Use of Irradiation as a HACCP, CCP Step for Bulk Soybeans Prior to Their Transit to Mars: Influence on Microbial Load, Functional Properties, and Yield of Soymilk and Tofu 2005-01-2925

Soybeans were chosen for lunar and planetary missions, where soybeans will be supplied in bulk or grown locally, due to their nutritive value and ability to produce oil and protein for further food applications. However, soybeans must be processed into foods prior to consumption. Wilson et al. (2003) raised questions about the influence of radiation (on germination and functional properties) that the soybeans would be exposed to during bulk storage prior to and during a Mars mission. The influence of radiation can be broken down into two components: the affect of surface pasteurization to ensure the astronauts safety from food-borne illnesses (HACCP, CCP), and the affect of the amount of radiation the soybeans receive during a Mars mission. Decreases in the amount of natural antioxidants, free radical formation, and oxidation-induced changes in the soybean will influence the nutritional value, texture, and quality of soyfoods. The objective of this study was to determine the influence of surface radiation on whole soybeans using gamma and electron beam radiation (pasteurization and sterilization) on microbial load, germination rate, ease of processing, and quality of soymilk and tofu. Surface radiation of whole dry soybeans using electron beam or gamma rays at 10 or 30kGy did provide microbial safety for the astronauts. However, these doses caused oxidative changes that resulted in soymilk and tofu with rancid aromas, dark color, lower tofu yields, more solid waste, paste-like okara, and loss of the seeds' ability to germinate. While lower doses may reduce these problems, we may lose the ability to ensure microbial safety of bulk soybeans. Counter measures could include vacuum packaging, nitrogen flushing, added antioxidants, and radiating under freezing conditions. A No Effect Dose for food quality, below 10kGy, with an effective kill step dose (CCP) for food-borne illness microorganisms needs to be investigated further.