14B-36

C. T. SHAO¹, P. Pangloli, S. L. Melton, J. L. Collins, and A. M. Saxton. (1) Food Science and Technology, Agricultural Experiment Station, The University of Tennessee, Knoxville, 114 McLeod Hall P.O. Box 1071, Knoxville, TN 37901-1071

JUSTIFICATION: Volatiles formed during use of different frying oils have been studied, but no reports were found in which solid phase microextraction (SPME) was used for volatile measurement. Also, simple rapid methods for measuring frying oil degradation are still needed. Oil viscosity has received renewed interest as such a method; but studies are needed to relate it to other degradation measurements for different oils.

OBJECTIVES: The objectives of this study were (1) to use SPME to determine volatiles from different oils during frying and (2) to determine oil viscosity and relate it to other degradation measurements.

METHODS: Cottonseed oil (CSO), sunflower oil (SFO), and 20 and 40% palm olein (POO) blends with SFO, used to fry potato slices in 3 reps, were sampled fresh, after break-in heating, and 2.5- and 5-hr frying. Samples were analyzed by SPME and viscosity (VIS) and for levels of fatty acids, total polar components (TPC), free fatty acids (FFA), conjugated dienoic acid (CDA), and Hunter color L, a, and b.

RESULTS: SPME identified 6 aldehydes from the used oils. Each heated oil had (p<0.05) highest levels of hexanal, nonanal, t-2-decenal and t,t-2,4-decadienal and, generally, the level of each decreased with increased frying time. VIS increased (p<0.05) from 46.3 (n=48) in fresh oils to 54.9 cP at 5-hr frying. In same period, TPC increased from 5.0 to 15.9%, FFA from 0.025 to 0.070%, CDA from 0.183 to 1.121, and b from 10.1 to 21.7 while L decreased from 93 to 85 and a from -4.0 to -5.9. VIS rate of change (p<0.05) was dependent on the oil type. For each oil, VIS had an r ³ ±0.90 with all measurements except L.

SIGNIFICANCE: SPME shows promise as a method for measuring different oil oxidation volatiles during frying. Results also indicate that while viscosity increases in oils during use, the dependence of increase rate on the type of oil limits its use as an universal measurement for frying oil degradation.