Dry Air Research Articles

Monitoring solids content development in pilot-scale through air drying of tissue paper

Abstract This study delves into the dynamic evolution of solids content in a pilot-scale through air drying tissue machine, aiming to enhance comprehension and refine optimization strategies for tissue manufacturing. It focuses on development of solids content throughout the process. Analyzing the interaction between process parameters and solids content provides deeper insights into water removal dynamics. The research employs solid contents monitoring techniques in pilot scale, offering a detailed view of solids content evolution from the wet web’s inception to the final tissue product. It significantly highlights the impact of key parameters, particularly pulp refining, on solids content across all positions of the pilot machine. Additionally, the study emphasizes the influence of vacuum system configurations, identifying the relationship between energy expended in the vacuum system and evaporation energy. Furthermore, the results indicate that compression and air displacement dewatering in vacuum boxes are less speed-sensitive compared to heat-driven evaporation in the TAD- and Yankee cylinders. Solid contents at all positions in the tissue machine correlates between various dewatering elements. Optimizing site-specific dewatering and evaporation strategies can potentially save drying energy in the Yankee drying phase which hold promise for enhanced energy and resource utilization, aligning with demands for sustainable manufacturing practices.

Oceanic maintenance of atmospheric blocking in wintertime in the North Atlantic

AbstractThe connection between atmospheric blocking over the North Atlantic and the diabatic influence of the Gulf Stream is investigated using potential vorticity and moist potential vorticity diagnostics in the ERA5 reanalysis data set during wintertime (1979 - 2020). In line with previous research, the reliance atmospheric blocking has on turbulent heat fluxes over the Gulf Stream and its extension, for induction and maintenance, is shown to be significant. The air-sea heat flux generates negative potential vorticity air masses in the atmospheric boundary layer. These air masses subsequently contribute to the block’s negative potential vorticity anomaly at upper levels through ascending motion in the warm conveyor belt. It is shown that the block’s size and frequency partially depends on oceanic preconditioning via anomalous oceanic heat transport and heat content, prior to the blocking event, both of which allow for stronger turbulent heat fluxes. It is further hypothesized that the block feeds back positively on itself through the advection of cold dry air over the Gulf Stream, sustaining this air-sea interaction. This in turn decreases ocean heat content, eventually halting this air-sea interaction and severing the atmospheric block from its maintenance pathway.

The prevalence and association of measured and perceived indoor air quality, housing characteristics, and residents’ behavior and health

BackgroundIn social housing buildings, poor indoor air quality (IAQ) has been shown to be more prevalent, and residents living in social housing areas are often more vulnerable and susceptible to adverse health effects from IAQ.AimTo examine the state and the association of measured and perceived IAQ, how housing characteristics and residents' behavior are associated with IAQ, and the association with residents' health.MethodThe HOME-Health study is a cross-sectional study among residents living in social housing in Denmark (n = 432). Seasonal measurements examined the IAQ by a 14-day period measuring carbon dioxide (CO2), temperature (TP), relative humidity (RH), and air change rate. Residents' self-reported behavior, comfort, and health were obtained from a structured interview.ResultsThermal discomfort and draught were the most common challenges. During summer, the mean TP was higher, the mean RH was lower, and residents more frequently reported dry air in homes where it was not possible to create cross ventilation. There were a higher mean CO2 and RH when crowdedness increased, particularly during winter. In addition, the proportion of residents reporting dry air was higher when CO2-level was below 1,000 ppm. When the mean RH-level was above 50%, a higher proportion of residents reported experiencing damp air, and when the mean RH-level was below 40% residents more frequently reported dry air. Perception of bad air quality was higher when the mean CO2-level exceeded 1,000 ppm. Additionally, residents reported being most thermally comfortable when the TP was within the range of 20–20.99°C and least comfortable within a range of 22–22.99°C. The residents' perceived experience of impaired IAQ was associated with negative general health symptoms.ConclusionIt is key that homes have the capability to create cross ventilation in order to allow for proper ventilation and to avoid overheating. When evaluating IAQ it is important to not only consider the measured parameters but to also include the residents' behavior and perception of IAQ as these both are related to the actual IAQ and associated health effects.

