EFFECTS OF EXPELLER PRESSED/PHYSICALLY REFINED SOYBEAN OIL ON FRYING OIL STABILITY AND FLAVOR OF FRENCH-FRIED POTATOES

Authors: Warner, Kathleen; Dunlap, Christopher

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2005
Publication Date: 3/13/2006
Citation: Warner, K.A., Dunlap, C.A. 2006. Effects of expeller pressed/physically refined soybean oil on frying oil stability and flavor of french-fried potatoes. Journal of the American Oil Chemists' Society. 83(5):435-441.

Interpretive Summary: Oils that are pressed without heating to remove oil from seeds do not get rancid as quickly as oils that are extracted from seeds with hexane solvent. Another type of oil extraction, known as expeller pressing, is similar to cold pressing except heat is applied to the seeds. Little is known about the resistance of these expeller pressed oils to rancidity. To determine the stability of expeller pressed oil, we fried french fried potatoes in expeller pressed soybean oil, standard hexane extracted soybean oil with an added antioxidant, and hydrogenated soybean oil. We found that the quality of the fried food and the frying life of the expeller pressed oil was similar to the oil with the antioxidant and that the quality of the french fried potatoes was better. We also found that the expeller processing helped to form natural antioxidants that inhibited rancidity. This new knowledge will help the oil industry find oils that have natural stability but without the need for either chemical antioxidants or chemical hydrogenation which produces undesirable trans fatty acids. These expeller pressed oils are naturally stable oils that are healthful and produce good quality foods.

Technical Abstract: To determine effects of expeller pressing/physical refining of soybean oil on the frying stability, studies were conducted with expeller pressed, physically refined, bleached, deodorized soybean oil (EPSBO); hexane extracted, refined, bleached, deodorized soybean oil (SBO) with tertiary butyl hydroquinone (TBHQ); and hydrogenated soybean oil (HSBO). All oils contained citric acid and dimethylpolysiloxane and were used for up to 35 h of intermittent frying of french fried potatoes. The oils were evaluated for frying stability by measuring total polar compounds and flavor quality of french fried potatoes was evaluated by a trained, experienced, analytical sensory panel. The frying stability of EPSBO as measured by polar compounds was similar to the stability of SBO with TBHQ or HSBO. In early frying stages, the potatoes fried in EPSBO had significantly lower intensities of fishy flavor than potatoes fried in SBO with TBHQ. Because of the differences in intensities and types of flavor attributes, the potatoes prepared in EPSBO had significantly higher (better) flavor quality scores than the SBO with TBHQ and the HSBO during the first 15 h of frying. During later stages of frying at 25 and 35 h, the french fried potatoes fried in EPSBO still had significantly better overall flavor quality scores than the potatoes fried in HSBO, but no significant differences were seen between the potatoes fried in EPSBO and SBO with TBHQ. Differences in frying stability of the oils and flavor quality of the french-fried potatoes may be because variations in minor oil constituents in the frying oils. For example, EPSBO had slightly more total tocopherols and phytosterols than did the SBO in the 0-Time samples. During frying, the presence of TBHQ in the SBO and compounds such as Maillard reaction products in the EPSBO probably inhibited the loss of tocopherols. Oil Processors might consider using expeller pressed/physically refined oil as an alternative to hydrogenation and/or additives.