Near-freezing Temperature Research Articles

Sensitivity of snow magnitude and duration to hydrology model parameters

Process-based hydrology models are critical for understanding streamflow and water supply under global change. However, these models require parameterization which introduces additional uncertainty into the models. The role that these parameters play in driving uncertainty is under-studied, especially for intermediary processes outside of streamflow. An important example in snowmelt dominant regions are intermediary processes related to snowpack accumulation and ablation. We examine the sensitivity of snow magnitude and duration to eleven parameters relevant to snow processes in the coupled crop-hydrology model VIC-CropSyst using a hybrid global–local Distributed Evaluation of Local Sensitivity Analysis approach. With the Pacific Northwest US as a case study, our specific research questions are: (a) What is the sensitivity response of peak snow water equivalent (SWE) and snow duration and how does it vary in the parameter space? (b) What are the key drivers of the sensitivity response? and (c) Which of the most sensitive parameters can we immediately improve by leveraging existing data products? Both target variables were sensitive to less than four of the eleven parameters. We found that peak SWE was most sensitive to either the precipitation partitioning temperature threshold or the albedo of new snow, depending on the geography and associated interplay between hydro-meteorological factors. In contrast, snow duration was primarily sensitive to the albedo of new snow and the albedo decay coefficient during snowmelt. Machine learning explainability workflows applied on the sensitivity response explained the model behavior and determined key geographic and hydro-meteorological drivers of the sensitivity response. Regions where the significant precipitation co-occurred with near-freezing temperature exhibited higher sensitivity of peak SWE to precipitation partitioning. In contrast, much colder high-elevation regions that have a delayed snowmelt-driven runoff when downward shortwave radiation is higher, displayed more sensitivity to albedo parameters. We also noted differences in the list of key parameters and in the level of sensitivity between our work and the limited comparable existing work. This highlights the need for comprehensive sensitivity analysis of snow metrics to become a routine component of hydrology model application studies in addition to streamflow. This is critical for us to better understand model behavior, identify key model parameters that can benefit from more dynamic representation in the models, and strategically improve models to best support decision-makers.

Storage temperature affects metabolism of sweet corn

Temperature is one of the critical factors affecting the postharvest storage quality of sweet corn, but effects of storage temperatures have not been elucidated at the molecular level. In this study, the effects of storage at 0 °C, 4 °C and 20 °C, on quality and associated effects on the transcriptome and metabolome were investigated. Compared with storage at 20 °C, cobs stored at 0 °C and 4 °C had up-regulated expression of genes associated with cell wall disassembly (PG, PE, BMY, β-Gal) and down-regulated expression of genes involved in lignin synthesis, the up-regulation of SPP, SPS and SUS involved in sucrose synthesis, and the down-regulation of IN, FK, HXK and PFK involved in sucrose catabolism. Most of the genes involved in ethylene biosynthesis and signaling were inhibited at 0 °C, except for ERFs, while abscisic acid synthesis and signal transduction were most active at this temperature. Near-freezing temperature also maintains the integrity of the cell membrane by inhibiting the expression of PLD, PLC and LOX, which encode membrane lipid-degrading enzymes. Metabolomics and combined analysis showed that the contents of lysophospholipid, glutathione and L-ascorbic acid in sweet corn increased at low temperatures. These results provide insight into the effects of low temperatures on sweet corn quality.

Characterization of ultrasonic-assisted antifungal film loaded with fermented walnut meal on Rosa roxburghii Tratt during near-freezing temperature storage.

Fermented walnut meal (FW) has antifungal activity against Penicillium victoriae, a fungus responsible for Rosa roxbughii Tratt spoilage. This study characterized and applied ultrasonic-assisted antifungal film loaded with FW to preserve R. roxbughii Tratt during near-freezing temperature (NFT). Results showed that O2 and CO2 transmission rates decreased by 80.02% and 29.05%, respectively, and antimicrobial properties were improved with ultrasound at 560W for 5min and 1% FW. Fourier transform infrared spectroscopy and X-ray diffraction results revealed ultrasound improved hydrogen bonds and inductive effect via ─NH, ─OH, and C═O bonds. The addition of FW led to the formation of CMCS-GL-FW polymer via C═O bond. Thermogravimetric analysis and transmission electron microscope results demonstrated thermal degradation process was decomposed by ultrasound, and the internal structure of P. victoriae was accelerated by the addition of FW. Compared to the U-CMCS/GL group, the vitamin C content, peroxidase, and catalase activities of U-CMCS/GL/FW were enhanced by 4.24%, 8.52%, and 14.3% during NFT (-0.8 to -0.4°C), respectively. Particularly, the fungal count of the U-CMCS/GL/FW group did not exceed 105 CFU g-1 at the end of storage, and the relative abundance of P. victoriae decreased to 0.007%. Our findings provide an effective route for agricultural waste as natural antifungal compounds in the active packaging industry. PRACTICAL APPLICATION: In this study, the barrier and antimicrobial properties of film were successfully improved by ultrasonic treatment and loaded fermented walnut meal. The ultrasonic-assisted antifungal film loaded with fermented walnut meal effectively delayed the degradation of nutrients and reduced microbial invasion of Rosa roxburghii Tratt. These results provide a theoretical basis for the application of agricultural waste in the food packaging industry.

