Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2001
Publication Date: 1/1/2002
Interpretive Summary: Several outbreaks of food-borne disease have been traced back to consumption of fruit juices contaminated with pathogenic microbes, such as E. coli O157:H7 and Salmonella. Ionizing radiation has been shown to be very effective in activation of these pathogens in juices. The effect of irradiation on quality of juices is a concern. This study was conducted to investigate the impact of irradiation on apple juice color, antioxidant activity, and accumulation of malondialdehyde (MDA), a possible carcinogenic agent. The results of this study indicated that irradiation at doses of pathogen elimination had some beneficial effects, such as reducing browning and increasing antioxidant activity. However, irradiation at doses for inactivating Salmonella increased MDA formation. The formation of MDA can be reduced by irradiating juice at low temperature, preferably in frozen states. These results will be useful for juice processors and consumers.
Technical Abstract: Apple juice was gamma irradiated at 5 degree C at doses ranging from 0 to 8.9 kGy, and then stored at 5 degree C for 15 days. Ionizing radiation reduced browning of apple juice, and increased antioxidant activity measured by the ferric reducing antioxidant power (FRAP) assay. The level of malondialdehyde (MDA) measured using the thiobarbituric acid reactive substrates assay increased at radiation doses above 3.56 kGy. The brownin of irradiated juice increased during storage at 5 degree C, but the irradiated juice was still lighter than controls at the end of storage. Differences in FRAP values disappeared during early periods of storage while higher MDA levels were observed in irradiated samples during most of the storage period. Compared to irradiation conducted at 5 and 20 degree C, treatment at -15 degree C was less effective in reducing browning and in increasing MDA formation, but elevated FRAP values. Exclusion of oxygen from juice promoted the increase in FRAP values and decreased the irradiation-induced MDA formation.