Cold Storage Research Articles

QPCR assay optimisation for a clinical study comparing oral health risk in Rett syndrome

PurposeThis study aimed to validate qPCR assays for specific microbiota, for use on dental plaque samples stored on Whatman FTA cards to compare relative oral health risk in Rett syndrome.MethodsSupragingival dental plaque samples were collected, using a sterile swab, (COPAN FLOQswab™) swabbed onto Whatman FTA™ cards. DNA extraction was performed using a modified Powersoil™ protocol. Where published assays were unsuitable, species-specific qPCR assays for caries-associated, gingivitis-associated and oral-health-associated bacteria were designed using multiple sequence alignment, Primer3Plus and PrimerQuest. Assays were run using absolute quantification. Limit of detection (LOD) and limit of quantification (LOQ) were calculated, and PCR products verified by Sanger sequencing.ResultsMost assays allowed detection using real-time qPCR with high specificity on samples collected on FTA cards. Several assays showed low or even single gene copy numbers on the test samples.ConclusionAssays were optimised for detection and evaluation of oral health risk in dental plaque samples stored on FTA cards when cold storage is not feasible, except for F. nucleatum. Several assays showed gene copy numbers less than the LOQ or outside the range of the standard curve, so there is merit in optimising these assays using digital droplet PCR.

The Risk of Microbial Transmission in Recipients of Donor Livers That Underwent Hypothermic or Normothermic Machine Perfusion.

Ex situ machine perfusion is increasingly used to preserve and assess donor livers before transplantation. Compared with traditional static cold storage (SCS), machine perfusion exposes livers to an additional risk of microbial contamination. However, information on the risk of microbial transmission during machine perfusion is lacking. All livers that underwent either hypothermic oxygenated machine perfusion (HOPE) or normothermic machine perfusion (NMP) in our center between September 2021 and September 2023, and during which samples were taken from SCS fluid and/or machine perfusion solution for microbiological examination, were included in this retrospective, observational clinical study. Microbial transmission was examined from SCS fluid to machine perfusion solution fluid and, subsequently, to recipients of these livers. A total of 90 cases of liver machine perfusion were included: 59 HOPE and 31 NMP. SCS preservation fluid cultures before HOPE or NMP were positive for at least 1 microorganism in 52% of the cases. After HOPE, there were no cases of positive machine perfusion fluid or evidence of microbial transmission to the recipients. After NMP, in 1 (3%) patient Escherichia coli was grown from abdominal drain fluid, the same bacterial strain that was also grown from the SCS preservation fluid before NMP. This E coli was resistant to the antibiotics that are routinely added to the NMP perfusion fluid. The risk of microbial transmission after machine perfusion is very low but not absent. We recommend routine sampling of machine perfusion fluid at the end of the procedure for microbiological analysis.

The Effect of Packaging Type and Storage Time on the Quality Characteristics of Chicken Nugget with Jack Bean (Canavalia ensiformis L.) Tempeh Flour Substitution

Chicken nuggets with jack bean tempeh flour substitution are a type of perishable food, thus having a short shelf life. The shelf life of chicken nuggets with jack bean tempeh flour substitution and its quality were affected by the storage conditions. This study aimed to determine the effect of packaging type and storage time during 20 days of cold storage on the quality characteristics of chicken nuggets with jack bean tempeh flour substitution. The research design consisted of two factors, the first factor was packaging type (nylon/polyethylene (PE), nylon-polyethylene (PE)/polyamide (PA), and polyethylene (PE)/polyamide (PA)) and the second factor was storage time (0 day, 5 days, 10 days, 15 days, and 20 days). The results showed that the packaging type and storage time significantly affected the quality characteristics of chicken nuggets with jack bean tempeh flour substitution. In conclusion, PE/PA was more effective in maintaining the quality characteristic of chicken nuggets with jack bean tempeh flour substitution on the 20th day of storage based on pH of 6.43, cooking loss of 9.85%, moisture content of 39.46%, protein content of 24.51%, and TPC of 5.36 log cfu/g. Meanwhile, the result of the sensory evaluation showed that scores for attributes were color 3.63, taste 3.5, texture 3.29, and overall 3.53 (like slightly) on the 20th day of storage.

