The effect of ultrasonic soaking assisted microwave drying on the optimum cooking time and physicochemical properties of brown rice were investigated. After the ultrasonic soaking, the optimum cooking time of brown rice was significantly reduced, and the physical properties improved. The rice bran treated with high-temperature soaking and high-power ultrasound showed a porous structure with dense striped gaps. Accordingly, faster heat and mass transfer brought about the acceleration of drying rate and the reduction of drying time. The pretreatment and microwave drying reduced the gelatinization enthalpy (ΔH), which was beneficial to enhance the degree of gelatinization of starch. Microwave drying obviously increase the breakdown viscosity of brown rice flour, bringing about better tasting qualities. The content of free fatty acids, color parameters, and crystalline structure remained stable after pretreatment and microwave drying.Novelty impact statement: Appropriate high-power ultrasound at the soaking temperature of 60°C assisted microwave drying significantly altered the structure of brown rice bran, reduced the optimum cooking time, and improved the physical properties of brown rice. Ultimately, our research proved that soaking and ultrasound-assisted microwave was a promising way to produce instant brown rice with high quality.
The work investigated the influences of blanching (B) and ultrasonic-assisted blanching (UB) as pretreatment on mass transfer, drying kinetics, color, contents of nutrient, and aroma compounds of hot-air-dried perilla leaves. The samples were pretreated at two temperatures (70℃ and 80℃) and two durations of pretreatment (1 min and 3 min). Principal component analysis and hierarchical cluster analysis were used to distinguish sample characteristics of different pretreatments. The results showed that the condition of UB pretreatment had a higher drying rate compared to B pretreatment. The effective moisture diffusivity (D eff ) of pretreatment for UB is higher than B. The UB pretreatment method yielded the lower ΔE value and higher preserved content of chlorophyll, flavonoid, and rosemary acid at the pretreatment temperature of 70℃. Moreover, GC-MS results showed a lower perilla ketone relative content under the same conditions. According to the results, the quality of the dried perilla leaves after performing low-temperature UB pretreatment (70℃) was improved relatively.
Practical applicationsPerilla leaves are rich in antioxidant substances and have extensive culinary usage given their characteristic aroma and flavor. Convective drying is known to have some adverse effects on agricultural products. However, Ultrasonic pretreatment, as a modern food processing technology, can shorten the drying time and preserve the color, aroma, and nutrient content of food. The purpose of this study was to investigate the quality of dried perilla leaves with B and UB pretreatments, and to compare the differences in drying characteristics, color, nutrient content, and aroma compounds by different pretreatments. The pretreatment and dehydration parameters should be considered with respect to further utilization of dried perilla leaves.Nonetheless, sonication is worth to be taken into account due to the significant effects of energy expenditures, inhibiting browning of perilla leaves without damaging the quality of final product.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.