Analysis of drying characteristic, effective moisture diffusivity and energy, exergy and environment performance indicators during thin layer drying of tea in a convective-hot air dryer

The objective of this study is mainly to analyze the drying kinetic parameters, effective diffusivity, and thermodynamic performance indicators (energy, exergy, heat, and mass transfer coefficients) of tea under different drying conditions of different drying temperatures (DT) and thin layer thicknesses (TT). Experimental drying was conducted at drying temperatures of 70°C, 80°C, and 90°C with thin layer thicknesses of 10 mm, 15 mm, and 20 mm. The results show that a higher drying temperature and a lower thin layer thickness can increase evaporation moisture content and shorten drying time. By evaluating and comparing the fitting of five drying models adopted by the coefficient of determination (R2) and chi-square (χ2), it can be found that the logarithmic model is the best to describe drying behavior. The effective moisture diffusivity shows a positively correlated trend with the increase in DT and TT, with the value of activation energy ranging from 14.030 to 22.344 kJ mol−1 K−1. The specific moisture evaporation rate (SMER), energy efficiency, exergy efficiency, and sustainability index (SI) descend as the TT increases at all DT; the specific energy consumption (SEC) and improvement potential (IP) rate perform in an opposite manner, but the TT remains unchange. The conclusion drawn from the thermodynamic parameters is opposite to the aforementioned. As the TT increases, the heat and mass transfer coefficients show a significant decrease trend. In addition, the heat and mass transfer coefficients are given as functions of DT and TT, and further knowledge shows that the mass transfer coefficient is positively correlated with DT but the heat transfer coefficient is negatively correlated. In conclusion, this article provides new insights into the effects of drying characteristics, energy consumption characteristics and heat and mass transfer characteristics in the process of tea drying under different drying conditions, and provides certain theoretical reference bases for promoting the optimization of industrialized tea drying production machinery design and drying process optimization.

Dry-air pretreatments effects on physiochemical properties, stability, antioxidants, phytosterol and tocopherol profiles of hemp oil

The study investigated effects of dry air pretreatment (DAP) at varying temperatures (160˚C, 180˚C, and 200˚C) and times (5-, 10-, 15-, and 20-min) on hemp oil (HeO) quality attributes. The total flavonoid (TfC) and phenolic (TpC) content, tocopherols, phytosterols, flavonoids, phenolic acids, oxidative stability index (OSI), colour attributes, Maillard products, fatty acid profile (FAP), physiochemical properties and radical scavenging activity (RsA) of HeO were studied. DAP had increased Maillard products, browning index, p-anisidine value, viscosity and ΔE while decreased peroxide, a* , b* and L* values of HeO. The TpC, TfC, RsA, phenolic acids (protocatechuic, 4-hydroxybenzoic, ellagic, chlorogenic, rosmarinic and trans cinnamic acids), epicatechin, total hydroxycinnamic and hydroxybenzoic acids and total flavonoids were highest in HeO upon DAP at 200 oC for 15 min. The tocopherols and phytosterols were highest upon DAP at 180 oC for 5 and 10 min, respectively. The highest HeO yield (25.85%) and OSI (6.80 h) was attained upon DAP at 180 oC and 200 oC for 10 min, respectively. In conclusion, the DAP had triggered a Maillard reaction, augmented the release of antioxidants, pigments and increased the OSI of HeO. The optimal DAP can be employed for the improvement of HeO quality attributes.