New approaches in pear preservation: Putrescine and modified atmosphere packaging applications to maintain fruit quality during cold storage

AbstractPear (P. communis L.), which is a climacteric fruit species, has a very short storage and shelf life, and significant losses occur due to high metabolic activity and the fruit's respiration rate after harvest. Therefore, preventing or reducing post‐harvest quality losses in pear is one of the most basic problems awaiting solution. In this study, we planned for this purpose; the fruits of the Ankara pear cultivar treated with modified atmosphere packaging (MAP), putrescine (1 mM), and MAP + putrescine were stored for 120 days at 1°C and 90 ± 5% relative humidity. The quality analyses and measurements, such as weight loss, decay rate, fruit firmness, soluble solids content (SSC), titratable acidity (TA), total phenolic compounds, antioxidant capacity, organic acids, and specific phenolic compounds, were performed on the 30th, 60th, 90th, and 120th days. Weight loss and decay ratios were lower for putrescine and putrescine + MAP‐applied fruit. With these applications, the softening of the fruit was slowed down, and the increasing SSC in the fruit and the decreasing TA rates were lower, and thus the ripening of the fruit was delayed. Changes in individual phenolic content and organic acids were lower in MAP and putrescine‐applied fruit. The study revealed that MAP and putrescine applications in pear can be used effectively to maintain fruit quality after harvest.

Involvement of energy and cell wall metabolisms in chilling tolerance improved by hydrogen sulfide in cold-stored tomato fruits.

Hydrogen sulfide improved cold resistance of tomato fruits by regulating energy metabolism and delaying cell wall degradation, thereby alleviating the damage of cold storage on fruits. Postharvest cold storage in tomato fruits extended shelf life but caused the appearance of chilling injury (CI), appeared by softness and spots on the surface of the fruits. These changes were linked closely with energy and cell wall metabolisms. Hydrogen sulfide (H2S), as the gaseous fresh-keeping regulator, was used in the present study to investigate the effects of H2S on energy and cell wall metabolisms in tomato fruits during cold storage. Fruits after harvest were fumigated with different concentrations (0, 0.5, 1, 1.5mM) of sodium hydrosulfide (NaHS) solution as H2S honor for 24h and stored at 4°C for 25days. The results showed that 1 and 1.5mM NaHS solution fumigation promoted the accumulation of endogenous H2S, followed by the increase in L-cysteine desulfurase (LCD) and D-cysteine desulfurase (DCD) activities in fruits during cold storage. It was also found that 1 and 1.5mM NaHS treatments improved H+-ATPase, Ca2+-ATPase, cytochrome C oxidase (CCO), and succinic dehydrogenase (SDH) activities. Moreover, the contents of cellulose and hemicellulose were increased by 1 and 1.5mM NaHS, following down-regulated activities of cellulase (CL), pectin lyase (PL), α-mannosidase (α-man) and β-Galactosidase (β-Gal) and down-regulated expression of PL1, PL8, MAN4 and MAN7 genes. Thus, H2S alleviates CI led by cold storage in tomato fruits via regulating energy and cell wall metabolisms.

Regulation of plum fruit cracking process during cold storage period by treatment of preharvest chitosan

Cracking fruit is a serious quality change phenomenon in the storage and transportation of postharvest plum fruit. To reduce the cracking rate of plum fruit during cold storage, the 'Guofeng No.7′ plum was sprayed with chitosan with 1.5% concentration 30d from preharvest. The postharvest plum fruit was stored at (0 ± 0.5) °C and (85–90) % relative humidity. The results showed that chitosan treatment could reduce the reactive oxygen species (ROS) level of plum fruit, effectively delaying the fruit cracking. Compared with the control, chitosan treated fruits inhibited the increase of free radical content such as O2−· and H2O2 and delayed the increase of membrane permeability and the accumulation of MDA (from 71.9 mmol/g to 53.5 mmol/g). It also regulates lipoxygenase (LOX), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) (enzymatic activity from 34.15 g/min to 42.21 g/min) and ascorbate peroxidase (APX) activity and gene expression during fruit cracking to maintain membrane integrity and intracellular compartmentalization, thereby increasing the crack tolerance of plum fruit during cold storage. These results indicate that preharvest chitosan treatment can inhibit the metabolism of active oxygen species, increase the activity of ROS scavenging enzymes and gene expression, and delay the postharvest cracking of plum fruit.

