Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2005
Publication Date: 9/1/2005
Citation: Warner, K.A., Laszlo, J.A. 2005. Addition of ferulic acid, ethyl ferulate, and feruloylated monoacyl- and diacylglycerols to salad oils and frying oils. Journal of the American Oil Chemists' Society. 82(9):647-652. Interpretive Summary: Vegetable oils and some types of fried food for the consumer market need to have long shelf lives. Some foods with certain types of oil do not have long shelf lives and can become rancid and unacceptable. To improve the shelf life of oils and fried food, we used various antioxidant-type additives in soybean oil. We found that some of the additives worked well when the oil was tested as the type of bottled oil purchased in the grocery store. Some of the other additives worked better in frying oil and in fried food. Based on these results, oil processors can use additives in oils that are most suitable for the use of the oil. These results will help food manufacturers and oil processors to produce good quality, healthful oils and oil-containing foods that will benefit consumers.
Technical Abstract: To determine the effects of phenolic compounds on the oxidative stability and of the frying stability of soybean oil and on the flavor stability of potato chips, several of these types of compounds were added to soybean oil. Additives included feruloylated monoacyl- and diacylglycerols, ferulic acid, ethyl ferulate, and tertiary butyl hydroquinone (TBHQ). Frying tests with potato chips were conducted with a soybean oil control and the same oil with either 0.9mM (200ppm) TBHQ or with 0.7mM feruloylated monoacyl- and diacylglycerols or 1.2mM ethyl ferulate or 0.6mM ferulic acid. Frying oils were analyzed for retention of the additives as well as for total polar compounds as an indication of oil fry life. Fresh and aged potato chips were evaluated for hexanal content and for rancid odor intensity. After a total frying time of 15 h of potato chips using 800g oil in a 1L fryer, 71% of the feruloylated monoacyl- and diacylglycerols were retained, whereas 55% of the ethyl ferulate was retained. In contrast, TBHQ and ferulic acid levels were low after 15h of frying at 6% and <1% respectively. Frying oils with ethyl ferulate or with TBHQ produced significantly lower levels of total polar compounds than the control. Potato chips fried in oil with TBHQ or with ferulic acid had significantly lower amounts of hexanal and significantly less rancid odor after 8 days of aging at 60 deg C. In stability tests as salad oils, oils were aged in oven storage conditions at 60 deg C and oxidative stability was analyzed by peroxide values, hexanal content and rancid odor. Oil with TBHQ or with feruloylated monoacyl- and diacylglycerols had significantly less peroxide and hexanal formation and rancid odor than the control. Feruloylated monoacyl- and diacylglycerols helped to inhibit the deterioration of the salad oils during storage at 60oC, whereas ethyl ferulate was effective as an antipolymerization agent in frying oil. Ferulic acid acted as an antioxidant in aged fried food. TBHQ helped to inhibit oil and fried food degradation at both temperatures.