Low Temperature Storage Research Articles

Melatonin enhances the synthesis of volatile esters and lactones in apricot during low temperature storage

Low temperature storage often leads to chilling injury in apricots, causing a loss of aroma and a decrease in its commodity value. In this study, melatonin (MT, 0.1, 0.2, and 0.4 mmol L−1) dipping treatment was used to improve the aroma quality of apricot (‘Jintaiyang’ and ‘Pingdingxiang’) at low temperature (4 °C). Results demonstrated that the application of 0.2 mmol L−1 MT treatment effectively maintained firmness and soluble solids content (SSC), and inhibit the ethylene production and respiration rate of apricots. Additional observations revealed that MT was capable of inhibiting the activities of LOX (lipoxygenase), HPL (hydroperoxidelyase), and ADH (alcohol dehydrogenase) enzymes, thereby reducing the levels of alcohols and aldehydes in apricots. Conversely, MT upregulated the activities of LOX, HPL, ADH, ACX (acyl-CoA oxidase) and AAT (alcohol acyltransfera) enzymes, promoting the biosynthesis of lactones and esters in apricots. Thus, melatonin might be an effective method for low temperature storage of apricot by promoting the recovery of aroma substances.

Untargeted Lipidomics Reveal Quality Changes in High-Moisture Japonica Brown Rice at Different Storage Temperatures.

Low temperatures are an effective way of delaying grain rancidity and deterioration. However, little is known about the difference in quality changes in high-moisture japonica brown rice at different storage temperatures. In this study, the storage quality changes in japonica brown rice with a 15.50% moisture content stored at 15 °C, 20 °C, and 25 °C were investigated. In addition, an untargeted lipidomics analysis coupled with gas chromatography and mass spectrometry (GC-MS) was applied to analyze the volatile compounds and metabolite changes in the high-moisture japonica brown rice. The results showed that storage at 15 °C could well maintain the color and aroma stability of the brown rice and delay the increase in fatty acid value (FAV). The lipidomics results showed that storage at 15 °C delayed glycerolipid and sphingolipid metabolism and reduced glycerophospholipid catabolism in the brown rice. The low-temperature environment regulated these three metabolic pathways to maintain higher contents of triglycerides (TG), phosphatidylserine (PS), abd phosphatidylethanolamine (PE), and lower contents of diglycerides (DG), OAcyl-(gamma-hydroxy) FA (OAHFA), ceramides (Cer), and glycosylceramides (Hex1Cer) in the high-moisture japonica brown rice, which maintained the storage stability of the brown rice. Our results proposed the cryoprotection mechanism of postharvest brown rice from the perspective of volatile compounds and metabolite changes, providing a foothold for the further exploration of low-temperature storage as a safe and efficient cryoprotectant in the grain storage field.

Analysis of The Addition of Natural Preservative Ingredients To The Saving Time of Squid (Loligo Sp.) (Study Of Various Studies Conducted)

Squid is one of Indonesia's marine fisheries resources that is nutritious and in high demand by the public, hence the need for good quality squid. The obstacle experienced in fulfilling the demand for squid is the quality of squid. Various research have been conducted to determine preservatives that are effective enough to maintain the freshness of squid for a long time and extend the shelf life. This research was conducted using a literature study technique, comparing and selecting the most effective of several natural preservatives used. Some of the preservatives compared were lactate solution from cabbage fermentation, yogurt, chitosan solution, picung seeds, and cucumber. This study aims to determine the effective preservatives that have the longest shelf life for squid. The results of the literature study showed that yoghurt was the most effective preservative for extending the shelf life of squid until day 11 with total lactic acid bacteria colonies of 4.8x 105 cfu/gram and pH value of 6.8 in low temperature storage. The concentration used was 1.5%.

