Reza Tahergorabi, Ph.D., right, and graduate student Sam Adegoke examine a test tube of the protein mixture used to coat food samples before frying.
Deep-fat frying gives chicken and fish filets a golden brown color and a hard-to-resist crunch. It also dramatically increases the fat content of these otherwise lean meats.
Fried foods are one of the culprits in the American obesity epidemic. Obesity rates recently climbed to 39.8 percent of adults and 18.5 percent of youth, according to the National Center for Health Statistics.
Obesity comes on a tray full of unsavory sides. Obese people are at higher risk of heart disease, Type 2 diabetes, certain cancers and other health problems. More than 600,000 people die of heart disease in the United States every year.
“Since 1921, cardiovascular disease has been the No. 1 killer in the United States,” said Reza Tahergorabi, Ph.D., an associate professor of food science. “We have not solved it yet. Part of the reason is because people don’t want to change their diet.”
If people won’t change what they eat, maybe there’s a way to make those favorite foods healthier, Tahergorabi thought. He and his graduate students are trying to find a way to keep the crunch and cut the fat.
In a lab on the first floor of Carver Hall, they’re creating and testing edible protein-based coatings as a way to seal in moisture and block fat absorption during frying. The coatings are made from readily available material – protein recovered from byproducts of processing the meat.
The research team made protein-based solutions of 5, 10 and 15 percent protein. They applied the protein recovered from fish to the fish fillets and the protein recovered from chicken to chicken pieces. The meats then were battered, breaded and fried.
For the meats coated with a 15 percent protein solution, fat absorption was reduced by 85 percent in fish and up to 75 percent in chicken. Additional testing with both lab equipment and human testers found that the coating did not hurt the appearance, flavor or texture of the meats. If the researchers can consistently produce healthier fried foods, this process could be a potent new weapon in the fight against obesity.
Understanding how the coatings work requires understanding how frying works. The problem with frying chicken and fish in the traditional way is that dunking the meat in hot oil causes its moisture to vaporize. The water that escapes is replaced by oil, causing the fat content of the meat to skyrocket. In some experiments conducted by other researchers, the fat content of fish was 100 times greater after frying than it was before, Tahergorabi said.
“The oil acts as a medium for heating, and at the same time the oil is absorbed into food when you fry it,” he said.
The protein coatings developed in Tahergorabi’s lab prevented moisture loss during frying, and thereby reduced fat absorption. The coating essentially acts as a fat blocker.
“When you are frying, there are pores developing in the chicken,” said Daniel Ananey-Obiri, a graduate student who worked with Tahergorabi on the research. “An edible coating blocks the pores and prevents the oil from entering the chicken. It sets up a barrier to fat absorption.”
Ananey-Obiri came to A&T from Ghana, completed his master’s degree in food and nutritional science and has started a Ph.D. in computational science engineering, also at A&T.
In addition to the potential health benefits, the use of by-products as coatings is good for the environment. Using by-products in frying reduces the need for their transportation and disposal. When a fish is filleted, as much as 70 percent of it can become waste.
The coatings are made from readily available material. Processing chicken and fish results in lots of high-protein by-products, like skin and meat left on the bones. The researchers have extracted the proteins through a process known as isoelectric solubilization and precipitation. Tahergorabi, an A&T faculty member since 2013, began using ISP when he was working on his Ph.D. at West Virginia University.
The first step is to grind the by-products and add water. Add a base, such as sodium hydroxide, to increase the pH, and the proteins unfold and dissolve in the water. When spun in a centrifuge at 10,000 revolutions per minute, the protein and water form a distinct layer in the test tube.
The protein solution is extracted, then an acid is applied to reduce the pH and to weaken the bonds between the water and the protein. Another spin in the centrifuge separates the protein from the water. The researchers are left with pure protein, in this case a white paste with the consistency of peanut butter.
Some consumers may be reluctant at first to eat a coating derived from by-products, Tahergorabi acknowledged, but the public has been won over before. He points out that some initially refused to eat foods that had been irradiated, but that practice is now commonplace.
Researchers at other institutions are exploring different sources for edible coatings, such as proteins from whey and soy, but those trigger allergies in some people. Tahergorabi’s process avoids this issue by using protein from the same food to which the coating will be applied.
Tahergorabi and his team are examining other modifications to the frying process that could provide additional health benefits. One is replacing the corn starch used in batter with sweet potato starch. His early results show that the sweet potato starch decreases water loss and fat uptake in fried foods.
He and his graduate students also are looking at other natural ingredients that could have health benefits when incorporated into the preparation of meats for frying. One such ingredient is quercetin, a compound contained in onion peels – another frequently discarded by-product. Quercetin has shown potential as having antibacterial, antioxidant and anti-obesity properties.
They also may investigate how the type of oil used for frying affects fat uptake during frying. Popular choices for restaurants and home cooks include peanut oil and canola oil, based on factors such as smoke point and flavor transfer.
One of Tahergorabi’s graduate students, Sam Adegoke from Nigeria, enrolled in the food and nutritional science master’s program at A&T in August. Adegoke is excited to be working with Tahergorabi and is looking forward to making a global impact.
“Fat uptake and the consumption of fat is a problem across the world, not just in the U.S.,” Adegoke said. “This research could allow us to have the foods we love to eat in a healthier presentation. The potential is big.”