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Constant power microwave heating (CPMH) based on solid-state generators, a new microwave heating system, shows better repeatability than traditional microwave heating (TMH) powered by magnetron when performing experiments, while its detailed heating patterns and field distribution are still not fully understood. In this study, numerical simulations for model juice (about 1–5 mL) heated by CPMH and TMH systems were carried out to compare the heating performance. The simulation was performed through coupling electromagnetic, thermal and fluid fields, using a laminar flow model to simulate the flow behaviour of the model juice during the heating operation. Both surface temperature distributions and inner point temperatures were investigated for model validation, and the simulated data agreed well with the experimental ones, indicating that the modelling was rational and correct. Results showed that CPMH gave higher heating efficiency and better temperature uniformity, which was verified by determining both inner point temperature and surface temperature distribution. Besides, influences of sample volume and microwave input power on the heating performance of the CPMH system were studied, suggesting that greater sample volume could cause worse temperature uniformity, although a faster temperature increase was observed. When fixing total microwave input energy to 3 kJ, different input powers were found to achieve similar final average volumetric temperatures (50.46 °C–51.22 °C) but significantly different heating uniformity (final coefficient of temperature variance: 0.065–0.115), indicating that smaller microwave input power could contribute to better heating uniformity. It is hoped that this study could provide references to further understand the heating effects of CPMH systems, leading to better design and upgrade for microwave heating systems. • Model juice heated by constant power microwave heating (CPMH) system was simulated. • Heating performance of traditional microwave heating (TMH) system was compared. • CPMH showed higher heating efficiency and better temperature uniformity than TMH. • Central zone of the model juice gained more microwave energy for heating. • For CPMH, greater power made heating faster but decreased temperature evenness. [ABSTRACT FROM AUTHOR]

Plants constitute the foundation of sustainable environmental systems and human health. However, the limitations of solar radiation and the increased challenges of plant cultivation pose a threat to the environment and human health. In the past years, artificial lighting sources have been a hot topic in many fields, especially in plant cultivation owing to their controlled nature of the conditions. However, traditional artificial lighting sources suffer from unstable light quality, high energy consumption, and a short lifespan, which hinders their widespread use in agricultural farming. In contrast, light conversion technologies offer unparalleled advantages such as high conversion efficiency, stronger light harvesting, good photostability, and superior biocompatibility. With the flourishing development of nanotechnology, nano light conversion agents have been demonstrated to be alternative tools to traditional artificial light sources. Therefore, light conversion agents-guided plant cultivation is a promising strategy in the development of sustainable systems. This review introduces the mechanism and classification of nano light conversion agents and summarises recent advances in the applications of light conversion agents for plant cultivation. The prospects and challenges of light conversion agents are also discussed in the current review. • Light conversion mechanisms and classification of plant cultivation were reviewed. • Applications of light converter platforms for plant cultivation were summarized. • Prospects and challenges in applying nano light conversion agents were presented. [ABSTRACT FROM AUTHOR]

• US-FT and MW-FT pretreatments were employed for improving infrared drying of RDFS. • US-FT and MW-FT modified microstructure to increase moisture diffusivity of RDFS. • Betalain and ascorbic acid contents of RDFS were improved by low-temperature US-FT. • High-power MW-FT enhanced color and textural properties of RDFS. • US-FT presented overall enhancements in the quality of RDFS. The effects of thermoultrasound (US-FT), microwave (MW-FT), and room temperature (RT-FT) freeze–thaw pretreatments were evaluated for improving drying kinetics and quality during infrared drying (IRD) of red dragon fruit slices (RDFS). Results indicated that microstructural alterations induced by the different pretreatments improved the moisture removal rate and effective diffusivity, and significantly reduced the drying time. US-FT pretreatments prompted more efficient drying and presented an overall enhancement in the quality of RDFS, particularly at low temperatures of 25 and 50 ℃, while enhancements in TFC, FRAP, and CUPRAC were associated with RT-FT. High-power (500 W) MW-FT pretreatments improved colour and structural properties, while low-power (100, 300 W) improved TPC, TFC, ascorbic acid, betalains, and antioxidant activity. Overall, cellular and chemical alterations prompted by pretreatments improved the drying process but presented adverse effects on betaxanthin. The study presented the fundamental background for improving the IRD of foods from the use of improved thawing approaches during freeze–thaw pretreatments. [ABSTRACT FROM AUTHOR]

In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol–water solution at 253.15 K) of potato spheres (0.02 m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25 kHz, 890 W m −2 ) was irradiated for different duty cycles (DCs = 0–100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30–70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process. [ABSTRACT FROM AUTHOR]