Combined application of hot water treatment and eucalyptus leaf extract postpones seneṣcence in harvested green chilies by conserving their antioxidants: a sustainable approach

BackgroundGreen chili is the predominant vegetable in tropical and subtropical regions with high economic value. However, after harvest, it exhibits vigorous metabolic activities due to the high moisture level, leading to a reduction in bioactive compounds and hence reduced shelf life and nutritional quality. Low temperature storage results in the onset of chilling injury symptoms. Therefore, developing techniques to increase the shelf life of green chilies and safeguard their nutritional value has become a serious concern for researchers. In this regard, an experiment was conducted to evaluate the impact of the alone or combined application of hot water treatment (HWT) (45 °C for 15 min) and eucalyptus leaf extract (ELE) (30%) on 'Golden Hot' chilies in comparison to the control. After treatment, chilies were stored at 20 ± 1.5 °C for 20 days.ResultsHWT + ELE-treated chilies had a significant reduction in fruit weight loss (14.6%), fungal decay index (35%), red chili percentage (41.2%), soluble solid content (42.9%), ripening index (48.9%), and reactive oxygen species production like H2O2 (55.1%) and O−2 (46.5%) during shelf in comparison to control, followed by the alone application of HWT and ELE. Furthermore, the combined use of HWT and ELE effectively improved the antioxidative properties of stored chilies including DPPH radical scavenging activities (54.6%), ascorbic acid content (28.4%), phenolic content (31.8%), as well as the enzyme activities of POD (103%), CAT (128%), SOD (26.5%), and APX (43.8%) in comparison to the control. Additionally, the green chilies underwent HWT + ELE treatment also exhibited higher chlorophyll levels (100%) and general appearance (79.6%) with reduced anthocyanin content (40.8%) and wrinkling (43%), leading to a higher marketable fruit (41.3%) than the control.ConclusionThe pre-storage application of HWT and ELE could be used as an antimicrobial, non-chemical, non-toxic, and eco-friendly treatment for preserving the postharvest quality of green chilies at ambient temperature (20 ± 1.5 °C).

Umami loss mechanism upon shiitake mushrooms under cold storage: Revisiting the role of energy metabolism via integrated physiological and transcriptomic analysis

Umami loss of shiitake mushrooms (Lentinula edodes) is still an inevitable developmental process and a significant challenge hampering its storage and marketing. The present study explores the physiological and molecular responses to umami quality loss involved in energy metabolism during postharvest storage under room temperature (RT) and low temperature (LT) in shiitake mushrooms. Results showed that LT storage prolonged the mushroom shelf life while inhibiting electrolyte leakage, malondialdehyde (MDA), mitochondrial permeability transition pore (MPTP), Ca2+, and H2O2 contents. Moreover, transcriptome analysis revealed that LT storage maintained high umami quality and sufficient energy supply by suppressing the degradation genes of umami nucleotides and the genes related to the mitochondrial energy metabolism pathway, including metabolic pathways and biosynthesis of secondary metabolites. Additionally, the depression activities and gene transcription levels of key enzymes related to umami nucleotide degradation contributed to maintaining umami taste in cold storage. A conceptual model was proposed to elucidate the molecular mechanism of cold storage alleviated umami loss in shiitake mushrooms. The results provide a theoretical foundation for the umami loss mechanism of mushrooms under cold storage.

Carbon dioxide treatment modulates phosphatidic acid signaling and stress response to improve chilling tolerance and postharvest quality in paprika

IntroductionPaprika (Capsicum annuum L.) is prone to chilling injury (CI) during low-temperature storage. Although recent findings suggest that CO2 treatment may protect against CI, the effects of short-term CO2 treatment on CI and the underlying molecular mechanisms in paprika remain unknown. Therefore, this study aimed to examine the effect of short-term CO2 treatment on CI and postharvest quality in paprika during storage at cold storage and retail condition at physio-biochemical-molecular level.MethodsPaprika was treated with 20 and 30% CO2 for 3 h and stored at 4°C for 14 days, followed by additional storage for 2 days at 20°C (retail condition). Fruit quality parameters, including weight loss, firmness, color, and pitting were assessed, and the molecular mechanism of the treatment was elucidated using transcriptomic and metabolomic analyses.ResultsShort-term treatment with 20 and 30% CO2 effectively maintained paprika quality during cold storage and retailer conditions, with reduced surface pitting, a common symptom of CI. Additionally, transcriptomic and metabolomic analyses revealed that 20% CO2 treatment induced genes associated with biosynthesis of phosphatidic acid (PA), diacylglycerol, triacylglycerol, and stress response, metabolites associated with phasphatidyl inositol signaling, inositol phosphate metabolism, and starch and sucrose metabolism.ConclusionCO2 treatment activates PA biosynthesis through PLD and PLC-DGK pathways, and induces inositol phosphate, starch, and sucrose metabolism, thereby regulating chilling stress response via the ICE-CBF pathway. These findings suggest that short-term CO2 treatment enhances resistance to cold-induced injury and preserves postharvest quality in non-climacteric fruits, such as paprika, through activation of PA signaling, which improves membrane stability during cold storage and distribution.