Impact of Different Technologies and Methods to Increase the Shelf Life and Maintain the Sulforaphane Content in Broccoli: A Review

Broccoli, a nutrient-rich vegetable known for its sulforaphane content and health benefits, faces challenges related to its short shelf life and susceptibility to spoilage. This study explores various techniques to maintain sulforaphane content and extend broccoli's shelf life. Freezing, although effective for long-term preservation, involves blanching that inactivates myrosinase, preventing sulforaphane formation. Cold storage at 4-5°C slows respiration and senescence, extending shelf life up to 14 days while preserving bioactive compounds. Modified atmosphere packaging (MAP) enhances shelf life by altering the package atmosphere, with active packaging using 15% CO2 and 7.5% O2 at 0°C proving particularly effective in reducing bacterial growth and preserving quality. Light exposure, especially with yellow LED lights and moderate UV treatment, retains high levels of glucosinolates and phenolic compounds. Irradiation effectively eliminates pathogens and preserves visual quality, with gamma irradiation slowing the oxidation of phenols and ascorbic acid, although further research is needed on its sensory and nutritional effects. High-pressure processing (HPP), a non-thermal method, significantly boosts sulforaphane bioactivity by converting glucosinolates at pressures up to 600 MPa, despite challenges such as high costs and operational safety, and prevents microbial growth, extending shelf life while maintaining nutritional quality. Additionally, techniques like steaming for optimal durations, microwaving at high power for short times, and stir-frying help preserve sulforaphane content during cooking. Preharvest chemical treatments like chitosan and calcium also enhance broccoli's defence mechanisms and bioactive compound levels. Overall, these methods offer a comprehensive approach to preserving sulforaphane content and extending broccoli's shelf life, providing valuable insights to enhance the storage, quality, and health benefits of broccoli for consumers.

Space electric field impacts on softening and cell wall modification of strawberry during cold storage

As an emerging non-contact cold chain preservation technology, the impact of the DENBA+ on plant cell wall metabolism and its mechanism of inhibiting softening have not been addressed. In this study, strawberries were used as an experimental model to investigate the effect of space electric field storage on cell wall metabolism. Compared with the control, 500 V DENBA+ treatment was able to reduce the firmness loss of strawberries by 18.3 % on 18 d. Additionally, the DENBA+ exhibited a pronounced ability to suppress fruit softening enzyme (FaPG1 and FaβGal4) expression, delay the rise in polygalacturonates (PG), pectin methyl esterase (PME), cellulase (Cx), and β-galactosidase (β-Gal) activities, postpone the decline in cell wall matrix (CWM), insoluble solid pectin (ISP), and colloidal soluble pectin (CSP) content along with hemicellulose and cellulose levels while attenuating water-soluble pectin (WSP) accumulation during cold storage period. These findings contribute to the maintenance of fruit cell wall structural integrity with the aim of sustaining strawberry firmness and retarding the progression of aging.

Pancreas Preservation: Hypothermic Oxygenated Perfusion to Improve Graft Reperfusion.

