Three-dimensional X-ray microtomograph images reveal changing pore structures inside fried potato disks. Photo by Pawan Takhar
URBANA, Ill., Feb. 25 (UPI) -- Researchers at the University of Illinois wanted to know what happens to the internal structure of various foods when they're dunked in a vat of hot oil.
To find out, scientists there have been taking micro X-ray images of fried foods.
Specifically, food scientist Pawan Takhar was interested in how oil is distributed throughout a food item's microstructure as it is fried.
"Through conventional lab techniques we can already see how much oil content is in food material, but we didn't know how it gets distributed throughout the material," Takhar explained in a press release.
A new imaging technology called X-ray micro-computed tomography, or micro-CT, allowed Takhar and his colleagues to capture 3D images of potato slices that had been fried for varying lengths of time.
The images offered new insights into how oil penetrates the potato's pores and pore networks.
"As you fry the material, you can see how those pore structures are forming," Takhar said. "We found that in the beginning of frying, the pore network is very complicated."
"The waviness in the pathway, the tortuosity, is very complex in the beginning so the material resists oil penetration," Takhar continued. "But as the frying progresses, those pathways become simpler. Pores open up and are easily accessible from the outside and oil can be taken up."
One aim of the Takhar's work is to develop fried foods with less oil.
"It is not easy to make a product that has no oil and still provides taste, flavor and texture that consumers enjoy," he explained. "People like that fried flavor and the texture of crispiness outside and softness inside."
Previous experiments suggest chicken nuggets, french fries and other moisture-rich fried foods are able to limit internal uptake of oil, relegating oil absorption to the surface.
But Takhar says he and his colleagues -- whose latest work was published in the Journal of Food Science -- are still some way from understanding how the frying process alters the internal microstructure of foods.