Microbial Food Safety Risks Associated with Fresh and Thawed Catfish Fillets during Refrigerated Storage

Fish processing environment is very favorable for the growth of microorganisms and highlights a potential risk associated with microbial hazards. The present study investigated the growth behavior of aerobic bacteria, yeasts and molds, and bacterial pathogens or surrogate (Listeria monocytogenes and Clostridium sporogenes) on thawed and fresh catfish fillets during refrigerated storage (5°C - 7°C). Thawed and fresh fillets were respectively inoculated with L. monocytogenes and C. sporogenes, and packaged in LDPE bags. In uninoculated catfish, the populations of aerobic bacteria, and yeasts and molds increased significantly (P C. sporogenes vegetative cells on fresh catfish fillets. These results indicated that the microbiological quality of refrigerated thawed catfish would become unacceptable within 3 - 4 days. Our results also implied that environmental pathogens such as L. monocytogenes and Clostridium sp. can survive on catfish fillets for extended periods during refrigerated storage. Proper sanitation and hygienic practices are essential to control microbial hazards during handling and processing of catfish fillets.

The Evaluation of Refrigerated and Frozen Osteochondral Allografts in the Knee

Between 1998 and 2002, 25 patients who were treated with a refrigerated or frozen allograft were evaluated. The mean patient age was 48 years. The mean lesion size was 4.5 cm2. Validated outcome instruments [Knee Society Score, Western Ontario and McMaster University Score] were used. Clinical and radiographic evaluations were performed pre-operatively and at the most recent follow-up. Histological and electron microscopic analysis was performed on grafts prior to implantation. Clinical follow-up averaged 46 months (range 24 - 60 months). The Western Ontario and McMaster University Score improved from 46 + 24 to 66 + 22 (p = 0.003). The Knee Society Score improved from 104 + 43 to 132 + 42 (p = 0.01). No correlation was noted between graft type and histological or electron microscopy scoring. Post-operative mechanical alignment was not correlated with an improvement in Western Ontario and McMaster University Score (p = 0.19) or Knee Society Score (0.27). Six patients (24%), all refrigerated allografts, were failures and underwent knee arthroplasty. Seventy-six percent of implanted frozen and refrigerated osteochondral allografts are in place 4 years after surgery. Frozen allografts appear to be surviving as well as refrigerated grafts. The use of magnetic resonance imaging may enable the evaluation of graft incorporation and articular cartilage integrity.

Energy Conservation Effect of Refrigerated Cabinets at Supermarket Utilizing the Exhaust Heat from Dispersed Power

Since the nuclear disaster occurred from huge earthquake in Japan 2011, Japanese energy generation system has been expected to prioritize safety and trustworthiness. To meet this requirement, distributed power supply systems are considered to be one of solutions. In this study, we aimed to conserve energy and reduce carbon dioxide emission of supermarket which installed a novel environment-friendly dispersed power. We focused the energy used by refrigerated cabinets. We built small scale model of supermarket which was equipped with dispersed power. From this scale model, the energy conservation effect of supercooling is from 10% to 25% during the summertime and intermediate time. At last, we found that when outside temperature is about 14 ℃ or more, supercooling was effective. In addition, since energy consumption of refrigerated cabinet is influenced by inside enthalpy, we controlled the inside air temperature and humidity by installing desiccant system and examined its effect.

