Effects of gamma irradiation on the quality of manila clam porridge and in vivo immunomodulatory activity of hesperidin as immunopotentiator for sterilized patient food

Abstract

This study investigated the optimal doses of gamma irradiation for the production of Manila clam porridge (MCP) as a hygienically safe and sterilized patient food. It also evaluated the effects of MCP with hesperidin, which was selected to improve the immune activities, of immune-suppressed model mice using gamma irradiation. As a result, the aerobic microorganisms were reduced by gamma irradiation exposure, and sterilized at 3 kGy. B. cereus, yeast, fungi, and E. coli were not detected. Gamma irradiation did not affect the pH, color, or moisture content except the lipid oxidation and viscosity of MCP. In the sensory evaluation results, all items except odor showed a preference toward normal (4 point) or more until 3 kGy. Specially, the preference survey for immunosuppressed patients showed good acceptance (5.00-5.43) of MCP irradiated with 3 kGy at freezing (−18 ± 3 °C) temperature in all categories. C57BL/6 male mice were orally fed a diet with 20% of freeze dried MCP (4 g kg−1•day−1) or normal diet for 4 weeks, and then exposed to gamma irradiation at 4 Gy followed by the oral administration of hesperidin (150 mg kg−1) for 1 week. Compared with the irradiated control group fed with a normal diet, white blood cell counts in the combined treated group with both MCP and hesperidin were significantly higher, whereas DNA damage to splenocytes in the combined treated group was significantly lower (p < 0.05). Comet assay shows MCP and MCP with hesperidin group significantly (p < 0.05 or p < 0.01) protected from radiation-induced DNA damage. Furthermore, the concentrations of serum cytokines, especially interleukin-1β, in the combined treated group exhibited significant differences from those in the irradiated control group, indicating a protective and inflammatory lowering effect of the combined treatment on immune cells in mice damaged by gamma irradiation. This study showed that gamma irradiation of 3 kGy would be a suitable way to achieve hygienically safe and sterilized patient food with an acceptable sensory quality, and combined treatment with hesperidin can help improve the radioprotective effect of patients as an immunopotentiator.