Effect of alternating magnetic field on ice crystal nucleation and its application for near-freezing temperature storage of grapes

The low temperature is an effective method for postharvest fruits preservation. However, the ice crystal nucleation caused by low temperature significantly decreases the quality of fruits. In this paper, the effects of alternating magnetic field (AMF) on the ice nucleation temperature of grape were investigated, and the AMF continued treatment and AMF intermittent treatment (20 Gs, 60 Hz) assisted near-freezing temperature (AMCT/AMIT-NFT) were used to store grapes at (−2.5 ± 0.2)°C. Compared with the untreated group, AMF decreased the ice nucleation temperature of grape by 1°C. Meanwhile, Results demonstrated that AMCT/AMIT-NFT storage improved sensory properties and antioxidant capacity of grapes, with the overall effect of AMIT treatment being the most favorable. After 9 days of storage, the color difference and polyphenol oxidase (PPO) activity of AMIT treatment were reduced by 17% and 12%, respectively, compared with the untreated group, and it effectively slowed down malonaldehyde (MDA) accumulation. These conclusions show that AMCT/AMIT-NFT storage is an effective tool for prolonging the shelf life of grapes.

Effect of Near-Freezing Temperature Storage on the Quality and Organic Acid Metabolism of Apple Fruit

Organic acids play critical roles in fruit physiological metabolism and sensory quality. However, the conventional storage of apple fruit at 0 ± 0.1 °C cannot maintain fruit acidity efficiently. This study investigated near-freezing temperature (NFT) storage for ‘Golden Delicious’ apples, and the quality parameters, organic acid content, and malate metabolism were studied. The results indicate that NFT storage at −1.7 ± 0.1 °C effectively maintained the postharvest quality of apple fruit when compared to traditional storage at 0 ± 0.1 °C. Fruit that underwent NFT storage showed a better appearance and lower respiratory rate, ethylene production, weight loss, and malondialdehyde (MDA) content but higher firmness and soluble solids content. Further, fruit after NFT storage contained higher titratable acid (18.75%), malate (51.61%), citrate (36.59%), and succinate (2.12%) content when compared to the control after 250 days. This was achieved by maintaining higher cytosolic NAD-dependent malate dehydrogenase (cyNAD-MDH), phosphoenolpyruvate carboxylase (PEPC), vacuolar H+-ATPase (V-ATPase), and vacuolar inorganic pyrophosphatase (V-PPase) activities that promote malate biosynthesis and accumulation while inhibiting enzyme activity that is responsible for malate decomposition, including phosphoenolpyruvate carboxylase kinase (PEPCK) as well as the cytosolic NAD phosphate-dependent malic enzyme (cyNADP-ME). Further, storage at NFTs maintained a higher expression of malate biosynthesis-related genes (MdcyNAD-MDH and MdPEPC) and transport-related genes (MdVHA and MdVHP) while suppressing malate consumption-related genes (MdcyME and MdPEPCK). The results demonstrate that NFT storage could be an effective application for apple fruit, which maintains postharvest quality and alleviates organic acid degradation.

