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Gas sensitive films (GSFs) of polyvinyl alcohol (PA), soluble starch (SS), and polyethylene glycol bis (3-aminopropyl) ether (PGE) containing blueberry anthocyanin (BA), curcumin (CU), and anthocyanin/curcumin complexes were created to monitor the quality changes of strawberries during storage (room temperature, 24 ± 2 °C). Using headspace-gas chromatography-mass spectrometry (HS-GC-MS), the volatile aroma gases released during storage of strawberries were analyzed. Results showed that the release of aldehydes was more closely associated to the quality of the strawberries. The BA, CU and BA/CU complexes (mass ratio: 1:2 and 2:1) were well dispersed in GSFs and improved the films' hydrophilicity, however, there was no effect on the water vapor permeability. The four GSFs were employed to monitor strawberry quality changes over the course of storage. The results showed that the changes in color of the four GSFs had a strong correlation with the quality of strawberries, which could be classified as fresh, sub-fresh and spoiled.

Bitter gourd is a versatile vegetable that brings health-promoting benefits to consumers. To maintain its high nutrition values and ensure year-round availability, proper post-harvest processes are essential for preserving its original properties. However, there is limited knowledge regarding how pretreatment methods impact the physicochemical properties of pretreated bitter gourd and the performance of subsequent hot air-assisted radio frequency drying (HARFD) process. In the present study, bitter gourd underwent osmotic dehydration (OD) and ultrasonic-assisted osmotic dehydration (UAOD) pretreatment with different ultrasound power levels (400, 800, and 1200 W). The physicochemical properties of the pretreated samples, such as mass transfer behavior, water migration status, dielectric loss factor, and others, were compared. The drying duration, energy consumption, and various quality attributes (e.g., color index, rehydration, nutritional compositions, antioxidant activity, etc.) of the HARFD dried products were also examined. The microstructure observations demonstrated that acoustic waves induced the structural changes and created microchannels. Additionally, physicochemical properties of the pretreated samples showed that OD and UAOD methods significantly facilitated water migration status and increased the dielectric loss factor. Compared to control and OD methods, three UAOD methods successfully reduced the drying duration by 7.9%–30.3% and total energy consumption by 5.8%–28.3% for the entire processing steps. Furthermore, UAOD methods improved the total phenolic content, total chlorophyll retention, DPPH and ABTS values of dried bitter gourds by 32.3%–36.7%, 12.6%–20.3%, 23.4%–31.6%, and 20.7%–26.3%, respectively, compared to the control methods. Overall, UAOD-400 W samples after drying exhibited improved quality characteristics, including reduced color difference, increased retention of bioactive compounds, higher rehydration ratio, and enhanced antioxidant capacity. This study underscores the effectiveness of UAOD application in improving both processing efficiency and quality of bitter gourds produced by HARFD.

Fresh foods are prone to deterioration in complex and variable condition's encountered in supply chains. Currently it is not possible for consumers to intuitively or visually know the quality of fresh food at the time of purchase or subsequent storage prior to consumption which can result in issues of food safety and even wastage. Therefore, it is important to devise technologies to monitor the quality of fresh foods during transportation and marketing as well as to be able to reliably predict its possible deterioration so as to provide visual warning to the stakeholders. In the context of digital and intelligent transformation, some emerging technologies have received more attention. Intelligent packaging and digital twin provide innovative ideas for providing visual feedback concerning product quality. Intelligent packaging, a packaging system for monitoring, displaying and tracing of food quality status in supply chain offers great advantages. Further, digital twin displays great potential to provide reliable and timely quality prediction and risk warning with strong support of blockchain, artificial intelligence and big data analysis. In order to better focus on the development and integration of these emerging technologies to achieve visualization requirements for stability, accuracy and timeliness, this review comprehensively discusses recent research and progress in application of intelligent packaging (indicators, sensors and data carriers) and Industrial 4.0 technologies (blockchain, artificial intelligence, big data analysis and digital twin) by focusing on data acquisition, traceability, processing and visualization in fresh foods supply chain. Moreover, challenges and potential of these technologies are presented. This will better help stakeholders to make optimal decisions throughout the supply chain of fresh foods to meet the challenges of food waste and food safety.