Chitosan Extends the Shelf-life of Filleted Tilapia (Oreochromis niloticus) During Refrigerated Storage

Shelf-life extension of aquatic products is of significant economical importance. To determine the potential effect of chitosan on the shelf-life of filleted tilapia, this study analyzed the bacterial community diversity in fresh and spoiled tilapia fillets stored at (4 ± 1)℃ and examined the antimicrobial activity of chitosan against relevant bacteria isolates. Results showed that Pseudomonas (20%) and Aeromonas (16%) were abundant in fresh tilapia fillets, whereas Pseudomonas (52%), Aeromonas (32%) and Staphylococcus (12%) were dominant in the spoiled samples. Chitosan showed wide-spectrum antibacterial activity against bacteria isolated from tilapia and 5.0 g L-1 chitosan was selected for application in preservation. We further determined the shelf-life of chitosan-treated, filleted tilapia stored at (4 ± 1)℃ based on microbiological, biochemical and sensory analyses. Results showed that the shelf-life of chitosan-treated, filleted tilapia was extended to 12 d, whereas that of untreated, control samples was 6 d. These indicate that chitosan, as a natural preservative, has great application potential in the shelf-life extension of tilapia fillets.

Intermodal Competition: Cargo Airships versus Long-Haul Trucking for Perishable Commodities

Intermodal competition changes with changes in technology, economics, and environmental concerns. Trucks and airships are generally considered not to be competitors, but this depends on the distance of haul. The tonne-kilometer cost of trucking rises much more quickly with distance than it does the cost of a cargo airship. At some distance, the two modes are direct substitutes. The costs of the Mexico-Canada refrigerated truck supply chain are compared with the costs of a 100t-lift, electrically-powered airship. The flight characteristics of the Hindenburg Zeppelin are used as a model for a modern cargo airship. The supply chain cost of trucking tomatoes is used to test the theorical proposition. The cost difference works out to about US10￠/kg (5￠/lb) advantage for trucking Mexican tomatoes to Canada. However, this cost disadvantage of the airship could be made up by their vibrationless ride, better air circulation and one-day service versus four days by truck. This alternative form of transportation could have a positive impact on worldwide north-south distribution of food. Airships can overcome trade barriers and distance to open new markets for perishable food exports. In addition, they would reduce the carbon emissions of transport. Canada imports 160,000 refrigerated truckloads of fruits and vegetables by from the southern US and Mexico. With an average driving distance of 3,000 km, these trucks emit 606,000 MT of CO2 annually. Airships powered by hydrogen fuel cells would have zero-carbon emissions. Markets are not yet incorporating the environmental advantage of airships in any freight comparison, but inevitably this will be important.

Magnetic and magnetocaloric effect of Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass

Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass exhibited excellent magnetic refrigeration material with a wide temperature range and high refrigeration capacity(RC)was reported.Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass was observed with typical spin glass behavior around 15.5 K.In addition,we find that the magnetic entropy change(-△S_(M))originates from the sample undergoing a ferromagnetic(FM)to paramagnetic(PM)transition around 20 K.Under a field change from 0 T to 7 T,the value of maximum magnetic entropy change(-△S_(M)^(max))reaches 12.5 J/kg·K,and the corresponding value of RC reaches 487.7 J/kg in the temperature range from 6 K to 60 K.The large RC and wide temperature range make the Er_(20)Ho_(20)Dy_(20)Cu_(20)Ni_(20)high-entropy metallic glass be a promising material for application in magnetic refrigerators.

Development of 400-μW cryogen-free dilution refrigerators for quantum experiments

We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 m K, with a minimum temperature of 7.6 m K and a cooling power of 450 μW at 100 m K. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.

Optimization performance of quantum endoreversible Otto machines with dual-squeezed reservoirs

We consider a quantum endoreversible Otto engine cycle and its inverse operation-Otto refrigeration cycle,employing two-level systems as the working substance and operating in dual-squeezed reservoirs.We demonstrate that the efficiency of heat engines at maximum work output and the coefficient of performance for refrigerators at the maximum c criterion will degenerate toη-=η_(C)/(2-η_(C))andε-=(√9+8ε_(C)-3)/2 when symmetric squeezing is satisfied,respectively.We also investigated the influences of squeezing degree on the performance optimization of quantum Otto heat engines at the maximum work output and refrigerators at the maximum X criterion.These analytical results show that the efficiency of heat engines at maximum work output and the coefficient of performance for refrigerators at the maximum X criterion can be improved,reduced or even inhibited in asymmetric squeezing.Furthermore,we also find that the efficiency of quantum Otto heat engines at maximum work output is lower than that obtained from the Otto heat engines based on a single harmonic oscillator system.However,the coefficient of performance of the corresponding refrigerator is higher.

