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Monitoring of yogurt fermentation process using ultrasonic technique

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Food Processing Automation Conference Proceedings, 28-29 June 2008, Providence, Rhode Island  701P0508cd.(doi:10.13031/2013.24553)
Authors:   Takahisa Nishizu, Kiyokazu Goto, Naoshi Kondo, Mami Kawabata
Keywords:   Ultrasonic technique, Phase velocity, Yogurt fermentation, Monitoring, Acidity, Hardness, Viscosity

The milk inoculated with yogurt dried culture was filled in the plastic container, on whose both side walls a pair of ultrasonic transducers were placed, and incubated in a temperature controlled environment. An ultrasonic pulse generated by one transducer propagated thorough the milk to the other transducer. The phase velocities were determined by analyzing the detected signals by FFT method. In parallel, pH, acidity, viscosity and hardness during fermentation were maeasured. The phase velocity of 1.5 MHz ultrasonic signal increased with incubation time and reached to steady state values. The changing trend of phase velocity was almost same as that of acidity, and the hardness rapidly increased when the acidity reached to the steady state level. The phase velocity should be very effective in monitoring the degree of fermentation.

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