Does the Harvest Type Affect Olive Health? Influence of the Harvesting System and Storage Time on the Chemical, Volatile and Sensory Qualities of Extra Virgin Olive Oils.

With the aim of investigating the effect of bruising and its development during the postharvest time, olive fruits (Frantoio and Moraiolo), manually and mechanically harvested, were stored in climatic chambers at two different temperatures (5 °C and 18 °C) for five days. Visual observations highlighted changes in the olive peel with discoloration in the damaged areas and tissue bruising. Olive fruit polyphenols, volatile organic compounds (VOCs) and other oil quality parameters (phenolic content, free acidity and peroxide index) and sensory assessment were evaluated. Analyses were carried out on fruits and experimental extra virgin oils at harvesting and after 5 days of fruit storage. The results highlight that low-temperature storage (5 °C for 5 days) may contribute to the maintenance of high olive oil quality, and the quality of olives stored at room temperature drastically decreases after 5 days of storage. Moreover, mechanical harvesting, compared to manual harvesting, does not seem to affect the final oil quality, at least at harvesting, but seems to determine differences in the long-term storage period. Finally, the samples stored at 18 °C showed a quality deterioration with the development of sensorial defects.

Oxidative Stability of Side-Streams from Cod Filleting-Effect of Antioxidant Dipping and Low-Temperature Storage.

Currently, side-streams (e.g., head, backbone, tail, and intestines) generated in the fish processing industry often end up as low-value products for feed applications or even as waste. In order to upcycle such side-streams, they need to be preserved to avoid oxidative degradation of the lipids between the generation point and the valorization plant. In the cod filleting industry, three main solid side-streams: viscera, heads, and backbones, are obtained. Hence, this study aimed to identify the most efficient antioxidant for preserving the cod side-streams using a dipping-based strategy prior to pre-valorization storage at low temperatures (ice and frozen storage). The dipping solutions evaluated contained: (i) a lipophilic rosemary extract (0.05% and 0.2% in 0.9% NaCl), (ii) Duralox MANC (a mixture of rosemary extract, ascorbic acid, tocopherols, and citric acid; 2% in 0.9% NaCl), and (iii) NaCl (0.9%) w/w solution. One group was not dipped. No dipping and dipping in NaCl were included as controls. The results showed a positive effect of dipping with solutions containing antioxidants as measured by peroxide value (PV), TBA-reactive substances (TBARS), and sensory profiling, e.g., rancid odor. Moreover, the oxidative stability increased with decreased storage temperature. The cod side-streams were in general most efficiently preserved by Duralox MANC, followed by the lipophilic rosemary extract (0.2%), compared to no dipping and dipping in NaCl solution and the lower concentration of the lipophilic rosemary extract (0.05%). The efficiency of the antioxidant treatments was independent of the side-stream fraction and storage temperature. Thus, using antioxidant dipping combined with low temperature storage is an efficient preservation method for maintaining the quality of the lipids in cod solid side-streams during their pre-valorization storage.

