Zheng Xianzhe

Comparative Experiment on Hot-Air and Microwave-Vacuum Drying and Puffing of Blue Honeysuckle Snack

A comparative drying experiment between the hot-air and microwave-vacuum method of blue honeysuckle slice has been completed. In hot-air drying, the temperature was 50°C when the velocity of air stream was kept at 0.5 m/s. In microwave-vacuum puffing, the microwave power and vacuum pressure were set at 2.68kW and 82 kPa, respectively. Comparing to the quality indexes viz. texture characteristics (hardness and crispness), color, cross-section structure and vitamin C content of blue honeysuckle snack, it was known that hardness of blue honeysuckle snack decreased by 3936g, crispness increased by 3, value of lightness, redness and yellowness increased by 2.09, 0.2, 0.27, respectively, and the retention rate of VC content increased by 9.67% using microwave-vacuum puffing than that using hot-air drying. Therefore, microwave-vacuum technique is a potential method to puff blue honeysuckle slices with high quality attributes.

Rapid Non-destructive Detection for Molds Colony of Paddy Rice Based on Near Infrared Spectroscopy

Abstract Near infrared spectrometer technology under a wavelength range of 918-1045 nm was used to rapidly detect paddy rice that was stored at 5°C, 15°C and 25°C. A total of 121 paddy rice samples were collected from artificial infection with moulds to build the calibration models to calculate the total number colony of moulds based on the principal component regression method and multiple linear regression method. The results of statistical analysis indicated that multiple linear regression method was applicable to the detection of the total number colony of moulds. The correlation of calibration data set was 0.943. The correlation of prediction data set was 0.897. Therefore, the result showed that near infrared spectroscopy could be a useful instrumental method for determining the total number colony of moulds in paddy rice. The near infrared spectroscopy methodology could be applied for monitoring mould contamination in postharvest paddy rice during storage and might become a powerful tool for monitoring the safety of the grain.

Drying Characteristics of Microwave-assisted Foam Drying of Corn Soaking Water

To improve the industrial utilization of corn soaking water, the yeast protein powder was produced by microwave-assisted foam drying. Firstly, preparation experiments were carried out, which included the foaming characteristic experiments of fermentation broth and that about the effects of carbon and nitrogen ratio on solid content in the fermentation broth. Secondly, the drying characteristics experiment of corn soaking water was studied, which selected the microwave power, material amount and thickness as the influencing factors for the single experiment. The results showed that the final moisture content (d.b.) and drying rate were significantly affected by those factors.

Process Parameter Study on Microwave-assisted Foam-mat Drying Properties of Corn Soaking Water

In order to study the microwave-assisted foam-mat drying properties of corn soaking water and optimize process parameters, a quadratic regression orthogonal rotary method was used to analyze the influence of microwave power, material weight, material thickness and drying time on moisture content (dry basis), color value and protein content. Results showed that the primary and secondary sequence of parameters with regard to moisture content (d. b.) was drying time, microwave power, material weight and material thickness; the primary and secondary sequence of parameters with regard to color value was material weight, drying time, microwave power and material thickness; the primary and secondary sequence of parameters with regard to protein content was drying time, material weight, microwave power and material thickness. Optimum conditions were obtained as microwave power of 560 W, material weight of 46.88 g, material thickness of 6.20 mm and drying time of 8.01 min. The results might provide the theoretical basis and technical support for the microwave-assisted foam-mat drying of corn soaking water to produce yeast protein power.

Kinetic Mechanisms for Preparing Silymarin via Microwave-assisted Extraction

Abstract The kinetic mechanism for the preparation of silymarin from milk thistle seeds was studied during the microwave-assisted extraction (MAE) process. The results showed that the transfer rate of silymarin from milk thistle seeds increased with the microwave output power and temperature during MAE processing. The apparent extraction rate constant k (s−1) was 1.2028×10−2, 1.2248×10−2, and 1.2485×10−2, and diffusion coefficient D (m2 • s−1) was 4.21×10−10, 4.29×10−10, and 4.37×10−10 at the microwave temperatures of 383, 393, and 403 K, respectively, in the silymarin MAE process. With the help of scanning electron microscopy (SEM), the microstructures of the samples extracted by MAE were observed. The results revealed that the increased efficiency and rate of MAE of silymarin could be attributed mainly to the subsequent cell change resulting from superheating effects during MAE.

Temperature Simulation of Berry Slices Under Microwave Vacuum Puffing Conditions

Abstract In order to study the temperature simulation of berry slices in microwave vacuum puffing process, numerical simulation method was used to simulate the temperature in different time according to theoretical calculation result and the deviation had been verificated throughout the experiment. The better uniform of temperature between experiment and simulation could be concluded except in the period of rapid temperature increase. The temperature reached the high point of 130.25°C in the middle point of slices at 100 s, while the temperature was over 50°C in external parts of slices for the reason of thermal diffusion. Conclusions could be drawn that the model was effective and numerical analysis could simulate the temperature simulation for berry leather in microwave vacuum puffing process.