The clinical standard for pancreas preservation for transplantation is static cold storage (SCS). Oxygenation during preservation has been shown to be advantageous in clinical studies. This study evaluates the efficiency of different oxygenation modalities during hypothermic pancreas preservation. Thirty-two porcine pancreases were procured in a controlled donation after circulatory death model and were divided to be preserved in 8 groups: (1) SCS, (2) hypothermic machine perfusion (HMP), (3) hypothermic oxygenated machine perfusion (HOPE) with 21% oxygen, (4) HOPE and 100%, (5) SCS and oxygen carrier, M101, (6) HMP and M101, (7) HOPE 21% and M101, and (8) HOPE 100% and M101. All the groups underwent 24 h of hypothermic preservation, followed by 2 h of normothermic reperfusion. Oxygen partial pressures were assessed using parenchymal probes. Perfusion parameters, perfusate samples, and tissue biopsies were analyzed. This study showed that HMP was linked to higher tissue oxygen partial pressures, lower succinate levels, and better reperfusion parameters. Furthermore, the addition of M101 to either SCS or HMP was associated with lower succinate and creatinine phosphokinase accumulation, suggesting a protective effect against ischemia. Our research has demonstrated the efficacy of machine perfusion in hypothermic conditions in providing oxygen to the pancreas during preservation and conditioning the pancreatic microvasculature for reperfusion during transplantation. Furthermore, the addition of M101 suggests a protective effect on the graft from ischemia.

Cost effectiveness of commercial portable exvivo lung perfusion at a low-volume US lung transplant center.

Portable exvivo lung perfusion during lung transplantation is a resource-intensive technology. In light of its increasing use, we evaluated the cost-effectiveness of exvivo lung perfusion at a low-volume lung transplant center in the USA. Patients listed for lung transplantation (2015-2021) in the United Network for Organ Sharing database were included. Quality-of-life was approximated by Karnofsky Performance Status scores 1-year post-transplant. Total transplantation encounter and 1-year follow-up costs accrued by our academic center for patients listed from 2018 to 2021 were obtained. Cost-effectiveness was calculated by evaluating the number of patients attaining various Karnofsky scores relative to cost. Of the 13 930 adult patients who underwent lung transplant in the United Network for Organ Sharing database, 13 477 (96.7%) used static cold storage and 453 (3.3%) used exvivo lung perfusion, compared to 30/58 (51.7%) and 28/58 (48.3%), respectively, at our center. Compared to static cold storage, median total costs at 1 year were higher for exvivo lung perfusion ($918 000 vs. $516 000; p = 0.007) along with the cost of living 1 year with a Karnofsky functional status of 100 after transplant ($1 290 000 vs. $841 000). In simulated scenarios, each Karnofsky-adjusted life year gained by exvivo lung perfusion was 1.00-1.72 times more expensive. Portable exvivo lung perfusion is not currently cost-effective at a low-volume transplant centers in the USA, being 1.53 times more expensive per Karnofsky-adjusted life year. Improving donor lung and/or recipient biology during exvivo lung perfusion may improve its utility for routine transplantation.

Volatile profiling of Lentinula edodes during cold storage: An integrated GC/MS and transcriptomic analysis

Cold storage is important for extending the shelf life of Lentinula edodes; however, the mechanism underlying aroma changes during cold storage is not understood. In this study, we analyzed the quality, volatile organic compounds, volatile precursors, and related enzyme activities of Lentinula edodes during cold and room temperature storage. The transcriptome was analyzed to determine the expression of aroma-related genes in Lentinula edodes. The results showed that cold storage maintained a better appearance and aroma profile than room-temperature storage. Fifteen volatile organic compounds were identified as potential biomarkers for monitoring the aroma changes in Lentinula edodes. Transcriptomic results revealed that lipoxygenase-related genes were important for regulating 1-octen-3-ol biosynthesis, whereas the three upregulated genes were related to terpenoid degradation. This study provides new insights into regulating aroma metabolism in Lentinula edodes during cold storage.