Novel food resources rich in nutrition particularly protein are superior alternative food resources to enhance the present food supply. Drying of novel food resources is very important for future food manufacturing due to their high moisture content. This review summarizes current drying techniques applied to the approved and potentially developed novel food resources (insects, microalgae, edible mushrooms, and coarse cereals) and evaluates their effects on the physicochemical, nutritional, and sensory properties of these food resources. Dried novel food resources are commonly regarded as functional ingredients to improve the nutrition characteristics and textural properties of conventional foods, meanwhile strongly contributing to the rapid development of future food. In this work, applications of these dried novel food resources in prepared dishes, 3D-printed foods, and functional foods are critically reviewed along with a concise discussion of challenges ahead in their commercial applications. The application prospects of novel food resources are also proposed. This review provides some useful information for choosing appropriate drying techniques applied to novel food resources. The use of dried novel food resources will greatly promote the multiple development of future food.

This study aimed to control printing ambient temperature and oxygen content collaboratively to achieve synchronous improvement of the sensory and nutritional quality of printed products. In this study, spinach juice and potato snowflake powder were used as raw materials to prepare printing materials. The results showed that the printing material with a 20% addition of potato snowflake powder had the best printing performance. Enhancing the flavor of the printed products in the printing process by increasing the printing ambient temperature, the printed product with better flavor quality was obtained at 40 °C. However, the increase in ambient temperature had adverse effects on the color and antioxidant capacity of the printed product, the ΔE value of the printed product at 40 °C was 6.18 ± 0.64. Based on this ambient temperature, reducing the oxygen content in the printing environment inhibited the adverse effects of rising temperature on the color and antioxidant capacity of printed products. When the oxygen content was below 1%, the printed product maintained the color and antioxidant capacity before printing, the ΔE value of the printed product was only 0.95 ± 0.09, and there was no significant difference in antioxidant properties (total chlorophyll content, total carotenoid content, total phenolic content, free radical scavenging activity). Therefore, while successfully improving the flavor of the product, this study achieved the maintenance of color, antioxidant capacity, and other qualities, which is an effective exploration of using 3D printing technology to produce high-quality food.

Intelligent colorimetric freshness indicator is a low-cost way to intuitively monitor the freshness of fresh food. A colorimetric strip sensor array was prepared by p-dimethylaminocinnamaldehyde (PDL)-doped poly(vinyl alcohol) (PVA) and chitosan (Chit) for the quantitative analysis of indole, which is an indicator of shrimp freshness. As a result of indole simulation, the array strip turned from faint yellow to pink or mulberry color with the increasing indole concentration, like a progress bar. The indicator film exhibited excellent permeability, mechanical and thermal stability, and color responsiveness to indole, which was attributed to the interactions between PDL and Chit/PVA. Furthermore, the colorimetric strip sensor array provided a good relationship between the indole concentration and the color intensity within a range of 50–350 ppb. The pathogens and spoilage bacteria of shrimp possessed the ability to produce indole, which caused the color changes of the strip sensor array. In the shrimp freshness monitoring experiment, the color-changing progress of the strip sensor array was in agreement with the simulation and could distinguish the shrimp freshness levels. The image classification system based on deep learning were developed, the accuracies of four DCNN algorithms are above 90%, with VGG16 achieving the highest accuracy at 97.89%. Consequently, a “progress bar” strip sensor array has the potential to realize nondestructive, more precise, and commercially available food freshness monitoring using simple visual inspection and intelligent equipment identification.

