Safe food storage practices
DEAR DR. BLONZ >>
My cooking class instructor mentioned that broths or gravies should never be covered with an airtight lid until they are cold, because botulism toxins can form in anything lukewarm and covered tightly.
How should one handle hot broth that you want to keep for a day or two?
— F.C., Sacramento
DEAR F.C. >> Botulism is an often-fatal form of food poisoning.
It's caused by eating foods that contain a toxin from the bacteria C. botulinum. These bacteria multiply by giving off spores, which produce the botulism toxin.
C. botulinum differ from other bacteria, such as E. coli, listeria and salmonella, in that they can grow without air (oxygen). In addition, the botulism-producing spores are heat-resistant.
Food preservation techniques such as canning must include a heat treatment that lasts long enough to kill C. botulinum, knocking out the ability to produce spores.
Ten minutes of boiling will destroy the toxin that causes the disease.
Outbreaks of botulism from canned foods are usually traced to inadequate heating times or temperatures.
Placing food in an airtight container does not increase the risk of botulism unless the bacteria are already present.
It's doubtful that these particular bacteria would be a problem in cooked foods when good sanitary practices have been followed.
In fact, leaving the lid off increases the chances that other airborne bacteria can enter any nutrient-rich food or broth.
It also increases the likelihood of picking up errant room or refrigerator odors.
It's a good practice to refrigerate leftovers immediately in a sealed container. By rapidly cooling leftovers to refrigerator temperature (40 degrees), you help ensure that the food will remain safe.
Consider cooling your broth in a covered container with a large surface area, such as a shallow baking dish. One technique I use is to have several flexible, reusable ice packs at the ready in my freezer.
That way, when some food needs to be chilled rapidly, the ice packs can be placed under, around or on top of the container.
Other sensible approaches are never eating or tasting from containers with bulges, or from any that spurt liquid when opened.
(Note that this is different from vacuumpacked items, which suck in air when opened for the first time.)
Find out more about botulism at b.link/ hv67cc. For a general reference on food poisoning, you can download the second edition of the Food and Drug Administration's Bad Bug Book at b.link/yg7nrk.