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To clarify the moisture migration and microstructure of taro in contact ultrasound enhanced far-infrared radiation drying (CUFRD), low-field nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), paraffin sectioning and microscopic observation techniques were applied to explore the changes of the drying curves, water status, microstructure, porosity, microscopic images and distribution curves of cell microstructure parameters of taro under different ultrasound powers of 0, 40, and 80 W. The results showed that applying contact ultrasound (CU) during drying was beneficial to accelerating the dehydration process and improving the porosity of taro slice. With the augment of CU power, the drying times of taro reduced by 16.67% to 25.00%, and the effective water diffusion coefficient was improved by 14.72% to 31.38%. In addition, the application of CU resulted in an increase firstly and then decrease in the cross-sectional area and perimeter distribution curves of taro cells and a widening of the peak shape of the distribution curve of taro cell roundness. In conclusion, CU application could cause faster internal moisture migration, and higher CU power had more obvious effect on microstructure and cell morphological parameters of taro during CUFRD. [ABSTRACT FROM AUTHOR]

In order to investigate the feasibility and the enhancing effect of contact ultrasound application during far-infrared radiation (FIR) drying, a contact ultrasound strengthened FIR (CUFIR) drying equipment was fabricated and used, and CUFIR drying experiments on pear slices were carried out to explore the synergetic effects of ultrasound power and FIR heating on drying characteristics, microstructure, and quality of dried pear products. The results show that the application of contact ultrasound could be obviously helpful to accelerate internal mass transfer in pear slices and improve the drying rate of FIR drying, and higher ultrasound power could lead to stronger strengthening effect. The enforcing effect of ultrasound increased at higher FIR power, and weakened with the reduction of moisture content during CUFIR drying. The Deff values ranged from 4.76 × 10−10 m2/s to 13.94 × 10−10 m2/s in this study and the increase of both FIR power and ultrasound power had significant and positive influence on the increasing of Deff values. With scanning electrical microscope (SEM), it was observed that the improvement of ultrasound power could enlarge the size of microcapillaries and even generate new micropores and microchannels on the ultrasound-treated surface and in the organism structure of pear slices. The increase of ultrasound power could improve total phenolic content (TPC) and total flavonoids content (TFC) of pear slices at FIR powers of 100 and 220 W. Yet, the application of contact ultrasound with ultrasound power of 60 W had negative influence on TPC and TFC at FIR power of 340 W. Although the ascorbic acid content (AAC) reduced as FIR powers increased during FIR drying without contact ultrasound assistance, the increase of ultrasound power could improve AAC at all FIR powers. The CUFIR drying at ultrasound power of 60 W and FIR power of 220 W achieved the lowest energy consumption. Therefore, the application of FIR drying combined with contact ultrasound is a promising method to improve drying rate as well as protect product quality. [ABSTRACT FROM AUTHOR]

Onions, rich in flavonoids, with antioxidant, antibacterial, and other biological activities, are often used as extraction of raw materials to obtain health products with high flavonoids content. However, the amount of raw material consumption is large due to low yield of extracts from fresh onions. As a result, dried onions often are used as extraction materials. The effects of air drying (AD), freeze-drying (FD), and microwave freeze-drying (MFD) on the flavonoids extraction yield of onions were investigated. The most effective and economical method was hot AD. On the other hand, the flavonoids extraction rate of onions dried by MFD was the fastest. FD could also obtain high extraction rate, but it cost the highest energy consumption. In order to obtain relatively rapid, economic, and effective extraction of onion flavonoids, onions can be dried by MFD or AD method. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of astragalin on the central nervous system. Astragalin is a monomeric compound found in the leaves of Eucommia ulmoides using a system solvent method. In the experiments, astragalin showed significant effects on mice, including reduced spontaneous activity, increased sleep ratio, shortened sleep latency and lengthened sleep time with a subthreshold or superthreshold dose of pentobarbital sodium. In addition, astragalin effectively reduced the convulsion rate and prolonged convulsion latency. These findings confirmed that astragalin had excellent sedative and hypnotic effects and has potential to be commercialised as a novel nutraceutical agent to promote calming and improve central nervous system-associated pathologies. [ABSTRACT FROM AUTHOR]

A drying technique using a combination of a contact ultrasound apparatus and a hot air dryer is developed to investigate the strengthening effect of contact ultrasound on hot air drying. The effects of drying parameters such as ultrasound power and drying temperature on drying characteristics, effective moisture diffusivity (Deff), microstructure, glass transition temperature (Tg), rehydration ratio, and color difference are discussed. The results show that the application of contact ultrasound causes a significant acceleration of internal mass transfer, and higher ultrasound power applied leads to faster drying rate. The effect of ultrasound power on drying rate decreases along with the reduction of moisture content during drying process. The increase in drying temperature significantly reduces drying time but has a little negative influence on the strengthening effect of ultrasound.Deffvalues range from 1.0578 × 10−10to 5.4713 × 10−10 m2/s in contact ultrasound-assisted hot air drying of purple-fleshed sweet potato and increase significantly with an increase in drying temperature as well as ultrasound power. The microstructure of purple-fleshed sweet potato is greatly different at different ultrasound powers during contact ultrasound-assisted hot air drying and shows more microchannels and dilated intercellular spaces in the cross-section of purple-fleshed sweet potato micrographs at higher ultrasound power. Contact ultrasound application during hot air drying could improve the mobility of water and consequently reduce glass transition temperature. Lower color difference and higher rehydration ratio could be achieved as drying temperature decreases and ultrasound power increases. The increase in contact ultrasound power could reduce energy consumption of drying process up to 34.60%. Therefore, contact ultrasound assistance is a promising method to enhance hot air drying process. [ABSTRACT FROM PUBLISHER]

Freeze drying (FD) yields the best quality of dried mushroom but at the cost of a long drying time and high overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high-quality product, a microwave–freeze drying (MFD) technique was developed to dry mushrooms. The relationship between dried mushroom quality and the glass transition temperature during the MFD process was studied to optimize the MFD process. According to the change tendency of the glass transition temperature of mushroom during MFD, a step-down microwave loading scheme for the MFD process was developed to obtain good product quality. [ABSTRACT FROM AUTHOR]

A mathematical model of mass and heat transfer for vacuum far-infrared drying of potato slices is introduced in this study on the basis of energy and diffusion equations. The finite difference method is used to mathematically simulate the sample temperature and moisture content in different drying conditions. Calculated results are compared with the experimental findings at varying conditions of heater temperature (120°C, 140°C, and 160°C), chamber pressure (1500, 8000, and 15000 Pa), sample thickness (0.004, 0.006, and 0.008 m), and radiation distance (0.08, 0.12, and 0.16 m). Comparison results show that the model fits well the changes in sample temperature and moisture content at different times of drying, with the values of the coefficient of determination close to 1.0 and the relative error values less than 10%. [ABSTRACT FROM AUTHOR]