The effect of different LED wavelengths used in the cultivation of Pleurotus ostreatus on quality parameters of the mushroom during the storage process

This study aimed to investigate the effects of light emitting diodes (LEDs) of different wavelengths (white, red, blue and green) used in Pleurotus ostreatus cultivation on post-harvest mushroom quality, storage process and maintenance of mushroom quality characteristics during storage. The mushroom was exposed to different LED wavelengths for 8 and 12 h per day during fructification period. The effects of these treatments were observed during post-harvest and storage periods, focusing on changes in color, weight loss, antioxidant capacity (FRAP), and total phenolic content (TPC). The harvested mushrooms were stored at 1 °C for 12 days, and samples were taken every 4 days to analyze mentioned parameters. After harvest, L*,a*,b* values of the fruiting bodies grown under different LEDs ranged 56.5 − 69.8, 2.0 − 3.84, 12.2 − 15.9 respectively, whereas TPC and FRAP values varied from 54.4 to 78.5 mg GAE/100 g fw and 6.14 to 7.59 µmol TE/g fw, respectively. The values of L*, a*, b*, browning index (BI), and yellowness index (YI) demonstrated a clear postponement of discoloration in the samples exposed to 8 h of red LED and 12 h of green LED compared to the control group at the end of the storage period. The TPC of the fruitbody cultivated under red LED (8 h per day) was markedly increased after 12 days (54.4 to 95.1 mg GAEs/100 g fw), but LEDs did not affect the maintenance of antioxidant capacity in P. ostreatus. The results showed that red LED applied for 8 h per day during the fructification period enhanced TPC with minimal effects on the color during cold storage.

Solar photovoltaic refrigeration system coupled with a flexible, cost-effective and high-energy-density chemisorption cold energy storage module

Owing to the environmental pollution and high costs associated with lead-acid batteries, this paper proposes a solar photovoltaic (PV) refrigeration system coupled with a flexible, cost-effective and high-energy-density chemisorption cold energy storage module. Its operation mode includes daytime solar PV refrigeration/cold energy charging mode and nighttime cold energy discharging mode. A novel composite sorbent SrCl2 is developed using expanded natural graphite as matrix and carbon coated aluminum as additive, exhibiting superior heat and mass transfer performance. A sorbent performance test bench is constructed, demonstrating that the cold energy storage density reaches 503.6 kJ/kg at an evaporating temperature of −15 °C, 1.5 times of ice storage. Compression-assisted desorption is adopted to regulate desorption temperature, so that 75–90 °C solar hot water from low-cost non-concentrating solar collectors can be utilized as the driving heat source. For an evaporating temperature of −10 °C and a solar hot water temperature of 90 °C, the electrical coefficient of performance for cold energy storage unit reaches 3.72, representing a 33 % improvement compared to conventional solar PV refrigeration systems. This novel system features characteristics such as low cost, high efficiency and eco-friendliness, offering a promising solution for solar refrigeration.

A novel liquid air energy storage system with efficient thermal storage: Comprehensive evaluation of optimal configuration

Liquid air energy storage (LAES) stands out as a highly promising solution for large-scale energy storage, offering advantages such as geographical flexibility and high energy density. However, the technology faces challenges inherent in the cold and heat storage processes. While systems with liquid-phase medium can offer high efficiency, it comes with drawbacks including environmental pollution, safety concerns, and high costs. Alternatively, systems with solid-phase media in packed beds can address these issues, yet it profoundly weakens system performance. Compounding these issues, many current economic evaluations of LAES rely on inaccurate or outdated data, resulting in skewed assessments. In response to these challenges and to drive scientific evaluation and engineering advancements in LAES, this study introduces an innovative LAES system with efficient thermal storage (ETS-LAES). An original thermal storage method is introduced for the first time, based on gravity-driven solid-phase particle flow and gas-solid direct contact heat transfer. The study establishes thermodynamic and heat transfer models, along with a universally applicable economic evaluation model. The ETS-LAES system is comprehensively assessed utilizing different operational modes introduced in the study. Research findings showcase a round-trip efficiency (RTE) of 58.76%, currently standing as the highest RTE record for cold and heat storage based on solid-phase media. The economic evaluation reveals substantial advantages for the ETS-LAES system during the transition from demonstration projects to commercial projects and guides the selection of the scale for the LAES system. The levelized cost of storage (LCOS) for the ETS-LAES system can decrease to 0.0982 USD/kWh as the capacity increases to 1000MW, due to the use of inexpensive solid-phase thermal storage media throughout. The investment payback period (IPP) is halved compared to conventional LAES systems, indicating a strengthening of the profitability. The proposed solution in this study holds great potential, particularly in offering valuable insights into the practical implementation and commercialization of LAES.

