Effect of Direct and Indirect Ultrasonic Methods on Microbial Load and Chemical Quality of Raw Wheat Germ

Abstract

Background: Thermal methods such as pasteurization and sterilization are currently used to eliminate microorganisms, but they may reduce nutrition value or disturb texture, flavor, taste and color. This study assessed the effect of direct and indirect ultrasonic methods on microbial load and chemical quality of raw wheat germ. Methods: The wheat germ was prepared from Shiraz, southern Iran. It was treated with two direct and indirect ultrasonic methods. In direct method using the frequency of 20 kHz and maximum time of 10 minutes, immersion of the device probe was undertaken in a reservoir containing wheat germ and in indirect way, ultrasound was applied at frequencies of 50-60 kHz for 30 minutes to the wall of the container with samples of wheat germ. The microbial and chemical characteristics of both treated groups were compared. Results: The direct method reduced the microbial load of the product by 0.6 logarithms, while in the indirect method, the microbial load of the product was not significantly reduced. Conclusion: It can be expected that the use of ultrasound waves in an appropriate manner for disinfecting the fresh edible plants, including sprouts, along with its remarkable benefits, in comparison with the traditional thermal methods such as pasteurization and sterilization as well as harmful environmental disinfectants, has a beneficial effect on reducing the microbial load of the germs and its effect on the micronutrients of this nutritious food is little or negligible.