw.” Are they crazy? Well, they might be (most chefs, like surgeons, get a bit nutty). But they sometimes are overdoing it when it comes to chicken or worrying about cross-contamination in a twenty- to thirty-minute contest. The funny thing is they will eat something that a chef has double-dipped. (The mouth has a far higher bacteria content, but if they would kiss it, they eat it!) The bottom line: overcooking foods ruins the flavor and texture. Pork can be pink, and chicken should not be cooked to an internal temperature of over 145°F ¾and please use a thermometer, because guessing is never precise.
Food poisoning (technically we doctors call it foodborne illness) happens when we eat or drink something that is contaminated with bacteria, parasites, or viruses, or with some chemical that causes illness. Every year forty-eight million people in the United States become ill from food, 128,00 are hospitalized, and three thousand people die from foodborne illnesses.
For beef, the FDA states that it is safe when kept at a temperature of 130°F for 112 minutes or 140°F for twelve minutes. The temperature of a rare steak is between 130°F and 139°F in the center. By cooking the steak for forty-five minutes at 136°F in a sous-vide water oven, you will keep well within the recommended limits. Some cook the steak longer—two to four hours—but I find that forty-five minutes for a one-inch-thick steak works well. The fast grilling of a steak or standard cooking will also kill those bacteria.
With chicken we worry about salmonella. However, if you’re cooking above 130°F, the salmonella bacteria are unable to grow, as are all other common bugs. Still, food safety is important. Wash hands after handling raw meat, and wash all surfaces and utensils after they come in contact with raw meat. It is more likely that the raw meat will contaminate those surfaces and that those surfaces will pass the bugs onto other foods than you will become sick from the meat directly.
The biggest issue with bacteria and food safety is cross-contamination. This means the bugs from one food are passively transferred to another food, where they grow. For example, if you wash some raw chicken in the sink where there is a cutting knife, you can contaminate that knife with bacteria. If you clean the knife insufficiently to rid it of the bacteria and then use it to cut some cooked eggs, these eggs can become the perfect place for bacteria to grow, especially if the eggs sit at room temperature. If you eat the eggs, you can get sick from the chicken. (So the chicken came first. Sorry¾I couldn’t resist.) The lesson here is that if you wash raw poultry in the sink, be sure to have that sink cleaned out well to avoid cross-contaminating other utensils or serving dishes. Anytime you handle any raw meat or eggs, treat everything they touch as if it just came out of the toilet. (3)
Do not use the same cutting board for raw and cooked meats. If you own only one cutting board, be sure to wipe it down with a bleach solution after cutting raw meat on it.
If you use a knife or fork or any instrument on raw meat, wash that utensil carefully. Essentially, consider raw meat to be contaminated, along with anything it touches: you, your clothes, your cooking utensils, your cutting boards, and your knives. Remember, when people get sick from the bacteria from raw meat, it is typically because of cross-contamination from other foods, from food workers’ improper techniques.
Those steam trays at buffets are doing a job. By keeping the temperature of the food at 140°F, they are preventing bacteria from growing. There are two ways to prevent bacteria from being a problem with food: one is to keep the food cool, and the other is to keep it very warm.
Make certain that your refrigerator is kept at 40°F or cooler, and that there is plenty of room for air to circulate in the refrigerator. Keep the freezer at or below 0°F.
Wash your hands carefully. I use a special soap made primarily from alcohol, the same type of soap surgeons use before scrubbing in the operating room. You can purchase this from most stores; one brand is Purell. Always wash after handling raw meat, poultry, fish, shellfish, produce, or raw eggs. Scrub and lather for at least for twenty seconds after handling any raw meat. An easy way to do that is to sing “Happy Birthday” to yourself twice while scrubbing your hands. (4)
Wash all fruits and vegetables under running water before eating or cooking them. Use a vegetable brush to scrub melons and cucumbers, and then dry with a paper towel. Consider the vegetable brush contaminated, so sanitize it frequently.
It is better to throw out food than to be sick. Don’t be afraid to toss out any food that makes you suspicious.