Exogenous Melatonin Treatments Maintain Berry Quality and Bioactive Compounds of Minimally Processed Table Grapes (‘Crimson Seedless’) During Cold Storage

Exogenous Melatonin Treatments Maintain Berry Quality and Bioactive Compounds of Minimally Processed Table Grapes (‘Crimson Seedless’) During Cold Storage

Indoor Air Temperature Distribution and Heat Transfer Coefficient for Evaluating Cold Storage of Phase-Change Materials during Night Ventilation

Indoor Air Temperature Distribution and Heat Transfer Coefficient for Evaluating Cold Storage of Phase-Change Materials during Night Ventilation

Studies of certain parameters affecting two parasitoid species, Trichogramma evanescens Westwood and Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), on egg host, Sitotroga cerealella (Olivier) (Gelechiidae: Lepidoptera)

BackgroundTwo Trichogramma spp., Trichogramma evanescens Westwood and Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), were studied to control one of the most cereal pests attacking various grains, Sitotroga cerealella (Olivier) (Gelechiidae: Lepidoptera). Experiments were carried out to evaluate S. cerealella egg-ages, parasitoids’ emergence time and cold storage host eggs on rearing the two tested parasitoids’ spp.ResultsThe age of S. cerealella eggs had significantly influenced the parasitization and adult emergence rates of the two parasitoid species. Parasitism rate resulted from old host eggs (32 h old) (44.93%) decreased than those of the fresh ones (2 h old) (95.85%). Emergence rate ranged between (62.64–97.85%) for T. evanescens and (62.90–95.54%) for T. bactrae from different S. cerealella egg-ages (0–32 h). Regardless to late emerged parasitoids, their population affected. T. evanescens parasitized rate ranged (73.79–95.06%), which comparatively lower than those of T. bactrae (88.81–96.90%), at parasitoid emerging times (0–64 h), respectively. Emergence times had significantly differences in the emergence rate of T. evanescens and/or T. bactrae. On the other hand, percentage of parasitism of the non-stored S. cerealella eggs was higher than the other cold-stored ones. The emergence rate of adult parasitoids, T. evanescens (66.00–91.16%) and T. bactrae (71.16–94.11%), was decreased at the cold storage durations (5–40 days) increased. In comparison to the tested biological aspects between the two parasitoid species, non-significant differences were recorded, at the three assessment parameters, which include host egg-ages, parasitoid emergence time and cold-stored eggs. Meanwhile, there were significant differences between F1 emerged rates for T. evanescens and T. bactrae obtained at each of the three tested parameters.ConclusionIt was concluded that low emergence time of the parasitoids, T. evanescens and T. bactrae, was relatively more effective when they parasitized the fresh egg-age and less cold storage periods of S. cerealella.

Study on the Effect of Sorghum Flour Particle Size on the Storage Quality of Leavened Pancakes.

Pancakes prepared with sorghum flour possess a high nutritional value, yet their quality is unstable and prone to degradation during storage. This instability can be attributed to the particle size of coarse cereal powder, which significantly influences the quality of flour products during storage. In this study, changes in the quality of these pancakes, prepared with varying particle sizes of sorghum flour, were meticulously analyzed during cold storage using advanced instruments such as a texture analyzer, nuclear magnetic resonance spectrometer, differential scanning calorimeter, X-ray diffractometer, and Fourier transform infrared spectrometer. Findings revealed that the hardness of leavened pancakes significantly increased over time. After a refrigeration period of 7 days, the hardness of wheat flour leavened pancakes increased by 56.60%. However, with a decrease in the particle size of sorghum flour, the increase in hardness diminished, thereby delaying the aging process of the pancakes. As the storage duration was extended, moisture migration within the pancakes occurred, and the sorghum flour pancakes with a smaller particle size exhibited a reduced moisture change rate, indicating an enhanced water holding capacity. In comparison to their wheat flour counterparts, sorghum flour leavened pancakes exhibited a substantial reduction in retrogradation enthalpy and crystallinity. The inclusion of sorghum flour effectively inhibited amylopectin recrystallization, thus slowing down the aging process of the pancakes. This inhibitory effect was more evident with decreasing sorghum flour particle sizes. Fourier transform infrared data indicated no significant alterations in absorption peaks across various wavelengths during cold storage. Although starch short-range orderliness increased with storage time, the use of sorghum flour with smaller particles reduced the degree of short-range orderliness in starch molecules throughout the cold storage period. Sorghum flour with a smaller particle size can inhibit water migration and amylopectin recrystallization, which subsequently delays pancake aging and enhances its quality stability during storage.

