If you enjoy fried things, and don’t enjoy gaining weight, then this picture represents the first stirrings of a science that might one day help you. It’s a picture of the structure inside a sliced potato as it’s being deep fried.
Scientists at the University of Illinois have used a technique called X-ray micro-computed tomography to look at what happens inside a 1.65mm potato disk as it is deep fried for different lengths of time. They described their results in a recent paper in the Journal of Food Science.
In the image above, the values on the left represent the different number of seconds the disk has been fried, and the pictures show how the pores inside a potato chip evolve over that time. The researchers hope that someday this will make fried foods just as delicious, but much healthier.
X-ray tomography uses X-rays to get two-dimensional images of the inside of an object. A computer then cobbles together many two-dimensional images to create a three-dimensional image of that object at a certain point in time. The images we’re seeing show the path of water inside an object as it fries in oil.
When food gets dropped into a fryer, it initiates a kind of battle between the internal water, which heats and escapes outwards, and the external oil. As the water escapes, it opens up pores in the food, allowing the oil to penetrate inwards. If a piece of food is really thick, there can be an impasse, as outward-pushing water prevents inward-pushing oil from penetrating all the way into the food. This is why deep-frying a turkey on Thanksgiving has become more and more popular. The oil keeps the water in, and the water keeps the oil out, making for cooked meat that’s neither dry nor greasy.
Potato chips don’t reach that balance. The water escapes, initially via winding, complicated paths through the chip. This keeps the oil out at first. But after a while, pores open up, and the walls between them are breached, making for straight routes and easier oil penetration. It also makes for a delicate honeycomb of crispy potato bits, which gives us the texture we love.
The scientists are hoping that, when we understand the process of frying more completely, we might be able to get the same structure other ways that don’t involve quite so much oil. For now, though, they’re just peering inside the potato.
And then, hopefully, trying a few.