Multi-objective optimization of multi-energy complementary system based on cascade utilization of heat storage

A multi-energy complementary system driven by solar energy and central grid is proposed to supply electricity and cooling/heating, in which a dual-tank thermal storage system is integrated to achieve cascaded solar heat energy utilization. The system integrates parabolic trough solar collectors, high-temperature and low-temperature thermal storage tanks, and an organic Rankine cycle to form an operational loop. The low-temperature thermal storage tank drives an absorption heat pump independently. Excess photovoltaic power drives the ground source heat pump for heating/cooling. Three indicators are defined and compared to show the renewable energy penetration rate in the complementary system. A multi-objective optimization model considering economic performance and renewable energy rate is constructed to optimize the system configurations. Three sets of objective functions are compared through the optimization Pareto frontiers. Then, the TOPSIS method is employed to select the optimum configuration through setting different weights of optimization objectives. Compared with the reference system, the proposed multi-energy complementary system improves the energy, economic and environmental benefits by 59.21%, 24.27% and 11.31%, respectively. Through a variety of equipment (PV, ORC, AHP, TES), solar energy supplies 86.2% and 72.2% of total electricity and heat loads, respectively.

Comparative Analysis of Metabolites of 'Hongro' Apple Greasiness in Response to Temperature.

Greasiness in apple skin reduces its quality, and its level varies depending on the variety. In this study, low-temperature (1 ± 0.5 °C) stored 'Hongro' and 'Fuji', which had differences in the occurrence of greasiness, were moved to room temperature (20 °C) and untargeted metabolite and fatty acids for skin and flesh along with quality changes due to greasiness occurrence were compared. Ethylene production differed noticeably between the two varieties and increased rapidly in 'Hongro' until 9 d of room-temperature storage. The ethylene production did not differ significantly between the two varieties on day 20 when greasiness occurred. According to the PLS-DA score plot, while 'Hongro' had similar amounts of unsaturated and saturated fatty acids, 'Fuji' had approximately twice as much unsaturated-fatty-acid content. 'Hongro', after 50 d of low-temperature (1 ± 0.5 °C) storage, produced excessive ethylene during room-temperature storage, which was directly related to greasiness development. As a result, the primary wax components of greasy 'Hongro' were nonacosane and nonacosan-10-ol. As the room-temperature storage period elapsed, pentyl linoleate and α-farnesene contents increased significantly. Furthermore, these greasiness-triggering characteristics of 'Hongro' may have been genetically influenced by the paternal parent used during breeding.

Double Carbon Networks Reinforce the Thermal Storage and Thermal Transfer Properties of 1-Octadecanol Phase Change Materials.

Using thermal storage materials with excellent thermal properties in the energy utilization system enables efficient use of renewable energy sources. Organic phase change materials (PCMs) have the advantages of high heat storage density, no corrosion, and low cost, but low thermal conductivity and insufficient heat transfer capacity have always been the bottlenecks in their application. In this paper, melamine foam@ reduction graphene oxide (MF@rGO) and carbon foam@ reduction graphene oxide (CF@rGO) composite foams with double carbon networks were prepared by self-assembly method and further employed in 1-octadecinal (OD) PCMs. The microstructure, chemical composition, phase change behavior, thermal conductivity, and photothermal conversion performance of MF@rGO/OD and CF@rGO/OD were studied in detail using SEM, FTIR, Raman DSC, and LFA. The melting and solidification enthalpies of CF@rGO/OD composite PCMs were 208.3 J/g and 191.4 J/g, respectively, its thermal conductivity increased to 1.54 W/m·K, which is 6.42 times that of pure OD. The porous structure and high thermal conductivity of the double carbon network substantially enhance the efficiency of energy storage and release in composite PCMs. CF@rGO/OD composite PCMs have excellent heat storage performance and heat transfer capacity, and a wide range of application prospects in the fields of low-temperature solar heat storage, precision instrument temperature control, and intelligent buildings.

Interplay between Shelf Life and Printability of Silica-Filled Suspensions.

Although fumed silica/siloxane suspensions are commonly employed in additive manufacturing technology, the interplay between shelf life, storage conditions, and printability has yet to be explored. In this work, direct ink writing (DIW) was used to print unique three-dimensional structures that required suspensions to retain shape and form while being printed onto a substrate. Suspensions containing varying concentrations of hydrophobic and hydrophilic silica were formulated and evaluated over a time span of thirty days. Storage conditions included low (8%) and high (50%) relative humidity and temperatures ranging from 4 °C to 25 °C. The shelf life of the suspensions was examined by comparing the print quality of pristine and aged samples via rheology, optical microscopy, and mechanical testing. Results showed a significant decrease in printability over time for suspensions containing hydrophilic fumed silica, whereas the printability of suspensions containing hydrophobic fumed silica remained largely unchanged after storage. The findings in this work established the following recommendations for extending the shelf life and printability of suspensions commonly used in DIW technology: (1) higher fumed silica concentrations, (2) low humidity and low temperature storage environments, and (3) the use of hydrophobic fumed silica instead of hydrophilic fumed silica.

