In 2004, more than 12 million tons of tomatoes nationwide were processed into tomato sauce, puree, paste, and whole and diced products, readily available in any grocery store. But tomato processors have long faced a dilemma: Peeling tomatoes for canning can be done effectively with a lye bath -- but the waste generated becomes an environmental issue of killer tomato proportions.

“After it’s used, lye is usually neutralized by making it into a salt, but then you have a salt disposal issue -- it’s a huge environmental issue,” said Sudhir Sastry, a professor of food engineering in Ohio State University’s College of Food, Agricultural, and Environmental Sciences. “Processors also use steam to peel tomatoes, but they don’t
end up with the same quality.

“We’re finding that with ohmic heating, we get peeled tomatoes equal in quality to highly concentrated lye solution, without the environmental implications.”

For nearly two decades, Sastry has been examining ohmic heating’s potential for processing and preserving foods. Ohmic heating runs an electric current through food, heating it directly and eliminating the need for a boiler room or smoke stacks at the food processing plant. The process heats foods much more quickly than conventional methods and leaves behind a fresher-tasting product.

Sastry has applied for a patent on the process, together with his former graduate student, Pisit Wongsa-Ngasri, who has returned to his native Thailand. Sastry is a researcher with the college’s Ohio Agricultural Research and Development Center.

“Our process uses a 1 percent lye solution, as opposed to a 12 to 18 percent solution in traditional methods, so you don’t produce the large amounts of caustic waste,” Sastry said.

“The other benefit is that, in a traditional peeling system, lye will eat up the peel so that it’s not usable anymore. With our process, you still have the peel. Processors can mash up the skin and put it back in a paste or puree product. And it’s not just filler -- many vitamins and phytochemicals, such as lycopene, are heavily concentrated in the skin area. Using the skin actually improves the product.”

The process works well on a bench-scale model, but now Sastry is looking for funding to ratchet it up to the pilot-scale level, which would peel one tomato per second. “When we get to that point, industry will really be able to see the benefit,” he said.

So far, both Ohio and California tomato processors have met the idea with enthusiasm, Sastry said.

In 2004, Ohio produced over 177,000 tons of processing tomatoes, valued at nearly $14 million.

A video of how ohmic heating peels a tomato can be viewed at
http://www.ag.ohio-state.edu/~news/story.php?id=3239

By Martha Filipic