Reanalysis of NOAA H2 observations: implications for the H2 budget

Abstract. Hydrogen (H2) is a promising low-carbon alternative to fossil fuels for many applications. However, significant gaps in our understanding of the atmospheric H2 budget limit our ability to predict the impacts of greater H2 usage. Here we use NOAA H2 dry air mole fraction observations from air samples collected from ground-based and ship platforms during 2010–2019 to evaluate the representation of H2 in the NOAA GFDL-AM4.1 atmospheric chemistry-climate model. We find that the base model configuration captures the observed interhemispheric gradient well but underestimates the surface concentration of H2 by about 10 ppb. Additionally, the model fails to reproduce the 1–2 ppb yr−1 mean increase in surface H2 observed at background stations. We show that the cause is most likely an underestimation of current anthropogenic emissions, including potential leakages from H2-producing facilities. We also show that changes in soil moisture, soil temperature, and snow cover have most likely caused an increase in the magnitude of the soil sink, the most important removal mechanism for atmospheric H2, especially in the Northern Hemisphere. However, there remains uncertainty due to fundamental gaps in our understanding of H2 soil removal, such as the minimum moisture required for H2 soil uptake, for which we performed extensive sensitivity analyses. Finally, we show that the observed meridional gradient of the H2 mixing ratio and its seasonality can provide important constraints to test and refine parameterizations of the H2 soil sink.

Impact of Dry Processing on Secondary Metabolites in the Petals of Marigold (Tagetes spp.) Cultivar

The edible flowers of marigold (Tagetes spp.) are cultivated for their aesthetic appeal and high utility as functional health food ingredients. Carotenoid and flavonoid contents in marigold petals highlight the importance of selecting the appropriate cultivar and its processing methods for their industrial applications. The comparative understanding of the effects of dry processing on functional components across different marigold cultivars is still lacking. Therefore, this study investigated functional compound changes in the dry processing effect on four marigold cultivars with distinct flower shapes (Durango, Inca) and colors (yellow, orange). The petals in hot air drying (HAD) with 30, 60, and 90 °C applications were analyzed for the measurement of their individual secondary metabolite contents, total phenolic and flavonoid contents, and antioxidant activities. In freeze drying (FD), the lutein content varied significantly based on flower color, exhibiting higher levels in cultivars with orange petals. Otherwise, the levels of quercetin derivatives displayed distinct differences based on varieties other than color, with Inca cultivars demonstrating higher levels of quercetin 7-O-glucoside (Q7G) than Durango cultivars. In HAD, the lutein levels show a tendency to increase above 60 °C regardless of the cultivar. The content of quercetin glycosides decreased, while the aglycone increased in HAD treatments, regardless of the temperatures. Correlation and PCA results highlighted the impact of phenol compounds on antioxidant activity. Overall, these findings underscore the significance of variety and color in determining the chemical composition and antioxidant properties of marigold flowers.

Experimental and data-driven chemical kinetic modeling study of alcohol-to-jet (ATJ) synthetic biofuel for sustainable aviation fuels

This work assesses the chemical ignition delay behavior of an isoparaffinic alcohol-to-jet (ATJ) fuel, one of the certified sustainable aviation fuels (SAFs). Chemical ignition delay measurements of ATJ were performed at a compressed pressure of PC = 2 MPa and three equivalence ratios (phi = 0.5, 1.0, & 1.3) in synthetic dry air, between 667 K and 1250 K. The unique chemical structures of isoalkanes result in high thermal decomposition rate, but low chemical oxidation reactivity. The new lumped mechanism (ARLMech-HC-ATJ) is developed using a genetic algorithm based on empirical ignition delays. The mechanism shows good performance over the temperature range from 667 K to 1250 K and varied equivalence ratios. Using the suggested mechanism, this study presents sensitivity analysis for the temperature range to understand chemical kinetics of ATJ fuel. The results show the impact of using ATJ modeling to design and optimize propulsion systems operating in the negative temperature coefficient (NTC) or low temperature chemistry (LTC) regime in the future and a methodology that can be adapted to other novel fuels.