A Review on Technologies for the Use of CO2 as a Working Fluid in Refrigeration and Power Cycles

The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.

Cooling High Power Dissipating Artificial Intelligence (AI) Chips Using Refrigerant

High power dissipating artificial intelligence (AI) chips require significant cooling to operate at maximum performance. Current trends regarding the integration of AI, as well as the power/cooling demands of high-performing server systems pose an immense thermal challenge for cooling. The use of refrigerants as a direct-to-chip cooling method is investigated as a potential cooling solution for cooling AI chips. Using a vapor compression refrigeration system (VCRS), the coolant temperature will be sub-ambient thereby increasing the total cooling capacity. Coupled with the implementation of a direct-to-chip boiler, using refrigerants to cool AI server systems can materialize as a potential solution for current AI server cooling demands. In this study, a comparison of 8 different refrigerants: R-134a, R-153a, R-717, R-508B, R-22, R-12, R-410a, and R-1234yf is analyzed for optimal performance. A control theoretical VCRS model is created to assess variable refrigerants under the same operational conditions. From this model, the coefficient of performance (COP), required mass flow rate of refrigerant, work required by the compressor, and overall heat transfer coefficient is determined for all 8 refrigerants. Lastly, a comprehensive analysis is provided to determine the most optimal refrigerants for cooling applications. R-717, commonly known as Ammonia, was found to have the highest COP value thus proving to be the optimal refrigerant for cooling AI chips and high-performing server applications.

Effect of konjac glucomannan and chitosan-based film coatings on the quality of fresh sea bass(Lateolabrax maculatus)under refrigerated condition

Sea bass(Lateolabrax maculatus)is one of the important seafood in China.Its shelf-life under refrigerated storage exponentially deteriorate due to the growth of spoilage microorganisms,protein degradation and lipid oxidation.In this study,4 coating materials namely,konjac glucomannan-whey protein isolate(KGM-WPI)film,chitosan-sweet potato starch(CHI-SPS)film,chitosan-bamboo fungus(CHI-BF)film,and chitosan-boehmite alumina(CHI-BAH)have been explored to enhance the shelf life of sea bass during 8 days of refrigerated storage.Overall,CHI-BF was observed to be best in retaining hardness,gumminess and maintaining total volatile basic nitrogen value.Whereas CHI-SPS was found to retain chewiness and maintain lower values for drip loss and peroxide value.CHI-BAH coating was observed to maintain the lower values for pH and EC values of sea bass under refrigerated storage.However,the least increase in total viable count and minimum change in b^(*)value was observed in the case of sea bass coated with KGM-WPI.The current research fi ndings provide a new practical storage method for the entire fresh fish.The fresh fish can be coated with different coating materials and store on the ice at 4℃without packaging during retailing.These film coated whole fresh fish retains its microbial and sensory quality.

Refrigerated and frozen storage impact aronia berry quality

Postharvest storage of many freshly picked berries affects polyphenol and sugar content. However, little is known about the impact of refrigerated and frozen storage on aronia berry composition. Therefore, the objective of this study was to characterize how storage at 4 ± 2 °C and − 20 ± 2 °C, and temperature cycles affect aronia berry polyphenols, total solid content, pH, titratable acidity, polyphenol oxidase (PPO) activity, sugar content, acid content, color, and cell structure. Refrigerated storage reduced proanthocyanidins (21%), anthocyanins (36%), and total phenols (21%) after 12 weeks. Frozen storage increased polyphenols in the first 6 mo. of frozen storage but then decreased polyphenols at mo. 8 to levels similar to initial values. Frozen temperature cycling reduced anthocyanins 18% but did not affect total phenols or proanthocyanidins. Scanning electron microscopy analysis indicated temperature cycling induced cell damage, shrinking, and fusion. This disruption led to the release of anthocyanins inside the berry tissue. PPO activity did not significantly correlate with the decrease in polyphenol content during storage. °Brix did not significantly change during refrigeration and frozen storage but did during the 12th temperature cycle. Aronia berries’ pH and titratable acidity were affected more by refrigeration than frozen and temperature storage. The pH increased by 4% during refrigeration, and titratable acidity decreased by 17% at 12 weeks. In conclusion, refrigerated storage results in a modest reduction of aronia berry polyphenols, but absolute extractable polyphenols are stable for up to 8 months of frozen storage.

