Ace Food Desk – New frying method makes healthier fries with less oil

French fries are hard to resist, and almost everyone knows that feeling. A plate of hot fries arrives, the crispy smell spreads through the air, and suddenly healthy eating feels less important. 

Frying gives food a crunchy outside and rich flavor, but the same process also adds a large amount of oil. 

Extra oil means extra calories, and eating foods like this very often can increase the risk of obesity, high blood pressure, heart disease, and Type 2 diabetes.

Because of these concerns, scientists have started looking for new ways to fry food. One recent idea involves microwave frying, which researchers explored while studying how to reduce oil in French fries.

Why French fries absorb oil

Frying has been used for a long time, and deep-fried foods became more popular as cooking methods improved. 

Oil helps cook food quickly and gives foods like French fries their crispy texture. However, some of that oil also moves into the food during frying.

When oil enters the food, the calorie content increases. This is why fried foods usually contain more energy than baked or boiled foods. 

Professor Pawan Singh Takhar studies this issue in the Department of Food Science and Human Nutrition at the University of Illinois Urbana-Champaign.

“Consumers want healthy foods, but at the time of purchase, their cravings often take over,” he said. “High oil content adds flavor, but it also contains a lot of energy and calories.”

“My research team studies frying with the aim of obtaining lower fat content without significant differences in taste and texture.” 

Scientists study frying physics

To understand how oil enters food, Professor Takhar and doctoral researcher Yash Shah studied French fries during frying. The team prepared potato strips before starting the experiments. 

Each potato was rinsed, peeled, and cut into long strips like regular fries. The strips were briefly cooked in hot water and lightly salted before frying.

The potato strips were then fried in soybean oil heated to about 356°F (180°C). During cooking, the researchers measured temperature, pressure, moisture, texture, and oil content to see what was happening inside the fries.

The experiments also tested microwave frying at two frequencies: 2.45 gigahertz and 5.8 gigahertz. The lower frequency is similar to the one used in a typical household microwave oven.

How oil enters French fries

A potato may look solid, but inside it contains many tiny pores filled with water. At the start of frying, these pores are full of water, so oil cannot easily enter the potato.

As frying continues, heat causes the water inside the potato to evaporate. This leaves empty spaces inside the food, and oil can move into those spaces.

Pressure inside the pores also changes during frying, which affects whether oil stays outside or moves into the food.

“Think about a straw in a drink. If you push air into the straw, it creates positive pressure and any liquid will be pushed out. But if you suck on the straw, the liquid moves upward,” Takhar said.

Takhar explained that food materials can be imagined as containing many tiny straw-like structures – when positive pressure is present, oil stays out, but when negative pressure forms, the oil begins moving inward.

Microwaves reshape the frying process

Traditional frying heats food from the outside first. Hot oil touches the surface of the potato, so the outer layer cooks quickly while the center warms more slowly.

Microwave heating works in a different way. Microwave energy moves through the food and heats water molecules inside the potato at the same time. As a result, heat forms throughout the potato instead of only at the surface.

“When we heat something in a conventional oven, the heat moves from outside to inside, but a microwave oven heats from the inside out because the microwaves penetrate everywhere in the material,” Takhar said.

“The microwaves oscillate water molecules, causing more vapor formation and thus shifting the pressure profile toward the positive side. The higher pressure produced by microwaves helps reduce oil penetration.”

Because microwave heating produces more vapor inside the potato, pressure inside the food stays higher for longer. This higher pressure slows the movement of oil into the food.

Combining microwaves and frying

Microwave frying can reduce oil absorption, but using microwaves alone does not create the crispy texture people expect from French fries. Fries cooked only with microwaves often turn out soft instead of crunchy.

“However, if you just use microwave frying, you get soggy food,” Takhar said. “To obtain a crispy texture and taste, you need conventional heating.”

“We propose combining the two approaches in the same unit. Conventional heating maintains the crispiness, while microwave heatinglowers the oil intake.”

A combined system could allow microwaves to reduce oil absorption while traditional frying creates the crispy outer layer.

Healthier fries ahead

The research suggests that microwave-assisted frying could help the food industry make fried foods like French fries in a healthier way. This method can reduce cooking time and also lower the amount of oil absorbed during frying.

Food manufacturers could modify existing industrial fryers by adding microwave generators. These devices are widely available and relatively inexpensive, which makes the approach practical for large-scale food production.

If companies use this method, future French fries could stay crispy and satisfying while containing less oil.

For people who enjoy fried foods, this change could make a familiar comfort food slightly healthier without changing the eating experience.

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