Efficient utilization of cold energy enabled by phase change cold storage brine gels with superior thermophysical properties towards biochemical reagent cold chain

Phase change cold storage, as an emerging cold chain method of maintaining a low-temperature environment and effectively ensuring the quality of biochemical reagents, is extensively utilized because of its benefits of high energy density, low cost, energy conservation and environmentally friendly mode. However, the low thermal conductivity of working medium affects its cold charging/discharging rate and operating efficiency. Meanwhile, the high leakage characteristic in the phase change process leads to a decrease of cold storage capacity and contamination of items. This work proposes the efficient utilization of cold energy enabled by leakage-free phase change cold storage brine gels with extraordinary high thermal conductivity towards biochemical reagent cold chain. Phase change thermal storage gel is prepared by confining brine in the sodium polyacrylate‑calcium alginate network and porous adsorption of expanded graphite. The prepared materials present leak free characteristics and almost 100% mass retention rate. Expanded graphite addition enables the thermal conductivity increase from 0.542 W m−1 K−1 to an extremely high value of 2.766 W m−1 K−1 (an increase of 510%). The enthalpy value of the cold storage brine gel is as high as 144 Jg−1, stably releasing cold at around −24 °C. By regulating the distribution of cold storage working medium, the minimum temperature difference inside the apparatus can be reduced from 6.7 °C to about 1 °C. Finally, performance-enhancing phase change cold storage materials and apparatus in the cold chain of biological reagents is fruitful, effectively providing a long-lasting and uniform low-temperature environment.

Preserving functional properties and inhibiting postharvest peel browning in guava during cold storage via 24-epibrassinolide application

Postharvest peel browning is one of the primary issues accountable for the subdued consumer acceptability and market value of guava fruit. However, postharvest treatment with brassinosteroid can reduce the peel browning to some extent through various modes of action. In current study, the influence of exogenous 24-epibrassinolide (EBL) application on antioxidant system and chilling injury (CI) characteristics of guavas during cold storage at 10 ± 1 ℃ were assessed. The mature green fruit exposed to various concentrations (15, 30, 45, 60 and 75 µg kg−1) of EBL displayed a notably lower fruit weight loss, respiration rate, electrolyte leakage and CI index, while higher consumer acceptability. Further, treatment with EBL has recorded lower amassing of hydrogen peroxide and malondialdehyde by suppressing lipoxygenase activity. Postharvest EBL application also heightened the content of total phenolics, ascorbic acid, total flavonoids and total antioxidant capacity. The enhanced activities of ascorbate peroxidase, catalase, superoxide dismutase and peroxidase due to EBL application impede the burst of reactive oxygen species. Moreover, correlation and regression analysis of tested biochemical parameters including enzymatic and non-enzymatic antioxidants exhibited a strong association and contributed 98.24–99.88 % variability in fruit weight loss, respiration rate, electrolyte leakage, CI index and consumer acceptability. Among different concentrations tested, 60 µg kg−1 EBL-treated guavas exhibited the desirable qualities and least CI index. From the study, it is concluded that the novelty of EBL can be gainfully harnessed in a postharvest handling system to induce cold tolerance and widen the storage life of cold-stored guava fruit.