Food ResearchInternational, Vol. 28, No. 4, pp. 431433, 1995 Elsevier Science Ltd zyxwvutsrqpon ELSEVIER Copyright 0 1995Canadian Institute of Food Science and Technology Printed in Great Britain. All rights reserved 0963-9969195 $9.50 + .OO 0963-9969(95)00031-3 Evaluation of oregano antioxidant activity in mackerel oil M. Tsimidou,* E. Papavergou & D. Boskou Laboratory of Food Chemistry and Technology, Faculty of Chemistry, Aristotle University of Thessaloniki. 54006 Thessaloniki, Greece Dry oregano was tested for its antioxidant activity in mackerel oil stored at 40°C in the dark. Its effectiveness at 0.5% level was comparable to that of 200 ppm BHA and 0.5% (w/w) dry rosemary and stronger to that of red chillies and bay leaf which did not improve the stability of the fish oil. Oregano at 1% (w/w) level had a similar effect to that of 200 ppm TBHQ. Keywords: Oregano, rosemary, antioxidant activity, mackerel oil. INTRODUCTION Herbs and spices are traditionally added to food for improving organoleptic properties and also as antioxi- dants and preservatives. Many spices or their extracts have been assessed for antioxidant activity in a variety of food products and lipid systems. Emphasis was given to edible oils and fats, emulsions and meat prod- ucts (Herrmann et al., 1981; Namiki, 1990; Schuler, 1990; Amr, 1991; Palic et al., 1993). Relatively little work has been carried out with fish oils and fish meat (Pizzocaro et al., 1985; Wada & Fang, 1992; Joseph et al., 1992; Ramanathan & Das, 1993; Boyd et al., 1993). Oregano, a characteristic ingredient of Mediter- ranean cookery, has increasingly gained the interest of many research groups as a source for natural antioxi- dants. The dry leaves and extracts with organic solvents as well as its essential oil are responsible for a remark- able antioxidant activity in lard (Ekonomou et al., 1991; Vekiari et al., 1993; Lagouri et al., 1993) salad dress- ings (Chipault et al., 1956), sardine flesh and oil (Pizzo- care et al., 1985) and food model systems (Bishov et al., 1977). This work is undertaken to study the effectiveness of dry oregano in an unsaturated lipid model system such as mackerel oil. For comparison, rosemary, bay leaf and red chillies as well as the synthetic antioxidants BHA and TBHQ were tested. Some weak antioxidant activity has *To whom correspondence should be addressed. been reported for bay leaf and red chillies (Chipault et al., 1956; Gerhard & Blat, 1984; Palic et al., 1993). The flavor of these spices is desirable in fish products. The rate of oxidation was followed by periodic determina- tions of peroxide values of the oil stored at 40°C. MATERIALS AND METHODS Materials Synthetic antioxidants BHA and TBHQ were pur- chased from Sigma Co. (St. Louis, MO); all the other chemicals were analytical grade. Dry oregano and bay leaves were purchased from a local merchant who col- lects them from the mountains of Macedonia (Greece). Imported dry chillies were donated by a local canning plant. Dry ground rosemary, commercially available as a food antioxidant, was obtained from McCormick Ingredients Europe Inc. (Haarlem, The Netherlands). Preparation of fish samples and extraction of fish oil Fresh mackerel (Scomber scombrus) which was truck delivered on ice was obtained from the local wholesale market. The fish were carried to the laboratory and after removing heads, gills and intestines, they were washed with tap water and filleted. The bones were removed and the fillets were ground in a blender for domestic use at maximum speed for 30 s. 431