PREVENTION OF LIPID RADIOLYSIS BY NATURAL ANTIOXIDANTS FROM ROSEMARY (ROSMARINUS-OFFICINALIS L.) AND THYME (THYMUS-VULGARIS L.)

Radiolysis of unsaturated linoleic fatty acid and subsequent generatio n of volatile alkane and alkene hydrocarbons was studied following rel atively low, 3-9 kilo-Gray (kGy) gamma-irradiation, i.e. within the ac cepted 10 kGy limit for commercial food pasteurization. The low-dose i rradiation generated relatively low quantities of hydrocarbons, totall ing 83 +/- 1-140 +/- 4 ng/mg for saturated myristic and stearic fatty acids. As expected, unsaturated fatty acids (UFA) were more susceptibl e to the gamma-irradiation; at 9 kGy dose, the total amount of C-10-C- 19 volatile hydrocarbons were, respectively, 602 +/- 18 ng/mg for arac hidonic acid and 751 +/- 60 ng mg(-1) for linoleic acid. Addition of p owdered (unextracted) rosemary or thyme, at 1/0.1 g lipid/plant ratio, decreased by 52.5-80.5% the radiolytic generation of C-10-C-19 hydroc arbons. In conclusion, rosemary and thyme, both known to contain natur al antioxidants, markedly reduced the gamma-radiolysis of linoleic aci d, when irradiated within the accepted 10 kGy limit for commercial foo d processing. (C) 1998 Canadian Institute of Food Science and Technolo gy. Published by Elsevier Science Ltd. All rights reserved.