When Every Day is Fry-Day
A lot of frying goes on at food manufacturing businesses around the country. Potato chips, chicken strips, fish sticks, onion rings, French fries: the list goes on and on. This adds up to a lot of fried foods, as well as to a lot of frying oil needed for their manufacture.
The quantity of frying oil needed is huge, which makes the dilemma of knowing when to change the oil an economic concern. It’s also a health concern. Cooking oil degrades over time, especially when exposed to high heat; and it produces unsavory compounds that at best make your food taste bad and at worst could be harmful to your health. Change the oil too late and food quality suffers; however, change the oil before it is necessary, and resources are wasted.
Chemical tests can accurately determine the degree of oil deterioration, but have been impractical for many industries—the tests are time consuming, require designated lab space, and create chemical waste. In looking for alternatives, food scientists at the University of Nebraska–Lincoln developed a method that uses near-infrared spectroscopy, which takes a few minutes to determine the state of an oil sample accurately without the need for special lab space or waste disposal. The work is described in an article published in the February 2007 issue of Journal of Agricultural and Food Chemistry (2007, 55, 593–597).
Randy Wehling and Susan Cuppett, professors of food science and technology at the University of Nebraska–Lincoln, and doctoral student, Choo Lum Ng, collaborated on the project, which involved developing statistical models that relate spectral data to the extent of degradation in a soy-based oil.
To develop their models, the researchers first created a series of progressively degraded oil samples. They then analyzed each sample by using two methods typically used in gauging oil deterioration: one to determine quantities of polar materials and the other to measure free fatty acids. A near-infrared spectrum also was obtained for each sample.
These two parallel sets of data, one chemical and the other spectral, made it possible for the researchers to use statistical techniques to build several calibration models. Calibration models are mathematical algorithms that describe the relationship between the quantities of degraded oil products in any sample and the amount of infrared light absorbed by that sample.
Once their calibration models were built, the team checked their validity by creating new sets of degraded oils and determining how well each model predicted degradation within these samples. Chemical testing of the samples provided bona fide measures of degradation that could be compared with values predicted by the calibration models.
The results verified that several of the models could successfully be used to determine oil deterioration.
However, because oil doesn’t sit alone in commercial frying vats, the researchers needed to determine how the presence of food in oil might affect their method. In a follow-up study, Wehling et al. repeated their model-building experiments using three cooking scenarios: one that tested oil used to make French fries, another to make tortilla chips, and a third to make chicken nuggets.
The results indicate that the team’s model-building efforts can adapt to real-life situations. “For the oil that we were using, we were able to develop a single model that could accurately predict its level of degradation no matter which of those three foods had been involved,” Wehling says. He and his colleagues presented these results a few weeks ago at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy.
Wehling expects that food production industries will be interested in the technique. Since no hazardous chemical reagents are used, there is no need for separate handling and disposal of chemical waste, so that an instrument can be set up next to a production line in a plant environment. “The goal ultimately would be to see if we could develop a small, portable hand-held type of instrument,” he says.
Wehling also notes that if such an instrument could be made to be inexpensive enough, it would be suitable for use in smaller food service establishments such as schools and restaurants.