Near-freezing temperature suppresses avocado (Persea americana Mill.) fruit softening and chilling injury by maintaining cell wall and reactive oxygen species metabolism during storage

To enhance the postharvest quality of avocado (Persea americana Mill.) fruit, this study investigates alterations in cell wall metabolism and reactive oxygen species (ROS) metabolism during near-freezing temperature (NFT) storage, and explores their impact on fruit softening. The fruit was stored at 25 °C, 5 °C, 2 °C, and NFT, respectively. NFT storage retarded firmness loss and chilling injury in comparison with 25 °C, 5 °C, and 2 °C. NFT storage delayed the decrease of ionic-soluble pectin (ISP) and cellulose (CLL) contents by suppressing cell wall degradation enzyme activities. Correlation analysis showed that cell wall degradation enzyme activities were positively correlated to rates of ethylene release and respiration. Moreover, NFT storage maintained higher levels of DPPH and ABTS scavenging abilities, activities of superoxide dismutase, peroxidase, and catalase, as well as ascorbate-glutathione cycle (ascorbic acid, glutathione, glutathione disulfide, ascorbate peroxidase, cycle-related enzymes), thereby inhibited the increase of ROS content, malondialdehyde content, and cell membrane permeability. Fruit firmness and chilling injury were correlated with the contents of hydrogen (H2O2), superoxide anion (O2.-), ISP, and CLL. These results suggested that NFT could suppress fruit softening and chilling injury by inhibiting cell wall degradation through delaying respiration and ethylene production and suppressing ROS production via activation of antioxidant systems, thereby maintaining quality and prolonged storage life during avocado fruit storage.

Near-Freezing Temperature Storage Improves Peach Fruit Chilling Tolerance by Regulating the Antioxidant and Proline Metabolism

Chilling injury (CI) in peach fruit (Prunus persica cv. Yuhualu) is generally caused by long-time low temperature (5 °C or 0 °C) storage. However, peach fruit stored at near-freezing temperature (NFT in this research is −1 °C), defined as within 0.5 °C above the biological freezing point of biological tissue, does not exhibit CI symptoms. The effect of NFT on the CI, proline metabolism, and antioxidant capability of peach fruit during storage was studied and compared with 5 °C and 0 °C storage as controls. The results exhibit that NFT completely inhibited the occurrence of CI in peach fruit. NFT significantly (p < 0.05) enhanced the activities of superoxide dismutase, catalase, ascorbate peroxidase, and 1,1-diphenyl-2-picrylhydrazyl scavenging capacity. Moreover, the increase of malondialdehyde, ion leakage, and H2O2 accumulation were inhibited remarkably by NFT, and decreases in the contents of phenolics and ascorbic acid were slowed significantly in peach fruit stored at NFT (p < 0.05). Additionally, NFT storage enhanced proline accumulation by modulating the activity of proline metabolizing enzymes. In conclusion, the above results suggest that NFT storage can improve the chilling tolerance of peach fruit by regulating the antioxidant defense and proline metabolism, which might represent a potential novel method to store fruits and vegetables for longer storage times.

Paleocene–Eocene age glendonites from the Mid-Norwegian Margin – indicators of cold snaps in the hothouse?

Abstract. The International Ocean Discovery Program (IODP) Expedition 396 to the mid-Norwegian margin recovered > 1300 m of pristinely preserved, volcanic-ash-rich sediments deposited during the late Paleocene and early Eocene from close to the centre of the North Atlantic Igneous Province (NAIP). Remarkably, many of these cores contain glendonites, pseudomorphs after the purported cold-water mineral ikaite, from sediments dated to the late Paleocene and early Eocene. These time intervals span some of the hottest climates of the Cenozoic, including the Paleocene–Eocene Thermal Maximum (PETM). Global deep-ocean temperatures are not thought to have dropped below 10 ∘C at any point during this time, making the occurrence of supposedly cold-water (near-freezing temperature) glendonite pseudomorphs seemingly paradoxical. This study presents a detailed sedimentological, geochemical, and microscopic study of the IODP Exp. 396 glendonites and presents an updated model for the ikaite-to-calcite transformation for these glendonites. Specifically, we show that early diagenesis of basaltic ashes of the NAIP appear to have chemically promoted ikaite growth in the sediments in this region. Together with existing knowledge of late Paleocene and early Eocene glendonites from Svalbard to the north and early Eocene glendonites from Denmark to the south, these new glendonite finds possibly imply episodic, short-duration, and likely localized cooling in the Nordic Seas region, which may have been directly or indirectly linked to the emplacement of the NAIP.

Changes in microbial population and physicochemical properties of fresh-cut cucumbers subjected to near-freezing temperature at −2 °C

Changes in microbial population and physicochemical properties of fresh-cut cucumbers subjected to near-freezing temperature at −2 °C

Effects of Near-Freezing Temperature Combined with Jujube Polysaccharides Treatment on Proteomic Analysis of 'Diaogan' Apricot (Prunus armeniaca L.).