The impacts of varying heating temperature on the flavor of Sichuan pepper essential oil (SPEO) have been studied. The high temperature heating was found to accelerate the oxidation of SPEO and caused the deterioration of its flavor (odor and pungency taste). With the intervention of antioxidants including RE, AP, and TPP, both thermal oxidation stability and flavor stability of SPEO were enhanced. Addition of 1.5% TPP had the best control effect, which significantly improved the overall flavor of heated SPEO and made the overall flavor of SPEO heated at 100 ˚C highly similar to that of original SPEO. According to the results of GC-MS and OAV analyses, the control effect of antioxidants on odor deterioration of SPEO was mainly through significantly inhibiting the decrease in content and OAV of both linalool and terpenes, and restricting the formation of some oxygenated compounds such as aldehydes. The results of HPLC analysis showed that the control effect of antioxidants on the thermal taste stability of SPEO was mainly dependent on blocking the chemical reactions of sanshools, especially hydroxy-α-sanshool.

The undesirable odor of crab meatballs was evident after boiling and cooling, high-voltage electrostatic field (HVEF), lysozyme and yeast extract (LY), and the combination (LYH) were all applied to pre-deodorize crab meatballs to estimate the effect in view of odor, pH, fat oxidation and protein oxidation. None of the tert-butylamine (1.58 ± 0.14 ng/g), (E, E)-2,4-Dodecadienal (18.52 ± 0.12 ng/g), 1-Octen-3-ol (13.51 ± 0.22 ng/g) and nonanal (681.55 ± 0.24 ng/g) in the control were detected in LYH group, while nonanal in HVEF and LY groups was reduced by 86.07% and 42.60%, respectively. Thirteen volatile substances with variable importance plot ≥1 contributed prominently to the odor of crab meatballs depended on partial least squares discrimination analysis. Protein oxidation of the pretreated crab meatballs was alleviated, as well as thiobarbituric acid reactive substances (TBARS) and lipoxygenase (LOX) activity, with the best inhibitory effect of LYH being 40.10% and 62.80% on the respective effects. The correlation analysis derived that fishy substances were significantly positively correlated with TBARS and pH. LYH was the optimal pre-deodorization, which involved promoting glycolysis and lactic acid bacteria colonization in the liquid medium, and inhibiting fat oxidation by affecting enzyme activity in HVEF.

This study aims to prepare and characterize non-metallic nitrogen-modified titanium dioxide (N–TiO2), film and expand its photocatalytic excitation wavelength to the visible blue-violet region. The film uses corn starch as a carrier. It is combined with blue-violet LED light to explore the effect of this combination on the quality of Agaricus bisporusduring storage. This study found that the mechanical properties and hydrophobicity of the corn starch film with nano-TiO2added were improved; the effect of adding N–TiO2was more pronounced; the tensile strength increased by 65% while the water contact angle increased by 11%. In the application of A. bisporusstorage, the film combined with blue-violet LED light can slow down the loss of moisture, reduce the respiratory rate, delay the appearance of the respiratory peak, and maintain the color and hardness of A. bisporus. After 15 d of storage, compared to the control group, the hardness decreased by 69%, browning index (BI) increased by 221%, the CS-N group hardness decreased by only 23%, and the BI increased by 89%. Under blue-violet LED light, the accumulation of secondary metabolites in A. bisporusincreased, and the polyphenol content also showed an increasing trend during storage.

The comprehensive utilization of food resources has been an issue of interest. In this study, carbon dots (CDs) were prepared by green hydrothermal method using four plant byproducts, and then the preparation of fluorescent CDs was verified by particle size, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis as well as UV and fluorescence spectroscopy. The results showed that all four CDs had particles smaller than 50 nm and at a concentration of 128 μg/mL, CDs had similar ability to scavenge DPPH free radicals as vitamin C. Also, all four CDs had extensive fluorescence properties. In addition, CDs showed good antibacterial properties and fluorescence properties against Escherichia coli, Staphylococcus aureusand Pseudomonas aeruginosa. These findings suggest that these four CDs have a promising future in the field of food detection and preservation, and provide useful information for the thorough utilization of food resources.

