Degree Type

Dissertation

Date of Award

1989

Degree Name

Doctor of Philosophy

Department

Food and Nutrition

First Advisor

Pamela J. White

Abstract

The high-temperature antioxidative activity of some plant sterols has been noted by several research groups and later was attributed to an ethylidene structure present on the effective sterols. Linalyl acetate (LA, a monoterpene alcohol that contains the ethylidene group) when present at a level of 0.04% and undecylenic acid (contains a terminal secondary double bond system) at a level of 0.5 to 2.0% reduced triglyceride oxidation in soybean oils heated at 180 C for up to 70 hr. There was a slight effect when LA was present at 0.02%. The high-temperature antioxidant activity of this compound with the ethylidene structure but without a sterol moiety strengthens the theory that the ethylidene group is responsible for the antioxidative activity;Lipid materials other than triglycerides also undergo oxidation. Among them, the oxidation of cholesterol results in some oxidation products, some of which have been shown to be cytotoxic and angiotoxic in animals and that are linked to causes of human atherosclerosis. In this study, the oxidation of cholesterol was monitored in lards heated at 180 C for 10 hr/day up to 240 hr. A method for identifying and quantifying the commonly found cholesterol oxidation products (COPs) was evaluated and modified for use in the experiments. Cholesterol and six other COPs were resolved, identified and quantified by slightly modifying a recently published method for measuring COPs;Finally, the effects of linalyl acetate and polydimethyl siloxane (MS) on cholesterol and triglyceride oxidation were examined in lard with two levels of added cholesterol, heated at 180 C intermittently for up to 240 hr. The percentage retention of cholesterol and the formation of six COPs were followed over the heating period, with and without the added LA and MS. In addition, the percentage retention of fatty acids was monitored. There was little effect of linalyl acetate on cholesterol oxidation and only slight protection of linoleic acid. The MS at 1.0 ppm protected lard containing two times the original amount of cholesterol, resulting in higher cholesterol, linoleate and linolenate retention. Recent reports on linalyl acetate and radical-trapping antioxidants were summarized to help explain the action of these compounds as antioxidants.

DOI

https://doi.org/10.31274/rtd-180813-10269

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Pearlly Shew Ying Yan

Language

en

Proquest ID

AAI9014970

File Format

application/pdf

File Size

109 pages

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