EVALUATION OF ANTIOXIDANTS FOR COD-LIVER OIL BY CHEMILUMINESCENCE ANDTHE RANCIMAT METHOD

Commercial blends of natural antioxidants, viz., tocopherol concentrat es, rosemary extracts, sage extracts, and lecithins, were tested for t heir ability to stabilize cod liver oil. The antioxidants were tested by using the Rancimat apparatus at 80 degrees C and by a method based on hypochlorite-activated chemiluminescence analysis of samples stored at 35 degrees C for 24 h in light. In addition, a stability study at 5 degrees C in the dark for 8 wk, under conditions realistic for norma l consumption of cod liver oil was carried out. A low correlation (r = 0.339) was found between Rancimat induction times and chemiluminescen ce data for the sixteen antioxidant systems tested, probably due to te mperature differences, and different ways of detecting oxidation produ cts. Based on Rancimat induction times, delta-tocopherol-rich antioxid ants and lecithin had the best stabilizing effect. However, based on t he chemiluminescence method, the tocopherols acted as prooxidants, whi le tocopherols with lecithin increased the stability. Both Rancimat an d chemiluminescence data showed stabilizing effects with rosemary and sage extracts, but no synergistic effect between the herbal extracts a nd lecithin or tocopherol was observed. Analyses of oil aged at 5 degr ees C for 8 wk showed the highest stability for cod liver oil containi ng rosemary extracts. The tocopherol mixtures showed only a minor effe ct on the stability. Ranking of antioxidants varied considerably depen ding on the method used, and increasing the temperature seemed to decr ease the usefulness of the method. Antioxidant evaluation has to be do ne by using as many evaluation methods as possible under conditions re levant for normal storage and use.