Given that I struggle to feed my son and I on a very limited budget, I stretch the limitations on food and whether it is safe to eat or not. I think I will plan to use stock before its 3 days old because the description in the excerpt below doesn’t sound very appealling. Click here to learn more or read an excerpt below.
For an expert opinion, I sent our recipes to O. Peter Snyder, a food scientist and veteran educator and consultant to the food-service industry, who has at times taken issue with government guidelines he considers unnecessarily conservative.
Dr. Snyder replied in an e-mail: “The process described by Mr. Ruhlman is a very high-risk procedure. It depends totally on reheating the stock before it is used to be sure that it doesn’t make anyone ill or possibly kill them.”
It’s a basic fact that every cook should know: bacteria that cause illness inevitably end up on nearly every ingredient we cook with, and even boiling won’t kill all of them.
Boiling does kill any bacteria active at the time, including E. coli andsalmonella. But a number of survivalist species of bacteria are able to form inactive seedlike spores. These dormant spores are commonly found in farmland soils, in dust, on animals and field-grown vegetables and grains. And the spores can survive boiling temperatures.
After a food is cooked and its temperature drops below 130 degrees, these spores germinate and begin to grow, multiply and produce toxins. One such spore-forming bacterium is Clostridium botulinum, which can grow in the oxygen-poor depths of a stockpot, and whose neurotoxin causes botulism.
Once they’ve germinated, bacteria multiply quickly in nourishing stock. They can double their numbers every 90 minutes at room temperature, every 15 minutes at body temperature. A single germinated spore can become 1,000 bacteria in a matter of hours, a billion in a few days.
As Dr. Snyder put it, “After sitting on the stove and growing bacteria for two or three days, Mr. Ruhlman’s stock almost certainly has high levels of infectious Clostridium perfringens cells, or Clostridium botulinum or Bacillus cereus cells and their toxins, or some combination thereof.”
Why has the Ruhlman family survived? Because Mr. Ruhlman boils the stock before he serves it, Dr. Snyder wrote. Any active bacteria are killed by holding the stock for a minute at 150 degrees or above, and botulism toxin is inactivated by 10 minutes at the boil.
But quickly reheating a contaminated stock just up to serving temperature won’t destroy its active bacteria and toxins, and the stock will make people sick.
“If Mr. Ruhlman ever has a cup of his three-day-old stock without thoroughly boiling it first, he will probably only do it once,” Dr. Snyder wrote. “It is irresponsible of any cook to prepare food in a way that actually creates a new and significant hazard, even though the hazard may be eliminated in a later step.”
Safety is one problem with keeping a stock at room temperature. Flavor is another. A reboiled three-day-old stock may be safe to eat, but it is now seasoned with millions to billions of dead bacteria and their inactivated toxins. It’s conceivable that they might add an interesting flavor, but more likely that the bacteria have feasted on the stock’s sugars and savory amino acids, the air has oxidized and staled the fat, and the stock has become less tasty.