An experimental system was set up to generate the impact force, measure the response wave signal, and analyse the frequency spectrum for physical property detection of biological product. The egg dynamic resonance frequency was obtained through the analysis of the dynamically measured frequency response of an egg excited by pendulum. The effects of excitation point, detected point, impact intensity, excitation material, egg mass, egg density, shell stiffness and shell crack on the dominant frequency were analysed. The results showed that the dominant frequency was significantly affected by the shell crack, shell stiffness, egg mass and egg density, and not significantly affected by excitation point, detected point, excitation velocity and impacting material. The dominant frequency increased with increasing of shell stiffness or egg density, and decreased with increase of the egg mass. The coefficient of determination (R2) of the quadratic relationship between the dominant frequency and the three egg physical properties was 0.62-0.68.

An experimental system was set up to generate the impact force, measure the response signal and analyse the frequency spectrum for physical property detection of biological products. The pear dynamic resonance frequencies were obtained based on analysis of the dynamically measured frequency response of an excited pear with changes in the excitation points, the detection points, the impact intensity and the excitation material, and under different pear firmness and mass conditions. As a result of the analysis, it was found that the dominant frequency was significantly affected by the pear firmness and mass. The excitation point, the detection point, the excitation intensity and the impacting material did not significantly affect the dominant frequency. The dominant frequency increased with increasing pear firmness and decreased with increasing pear mass. A good relationship was obtained between the dominant frequency and the pear firmness or the pear mass, and the firmness index regressed on the Magness-Taylor firmness also showed a good relationship.

Little detailed information is available on the microwave drying characteristics of potato and the use of different microwave powers to dry food products. Experiments were conducted to study the microwave drying characteristics and the dried quality of potato. The study focuses on describing the microwave drying characteristics of potato and discussing the effect of sample thickness, drying power and mass. The results show that if the power level increases, the mass load decreases and the thickness of the sample decreases, the dehydration rate increases and the drying energy consumption decreases. There are two falling rate periods during microwave drying of potato: the first falling rate period is for a moisture content of more then 1.1 (dry basis, DB); the second falling rate period is for a moisture content of less than 1.1 (DB). The same water loss will consume more energy when the moisture content is less than 1.1 (DB). A two-stage drying process was employed during microwave drying of potato. The microwave power of the first drying stage differed form that of the second drying stage. The moisture content of the breakpoint for the conversion of the first drying stage into the second drying stage is a moisture content of 1.1 (DB). A quadratic orthogonal regression experiment was conducted, and the effects of slice thickness, the first drying load power and the second drying load power on sensory quality, the rehydration ratio and the energy consumption rate were established. The slice thickness, the first drying load power and the second drying load power linearly affected the three indices. The effect of the product of the second drying load power and the potato slice thickness on the rehydration ratio and the energy consumption rate is significant. The optimum drying parameter combination for the three indices was obtained. The rehydration ratio of the dried products decreased with an increase of the second drying load power and the slice thickness. The concave curves of the sensory quality versus the three factors were shown.

Few studies on the irradiation effects on dehydration characteristics and quality of dried-product ha ve been reported in the past three decades. This study focuses on drying characteristics of bio-products by hot-air after they are pretreated by gamma irradiation. Experiments were made to study the influence of different irradiation dose, air temperature, slice thickness of apple on the ehydration rate, and appearance quality (L-values), vitamin C content, and the rehydration ratio of dried apple. A conclusion is reached that the three factors of irradiation dose, hot-air temperature, and initial slice thickness significantly affected the four indices of appearance quality (L-values), vitamin C content, dehydration rate and rehydration ratio.

The technology of drying by hot-air on fruit and vegetable is widely used in practice because of its convenience. However, it has some defects such as a low efficiency and the inferior quality of the dried products, which are the obstacles to its further application. This study focuses on improving the current technology and a new technology is introduced, that is, to dry bio-products by hot-air after they are pretreated by gamma irradiation. Experiments are made to study the influence of different irradiation dosages, air temperatures, slice thicknesses of apple on the dehydration rate and temperature of samples. A conclusion is reached that the three factors affect the dehydration rate and temperature of slice apple, and, the higher the dosage, the greater the rate of dehydration of apple, and the higher the temperature.