Improving urban CO2 spatial distribution modelling using multi-source data

Urban areas contribute approximately 70% of the total anthropogenic CO2 emissions, making them the primary focus of global carbon monitoring. However, accurate modelling of urban meteorology is challenging because of complex artificial landscapes. Reducing errors in urban meteorological simulation and improving the accuracy of modelling the spatial distribution of urban CO2 is of great significance for the “top-down” CO2 emissions estimation in urban areas. In this study, local urban datasets were constructed based on multiple data sources to overcome the limitation of insufficient information from a single data source. In the development of urban datasets, grid-by-grid data processing is realized, and the evaluation results show that the developed urban datasets are greatly improved compared with the default. The developed urban datasets were applied to WRF-Chem with 1-km spatial resolution, and the simulated column-averaged dry air mole fraction of CO2 (XCO2) was verified with the EM27/SUN observed data considering the slant observation path. The results show that urban datasets strongly influence the spatial distribution modelling of XCO2, depending on the state of the atmosphere near the surface, especially wind velocity. Accurate local urban datasets can effectively reduce the bias in urban XCO2 spatial distribution modelling and improve the capability of the atmospheric CO2 transport model in urban carbon emission estimation.

Impact of different drying methods on physicochemical characteristics and nutritional compositions of bee larvae

This article presents a comprehensive analysis of three distinct drying methods, namely hot air drying (HAD), microwave oven drying (MD), and vacuum freeze drying (VFD), applied to bee larvae. Through rigorous experimentation and analysis, we evaluated various parameters, including moisture content, color, fat, protein, fatty acid composition, aroma components, and protein secondary structure. Our findings reveal distinctive characteristics of bee larvae aroma, notably including E-2-curenal, palmitic acid and 10-undecenal, with palmitic, linolenic, and oleic acids being the dominant fatty acids. Among the drying methods, MD at 10 W/g demonstrated significantly higher levels of volatile components. Noteworthy, VFD-assisted drying closely resembled the composition of fresh bee larvae, with fat and protein contents of 26% and 57%, respectively. Analysis of protein secondary structure unveiled that MD at 10 W/g exhibited the highest β-folding content, 80%, followed closely by VFD at 45 °C, 73%. Remarkably, VFD at 45 °C exhibited as the superior method, yielding dried bee larvae of unparalleled quality among the three techniques investigated. This study provides valuable insights into the impact of different drying methods on the composition and quality of bee larvae, offering significant implications for the processing, preservation and utilization of this valuable resource.

Infrared drying characteristics and optimization of ginseng

Fresh ginseng has a high moisture content and is easy to be deteriorated, thus an effective drying method is needed. Infrared drying is known as low energy consumption, and high heat transfer, thus the far infrared (FIR) and near infrared (NIR) drying characteristics of ginseng were investigated and compared. Influences of infrared temperature, radiation distance, and slice thickness on the drying kinetics, specific energy consumption, color change and rehydration ratio were analyzed. Results indicated that the drying rate of ginseng increased with increasing infrared temperature and decreasing radiation distance and slice thickness. The drying time under FIR was shortened by 33.3%, 25% and 20% at 40 °C, 50 °C, 60 °C compared to that under NIR, indicating that the drying efficiency of FIR was superior to that of NIR and with the decrease of temperature, this improvement became more obvious. The specific energy consumption can be reduced by up to 40% under FIR and the infrared drying was much more energy-efficient than hot air drying, with an energy reduction by up to 51.1%. Optimization of FIR drying showed that the optimal conditions were at a drying temperature of 50 °C, a slice thickness of 2 mm and a radiation distance of the 4th layer.

