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Sci-Tech

The juicy payoff of peeling tomatoes with infrared energy

Using IR blasts and a vacuum chamber, a new process developed by USDA researchers could save water and lead to better canned tomatoes.

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Researchers test a prototype of the machine that can peel tomatoes like no machine before. Z. Pan Laboratory

It sounds like a Zen meditation: How do you perfectly remove the skin from a tomato without removing any of the flesh inside? But it's not monks on a mountaintop who have figured out the answer to the tricky question. It's scientists at the USDA's Agricultural Research Service.

The process they've come up with involves sending Roma tomatoes along a conveyor belt, where they get blasted by infrared energy from special tubes for about 60 seconds. Infrared is a type of invisible electromagnetic radiation that has wavelengths longer than visible light but shorter than radio waves. After the tomatoes get blasted by the waves, which cause their skin to crack, they pass into a vacuum chamber where pinch rollers remove the outer layer.

The team that came up with the method was led by engineer Zhongli Pan, and tested the process on 6,000 tomatoes over the course of five years. Their research was published in the January issue of Agricultural Research magazine.

The researchers say their method has three distinct advantages over current tomato-skin-removing processes, which include steam-heating or blasting the fruits with hot jet sprays of sodium hydroxide or potassium hydroxide and then rinsing them in tap water.

First, their method is "dry," meaning that all that water involved in current methods can be saved, and the secondary water-treatment processing that arises from modern methods can also be eliminated.

Second, the process removes just the skin and the slightest bit of the tomato beneath it, unlike today's methods that can over-peel the tomatoes. "In a study published in 2014, the researchers showed that peel-related-loss -- measured by comparing the tomato's weight before and after peeling -- was about 8 to 13 percent with the infrared heating and about 13 to 16 percent with sodium hydroxide-based peeling," says the article about the research.

Finally, the infrared method seems to be an improvement because the structure of the tomato tends to hold up better and doesn't get mushy.

Of course, if you've ever tried getting the peel off tomatoes at home, you have some sense of what the researchers are talking about. You can drop them in boiling water to get their skins to come off, but it does tend to make the fruit kind of mushy. Roasting them works too, but that also cooks the tomato, which might not be ideal for your purposes.

Although this research was aimed at the tomato-canning industry, who knows? Maybe one day there will be a Ronco automatic infrared tomato peeler on kitchen counters across America.