Chlorophyll breakdown by gamma irradiation in a model system containing linoleic acid

The possible breakdown of chlorophyll by irradiation was investigated. Chlorophyll b standard (3 ppm) was added to a methanol solution containing 1% linoleic acid. Irradiation up to 20 kGy was performed with or without N-2-bubbling, and nonirradiated control was also prepared. Residual chlorophyll b content was analyzed by HPLC and UV-visible spectra after irradiation, and color was measured during 6 h of light exposure (3,300 lux, light intensity) to induce photooxidation. The added chlorophyll b was destroyed by irradiation at 20 kGy with or without N-2-bubbling. With N-2-bubbling the oil sample did not develop lipid oxidation during irradiation, and irradiated samples did not develop photooxidation during storage under light. Without N-2-bubbling, irradiated oil samples had higher PV than nonirradiated samples. The Hunter color a-value of oil increased and the b-value decreased with irradiation at 20 kGy. UV-visible spectra also supported the breakdown of chlorophyll b in solution by irradiation. Irradiation at 2.5 kGy or above destroyed all added chlorophyll b. The results indicate that irradiation technology could be applied to reduce or eliminate the residual chlorophyll in oil processing without developing lipid oxidation during the irradiation process, which would prolong the shelf life of oil products by protecting them from photooxidation during display.