Dynamical study of three African Easterly Waves in September 2021

AbstractThree convectively active African easterly waves (AEWs) that propagated south of the African easterly jet were observed over the northeast Atlantic Ocean in September 2021. Their evolution is studied using a suite of theoretical frameworks, as well as the European Centre for Medium‐range Weather Forecast reanalyses and satellite‐derived brightness temperature observations. The environment of these AEWs was sampled during the Cloud–Atmospheric Dynamics–Dust Interactions in West Africa campaign near Cape Verde with the goal to assess their potential for developing into tropical cyclones. We highlight the processes that inhibited the development of the first AEW (which evolved into tropical disturbance Pierre‐Henri) and that played a role in the development of the later two into tropical storms Rose and Peter on September 19, 2021. The three AEWs developed a so‐called “marsupial protective” pouch. For Peter and Rose, the pouch was associated with a vertically aligned vortex at low levels and efficiently protected the convective systems inside from dry and dusty air intrusion. The development of this low‐level vortex is associated with an interaction with the monsoon trough for Rose and with a vorticity center associated with a wave propagating north of the African easterly jet (AEJ) in the case of Peter. The presence of a dust flux toward the convective core near the surface is highlighted for Rose and Peter in spite of the presence of the protective marsupial pouch. On the other hand, Pierre‐Henri interacted positively with both the monsoon trough and an AEW north of the AEJ but failed to develop into a tropical cyclone. The wave north of the AEJ brought Saharan air layer air masses inside the pouch that led to a drying of the circulation that may explain the decrease in convective activity.

Indoor air quality and sick building syndrome symptoms in administrative office at public university

Sick Building Syndrome (SBS) is an illness among workers linked to time spent in a building. This study aimed to investigate the Indoor Air Quality (IAQ) and symptoms of Sick Building Syndrome (SBS) among administrative office workers. The IAQ parameters consist of ventilation performance indicators, and physical and chemical parameters were measured using specified instruments for three days during weekdays. The SBS symptoms were assessed by a questionnaire adopted from the Industry Code of Practice of Indoor Air Quality (ICOP-IAQ) 2010 among 19 employees from the office in East Coast Malaysia. Relationship between past symptoms and present symptoms which are draught (past symptoms) with feeling heavy headed (present symptoms) (r = 0.559, p < 0.05), room temperature too high (past symptoms) was highly correlated with feeling heavy headed (present symptoms) (r = 0.598, p < 0.01) and cough (present symptoms) (r = 0.596, p < 0.01). Room temperature (past symptoms) has a positive medium relationship with cough (present symptoms) (r = 0.477, p < 0.05) and scaling itching scalp or ears (present symptoms) has a relationship between stuffy bad air (r = 0.475, p < 0.05) and dry air (r = 0.536, p < 0.05). There was a significant association between RH with drowsiness (χ2 = 7.090, p = 0.049) and dizziness (χ2 = 7.090, p = 0.049). The association was found between temperature and SBS symptoms between temperature with headache (χ2 = 7.574, p = 0.051), feeling heavy-headed (χ2 = 8.090, p = 0.046), and skin rash itchiness (χ2 = 7.451, p = 0.044). Air movement also showed a positive association with symptoms of feeling heavy-headed (x2 = 8.726, p = 0.021). PM10 has positive significance with SBSS which are feeling heavy-headed (χ2 = 7.980, p = 0.023), and eyer's irritation (χ2 = 7.419, p = 0.038). The conclusion of this study showed that there were positive significant between temperature and relative humidity toward SBSS.

High Performance Methyl Salicylate Gas Sensor based on Noble Metal (Au, Pt) Decorated WO3 Nanofibers

Methyl salicylate (MeSa) is known as a volatile plant pathogen biomarker and a chemical warfare agent simulant. Herein, high performance MeSa gas sensors were developed by optimizing morphology and composition of noble metal decorated tungsten trioxide (WO3) nanofibers. Using optimized nanofibers, 100 ppb of MeSa were readily sensed in dry air whereas the calculated low limit of detection (LLOD) is expected to be in a few tens of ppb. Pt-WO3 (1.1 at. % Pt) nanofibers also show an excellent selectivity over other volatile organic compounds including aromatic compounds (i.e., benzene, toluene, ethyl benzene, p-xylene). Systematic characterization of sensors in environments with different oxygen contents indicated that surface carrier concentration significantly altered as a function of Au and Pt content. Although 1.7 at. % Au-WO3 nanofibers based sensor has higher sensing response toward MeSa, 1.1at.% Pt-WO3 nanofibers were found to be a more promising sensing material for MeSa detection because of higher selectivity over other VOCs and lower calculated LLOD ( ~41 ppb).

