Folklore says if you make crab soup during a thunderstorm the soup will spoil. Believers say it has happened to them. They blame anything from a drop in atmospheric pressure to the electrical charge in the storm air for turning their soup.
Skeptics say thunderstorms have nothing to do with spoiled soup. They contend the spoilage is usually caused by improper cooling of the cooked soup when it is stored in a refrigerator.
A few cooks say they don't know if there is any scientific basis to their behavior, but they don't make soup during a thunderstorm because their Mama and Papa told them not to.
That is what I found out when I called cooks and scientists around Maryland and attempted to find out if there was any fact behind this nugget of Maryland folk wisdom. The truth of the matter, like the soup itself, seems turbid.
Chef Mark Henry, owner of the Chester River Inn, in the Kent County town of Chester, said he is a believer in the dangers of thunderstorms to culinary efforts. Henry said several years ago he was working at a restaurant in Columbia called Crystal's when a thunderstorm hit and his crab soup spoiled. That taught him a lesson, he said. "There is a drop in pressure when a thunderstorm comes through. And your soup boils at a lower temperature. So you think you have cooked your soup all the way through and you haven't."
When the partially cooked soup ingredients are stored, the bacteria in them remains active and turns the soup, he added. So now when Henry sees dark clouds on the horizon, he cooks his crab soup longer.
Fred Davis, the National Weather Service's chief meteorologist at Baltimore-Washington International Airport, confirmed that atmospheric pressure drops when a thunderstorm rolls through the area. Once the storm leaves, the pressure goes back up, he said. And Dick Berg, a physicist at the University of Maryland in College Park, said it is fundamental physics that when the atmospheric pressure drops, so does the boiling point of liquids. But he was skeptical that a slight drop in the pressure during a passing thunderstorm would have a significant impact on the temperature of the crab soup.
Chef Mike Baskette, who teaches at Baltimore International Culinary College, also doubts that a slight drop in the boiling point of the soup would cause the soup to spoil. Even though the soup might boil at a lower temperature, because of the drop in pressure, that temperature would still be high enough to wipe out bacteria, he said.
Baskette suspects two other culprits for spoiling the soup. One is the soup pot. Uncoated aluminum pots, for instance, can increase the chance of spoilage. During a thunderstorm the electrical charge in the air could facilitate a reaction between the pot's aluminum surface and the acid in tomatoes used for making crab soup, he said. The reaction could cause the soup to spoil.
Baskette recommends using either a stainless-steel pot, or an aluminum pot lined with stainless steel. He added that the reaction between the pot and the acid could also occur on a sunny day, but that the chances for spoilage were probably higher during the charged air of a thunderstorm.
Another common soup spoiler is improper cooling, Baskette said. Sometimes containers of cooked soup stored in a fridge do not cool down below 40 degrees, he said. Usually the soup around the edge of the pot cools down, but the soup in the center of the pot stays hot, even in the fridge. This means that bacteria in the warm center of the soup go to town. He recommends storing the soup in small containers, checking the temperature of the soup as it cools, and stirring it.
Finally, I came across some cooks who don't believe that thunderstorms spoil crab soup, yet can't bring themselves to make it in stormy weather. One is Bill Cusick, a retired Baltimore Gas and Electric Co. worker, who whips up 8- to 10-gallon batches of crab soup at home for special occasions. Cusick said that when he is thinking of making soup in his Timonium home and "sees those dark clouds gathering up over Cockeysville," he hears his father's voice.
"My father was from the Eastern Shore down around Fishing Creek and he always told me if you make crab soup in a thunderstorm, the soup would spoil," Cusick said.
And so, as a tribute to his father, Cusick postpones his soup-making plans. "No matter what my father told you, he was right," Cusick said. "Even if he wasn't."