This study involved the extraction of polysaccharides from jujube for application in apricot storage. Although near-freezing temperature (NFT) storage is commonly employed for preserving fresh fruit, its effectiveness is somewhat limited. Incorporating jujube polysaccharides was proposed to augment the preservative effect on apricots. Our findings demonstrated that the combined use of NFT and jujube polysaccharides can maintain fruit color, and effectively inhibit decay. Additionally, Tandem Mass Tag (TMT) quantitative proteomic technology was utilized to analyze protein variations in 'Diaogan' apricots during storage. This dual approach not only markedly lowered the activity of polyphenol cell wall-degrading enzymes (p < 0.05) but also revealed 1054 differentially expressed proteins (DEPs), which are related to sugar and energy metabolism, stress response and defense, lipid metabolism, and cell wall degradation. The changes in DEPs indicated that the combined use of NFT and jujube polysaccharides could accelerate the conversion of malic acid to oxaloacetic acid and regulate antioxidant ability, potentially extending the storage lifespan of apricot fruit.

Exploration of Postharvest Conditions for Codonopsis pilosula Nannf. var. modesta (Nannf.) L. T. Shen Roots Based on Sensory Quality, Active Components, Antioxidant Capacity and Physiological Changes at Different Storage Temperatures.

The promotion of industrial-mode production of Codonopsis pilosula Nannf. var. modesta (Nannf.) L. T. Shen (C. pilosula) has expanded the demand for the postharvest storage of fresh roots. Further research is needed to establish comprehensive methods to evaluate the impact of storage conditions. This study simulated the storage process of roots at near-freezing temperature [NFT (-1 °C)] and traditional low temperatures (-6 °C, 4 °C and 9 °C) for 40 days. At different storage stages, correlation analysis was conducted using quantitative data on 20 parameters, including sensory quality, active components, antioxidant capacity and physiological changes. Appearance and principal component analysis could distinguish between fresh and stored samples, while NFT samples on the 40th day of storage were similar to fresh ones. Correlation analysis indicated that NFT storage could maintain the sensory quality by increasing the antioxidant enzyme activity and active components, reducing the accumulation of reactive oxygen species and malondialdehyde and reducing the activity of browning-related enzymes and cell-wall-degrading enzymes. These findings highlight the importance of the overall quality evaluation of fresh roots and emphasize the potential to improve fresh root and dried medicinal material quality by regulating storage conditions such as temperature.

Transcriptome analysis reveals the mechanism of delayed softening of ‘France’ prune (Prunus domestica L.) during storage at near-freezing temperature

Rapid loss of firmness of ‘France’ prune after harvest limits the commercial potential of the fruit. Therefore, the present study aimed to explore the potential mechanism by which near-freezing temperature (NFT) maintains fruit quality and delays the softening of ‘France’ prune. We found NFT maintained higher fruit firmness (91.34 %), delayed the decomposition of cellulose (53.87 %) and hemicellulose (41.41 %), and inhibited the activity of softening-related enzymes compared with the control group. RNA-sequencing data showed that 4984 differentially expressed genes (DEGs) were detected in the control group (CK30)-vs-NFT group (B30) comparison. These DEGs are mainly involved in plant hormone signal transduction, secondary metabolite biosynthesis, galactose metabolism, and the pentose-glucuronate interconversion pathway. By screening and identifying DEGs, we found that the PG, PME, CEL, ACS, PER, UGT, and transcription factor (TF) genes (NAC089, ERF026, and NAC083) may be involved in the softening of ‘France’ prune. In conclusion, NFT delays the softening of ‘France’ prune likely by regulating the expression of related genes and metabolic pathways. These findings provide a theoretical basis for understanding the mechanism of NFT-mediated delay of ‘France’ prune fruit softening.

Hybrid Assimilation of Snow Cover Improves Land Surface Simulations over Northern China

