Health Law

Harmful Bacteria In Produce Cannot Hide From New Irradiation Technology

By Colin Caywood

Researchers at AgriLife Research appear to have devised a new irradiation technique that effectively kills 99.9% of harmful bacteria, such as Salmonella and E. coli, while requiring only half the usual amount of irradiation, according to an article in today's Science Daily. The technique involves packing the produce in a Mylar bag filled with pure oxygen.

The U.S. Food and Drug Administration recently approved the use of irradiation at dosages of up to 4,000 Gray on leafy greens such as spinach,  said Dr. Carmen Gomes, AgriLife Research food safety engineer.

A Gray is a measure of ionizing radiation dose and it is equal to the absorption of 1 Joule of ionizing radiation by 1 kilogram of matter.

"That dosage was determined as what was necessary to achieve an 100,000-fold reduction of such pathogens as E. coli O157:H7 and salmonella," said Gomes, who is one of a three-member Texas AgriLife Food Safety Engineering Team. "However, we know based on previous research conducted by our group that above 1 kilo Gray (1,000 Gray) the quality of leafy vegetables starts to decay and they lose their freshness."

An 100,000-fold reduction corresponds to a 99.999 percent kill rate, according to Dr. Rosana Moreira, another member of the team.

"If you had 100,000 bacteria in your vegetable, it means you would end up with just one bacteria still living," Moreira said.

Despite the pathogen reduction benefits of irradiation, many consumers continue to express concern about the effect of radiation on the food.  "Would it mean my lettuce is full of radiation?"  The article does a nice job explaining why this process is not the equivalent of turning your salad into a green pile of radioactive waste:

Though being exposed to a Gray of radiation would be lethal for a human, the radiation leaves no residue on the vegetables, and the vegetables are perfectly safe for human consumption after the process, according to Gomes.

"It is analogous to the heat treatment when you expose milk, juices and cans of vegetables to very high temperatures for a period of time to kill pathogens," Gomes said. "If we humans were exposed to the same heat treatment we would suffer heat trauma as well. Moreover, the irradiating process is very well regulated. The energy of electrons we use is too low to produce radioactive materials."

Also, ionizing radiation it is not so likely to reduce nutrients such as chlorophyll, carotenoids and valuable antioxidants as thermal processes do, said Dr. Elena Castell-Perez , the third member of the team.

"Ionizing radiation can actually enhance some nutrients such as carotene and other antioxidants," Gomes said. "And irradiated food stays fresh longer."

Full post as published by Food Poison Blog on December 06, 2010 (boomark / email).