Acoustic sensor approach for rapid measurement of cheese quality

Novel acoustic systems, such as the piezoelectric and the non-contact air instability compensation ultrasound sensors were explored for rapid determination of cheese quality. Although fusion of the piezoelectric sensor and contact ultrasound measurements with an artificial neural network improved the prediction accuracy of mechanical properties of cheese, they are partially destructive owing to contact with the sample and use of a couplant, such as a gel.; A novel non-contact ultrasound system constructed by integrating the newly developed efficient air-coupled ultrasound sensors and an advanced signal processing technique used in radar signal detection was explored and demonstrated in this research. It was hypothesized that the non-contact ultrasound technique is an exciting alternative since it eliminates not only the contamination problem due to contact but also the contact procedures which make the scanning process and rapid measurement cumbersome.; Even though the novel non-contact ultrasound technology has tremendous advantages, critical pitfall exists. Since non-contact ultrasound utilizes air as its medium, it is highly dependent on the conditions of the air. The air column instability between ultrasound sensors causes errors in non-contact ultrasound measurements. To overcome the air instability problem, an air instability compensation ultrasound sensor was designed by placing a small fixed metal reference in front of the normal air-coupled ultrasound sensor. The reference was designed to reflect a small amount of energy so that most of the energy was directed to the sample. Hence, the design criterion was to limit the reflected energy to as low as possible and to maximize the transmitted energy through the reference. The reference was optimized using computer simulation based on spatial impulse response theory which can be applied to the calculation of complex energy distributions in front of the ultrasound sensor. The constructed non-contact air instability compensation ultrasound sensor demonstrated the improved performance for measurements in varying environmental condition, as in a food manufacturing plant or a process industry. This is the first concept ever tested and applied to, in food research.; The non-contact air instability compensation ultrasound sensing system was used to evaluate the mechanical and texture properties of cheese, one of the most important factors of consumer acceptance.; By incorporating the non-contact ultrasound imaging system with a two axis scan unit, a high resolution ultrasound image could be obtained. The ultrasound imaging can be used as a strong detector of foreign materials and internal defects in food materials. The foreign fragments of minimum 3 x 3 mm2 in size in cheese and poultry and cylindrical objects of minimum 1.5 mm in diameter in food materials could be clearly detected. (Abstract shortened by UMI.)...