Abstract Ensemble data assimilation (DA) is an efficient approach to reduce snow simulation errors by combining observation and land surface modeling. However, there is a small spread between ensemble members of simulated snowpack, which typically occurs for a long time with 100% snow cover fraction (SCF) or snow-free conditions. Here, we apply a hybrid DA method, in which direct insertion (DI) is a supplement of the ensemble square root filter (EnSRF), to assimilate the spaceborne SCF into a land surface model, driven by China Meteorological Administration Land Data Assimilation System high-resolution climate forcings over northern China during the snow season in 2021/22. Compared to the open-loop experiment (without SCF assimilation), the root-mean-square error (RMSE) of SCF is reduced by 6% through the original EnSRF and is even lower (by 14%) in the combined DI and EnSRF (EnSRFDI) experiment. The results reveal the ability of both EnSRF and EnSRFDI to improve the SCF estimation over regions where the snow cover is low, while only EnSRFDI is able to efficiently reduce the RMSE over areas with high SCF. Moreover, the SCF assimilation is also observed to improve the snow depth and soil temperature simulations, with the Kling–Gupta efficiency (KGE) increasing at 60% and 56%–70% stations, respectively, particularly under conditions with near-freezing temperature, in which reliable simulations are typically challenging. Our results demonstrate that the EnSRFDI hybrid method can be applied for the assimilation of spaceborne observational snow cover to improve land surface simulations and snow-related operational products. Significance Statement Due to the small spread between the seasonal snowpack of ensemble simulations, ensemble snow cover fraction (SCF) data assimilation (DA) proves to be ineffective. Therefore, we apply a hybrid method that combines the direct insertion (DI) and ensemble square root filter (EnSRF) to assimilate the spaceborne SCF into a land surface model (LSM) driven by high-resolution climate forcings. Our results reveal the applicability of the EnSRFDI to further improve snow cover simulations over regions with high SCF. Furthermore, the DA experiments were validated through a large number of in situ observations from the China Meteorological Administration. The uncertainties of snow depth and soil temperature simulations are also slightly reduced by the SCF DAs, particularly over regions with a poor LSM performance.

Microbial membrane lipid adaptations to high hydrostatic pressure in the marine environment.

The deep-sea is characterized by extreme conditions, such as high hydrostatic pressure (HHP) and near-freezing temperature. Piezophiles, microorganisms adapted to high pressure, have developed key strategies to maintain the integrity of their lipid membrane at these conditions. The abundance of specific membrane lipids, such as those containing unsaturated and branched-chain fatty acids, rises with increasing HHP. Nevertheless, this strategy is not universal among piezophiles, highlighting the need to further understand the effects of HHP on microbial lipid membranes. Challenges in the study of lipid membrane adaptations by piezophiles also involve methodological developments, cross-adaptation studies, and insight into slow-growing piezophiles. Moreover, the effects of HHP on piezophiles are often difficult to disentangle from effects caused by low temperature that are often characteristic of the deep sea. Here, we review the knowledge of membrane lipid adaptation strategies of piezophiles, and put it into the perspective of marine systems, highlighting the future challenges of research studying the effects of HHP on the microbial lipid composition.

Delaying fruit softening of ‘France’ prune (Prunus domestica L.) using near-freezing temperature storage

To delay ‘France’ prune fruit softening during storage, the effects of near-freezing temperature storage (NFTS; −1.5 ∼ −1 °C) on cell wall polysaccharides, cell-wall-modifying enzyme activities, cell-wall-modifying genes, and tissue ultrastructure of ‘France’ prune fruit were determined. The results showed that NFTS kept a higher fruit firmness (70.9%) compared to the control group (22.6%) at the end of storage. Besides, after 12-day storage, NFTS suppressed the activities of cell-wall-modifying enzymes, the expression of key cell-wall-modifying genes, the dissolution of chelate-soluble pectin (53.1%), Na2CO3-soluble pectin (114.6%), cellulose (81.3%), and hemicellulose (95.2%), and ethylene production (19.7%), and maintained lower water-soluble pectin (38.2%) and lignin contents (16.0%), compared to the control group. Ultrastructural observation showed that NFTS could delay the disassembly of pectin components and protect cell wall structure. In conclusion, NFTS can effectively inhibit fruit softening and maintain fruit quality.

Unique thermal expansion properties of water key to the formation of sea ice on Earth.

The formation of sea ice in polar regions is possible because a salinity gradient or halocline keeps the water column stable despite intense cooling. Here, we demonstrate that a unique water property is central to the maintenance of the polar halocline, namely, that the thermal expansion coefficient (TEC) of seawater increases by one order of magnitude between polar and tropical regions. Using a fully coupled climate model, it is shown that, even with excess precipitations, sea ice would not form at all if the near-freezing temperature TEC was not well below its ocean average value. The leading order dependence of the TEC on temperature is essential to the coexistence of the mid/low-latitude thermally stratified and the high-latitude sea ice-covered oceans that characterize our planet. A key implication is that nonlinearities of water properties have a first-order impact on the global climate of Earth and possibly exoplanets.

Near-freezing temperature (NFT) storage alleviates chilling injury by enhancing antioxidant metabolism of postharvest guava (Psidium guajava L.)

