This study was conducted to determine the fatty acid (FA) compositions and oxidative stabilities of cold-pressed cranberry, carrot, hemp, and caraway seed oils. The cold-pressed cranberry and hemp seed oils exhibited higher ␣ ␣ ␣ ␣ ␣-linolenic acid (18:3n-3) contents with levels of 22 and 19 g/100 g fatty acids, respectively. Coldpressed carrot seed oil contained about 82% oleic acid and had the lowest total saturated fatty acids among all tested oils. Cold-pressed caraway seed oil had the greatest oxidative stability with an OSI value of 150 hours. In addition, cold-pressed carrot seed oil had the lightest color while hemp seed oil was the darkest among all the oils tested.

Conjugated linoleic acid (CLA) isomers were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH(*)) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR measurements confirmed that both c9,t11-CLA and t10,c12-CLA directly reacted with and quenched DPPH radicals, whereas spectrophotometric analysis demonstrated that c9,t11-CLA and t10,c12-CLA differed in their kinetic and thermodynamic properties in reacting with DPPH radicals. t10,c12-CLA was shown to exhibit a greater initial velocity in CLA-DPPH radical reactions at levels of 2.5-80 mg/mL, and c9,t11-CLA scavenged more DPPH radicals at steady state. Similar dose and time relationships were observed for both isomers. In addition, a mixture of c9,t11- and t10,c12-CLA isomers demonstrated a greater initial velocity in quenching DPPH radicals than either isomer alone on the same concentration basis, suggesting that a synergistic effect between CLA isomers existed in their reactions with DPPH radicals. These results support the conclusion that individual CLA isomers differ in their biological actions and indicate that interaction(s) between isomers may contribute to their beneficial effects.

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