Antioxidant and pro-oxidant factors in oregano and rosemary gourmet olive oils

The study was carried out to examine the presence of antioxidants and pro-o xidants in oregano and rosemary gourmet oils. Dry, ground plant material (5 % w/w) was infused to olive oil for 24, 48 and 72 hours and then it was rem oved by filtration. All preparations were found acceptable using a panel te st. The total polar phenol content increased 3.5 and 1.7 times in oregano a nd rosemary gourmet oils with respect to that of the control sample. A qual itative enrichment of the methanol:water fraction of olive oil with phenoli c compounds from herbs were found using HPLC. No rosmarinic acid was detect ed in the gourmet oils. Vanillic acid was only found in the rosemary gourme t oil. The presence of flavonoids was assessed using TLC. alpha -Tocopherol content of the oil matrix was not changed after herb infusion. A significa nt increase was found in pheophytin, alpha,beta -carotene and lutein conten t of oregano flavoured oils. The oxidative stability of gourmet oils was gr eater to that of the control using the Rancimat test. In photo-oxidation, o regano flavoured oil was less stable than the rosemary one. Total chlorophy ll content may be a critical factor for the shelf life of these preparation s. Suitable labelling suggesting avoidance of light may be useful for a saf e domestic use.