Study On Acoustic Properties Of Sugar Solutions And Application Of Ultrasonic Measurement In The Detection Of Sugar Concentrations

Ultrasonic measurement is based on the use of low-intensity ultrasonic, which range at intensities lower than 1 W/cm2 and at frequencies higher than 100 kHz. When traveling through a medium, the ultrasound wave changes its characteristic and the analysis of this change allows assessment of inner structure and physical chemistry properties of the medium. Ultrasonic measurement has broad applications in food industries both in process control and product assessment for its particular advantages of rapid, nondestructive, noninvasive and inexpensive. In this paper, low-intensity ultrasonic was used to study the acoustic properties of sugar solutions. The relationships between the sugar contents and the ultrasonic velocity in sugar solutions were investigated. Furthermore, the models were determined and used to detect the sugar contents in fruit juices and drinks. The results obtained from ultrasonic measurement were proved to be satisfied. The main results indicated as below:(1) The acoustic velocity in the pure sugar solutions was measured as a function of sugar contents. In all species of sugar solution, the velocity increased monotonously with increasing of concentration, and the corresponding regressive equations of were obtained with R2 > 0.998. The diverse of sugar structure is one of the main factors affect on the difference of ultrasonic velocity in different sugar species. On the other hand, the adiabatic compressibility, calculated from velocity, was proved to be more sensitive with the interaction between sugar and water molecules than the partial molar volume. Therefore, adiabatic compressibility can be used to study the interaction between solute and solvent.(2) The data of ultrasonic velocity in mixed sugar solutions were plotted regularly in one curing plane in the 3-D picture. The binary regressive polynomial equations of experimental curves were obtained to show the relationship between ultrasonic velocity and the concentrations of different compositions. It also showed that the ultrasonic velocity was affected notably by the interaction of the compositions in higher concentrations, while indistinctively in lower sugar concentrations (round about 30%). The sugar concentrations were predicted by the models, which were proved to be indistinctive with the theoretic value.(3) The sugar contents of fruit juices and drinks were determined by ultrasonic measurement. This method was well consistent compared with the chemical method and HPLC method. As compared with HPLC, ultrasonic measurement is better than other methods. Furthermore, the acoustic velocity decreased linearly with the content of fruit juice, so it can be used to confirm the content of fruit juice in the dilutions.