Effects of the Application of Hydrogen Peroxide on the Preservation of Firm Tofu

Abstract

In this study, hydrogen peroxide concentrations for treatment of firm tofu was investigated. Because firm tofu has high moisture content, high water activity, and is a low-acid food, it is difficult to preserve. Hydrogen peroxide treatment could possibly be a good preservative. The analytical methods for hydrogen peroxide, obtained regression equations by the peroxidase method and Merck RQflex. Reflectometer methods were Y=0.314X-0.0845 (R2=0.998) and Y=1.03X-0.438 (R2=0.977), respectively. These were accurate methods for hydrogen peroxide analysis, with the Merck RQflex Reflectometer method being the more convenient method. The shelf-life at room temperature of firm tofu is 1 day without hydrogen peroxide treatment. The shelf-life at room temperature of firm tofu was extended to 2 and 3 days when the hydrogen peroxide contents were 95 and 395 ppm, respectively. If the initial count is less than 103 cfu/g, the products can be stored at 4°C for 1 to 4 days without hydrogen peroxide treatment. Hydrogen peroxide treatment significantly increased the Hunter L value, but had no significant effect on the Hunter a value and the Hunter b value of the products. Alcohol treatment was not an effective method for preserving firm tofu. Cooking foods containing hydrogen peroxide reduced the amount of residual hydrogen peroxide, however it was not easy to remove all residual hydrogen peroxide by cooking when the hydrogen peroxide concentration was high.