Sterilization of Freeze Dried Manila Clam (Ruditapes philippinarum) Porridge for Immuno-Compromised Patients

This study was conducted to evaluate the combined effect of gamma irradiation and different conditions (vacuum packaging, antioxidant and freezing) on the microbiological and sensory characteristics of freeze dried Manila clam porridge (MCP) for immuno-compromised patient food. MCP can be sterilized at 1 kGy to 10 kGy. The initial counts of total aerobic bacteria and yeast molds in the non-irradiated MCP were $2.4{\pm}0.5$ and $1.2{\pm}0.3{\log}\;CFU\;g^{-1}$, respectively, but gamma irradiation significantly decreased the total aerobic bacteria to below the detection limit ($1{\log}\;CFU\;g^{-1}$) (5 kGy). Moreover, gamma irradiation effectively eliminated yeasts/molds at dose below than 1 kGy. However, gamma irradiation accelerated the increase of lipid oxidation and therefore, decreased the sensory characteristics of MCP as irradiation dose increased. To improve the sensory qualities of gamma irradiated MCP, combination treatment (vacuum packaging, 0.1% vitamin C) were applied. There was no significant difference in the overall acceptance scores between the combined-treatment sample (5.6 points) and the non-irradiated samples (6.0). The results indicate that combination treatment (vacuum packaging, 0.1% vitamin C) may help to maintain the quality of MCP. Therefore, it considered that irradiation of MCP with combined treatment and this is an effective method for the consumption as a special purpose food such as for space travel or immuno-compromised patients.