Doctoral Dissertations

Date of Award

5-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

Sharon L. Melton

Committee Members

Marjorie P. Penfield, Carol Costello, Jim Bailey, John R. Mount

Abstract

The stabilities of 4 oils, high oleic sunflower (HOS) and regular sunflower (RCO) oils from the USA and a regular sunflower-corn oil blend (SOS) and regular sunflower (SVS) oil, processed in the Republic of South Africa (RSA) and used in Swaziland, were evaluated during frying. For each oil, 24 batches of 2 plain, yeast-raised doughnuts/batch were fried for 4 hr/day for 5 days. Samples taken from each oil during TIME (fresh, break-in heated and on each of the 5 days) were evaluated by measuring levels of a- and Y~tocopherols, total polar components (TPC), Food Oil Sensor reading (FOS), free fatty acids (FFA), conjugated dienes (DIENES), C18:2/C16:0 ratio, and Hunter color values, L, a, b and AE. Crust flavor and color likability, crust color intensity, mouthfeel (greasiness) and overall acceptability of doughnuts fried on days 2 and 4 in each oil were evaluated by a 48-member consumer panel.

When fresh, USA oils contained lower levels of tocopherols and were less yellow than RSA oils; HOS contained the lowest amount of tocopherols of all oils. Levels of each tocopherol decreased while levels of TPC, DIENES, C18:2/C16:0 ratio, b and AE increased over TIME (p<0.05), but the change in any one component differed among the oils. Levels of FFA and a increased and L decreased (p<0.05) across TIME similarly for each oil. Levels of TPC (19.5-20.9%), FOS (1.75-2.13) and FFA (0.058-0.067% oleic acid) on day 5 were the same in all oils and were below recommended levels for oil discard. Although HOS had lowest levels of tocopherols and had a greater AE than RCO or SVS, it was comparable in stability with the other oils. None of the sensory scores were affected (p<0.05) by type of oil or time. Mean (n=192) crust flavor and color scores were midpoint on 9-point hedonic scales. Overall acceptability was midpoint on an extremely unacceptable to extremely acceptable scale. Crust color and mouthfeel scores were midpoint on 9- point scales (light brown and dark brown and not at all greasy - extremely greasy). Results show that HOS is feasible as a frying oil for small food vendors in Swaziland.

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