Condensation shock topologies in carbon dioxide and a non-condensable gas mixture in supersonic nozzles

Condensation shock waves may occur in many flow expansion devices such as turbomachinery, gas ejectors, micro thrust-nozzles, and supersonic gas flow separators. However, their experimental analysis has been barely addressed as condensation shocks comprise complex phenomena such as compressible flow behavior, a shock-like phase transition, and a two-phase flow expansion. This work characterizes experimentally some condensation shock topologies of a mixture of carbon dioxide and dry air at several compositions in a Laval nozzle. Experiments were carried out in a test-rig instrumented with high-response pressure transducers installed along the Laval nozzle wall along with a Schlieren setup equipped with a high-speed video camera imaging the flow behavior within the nozzle. The nozzle wall profile was built by using the method of characteristics developed from a real equation-of-state suited for the testing mixture. Results revealed the influence of the nozzle wall profile on the condensation shock location and topology. Moreover, there types of flow behavior were captured and named as conventional, transition, and Mach wave condensation shocks. The transition from one topology to another occurred due to the interaction between cancelation waves originated from the nozzle wall and the phase-change phenomenon, giving rise to two distinct regions characterized by certain observable droplet population density. The current investigation presents an in-depth phenomenological discussion of the three types of condensation shock topologies as such assessment has not been previously developed.

A Review of the Interactions between Tropical Cyclones and Environmental Vertical Wind Shear

Abstract Tropical cyclone (TC) structure and intensity are strongly modulated by interactions with deep-layer vertical wind shear (VWS)—the vector difference between horizontal winds at 200 and 850 hPa. This paper presents a comprehensive review of more than a century of research on TC–VWS interactions. The literature broadly agrees that a TC vortex becomes vertically tilted, precipitation organizes into a wavenumber-1 asymmetric pattern, and thermal and kinematic asymmetries emerge when a TC encounters an environmental sheared flow. However, these responses depend on other factors, including the magnitude and direction of horizontal winds at other vertical levels between 200 and 850 hPa, the amount and location of dry environmental air, and the underlying sea surface temperature. While early studies investigated how VWS weakens TCs, an emerging line of research has focused on understanding how TCs intensify under moderate and strong VWS (i.e., shear magnitudes greater than 5 m s−1). Modeling and observational studies have identified four pathways to intensification: vortex tilt reduction, vortex reformation, axisymmetrization of precipitation, and outflow blocking. These pathways may not be uniquely different because convection and vortex asymmetries are strongly coupled to each other. In addition to discussing these topics, this review presents open questions and recommendations for future research on TC–VWS interactions.

A Comparison between the Only Two Documented Tornado Outbreak Events in China: Tropical Cyclone versus Extratropical Cyclone Environments

Abstract This study documents the features of tornadoes, their parent storms, and the environments of the only two documented tornado outbreak events in China. The two events were associated with Tropical Cyclone (TC) Yagi on 12 August 2018 with 11 tornadoes and with an extratropical cyclone (EC) on 11 July 2021 (EC 711) with 13 tornadoes. Most tornadoes in TC Yagi were spawned from discrete minisupercells, while a majority of tornadoes in EC 711 were produced from supercells imbedded in QLCSs or cloud clusters. In both events, the high-tornado-density area was better collocated with the K index rather than MLCAPE, and with entraining rather than non-entraining parameters possibly due to their sensitivity to midlevel moisture. EC 711 had a larger displacement between maximum entraining CAPE and vertical wind shear than TC Yagi, with the maximum entraining CAPE better collocated with the high-tornado-density area than vertical wind shear. Relative to TC Yagi, EC 711 had stronger entraining CAPE, 0–1-km storm relative helicity, 0–6-km vertical wind shear, and composite parameters such as an entraining significant tornado parameter, which caused its generally stronger tornado vortex signatures (TVSs) and mesocyclones with a larger diameter and longer life span. No significant differences were found in the composite parameter of these two events from U.S. statistics. Although obvious dry air intrusions were observed in both events, no apparent impact was observed on the potential of tornado outbreak in EC 711. In TC Yagi, however, the dry air intrusion may have helped tornado outbreak due to cloudiness erosion and thus the increase in surface temperature and low-level lapse rate.

