Study On Ultrasonic Properties Of Liquid Food And Measurement Technique Of Liquid Food Quality Based On Ultrasonic

Low-intensity ultrasound frequently ranges at intensities lower than 1W/cm² and at frequencies higher than 100 kHz. When traveling through a medium, the ultrasonic waves change their characteristics and the analysis of this change allows assessment of inner structure and physico-chemical properties of the medium. Ultrasonic measurement has been widely used in the fields of non-destructive detection and medical image. For their particular advantages of rapid, nondestructive, noninvasive and inexpensive, low-intensity ultrasound has great potential in food industries both for process control and for product quality evaluation, especially for testing of high concentration solution and some opaque material. In this dissertation, two popular liquid food ingredients, alcohol and sugar solution, were used as a material, the relation of their microstructure and ultrasonic properties was investigated. The potentiality of quantitative determination and qualitative analysis by means of ultrasonic for these liquids was discussed. An instrument for determination of milk composition was designed and developed. The main results were as follows.1. Ultrasonic propagation properties in different kinds of alcohol and sugar solutions were studied as affected by their microstructure. It was found that ultrasonic velocity of alcohol and sugar solution was affected by their microstructures, stereo-chemical structures and concentrations. These findings indicate that it is possible to measure microstructure properties of liquids by ultrasonic properties, especially ultrasonic velocity.( 1 ) Intermolecular free length (IMFL), molecular free volume(MFV) and molecular internal pressure (MIP) are important microstructure properties of solution. A laboratory model study for relation of ultrasonic velocity and IMFL, MFV, MIP was carried out. It was found that there existed some significant correlation between ultrasonic velocity and IMFL, MFV, MIP. IMFL, MFV, MIP could be determined by ultrasonic velocity. It was found that there were some differences of molecular structure (molecular weight, hydroxyl number, length of hydrocarbon chain) between theoretic data and data calculated both from thermodynamic principle and volume properties. This problem could be improved by assisting of ultrasonic properties analysis. Furthermore a model for relation of ultrasonic velocity and MIP, IMFL was obtained in c=K₀ ρ^aVf^b Ï€ i^c with very high regressive coefficient Experimental data determined by this model showed that three are no difference between true and that from model. These results suggest that ultrasonic velocity could be used as a main parameter to measure...