How do food experts decide how much and how long to cook?
Microbiologists have determined how much heat and time is needed to kill ninety percent of the bugs To kill ninety-nine percent of the bugs you have to cook the food for twice as long (or increase the heat).
Myth: Chicken is the predominant source of salmonella.
Reality: A rising number of salmonella infections come from produce, vegetables, fruits, and nuts. Most of the salmonella in produce is not something you can eliminate by washing off the leaves, because the bacteria are in the produce. Your best defense against foodborne bugs in produce is to get the produce fresh and use it quickly. If you can get it from local sources it is often better. Avoid non-pasteurized juices
Cooking food at lower temperatures than ovens worries some people, but sous-vide cooking, as described, is quite safe from bacteria. Chicken held at 148°F for three minutes will kill 99.999999% of salmonella. While most conventional recipes say take chicken out at an internal temperature of 160°F, it only takes fourteen seconds to kill 99.999999% of bacteria. But at 160°F the proteins unfold, release their moisture, and become dry. Cooking at a lower temperature using sous-vide allows you to get that same “kill” rate of bacteria without sacrificing the quality of the meat or vegetables.
The time and temperature combinations for beef can be found from the Food Safety and Inspection Service guidelines.
Their chart is shared below.
|Min Internal Temp °F||6.5 log lethality||7.0 log lethality|
|130°F||112 min||121 min|
|135°F||36 min||37 min|
|140°F||12 min||12 min|
|145°F||4 min||4 min|
|150°F||67 seconds||72 seconds|
The 6.5 log lethality means you are killing 99.99997 percent of the bugs (also called 6.5D). A 7D lethality means you are killing 99.9999999 per cent of the bugs. If you have highly contaminated poultry (37,500 bacteria per gram of raw meat) then 3.5 ounces of meat would have 5.4 million Salmonella. To drop 7D means you would reduce ten million pathogens to one bug. It takes about 105 Salmonella per gram of food to cause illness; fewer Salmonella than that cause no clinical symptoms. Thus, with worst-case scenario you could kill just 99.999 per cent of the bacteria and not have symptoms (a 5D reduction).
The bacteria E. coli strain 0157 can cause illness with as little as ten bacteria per gram of food. Thus a 6.5 D would not be adequate but a 7D would.
As you increase the temperature, it decreases the time. It is a logarithm scale, which is why the drop in time with an increase in temperature.
In low temperature cooking (sous-vide), medium rare beef is typically cooked at 136°F for forty-five minutes to an hour. That provides a large margin of safety when combined with the searing of the surface at 400°F (most bacteria would reside on the surface of the meat) and seasoning the surface of the meat with salt, which also kills bacteria.
Most bacteria do not live above 120°F, and as you increase the temperature you kill more of them. At 102°F most bacteria can no longer reproduce, which is the protective nature of human fevers.
Bottom line: use a thermometer; Sous vide is OK; and don’t overcook your food.
It turns out the risk of chicken is more from using the same cutting board for raw chicken without cleaning it, or spreading the germs from the raw chicken by not washing the utensils or hands properly. This cross-contamination is more of a risk than undercooking poultry or eggs.
Int J Food Micro 2009
Pub Med 19272666
Fresh produce is increasingly found to be at risk for foodborne illness. It has been found in lettuce, pre-made salads, juice, berries, and sprouts. If you purchase pre-washed foods, or foods that are nicely packaged, watch the shelf life, and don’t be afraid to throw it out. It is cheaper to throw out food than to get sick.
J Food Prot 2004
Pub Med ID 15508656
Remember when you were taught that you needed to wash produce in order to prevent foodborne illness? Turns out that isn’t enough. The produce is contaminated before harvest, as the bacteria are internalized into the produce from the root system and into the plant. This prevents removal of the bugs by just washing the produce or using sanitizers on it. We could radiate the food as the only way to insure it free from contamination. Be careful out there. Another reason to think about growing your garden, or getting food from a local farm.
Foodborne Pathog Dis. 2012
Pub Med ID 22458717