Natural polysaccharides of plant and animal origin include polysaccharides with nutritional effects but no pharmacological activity, and bioactive polysaccharides with pharmacological activity. Using polysaccharides and their derivatives as additives can impart unique consistency, structure and texture to food products to facilitate individualized design. Appropriate drying technologies will not only help preserve the inherent biological activity and physicochemical properties of polysaccharides, but also to enhance the potential of polysaccharide-based materials for new applications; these include polysaccharide-based microencapsulation and food gel systems for encapsulating bioactive compounds and simulation of texture of future foods. In this review, we start with the applications of plant and animal-derived polysaccharides in future food products followed by discussion of conventional and innovative drying technologies used for different origin bioactive polysaccharides. Secondly, we analyze the drying technologies used for polysaccharide-based micro- and nanocapsules encapsulating bioactive compounds. Furthermore, we summarize prospects of innovative drying technologies for polysaccharide-based food gel systems -mainly oleogels and aerogels-involved in the development. Finally, we look at the opportunities and challenges of drying technology innovation for polysaccharide-based food packaging in anticipation of the development of superior packaging technologies for future foods based on polysaccharides.

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A proper control and management of dust dispersion is essential to ensure safe and productive underground working environment. Brattice installation to direct the flow from main shaft to the mining face was found to be the most effective method to disperse dust particle away from the mining face. However, it limits the movement and disturbs the flexibility of the mining fleets and operators at the tunnel. This study proposes a hybrid brattice system - a combination of a physical brattice together with suitable and flexible directed and located air curtains - to mitigate dust dispersion from the mining face and reduce dust concentration to a safe level for the working operators. A validated three-dimensional computational fluid dynamic model utilizing Eulerian–Lagrangian approach is employed to track the dispersion of dust particle. Several possible hybrid brattice scenarios are evaluated with the objective to improve dust management in underground mine. The results suggest that implementation of hybrid brattice is beneficial for the mining operation: up to three times lower dust concentration is achieved as compared to that of the physical brattice without air curtain.

AbstractThis paper presents analysis and optimization of turbine bade cooling systems. Since the temperature of combustion gases is very high sometimes reaching 2400 K, the turbine blade cannot sustain the resulting thermal stress. Moreover, for higher efficiency for advanced gas turbines, increase of inlet temperature is needed. Common blade cooling methods are film cooling, convection cooling, impingement cooling and combined cooling. In this paper, a numerical solution of the thermal and flow fields in film cooling technique on the AGTB expand symmetrical turbine blade was obtained and the results were validated with experimental data. Then the turbine blade geometry was changed and two combined cooling (impingement/convection cooing and impingement/film cooling) techniques were evaluated. The low Reynolds number k-ε turbulence model (AKN) was used for the turbulent flow simulations at various blowing ratios for two blade thicknesses. Comparisons of the results between the available experimental and numerical data showed that the AKN model is capable of predicting the turbulent flow and heat transfer in turbine blade cooling. Combined techniques (impingement/convection cooling and impingement/film cooling) were also carried out and more cooling effectiveness and uniform temperature distribution were found than film cooling method only.

Carbon dots (CDs) were synthesized with the facile hydrothermal method to produce CDs/polyvinyl alcohol (PVA) active food packaging films. The CDs had a diameter ranging from 2.01 to 5.61 nm and were well-dispersed. The effects of different concentrations of CDs on mechanical strength, water resistance, morphology, optical, and thermal performance of the CDs/PVA films were discussed. The incorporation of CDs in the PVA film improved its mechanical properties, water resistance properties, UV blocking properties, and thermal stability and endowed the composite film with antioxidant and antimicrobial properties. The maximum scavenging rates of 2,2-diphenyl-1-picrylhydrazyl and ABTS free radicals by the 0.50% CDs/PVA film were 72.81 and 97.08%, respectively. The inhibition zone diameters of the 0.50% CDs/PVA solution against Staphylococcus aureus(S. aureus), Bacillus subtilis(B. subtilis), and Escherichia coli(E. coli) were 9.52, 8.21, and 9.05 mm, respectively. Using the 0.50% CDs/PVA film as active packaging, the shelf life of banana, jujube, and fried meatballs was observed to be extended significantly. These results demonstrate the viability of the CDs/PVA composite film as a promising active food packaging material.