Sucrose and brassinolide alleviated nitrite accumulation, oxidative stress and the reduction of phytochemicals in kale sprouts stored at low temperature

Browning, nitrite accumulation, oxidative stress, and loss of nutrients in postharvest sprout during low-temperature storage are important issues that affect storage quality of sprouts. This study evaluated the effects of sucrose, brassinolide (BR), and their combination on the growth and development of fresh kale sprouts, and reactive oxygen metabolism, ascorbate-glutathione (AsA-GSH) cycle, browning, nitrite content, and bioactive ingredients of kale sprouts stored at low temperature, in order to improve the physiological traits of postharvest sprouts, resist the oxidative stress in sprouts during low-temperature storage and inhibit the loss of plant nutrients. Compared with sucrose or BR alone, the combined treatment increased fresh weight, hypocotyl length, AsA/DHA ratio, glutathione reductase activity, riboflavin, cellulose, and free amino acid contents, and decreased weight loss rate, browning index (BI), malondialdehyde (MDA) and dehydroascorbic acid content, ascorbate peroxidase and dehydroascorbate reductase activities in sprouts stored at low temperature. The riboflavin, cellulose, and free amino acid contents in the combined-treated group were higher 57.5%, 119.9%, and 66.7% than those in the control group of fresh samples (CK0), respectively, and there were no significant differences in BI and MDA content between CK0 and the combined-treated groups. These results indicated that the combination of sucrose and BR could better alleviate the reduced quality of kale sprouts stored at low temperature by regulating the weight loss rate and AsA-GSH cycle, so as to maintain the nutrients and antioxidant capacity of kale sprouts to the maximum extent.

Influence of storage conditions, packaging, post-harvest technology, nanotechnology and molecular approaches on shelf life of microgreens

Microgreens have achieved importance recently due to their high nutritive value, easiness of cultivation and year round availability. However, being very tender and having high moisture content, their shelf life is too short. Studies show that the physical quality, chemical quality and shelf life deterioration in post harvest of micro greens can be improved with effective storage conditions, packaging matters, nanoparticle application, physiological treatments and molecular approaches. Low ambient or storage temperature and effective storage system improve and sustain the shelf life, and quality and restrict microbial activity in micro greens. Packaging with bioplastic clamshell, cardboard clamshell, bioplastic pouch, kraft paper box, or classified polymer upgrades the shelf life and reduce antimicrobial activity under controlled temperature. The interventions with nanoparticles such as nano packaging, nano coatings and nano bubble modify the shelf life and quality and forbids microbial outbreak, solvent discharge and unstable gaseous exchange. The real time signal processing nano sensor technology can detect pesticides, pathogens, toxic materials, contaminants, and microbes in microgreens. The emission of light emitting diodes with stable ratio of wavelength extends shelf life. High carbon dioxide and low oxygen pressure at 5 °C temperature exhibits control respiration rate and prolonged shelf life. The standard packaging materials and post harvest technology may be recognized for extending shelf life and quality in harvested microgreens. The integration of molecular tools can be used to screen genome, replication, transcription, translation, post translation and gene regulation for shelf life improvement and desired traits.

Scalable façade-integrated PVT-systems for upward extensions in the urban context

This article presents a building concept, realised in a timber demonstration house. It is characterized by vertical, façade-integrated PVT collectors and a newly developed active layer as low-temperature storage system. We developed a scalable and transferable energy system design. Especially for multi-storey additions, where the roof area does not grow with the floor space, the concept increases - very much needed - power and energy density in urban areas. The novelty of the presented concept is the sole reliance on vertically mounted PVT-Panels as a heat source, without any seasonal energy storage (e.g., ice storage or geothermal) in combination with the active layer storage below the underfloor heating. Together they allow scaling of energy storage and solar gains with the usable space in the urban context of adding floors to existing buildings.

