The effect of oyster shell powder on the extension of the shelf life of tofu

The effects of oyster shell powder addition (0%, 0.05%, 0.1% and 0.2% of soy milk) on quality and shelf life of tofu (soybean curd) were investigated. Yield and moisture of tofu prepared with 0.1% of shell powder were higher than that coagulated with a single use of MgCl₂. Syneresis was low when shell powder was added to tofu, but higher when MgCl₂ was added. Shell powder addition (0.05% and 0.2% of soymilk) showed a high level in hardness and gumminess comparing with tofu prepared with a single use of MgCl₂. However, there was no significant difference (p > 0.05) between 0.05% and 0.2% addition of shell powder. When 0.05% of shell powder was added, overall acceptability showed a high score because tofu had a good mouthfeel, moderate firmness and lower beany-flavour. However, there was not a significant difference (p > 0.05) between no addition and 0.05% and 0.1% addition of shell powder. Tofu prepared with shell powder (0.05% and 0.1% addition) had a shelf life of above 2 days longer than that prepared with a single use of MgCl₂. The addition of shell powder (0.05% and 0.1%) for tofu manufacturing resulted in a good sensory evaluation and the extension of shelf life.