Magnetocaloric properties of phenolic resin bonded La(Fe,Si)13-based plates and its use in a hybrid magnetic refrigerator

We present a simple hot press-based method for processing La(Fe,Si)13-based compounds consisting of La–Fe–Co–Si–C particles and phenolic resin. The magnetic entropy change △S per unit mass for the La Fe_(10.87)Co_(0.63)Si_(1.5)C_(0.2)/phenolic resin compounds have nearly the same magnitude with the base materials. With the content of phenolic resin of 5.0 wt%, the compound conductivity is 3.13 W·m^(-1)·K^(-1). In order to measure the cooling performance of La(Fe,Si)13-based compounds,the La(Fe_(11.6-x)Co_(x))Si_(1.4)C_(0.15)(x =0.60, 0.65, 0.75, 0.80, 0.85)/phenolic resin compounds were pressed into thin plates and tested in a hybrid refrigerator that combines the active magnetic refrigeration effect with the Stirling cycle refrigeration effect. The test results showed that a maximum cooling power of 41 W was achieved over a temperature span of 30 K.

Effect of Refrigerant on the Performance of a C3/MRC Liquefaction Process

The Mixed Refrigerant(MR)component is an important factor influencing the performances of natural gas lique-faction processes.However,there is a lack of systematic research about the utilization of propane pre-cooled(C3/MRC).In this paper,this mixed refrigerant cycle liquefaction process is simulated using the HYSYS software and the main influential parameters involved in the process are varied to analyze their influence on the liquefaction rate and power consumption.The results show that an effective way for lowering the power consumption of the compressor consists of reducing the flow through the compressor through optimization of the percentage of mixed refrigerant.The power consumption of the compressor in the hybrid refrigeration process is affected by both flow and pressure ratios.Its specific power consumption can be reduced by increasing the flow and decreasing the pressure ratio at the same time.The increase in refrigerant pressure at the high-pressure end can significantly mitigate the energy loss of the heat exchanger and compressor.

A Systematic Review of Thermoelectric Peltier Devices: Applications and Limitations

Conventional refrigeration processes release ammonia and freon into the atmosphere,which results in global warming.These problems may be overcome by using thermoelectric modules because of the absence of coolants or refrigerants in these systems.However,the cooling performances of such modules are relatively small in comparison to those of conventional refrigerators.In this paper,the working principles of thermoelectric modules are discussed together with a review of different relevant aspects,namely:the thermoelectric materials,and their mechanical properties used to build thermoelectric devices,different types of thermoelectric devices available on the market,mathematical modeling of thermoelectric materials,and various applications of thermoelectric materials in different fields.

Effect of an Internal Heat Exchanger on the Performances of a Double Evaporator Ejector Refrigeration Cycle

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.