Inactivation Kinetics of Foodborne Pathogens in Carrot Juice by High-Pressure Processing.

In this study, Salmonella Typhimurium, Escherichia coli, and Listeria monocytogenes were separately inoculated in sterilized carrot juice and subjected to various types of high-pressure processing (HPP) at 200-600 MPa for 0.1-15 min to observe the effects of HPP on the inactivation kinetics of foodborne pathogens in carrot juice. The first-order model fits the destruction kinetics of high pressure on foodborne pathogens during the pressure hold period. An increase in pressure from 200 to 600 MPa decreased the decimal reduction time (D values) of S. Typhimurium, E. coli, and L. monocytogenes. Under pressure ≥ 400 MPa, the D values of E. coli were significantly higher than those of S. Typhimurium and L. monocytogenes, indicating that E. coli had greater resistance to high pressures than the others. The Zp values (the pressure range that causes the D values to change by 90%) of E. coli, S. Typhimurium, and L. monocytogenes were 195, 175, and 170 MPa, respectively. These results indicated that L. monocytogenes and E. coli were the most and least sensitive, respectively, to pressure changes. Additionally, the three bacteria were separately inoculated into thermal-sterilized carrot juice and subjected to 200-600 MPa HPP for 3 min. The treated carrot juices were stored at 4 °C for 27 d. Following S. Typhimurium and E. coli inoculation, the bacterial counts of the control and 200 MPa treatments remained the same during the storage duration. However, they decreased for the 300 and 400 MPa treatment groups with increasing storage duration. During the storage period, no bacterial growth was observed in the 500 and 600 MPa treatments. However, the bacterial number for the control and pressure treatment groups increased with prolonged storage duration following inoculation with L. monocytogenes. Therefore, following HPP, residual L. monocytogenes continued growing stably at low temperatures. Overall, HPP could inhibit and delay the growth of S. Typhimurium and E. coli in carrot juice during cold storage, but it was ineffective at inhibiting the growth of L. monocytogenes. There was a risk of foodborne illness despite the low-temperature storage of juice. The innovation of this preliminary study is to find the impact of high pressure on the inactivate kinetics of three food pathogens in carrot juice and its practical application in simulated contaminated juice.

The stability and immunogenicity of formalin-inactivated Enterovirus A71 whole virion vaccine after ten years of low temperature storage

BackgroundVaccine stability is an important issue for vaccine development, which affects whether the vaccine product is effective within a certain period of time in each progress. Hand, foot, and mouth diseases (HFMD) is an epidemic disease in young children usually caused by Enterovirus A group viruses, and the Enterovirus A71 (EV-A71) had caused several pandemics and public health issues around the world. After two decades of research and development, formalin-inactivated EV-A71 (FI-EV-A71) vaccines are the first to complete the phase III clinical trials for protection against EV-A71 infection. Currently, the shelf life of FI-EV-A71 vaccine product is set to be within 18 months, but the stability and the effectiveness of the FI-EV-A71 whole virion when stored long-term at low temperature remains undetermined. MethodsAssessing the long-term storage properties of viral particles facilitates flexibility in manufacturing of vaccine products. In this study, the stability profiles of FI-EV-A71 vaccine lots and bulks after long-term of low temperature storage were analyzed by protein tests, particle measurement and animal immunization study. ResultsAfter over ten years of storage, the reduction of protein concentration in the FI-EV-A71 bulk samples is less than 30 % and the antigenic content remained in a suspended, particulate state. Both the packed FI-EV-A71 final vaccine products and the FI-EV-A71 antigens adjuvant premix bulk could elicit strong neutralizing responses in mice. ConclusionAfter ten years of low temperature storage, the FI-EV-A71 vaccine still presents decent stability and good immunogenicity.