Pt/GaN Schottky Barrier Height Lowering by Incorporated Hydrogen

Changes in the hydrogen-induced Schottky barrier height (Φ B) of Pt/GaN rectifiers fabricated on free-standing GaN substrates were investigated using current–voltage, capacitance–voltage, impedance spectroscopy, and current–time measurements. Ambient hydrogen lowered the Φ B and reduced the resistance of the semiconductor space–charge region while only weakly affecting the ideality factor, carrier concentration, and capacitance of the semiconductor space–charge region. The changes in the Φ B were reversible; specifically, the decrease in Φ B upon hydrogen exposure occurred quickly, but the recovery was slow. The results also showed that exposure to dry air and/or the application of a reverse bias to the Schottky electrodes accelerated the reversion compared with the case without the applied bias. The former case resulted in fast reversion because of the catalytic effect of Pt. The latter case, by contrast, suggested that hydrogen was incorporated into the Pt/GaN interface oxides as positive mobile charges. Moreover, both exposure to dry air and the application of a reverse bias increased the Φ B of an as-loaded sample from 0.91 to 1.07 eV, revealing that the Φ B of Pt/GaN rectifiers was kept lower as a result of hydrogen incorporation that likely occurred during device processing and/or storage.

Effect of Different Drying Methods on the Quality of Oudemansiella raphanipes.

In this study, we used fresh Oudemansiella raphanipes as raw materials and pre-treated through hot air drying (HD), infrared radiation drying (ID), and vacuum freeze drying (VD) to investigate the effects of different drying methods on the rehydration rate, appearance quality, microstructure, and volatile flavor components of the dried products, as well as to determine the physicochemical properties and bioactivities of the polysaccharides in the dried O. raphanipes. The results showed that the VD O. raphanipes had the highest rehydration rate and the least shrinkage in appearance, and it better maintained the original color of the gills, but their aroma was not as strong as that of the HD samples. The scanning electron microscopy results indicate that VD maintains a good porous structure in the tissue, while HD and ID exhibit varying degrees of shrinkage and collapse. Seventy-five common volatile substances were detected in the three dried samples, mainly alkanes, alcohols, and esters. The polysaccharides (PS-H, PS-I, and PS-V) extracted from the dried samples of these three species of O. raphanipes had similar infrared spectral features, indicating that their structures are basically consistent. The highest yield was obtained for PS-V, and the polysaccharide content and glucuronic acid content of PS-I were higher than those of the remaining two polysaccharides. In addition, PS-V also showed better antioxidant activity and inhibitory activity against α-glucosidase as well as α-amylase. In conclusion, among the above three drying methods, the quality of O. raphanipes obtained by vacuum freeze drying is the best, and this experiment provides a theoretical basis for the selection of drying methods for O. raphanipes.

Effect of osmotic dehydration combined with vacuum freeze-drying treatment on characteristic aroma components of peach slices

Hot air drying (HD), vacuum freeze drying (FD), and pilot-scale freeze drying (PSFD) are extensively used to prepare peach slices. However, the aroma of hot air drying and vacuum freeze-drying is yet to be addressed. In this study, HS-SPME-GC–MS was used to characterize and quantify the volatile compounds in peach slices. First, 33, 36, and 46 volatile compounds were identified and quantified in the HD, FD, and PSFD groups, respectively. PSFD is preferable to HD and FD in terms of the volatile compound types, content, and aroma profiles. PSFD was selected for subsequent permeation and dehydration experiments. The key aroma compounds with an OAV ≥ 1 were found in the PSFD30 group. GC-O analysis was conducted on the PSFD30 group, leading to the preliminary identification of 2-methylbutanal, pentanal, hexanal, 2-hexenal, phenylacetaldehyde, ethyl acetate, 2-methylbutyl acetate, ethyl lactate, linalool, methyl heptenone, and γ-octalactone as distinctive aromas in dried peach slices.