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Title: EFFECT OF OLEIC AND LINOLEIC ACIDS ON THE PRODUCTION OF FRIED FOOD ODORS INHEATED TRIOLEIN AND TRILINOLEIN

Author
item Warner, Kathleen
item Neff, William
item BYRDWELL, WM CRAIG - FORMER, USDA-ARS-NCAUR

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Frying oils that are high in a fatty acid known as oleic acid do not usually produce fried foods that have good flavor, which can limit the utilization of these oils. Because more than 6 billion pounds of frying oils are used in the United States each year, it is important to understand the chemical basis for this effect. In this study, oils made from 100 percent oleic acid were compared with oils made from 100 percent linoleic acid, a fatty acid that does produce good fried food flavor. After the oils were heated, the chemical compounds responsible for fried food flavor were identified and were found to be very low in the 100 percent oleic acid oil. However, these compounds increased as heating time increased, indicating that the 100 percent oleic acid oil can produce some fried food flavor but still much less than from the 100% linoleic acid oil. These results showed that the composition of frying oils significantly affects the flavor of fried food. Food manufacturers and plant breeders can use this information to produce oils with the right fatty acid compositions for good quality fried food.

Technical Abstract: To determine possible sources of the desirable fried food aroma and flavor in heated oils and fried foods, oxidation products from heated model oil systems, triolein and trilinolein, were evaluated by purge and trap GC-MS-olfactometry and RP-HPLC coupled with APCI-MS. Both were heated at 190 deg C with added water to partially simulate frying until total polar compounds ranged from 5 to 31% representing low, moderate, and high amounts of lipid degradation. Olfactometry and volatile compound analyses of fractionated and non-fractionated heated triolein and trilinolein showed that three alkadienals, (E,E)-2,4- nonadienal, and (E,E; E,Z)2,4-decadienal produced a fried food odor at moderate to strong intensity in the heated trilinolein that contained 25% total polar compounds. In addition, 2 alkenals, 2-heptenal, and 2-octenal produced moderate intensity fried food odors in heated trilinolein, whereas 2,4-octadienal and (E,Z)-2,4-nonadienal provided weak food odor. 2-octenal, 2,4-nonadienal, 2,4-decadienal, and 2,4-undecadienal were found in triolein heated for 6 hr to reach 31% total polar compounds but were present in low amounts and the olfactometry intensity levels for fried food odor were also low. RP HPLC-APCI-MS of the fractionated triolein and trilinolein showed that the greatest amounts of the aldehydes producing fried food odor were from the hydroperoxy fraction with the least found in the epoxy and dimer. These decomposition products represented molecular markers for the pathways of the 2-alkenals and 2,4-alkadienals that produced fried food aroma.