Antioxidants and Shelf Life of Foods - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 194

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FIGURE 6.18 Antioxidative activity of catechins isolated from buckwheat. 83 With permission.

Almost half a century ago, Chipault 85 investigated the antioxidant activity of a
number of these spices reporting rosemary and sage to be the most effective ones
in lard, while clovesproved more effective in an oil-in-water emulsion. Subsequent
research by Chipault 86 screened 17 different spices for antioxidant activity in may-
onnaise-type products and reported oregano as the most beneficial. These studies
pointed to the importance of identifying the type of food system used in the evalu-
ation process. In recent years there has been a flurry of activity in identifying the
antioxidant active components in herbs and spices, the majority of which appear to
be phenolic compounds. Since herbs and spices have been used for centuries, their
antioxidant active components are considered harmless. 87
Aeschbach and co-workers 88 first established that the efficacy of thymol and
cavracol isomers to inhibit peroxidation of liposome phospholipids was concentra-
tion dependent. These antioxidants were identified in the essential oils from plants
of the oregano species. 89 Yanishleva et al. 90 examined the antioxidant activity and
mechanism of action of thymol and cavracol on the autoxidation of purified triacyl-
glycerols of lard and sunflower oil. At ambient temperature, thymol was reported to
be an effective antioxidant.
A number of studies examined the antioxidant properties of essential oil of
thyme. 91,92 These properties were attributed to the phenolic components, cavracol
and thymol. Schwartz and Ernst 93 studied the anitoxidant properties of a non-polar
fraction isolated from thyme leaves. Besides cavracol and thymol, these researchers
isolated a new phenolic compound ,p -cymene-2,3-diol (2,3-dihydroxy-4-isoprpro-
pyl-1-methylbenzene) ( Figure 6.19 ). Using the Rancimat and Schaal Oven test
( Figure 6.20 ), p -cymene-2,3-diol proved to be the most potent antioxidant and was