A computational fluid dynamic (CFD) model was developed to study the fluid flow phenomena taking place in an industrial tundish. Numerical results showed spatial distributions of the velocity vectors, the residence time and fields of turbulence kinetic energy. Selected computer simulation results were validated with experimental data. The effect of the impact pad and interior dams on the hydrodynamics of liquid steel flow were studied numerically and optimized to reduce the fraction of dead volume zones and augment nonmetallic inclusions to float into the slag. A novel design of a turbo-stopper was proposed and its function to decelerate the ladle shroud jet and direct the flow back to reduce slag entrapment was discussed. Such numerical results improved our understanding of the hydrodynamics of liquid steel flow in the tundish and contribute to an optimized operation.

High-aspect-ratio arrayed structures find application in the creation of deep blind holes used in ink-jet nozzles, air-bearings, etc. This paper focuses on the use of reverse micro-electric discharge machining (micro-EDM), to generate high-aspect-ratio micro-rod arrays. A micro-rod of 60 μm in diameter and a high-aspect-ratio of 33 is successfully fabricated using the process. An L8 orthogonal array is used to study the effect of gap voltage, capacitance, threshold, and feed rate on the process response variables. The measured process responses are dimensional accuracy (measured at various locations along the length of the micro-rod), zero error length, and surface roughness. Furthermore, the surface morphology and chemical composition at the root and tip of the generated structure are studied. Analysis of variance studies show that the statistically significant factors that influence response variables are the gap voltage and capacitance. The gap voltage is identified as the single most important factor governing the accuracy of the micro-rods at almost all locations. Analysis of surface morphology reveals that there are more craters at the tip of machined rods whereas, the area around the base is relatively smooth. Value of surface roughness varies from 1.6 μm Ra to 6.3 μm Ra under different experimental conditions. A variation in chemical composition is observed along the length of the rod. Plausible explanations are presented for the various phenomena observed during the reverse micro-EDM process.

There has been an explosive growth in the Research and Development (R&D) effort devoted to drying R&D over the past three decades. This growth was stimulated by the energy crisis of the early 1970s and by the increased consumer demand for better quality products. Many of the innovative new technologies were triggered by their potential for application in industrial drying in diverse industrial sectors. A majority of drying R&D efforts today is devoted to the food and agricultural sectors. Preservation of food and agro-products and value addition are the key incentives for examining new dehydration technologies for their appropriateness in postharvest processing. Since most biologically originated products are heat sensitive, it is important to reduce their water activity to increase shelf life without degrading their quality attributes.

The present study aimed at investigating the drying rates and inversion temperatures of model porous particles undergoing low-pressure superheated steam and vacuum drying. Molecular sieve beads, which were used as the model material in this work, were dried as a single layer in a low-pressure superheated steam dryer. The effects of steam temperature and pressure on the drying rates of these particles were determined. The same dryer was also operated in a vacuum mode to determine the effects of the above-mentioned operating parameters as well as the variation of the inversion temperature of the processes with the operating pressure. The differences between the values of the inversion temperature calculated only from the rates of drying in the constant rate period and those calculated from the whole drying period are pointed out and discussed. Page's equations and a single-term exponential equation were found to satisfactorily describe the kinetics of low-pressure superheated steam- and vacuum-drying systems, respectively.

Heat transfer in a dilute gas−particle suspension flow in multiple-slot impinging jets has been numerically investigated using a new Eulerian−Lagrangian method that accounts for conduction heat transfer due to particle−wall collisions. The numerical results are compared with available experimental data. Good agreement between experiment and simulation is obtained only if the additional conduction heat transfer due to particle−wall collisions is considered in the model. The effects of particle diameter, particle material properties and loading ratios, jet Reynolds number, impingement wall temperature, and direction of the gravitation vector on heat transfer are discussed.

