URBANA, Ill. – Food drying or dehydration is an important part of the food processing industry as many products are dried for preservation or to extend shelf life—think of dried fruit, like strawberries or apples, or other food products.
But the dehydration process, especially thermal drying, consumes a significant amount of energy and can ultimately affect the quality of the product.
Researchers from the University of Illinois were recently awarded $910,000 Agriculture and Food Research Initiative (AFRI) from USDA’s National Institute of Food and Agriculture to develop two innovative drying technologies, with the goal of reducing costs and improving food quality during the food drying process.
Hao Feng, professor in the Department of Food Science and Human Nutrition at U of I serves as a project director on the study. Feng and his research team will look at the use of ultrasonic contact drying (versus thermal), as well as an innovative impinging jet drying technology developed by co-project director, professor Jamal Yagoobi from Worcester Polytechnic Institute.
“In food science and food processing, drying has been a very important part of process operations for a long time,” Feng says. “It is also a very energy-intensive process; it takes a lot of energy to remove water. Drying accounts for approximately 10 percent (1.2 quads) of all process energy used in American manufacturing.
“That’s a huge percentage just for drying, and food agricultural products are a huge portion of that,” he adds.
Along with energy costs, food quality is also a big issue. “If you apply heat in order to dry food, you destroy heat-sensitive nutrients. And you change color. If you’re drying strawberries, for example, the color is not always good and vitamin C will be diminished. Drying is very important in terms of quality and nutrients, as well as consumer liking. It’s an important topic of how to improve quality when drying.”
Feng has worked to improve food drying issues through his work with the Center for Advanced Research in Drying, funded by the National Science Foundation, especially focusing on the use of ultrasonic drying technology.
“Many people want to improve energy consumption, but don’t deal with quality. Food scientists care about quality and this project deals with both issues,” he says.
Feng and his team have proposed a non-thermal, ultrasonic drying method in which heat is not applied to the food. “That is potentially a big advantage because if you don’t apply heat, you can conserve energy. Also there is no damage caused by heat.”
Instead, the use of ultrasonic vibration for drying converts electrical energy into high-frequency mechanical vibration that is more efficient than thermal drying, Feng explains. And it’s quiet. Normally humans can’t hear frequencies above 18 kHz; the ultrasonic vibration used in this drying method is in frequencies of above 20 kHz.
“We are looking at ultrasonic contact drying because we are good at this. We’ve worked on ultrasound for 17 years on different applications. This project is a new application,” Feng says.
The impinging jet drying technology, created by Yagoobi, has promise because the jet drying causes no damage to the surface it is applied to, in this case, food products. Like the ultrasonic drying technique Feng brings to the table, the impinging jet process is also unique and innovative.
“It has been used in the paper industry to dry paper,” Feng says. “It is high efficiency and causes no damage to the tissue. There may be other advantages as well. This is new technology, especially in the food industry.”
The research will include mechanical engineering, food chemistry, food processing, and agricultural engineering to develop the technologies and evaluate the quality of the food after drying.
For now, the researchers will test their technologies on fruits and vegetables, including strawberries and apple slices. “We don’t know now, but in the future, this method can likely be used to dry other products,” Feng says.
The project, the first in AFRI’s Food Manufacturing Technologies program, is funded for three years.