1-Methylcyclopropylene and heat treatment alleviate chilling injury in purple sweet potato by regulating ROS homeostasis

Postharvest purple sweet potato is vulnerable to chilling injury (CI) under low temperature storage. In this study, the effects of heat air treatment (HA, 45 °C, 3 h), 1-methylcyclopropene (1-MCP, 1.0 μL L–1, 24 h), and a combination of HA and 1-MCP on CI in purple sweet potato stored at 4 °C were investigated. The results showed that HA, 1-MCP, and HA combined with 1-MCP treatments, all significantly slowed down the increase in CI index, malondialdehyde (MDA) content, and electrolyte leakage of purple sweet potato than found in control, while the combination treatment was proved the most effective method for enhancing chilling tolerance in purple sweet potato. Based on transcriptome analysis, glutathione metabolism was activated with high gene expression of IbPMM, IbGMP, IbGME1, IbGME2, IbGGP, IbGaIDH, IbGCS, IbGS2, IbMDHAR, IbDHAR, IbGR, and IbAPX in the combined treatment of HA and 1-MCP. In addition, HA+1-MCP exhibited reduced hydrogen peroxide (H2O2) and superoxide radical (O2·−) content and high levels of ascorbic acid (AsA) and glutathione (GSH), as well as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities in purple sweet potato. In conclusion, HA+1-MCP can effectively reduce chilling injury in purple sweet potato by enhancing enzymatic and non-enzymatic antioxidative level to maintain reactive oxygen species homeostasis during cold storage.

Experimental analysis of one and two-stage thermoelectric heat pumps to enhance the performance of a thermal energy storage

This experimental study demonstrates the possibility to enhance the performance of a low-temperature thermal energy storage system (∼160 °C) based on airflow heating using electrical heaters by including thermoelectric technology. An improvement of the 17 % on COP is reached by using an optimized thermoelectric heat pump system to preheat the airflow, consisting of three one-stage and three pyramidal two-stage thermoelectric heat pumps sequentially installed along the airflow that is heating.This research experimentally analyses and compares the COP of three different configurations of thermoelectric heat pumps: one-stage, square two-stage, and pyramidal two-stage thermoelectric heat pumps. The experimental study aims to characterize the operation of each configuration for heating an airflow of 16.5 m³/h at 25 °C as ambient temperature. To that purpose, the airflow inlet temperature, voltage supply, and voltage ratio between stages have been modified.The experimental results show that for 25 °C as inlet temperature the one-stage thermoelectric heat pump has the best performance with a maximum generated heat of 78 W. Whereas, a two-stage thermoelectric heat pump is required when the inlet temperature increases. At 40 °C as inlet temperature, the square two-stage configuration provides the best performance with a voltage ratio of 2, which reaches a COP of 3.29 generating only 20 W of heat. However, the pyramidal two-stage configuration is able to achieve the maximum heat outputs with a voltage ratio of 1, generating 172; 161; 149 and 138 W, with corresponding COP values of 1.17; 1.16; 1.14 and 1.11 for inlet temperatures of 25; 40; 55 and 70 °C. This configuration is the one that achieves the greatest COP values with high inlet temperatures.

Influence of Long-Term CaO Storage Conditions on the Calcium Looping Thermochemical Reactivity.

Long-term storage capability is often claimed as one of the distinct advantages of the calcium looping process as a potential thermochemical energy storage system for integration into solar power plants. However, the influence of storage conditions on the looping performance has seldom been evaluated experimentally. The storage conditions must be carefully considered as any potential carbonation at the CaO storage tank would reduce the energy released during the subsequent carbonation, thereby penalizing the round-trip efficiency. From lab-scale to conceptual process engineering, this work considers the effects of storing solids at low temperatures (50-200 °C) in a CO2 atmosphere or at high temperatures (800 °C) in N2. Experimental results show that carbonation at temperatures below 200 °C is limited; thus, the solids could be stored during long times even in CO2. It is also demonstrated at the lab scale that the multicycle performance is not substantially altered by storing the solids at low temperatures (under CO2) or high temperatures (N2 atmosphere). From an overall process perspective, keeping solids at high temperatures leads to easier heat integration, a better plant efficiency (+2-4%), and a significantly higher energy density (+40-62%) than considering low-temperature storage. The smooth difference in the overall plant efficiency with the temperature suggests a proper long-term energy storage performance if adequate energy integration is carried out.