19 Sep 2013 Dishwasher cooking trend raises eyebrows among food-safety experts
It’s a type of sous vide – the phenomenon of dishwasher cooking that’s recently been getting a lot of exposure in articles and blogs. Chefs and foodies recommend it, Whirlpool and General Electric don’t. However, very little data exist to guide discussions on the safety of the practice.
According to an article in Food Safey News, Lisa Casali, an Italian food author who has written a book on the subject of dishwasher cooking, spent some time studying the safety of the practice.
Before writing “Cucinare in Lavastoviglie” (“Cooking in the Dishwasher”), she had an Italian chemical laboratory analyze samples of food cooked in various containers in a dishwasher. She said that the results showed that food cooked in vacuum-sealed plastic bags or hermetically sealed jars doesn’t risk contamination from the water or detergent used in the dishwasher.
However, that’s not the only concern about the practice for North Carolina State University food specialist Ben Chapman. There’s also the question of whether dishwashers heat up the food enough to kill pathogens such as Salmonella enteritidis and clostridium botulinum.
“I have no idea what temperature my dishwasher reaches,” Chapman said. “That matters here because, with fish, the recommended endpoint temperature is 145°F (62.7°C).”
Casali said Electrolux representatives told her that the dishwashers she used while researching for her book reach 131-167°F (55 to 75°C).
Chapman said the scientific literature provides specific cooking temperatures to make specific foods such as poultry, beef, pork and fish safe to eat, much in the 145 to 160°F (62,7 – 71°C) range. But, especially for eggs, the dishwasher would need to reach some of its highest temperatures to ensure that any pathogens in the food were destroyed. For fruits, vegetables and food that can be eaten raw, he said that cooking temperature might be less of a problem.
Chapman’s concern with C botulinum involves food being left in a sealed space for an extended period of time. He said that the best environment for the bacterium’s cells to vegetate in is one of less than 240°F (115.5°C) with little or no oxygen.
“We’ve seen outbreaks of botulism from the environment people have created in their home, where they can their food, then leave it in their pantry for weeks,” Chapman said.
Using a dishwasher over cooker for canning (or preserving) also concerns Chapman because, although boiling water (212°F or 100°C) will kill vegetative cells, it is not enough to kill inactive spores. Cookers for canning reach 240°F (115.5°C) degrees for canning and other processes because they inactivate the spores.
Less heat than that in an environment without oxygen can result in spores germinating and outgrow resulting in vegetative cells. Chapman said a byproduct of cell multiplication is toxin.
“So you need to get to 240 to inactivate the spores – or once they are vegetative,” he said.
US FDA spokesman Sebastian Cianci said he could find no reports of illness related to dishwasher cooking, although he said cooking methods might not be included in such statements.
Casali stressed that dishwasher cooking isn’t the only time people are served food prepared at low temperatures.
“Cooking at low temperature is a popular technique in restaurants and … every day such dishes are served by the thousands,” she said…..