The effects of near-freezing temperature (NFT) storage on chilling injury and antioxidant metabolism of postharvest guava were investigated in comparison with 6 °C and 10 °C storage. NFT storage showed significant inhibition effects on guava chilling injury occurrence, increment in cell membrane permeability and malondialdehyde accumulation, and contributed to compact and well-organized cell structure at the end of storage. Besides, remarkable enhancements in radical scavenging activities (DPPH, ABTS), ascorbic acid (ASA) and glutathione (GSH) contents, and activities of catalase (CAT), superoxide dismutases (SOD), peroxidase (POD) and the ASA-GSH cycle-related enzymes were observed in NFT group, leading to the elimination of excessive hydrogen peroxide (H2O2) and superoxide anion (O2−.). Further investigation of expression levels of genes related to the ASA-GSH cycle confirmed that NFT induced the transcriptions of PguAPX2, PguMDHAR1, PguMDHAR3, PguGR1 and PguGR2, and activated antioxidant related enzymes, alleviating cell membrane damage and cell disintegration during storage, thus inhibiting chilling injury of guava.

Effects of Harvest Maturity on the Fruit Quality of Different Flesh-Type Peach Stored at Near-Freezing Point Temperature.

To investigate the peach fruit flesh types (soft-melting, hard-melting, stonyhard and non-melting) and harvest maturity level suitable for near-freezing temperature storage (NFTS), eight peach cultivars that had four flesh types were used as test materials. Changes in fruit respiration intensity and ethylene release rates, as well as the differences in quality indexes, such as soluble solids content (SSC), firmness, color difference, pigment content, soluble sugar and organic acid component content, of three fruit maturity levels (70%, 80% and 90% maturity) under NFTS conditions were analyzed and compared. The fruit quality indexes of peach having different maturity levels and flesh types changed little during NFTS. The SSC and total sugar content of hard-melting and stonyhard peach fruit were higher than those of other flesh types during NFTS. Those fruit maintained greater firmness at the end of the storage period. The differences in respiration intensity and ethylene release rate were small, but for fruit coloring, hard-melting fruit performed better than stonyhard fruit. The 80%, compared with the 90%, maturity stage maintained more fruit moisture, had less fruit mass loss and maintained a greater edible firmness. It effectively impeded the fruit senescence process and was the most suitable maturity for NFTS. Thus, the hard-melting peach maintained the highest commercial value and desirable storage characteristics under NFTS conditions, and its 80% maturity level was the most suitable for NFTS.

Near-freezing temperature storage improves shelf-life and suppresses chilling injury in postharvest apricot fruit (Prunus armeniaca L.) by regulating cell wall metabolism

To avoid chilling injury (CI) of apricots during storage, 1–2 °C and 4–6 °C storage as controls, the relationship between changes in cell wall characteristics and the occurrences of chilling injury under near-freezing temperature (NFT) storage was studied. NFT-stored improved apricots quality and inhibited CI index, membrane permeability and malondialdehyde (MDA) content; This also significantly inhibited the activity of cell wall modifying enzymes, delaying the solubilization of water-soluble pectin (WSP) and the degradation of cellulose. Transmission electron microscopy (TEM) imaging revealed that the density of the middle lamella in stored for 49 d was higher NFT than controlled temperature, delaying cell wall and chloroplast disintegration. Additionally, NFT-stored has no CI during the shelf life, and can be normal after ripening, maintaining higher commodity rate and sensory characteristics. These conclusions show that NFT storage can effectively improve the cold resistance of apricot fruit.

Changes in quality, ultrastructure, reactive oxygen species and cell wall metabolisms of postharvest Coprinus comatus stored at different temperatures

Storage in refrigerated conditions is the simplest method to maintain the quality of mushrooms. However, unreasonable low temperatures may limit the effect and even induce postharvest chilling injury. To maximally maintain its quality, Coprinus comatus fruiting body was stored at near freezing temperature (NFT), 4 °C and 8 °C, respectively, and the changes of physicochemical properties, reactive oxygen species and cell wall metabolisms were investigated and compared. Results showed that NFT storage slowed the rate of declines in firmness, ascorbic acid and glutathione, as well as increases in browning degree, electrolyte leakage, reducing sugar and malondialdehyde, thereby improving the overall quality of C. comatus. Biochemical analysis demonstrated that NFT storage suppressed the production of reactive oxygen species, and retarded the onset of peak activities of antioxidant enzymes and cell wall degrading enzymes, therefore, maintaining higher levels of cell wall components and cell structure integrity. These results indicated NFT storage could effectively slow the senescence process and be a promising strategy to prolong the storage period of C. comatus mushroom.