Manipulating porosity reduces salt and fat content in processed foods

How do you make salty, fried food healthier? By manipulating its porosity, two food scientists from the University of Illinois have found.

Researcher Youngsoo Lee has found that controlling the number and size of pores in processed foods allows manufacturers to use less salt while still appealing to consumers. Fellow researcher Pawan Takhar discovered that managing pore pressure in foods during frying reduces oil uptake, resulting in lower-fat snacks without affecting texture and taste.

70% of the salt that Americans consume comes from processed foods, so Lee studied the relationship between the microstructural properties of these foods and the way salt is released when it is chewed.

“Much of the salt that is added to these foods is not released in our mouths where we can taste it, and that means the rest of the salt is wasted,” Lee said. “We wanted to alter porosity in processed food, targeting a certain fat-protein emulsion structure, to see if we could get more of the salt released during chewing. Then food manufacturers won’t have to add as much salt as before, but the consumer will taste almost the same amount of saltiness.”

Increasing porosity also changes the way foods break apart when chewed, exposing more surface area and increasing saltiness, he said.

Takhar works with complex mathematical equations that describe the physics involved in the transport of fluids and in textural changes in foods.

“Frying is such a complicated process involving more than 100 equations. In a matter of seconds, when you put the food in the fryer, water starts evaporating, vapors form and escape the surface, oil penetration starts and heat begins to rise, while at the same time there’s evaporative cooling off at different points in the food,” he said.

Within 40 seconds of frying, the texture of gently fried foods like crackers is fully developed. Frying for longer simply allows more oil to penetrate the food.

“A lot of frying research has focused on capillary pressure in the oil phase of the process, but we have found that capillary pressure in the water phase also critically affects oil uptake,” Takhar said.

Capillary pressure makes overall pore pressure negative, and that negative pressure tends to suck oil from inside. Takhar’s simulations show when that pressure is becoming more negative.

“The trick is to stop when pore pressure is still positive (or less negative) - that is, when oil has had less penetration. Of course, other variables such as moisture level, texture, taste and structure formation must be monitored as well. It’s an optimisation problem,” he said.

When this balance is achieved, lower-fat, healthier fried foods are the result, he added.

Lee’s research was published in the Journal of Food Science. Takhar’s research was published in Food Research International.