This study was conducted to evaluate the effect of gamma irradiation (0.4, 0.6, 0.8, 1 and 1.5 kGy) on the microbiological, physicochemical and sensory qualities of imported orange. The storage period were 3℃ for 60 days and 20℃ for 15 days.
In condition at 3℃ for 60 days, total aerobic bacteria and yeast/mold counts in non-irradiated oranges were 3.59 and 3.75 log CFU/g, and irradiated oranges at 1.5 kGy were decreased to 1.75 and 2.26 log CFU/g, respectively. Those counts were decreased significantly according to dose-dependent manner after gamma irradiation. The vitamin C contents were decreased significantly according to dose-dependent manner and storage time after gamma irradiation. Antioxidant activity was revealed no significant difference between control and irradiated samples. Sensory evaluation was revealed no significant difference between control and irradiated samples, except 1.5 kGy. Samples irradiated at 1.5 kGy were the lowest one throughout color, sweetness, sourness, flavor, texture and overall acceptance.
In condition at 20℃ for 15 days, total aerobic bacteria and yeast/mold counts in non-irradiated oranges were increased significantly according to storage time. Irradiated oranges have significant reduction effect in microbiological as increase of irradiation dose. The Vitamin C contents were decreased significantly according to dose-dependent manner and storage time after gamma irradiation. Antioxidant activity was revealed no significant difference between control and irradiated samples. Sensory evaluation was decreased according to dose-dependent manner and storage time, except color.
The results suggest that gamma irradiation were effective to ensure the microbiological safety, but irradiated oranges at 1 and 1.5 kGy were not good on physicochemical and sensory qualities. Therefore, we can use the sample irradiated at 0.4~0.6 kGy as optimum-dose to be minimize on quality changes.