| Summary: | 博士 === 臺灣大學 === 生物產業機電工程學研究所 === 95 === Abstract
This study utilized the ultrasonic pulse-echo method and acoustic emission technology to evaluate the internal qualities of agricultural products and meat. Those researches covered the areas of freezing rate evaluation of beef and pork, physiological properties evaluation of mango fruit, and life history monitoring of the Callosobruchus maculatus inhabiting in beans.
The beef texture is influenced by the depth of freezing front during freezing process. The ultrasound speed in frozen beef was obtained by measuring echo response time and transmitting distance of the ultrasound. The ultrasound velocity is constant above freezing point. The latent heat effect is obvious at the freezing point. The zone of maximum ice crystal formation occurs between 0 °C and -5 °C. The maximum freezing rate was observed as the meat fiber direction paralleled the heat flow during meat freezing process. The amount of energy for latent heat released and ultrasound speed measured at the zone of maximum ice crystal formation were respectively about 72% of total input energy and 63.64% of ultrasound speed range during the freezing process. The coefficients of determination for the regression of meat thermal center temperature against ultrasound velocity and the regression of freezing ratio against ultrasound velocity were 0.86 and 0.95 respectively. It is feasible to estimate the meat thermal center temperature and freezing ratio from the ultrasound velocity.
Due to expansion of frozen water contained in the cell or intercellular space, the texture of frozen pork meat will be influenced by different freezing rates. The experimental results show that the meat muscle fiber fragmentation situation is serious in slow-freezing as compared to rapid-freezing. It means that the degree of Zenker’s degeneration increases at low freezing rate. The ultrasound speed in pulse-transmission system increases as freezing degree increases. Therefore the ultrasonic technology can be adopted to evaluate pork meat quality during freezing process.
The immersion ultrasonic testing technology was used to establish quantitative relations between ultrasonic diagnostic indices and physiological properties of mango fruits. Pulse-echo ultrasonic testing of submerged mango fleshes indicated that the ultrasound waveforms changed as it propagating through the different fruit texture. The relationship between ultrasound attenuation and physiological properties of ripening mango was analyzed in this study. The Fisher Z transformation procedure was used to estimate the characteristics of a population with ultrasound attenuation and physiological parameters. Ultrasound attenuation subject to other parameters is analyzed with regression analysis. As validated by experiments, disordered fruits usually have a higher density and attenuate ultrasound more than healthy fruits. This work found that the correlations of ultrasound attenuation with the density and Young’s modulus of fruit exhibit linear and power relationships, respectively. Experimental results show that a healthy flesh has less ultrasound attenuation, less SSC (soluble solids content)/acid ratio, and higher Young’s modulus in comparison with a disordered one.
An ultrasonic monitoring system was developed for exploring the life history of Callosobruchus maculatus inhabiting in beans. Callosobruchus maculatus only feeds before eclosion and the demand for food is different in every life stage. The feeding process cracks bean texture fibres and produces feeble ultrasound. Hence the life history of an inhabitant can be explored through spying the feeding cracks. The developed ultrasonic monitoring system consists of a delicate electronic signal conditioning module which amplifies, filters, and transforms a biting crack into a square pulse. A computer equipped with software developed in house acquires biting pulses and displays the life history on line. Acquired data are stored for subsequently off-line analysis. The system has been successfully applied to exploration of the life histories of Callosobruchus maculatus inhabiting in Azuki beans and mung beans.
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