Ultrasonic measurement device for the characterization of microbiological and biochemical processes in liquid media

Abstract

A measuring device for the characterization of liquid media based on the propagation of ultrasonic waves is presented. It is a four-channel system especially designed for monitoring microbiological and biochemical processes. The liquid samples are placed in commercial glass bottles which can be sterilized. The bottles have inlet and outlet tubes, which can be used for adding substances or extracting samples during the measuring process without interruption. Magnetic stirring can be used to keep the liquid agitated for homogenization purposes. Thermal control elements assure the temperature stability during the measurement. The liquid characterization is based on the detection of amplitude and time-of-flight changes in the sample under study. The main features, operation and performance of this ultrasonic device are analysed in this work, and some measurements and preliminary results are shown.

Time-domain simulations of sound propagation in a stratified atmosphere over an impedance ground

“…2 and the literature, 5,6 an equation relating c in melamine-adulterated skim milk to melamine mixture concentration M in percent and temperature T near 40°C may be derived, for M up to 30% by weight:…”

“…Differential path solutions 9 may obviate such on-line clamp-on potential problems. While not investigated in the present study, one might utilize scattering, attenuation, or received amplitude 5 as the basis of further ultrasonic methods to detect undissolved adulterants such as settled melamine powder in closed vessels. The practicality of an on-line ultrasonic detection system for screening or other purposes is limited in part by contributions to c by interfering variables.…”

“…As the melamine mixture was continuously added to the milk, time of flight variations were measured using the ultrasonic device developed by Elvira et al 5 The liquid sample was put in a 125 ml commercial glass bottle which was placed inside one of the ultrasonic measurement cells. The liquid path was 36 mm, traversed once.…”

A new ultrasonic signal amplification method for detection of bacteria

“…In these media, largescale bubble formation does not typically occur and sound speed measurements using a thermally controlled ultrasonic device are better suited for detection purposes. In order to measure propagation times and concentration thresholds in these conventional media, a different instrument from that described in section 2.2.1 was used (a Milisound device, described in detail in [10]). …”

On-line characterization using ultrasound of pectin hydrolysis catalyzed by the enzyme pectinmethylesterase

“…In addition it can be used to analyze systems that are optically opaque and the rapid advances in microelectronics have led to the development of relatively inexpensive ultrasonic instrumentation that is now commercially available [5]. The objective of this work was to characterize on-line the pectin hydrolysis catalyzed by pectinmethylesterase enzyme from orange peel and from Aspergillius niger, using an ultrasonic measurement device based on the propagation of low-intensity pulsed ultrasonic waves developed to monitor biological process [6]. Although, there are lots of researches on pectin hydrolysis, no published data have been found in the literature on ultrasonic techniques to characterize on-line this process.…”