Sensory thresholds of selected phenolic constituents from thyme and their antioxidant potential in sunflower oil

The odor detection thresholds of carvacrol (5-isopropyl-2-methyl-phenol), thymol (2-isopropyl-5methyl- phenol) and p-cymene 2,3-diol (2,3-dihydroxy-4isopropyl- 1-methyl-benzene) in sunflower oil, determined by the three-alternative, forced-choice procedure, were 30.97, 124 and 794.33 mg kg(-1), respectively. Sunflower oil containing 13, 70, or 335 mg kg(-1) of carvacrol, thymol or p-cymene 2,3-diol, respectively, was judged to be similar (P < 0.01) in taste and odor to its antioxidant-free counterpart. The rate constant of sunflower oil oxidation, measured from the increase in peroxide value during storage at 25 degrees C, was 9.2 x 10(-9) mol kg(-1) s(-1) while the rate constants were 9.3 x 10(-9), 9.8 x 10(-9), and 4.3 x 10(-9) mol kg(-1) s(-1) in the presence of 13 mg kg(-1) carvacrol, 70 mg kg(-1) thymol, and 335 mg kg(-1) p-cymene 2,3-diol, respectively. At a level of 335 mg kg(-1), p-cymene 2,3-diol did not impart flavor taints and effected a 46.7% reduction in the rate of oxidation of sunflower oil. These findings indicate that the diphenolic p-cymene 2,3-diol could potentially replace synthetic antioxidants and is a valuable addition to the antioxidants used by the food industry in its quest to meet consumer demands for synthetic-additives-free and 'natural' foods.