Impinging jets of various configurations are commonly used in numerous industrial applications such as drying of tissue, paper, textiles, and photographic films and cooling of high power density electronic components, because of their highly favorable heat and mass transfer characteristics. Despite an extensive body of research literature on the subject over the past two decades, impinging jet heat transfer remains an active area of research covering both the experimental and computational fluid dynamics aspects because of its inherently complex fluid and heat flow characteristics. This paper presents simulation results for a single semiconfined turbulent slot jet impinging normally on a flat plate. Effects of turbulence models, near wall functions, jet turbulence, jet Reynolds number, as well as the type of thermal boundary condition at the target surface are discussed in the light of experimental data. The computed results compare favorably with the experimental results for large nozzle-to-target spacing, but the predictions for small nozzle-to-target spacing call for further improvement in the simulation.

A pulsating fluidized bed is operated with two sequential durations designated as an on‐period with injecting fluidization gas and an off‐period without it. The heat transfer coefficient between a vertically immersed heater and bed in a pulsating fluidized bed is measured under various pulse cycles and fluidized particles. The obtained results are compared with those in a normal fluidized bed with continuous fluidization air injection. The relationship between heat transfer coefficients and bubble characteristics, evaluated using a digital video camera, has also been investigated. For certain fluidized particles and operating pulse cycles, the fluidization of particles and the increment of heat transfer coefficients can be obtained under a mean air velocity based on a pulse cycle duration smaller than the minimum fluidization air velocity in a normal fluidized bed. Under the pulse cycles where a static bed through the whole bed is formed in the off‐period duration, the improved heat transfer rate over that in a normal fluidized bed can be measured. This may be attributed to large bubble formation. As heat transfer in the pulsating fluidized bed is obstructed with increasing time to keep a static bed due to the excessive off‐period duration, it is indicated that there is an optimum off‐period duration based on the heat transfer rate. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 307–319, 2002; Published online in Wiley InterScience (). DOI 10.1002/htj.10038

Abstract:  Microchannels are currently being used in many areas and have high potential for applications in many other areas, which are considered realistic by experts. The application areas include medicine, biotechnology, avionics, consumer electronics, telecommunications, metrology, computer technology, office equipment and home appliances, safety technology, process engineering, robotics, automotive engineering and environmental protection. A number of these applications are introduced in this paper, followed by a critical review of the works on the flow and heat transfer for gas flowing in microchannels. The results show that the flow and heat transfer characteristics of a gas flowing in microchannels can not be adequately predicted by the theories and correlations developed for conventional sized channels. The results of theoretical and experimental works are discussed and summarized along with suggestions for future research directions.

This paper presents a study of turbulent mixing in two-dimensional confined impinging streams. A new composite turbulence model is proposed and verified by comparing its predictions with available experimental impingement heat-transfer data as well as the experimental temperature distributions in impinging streams obtained in this work. Better agreement between experimental and numerical impingement heat-transfer results predicted by this new model is noted compared to those predicted by two other low-Reynolds number k−ε turbulence models. The model was then used to perform a parametric study of the thermal mixing characteristics of two-dimensional turbulent confined impinging streams. It is found that both the operating and geometric parameters of the system have strong effects on mixing in impinging streams.

Post‐cyclone (PoC) is a novel secondary dust separator, which collects a certain fraction of the particles escaping through the vortex finder of a reverse flow cyclone. Due to the residual swirl in the vortex finder, the particles in the effluent air are concentrated at the wall of the vortex finder in an outer annulus. The particles in the outer annulus are split from the main stream and collected in a bleed flow. This paper presents the experimentally determined collection efficiencies of various designs of PoC. Depending on the design, operating conditions and the size and density of the particles, PoC can reduce the emission of the parent cyclones by 5% to 50%. In some experiments, the bleed flow from PoC is recycled back to the inlet of the cyclone. Significant improvement in the removal of fines occurs when the bleed flow is recycled to the inlet.