Structure, magnetism and magnetocaloric effects in Er_(5)Si_(3)B_(x)(x=0.3,0.6) compounds

We investigate the structure, magnetic properties, magnetic phase transitions and magnetocaloric effects(MCEs) of Er5Si3Bx(x=0.3,0.6) compounds. The Er5Si3Bx(x = 0.3, 0.6) compounds crystalize in a Mn5Si3type hexagonal structure(space group: P63/cm) and exhibit a successive complicated magnetic phase transition. The extensive magnetic phase transitions contribute to the broad temperature range of MCEs exhibiting in Er_(5)Si_(3)B_(x)(x=0.3,0.6) compounds, with maximum magnetic entropy change(-ΔSM_(max)) and refrigeration capacity of 10.2 J·kg^(-1)·K^(-1), 356.3 J/kg and 11.5 J·kg^(-1)·K^(-1),393.3 J/kg under varying magnetic fields 0–5 T, respectively. Remarkably, the δTFWHMvalues(the temperature range corresponding to 1/2×|-ΔSM_(max)|) of Er5Si3Bx(x=0.3,0.6) compounds were up to 41.8 K and 39.6 K, respectively. Thus, the present work provides a potential magnetic refrigeration material with a broad temperature range MCEs for applications in cryogenic magnetic refrigerators.

Performance optimization on finite-time quantum Carnot engines and refrigerators based on spin-1/2 systems driven by a squeezed reservoir

We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation-Carnot refrigeration cycle,employing a spin-1/2 system as the working substance.The thermal machine is alternatively driven by a hot boson bath of inverse temperatureβ_(h)and a cold boson bath at inverse temperatureβ_(c)(>βh).While for the engine model the hot bath is constructed to be squeezed,in the refrigeration cycle the cold bath is established to be squeezed,with squeezing parameter r.We obtain the analytical expressions for both efficiency and power in heat engines and for coefficient of performance and cooling rate in refrigerators.We find that,in the high-temperature limit,the efficiency at maximum power is bounded by the analytical valueη_(+)=√sech(2r)(1-η_(C)),and the coefficient of performance at the maximum figure of merit is limited byε_(+)=√sech(2r)(1+ε_(C))/sech(2r)(1+ε_(C))-εC)-1,whereη_(C)=1-β_(h)/β_(c)andε_(C)=β_(h)/(β_(c)-β_(h))are the respective Carnot values of the engines and refrigerators.These analytical results are identical to those obtained from the Carnot engines based on harmonic systems,indicating that the efficiency at maximum power and coefficient at maximum figure of merit are independent of the working substance.

Analysis of a Water-Cooled Unit under Different Loads

In order to ensure the safe operation of the compressors used in water chillers,in the present study some interlock protections have been added to the related design.These include a low pressure protection,a high pressure protection,an exhaust temperature protection and a differential pressure protection.Some tests have been conducted by tuning the saturation suction and exhaust temperatures of the compressor through adjustment of the cold source outlet temperature and the ambient temperature.The results show that the ambient temperature increases with decreasing device load and increasing fan speed under the same saturated suction temperature;the device refrigerating capacity steps up with augmenting load and dropping saturation exhaust temperature,while it is not greatly affected by the fan speed.Moreover,the Energy efficiency ratio(COP)decreases with the rise of the saturation exhaust temperature.This parameter is not affected much by the device load and fan speed at high saturation exhaust temperature,while it improves on increasing the device load and decreasing the fan speed at low saturation exhaust temperature.

Performance Analysis of a Solar Continuous Adsorption Refrigeration System

A study is conducted on the performances of a solar powered continuous-adsorption refrigerator considering two particular days as references cases,namely,the summer solstice(June 21st)and the autumn equinox(September 21st).The cooling capacity,system performance coefficient and the daily rate of available cooling energy are assessed.The main goal is to compare the performances of a solar adsorption chiller equipped with a hot water tank(HWT)with an equivalent system relying on solar collectors with no heat storage module.The daily cooling rates for the solar refrigerator are found to be 102.4 kWh and 74.3 kWh,respectively,on June 21st and on September 21st,using a total collector’s area of 43.47 m2.The corresponding values for the adsorption chiller equipped with a hot water tank of 2 m3(and using a total collector’s area of 72.45 m2),are 127.1 kWh and 106.13 kWh,respectively.