Non-destructive characterization of the air influence on the UHT milk quality by ultrasonic technique

In this work, we have exploited the ultrasonic transmission technique to evaluate the quality of UHT milk inside its pack in a non-destructive manner. This control is based on monitoring the evolution of ultrasonic parameters namely velocity and attenuation through the pack in different temperatures. To check the reliability of this technique, we have followed the evolution of these ultrasonic parameters in two particular cases: the sterilized pack (without hole) and the non-sterilized pack (with hole). The function of this hole is to allow air infiltration inside the pack. By comparing the results issued from this experimental study, we demonstrated the ability of this method to detect the presence of an air-trace inside the pack. This fact is confirmed by detection of a divergence at a given time for each ultrasonic parameter between both cases. We explained this as a translation of bacterial activity. In addition, this study has shown that the temperature 35 °C is the most suitable to bacterial growth.