Doctoral Dissertations

Date of Award

5-1989

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

Sharon L. Melton

Committee Members

H. O. Jaynes, J. R. Mount, B. C. Mullin

Abstract

The objectives of this experiment were to compare the frying performance of partially hydrogenated soybean oil versus palm olein during laboratory frying and to determine the effect of these frying oils on the flavor of fried potatoes. A replication consisted of 2 partially hydrogenated soybean oils (PHSO), A with an iodine value (IV) of 94 and B with an IV of 102, and palm olein (PO), with each oil used to fry potatoes every hour for 8 hours/day for 4 consecutive days. Two replications were completed. Oil samples were collected at the beginning of the frying and at the end of each day for analysis of dielectric constant by Food Oil Sensor (FOS), change in color (Hunter color values. "L", "a" and "b") and total change in color (ΔE), % total polar components (TPC) and % free fatty acids (FFA). The first batch of potatoes fried in each oil and the next to last batch of potatoes fried each day were evaluated for flavor desirability by a sensory panel (n=32). The second batch of potatoes fried on the 1st day and the last batch fried on the 4th day were analyzed for flavor volatiles by gas chromatography-mass spectroscopy (GCMS).

PO became darker, more yellow and redder than either PHSO A or B during 4 days of frying. With increasing frying time, the Hunter color "L" value decreased linearly, and the "a" value increased linearly, while the "b" value and ΔE increased quadratically. FOS did not differ significantly among the frying oils, but % TPC and FFA did. During frying, PO had a higher level of FFA than PHSO A or B, and PHSO A had a higher level than PHSO B. PO also had a higher level of TPC than either PHSO during frying, but there was no difference in % TPC between PHSO A and PHSO B. FOS, % FFA and % TPC all Increased with increasing time of frying.

As a whole, the sensory panel liked the flavor of potatoes fried in PO slightly less than that of potatoes fried in either PHSO. The panel particularly did not like the flavor of potatoes fried in fresh PC; however, with increasing frying time, they liked PO fried potatoes better. In contrast, the flavor score of potatoes fried in PHSO A decreased linearly with increasing frying time while that of potatoes fried in PHSO B did not change (p<.05). The sensory panel was composed of those (Panel A, n=15) who liked the flavor of potatoes fried in PO better than those fried in PHSO A while the rest of the panel (Panel B, n=17) liked the potatoes fried in any PHSO better than those fried in PO. The levels of 19 identified compounds and 8 unknown compounds (for which mass spectra were obtained) were measured in the volatiles of the fried potatoes. The levels of 1 1 volatiles: 2-methyl pyrazine, t-2-octenal; benzaldehyde; t,t-2,4-heptadienal, t,c.-2,4- decadienal, c,t-2,4-decadienal, t,t-2,4-decadienal and 3 unknowns were different among the oils (p<. 10) and concentrations of 15 volatiles were less in potatoes fried at 4 days than those fried in fresh oil (p<.10). Flavor desirability scores from the entire panel or from Panel A were not significantly correlated with levels of any of the volatiles, but the flavor desirability scores of Panel B were significantly correlated with concentrations of t-2-octenal (r = .61), cyclohexenone-2-one (r = .60) and an unknown.

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