Commercial Freezers Research Articles

Effects of the precooling process on the preservation of fresh‐cut durian

AbstractThe export of fresh‐cut durians has increased steadily. However, the shelf life of durians remains limited. The shelf life can be extended by decreasing the temperature of durian. Although the optimal temperature for storing fresh‐cut durians has been examined previously, few studies have addressed the efficiency of cooling systems. This study aimed to determine the parameters that affected the forced‐air precooling of 15 kg of fresh Monthong durians to 7°C, taking into account room temperature conditions of 6, 3.5, and 1°C. Experiments showed that the highest performance was attained with a precooling temperature of 1°C, which reduced the pulp temperature from 29 to 7°C in 266 min while using .83 kWh. After a 6‐h precooling time, the pulp maintained its firmness, color, and TSS, although its weight dropped by 2.30%. The pulp met the quality standards and exhibited only minor changes compared to fresh durians.Practical applicationAs a major exporter of fresh‐cut durians, Thailand faces the challenge of meeting growing demand while ensuring efficient precooling and product quality. Although small and medium‐sized businesses commonly use commercial freezers for durian chilling, the impact on quality remains uncertain. Precooling, which rapidly lowers the temperature before storage or shipment, is essential for maintaining cold chain efficiency. However, research on the effects of precooling specifically for fresh‐cut durians remain limited. This investigation aims to fill the gap in knowledge by studying the preservation effects of precooling at different temperatures (6, 3.5, and 1°C) and placements. The findings could greatly benefit small and medium‐sized enterprises by improving their ability to precool fresh‐cut durians using commercial refrigerators. This, in turn, can enhance the export value of durians and boost Thailand's agriculture revenue. By optimizing precooling efficiency and product quality preservation, Thailand can strengthen its position as a leading exporter of fresh‐cut durians.

Effect of oscillating magnetic fields on freezing of a colloidal dispersion of superparamagnetic nanoparticles

Several studies suggest that single-domain biogenic magnetic nanoparticles could play a major role on the effectiveness of oscillating magnetic fields (OMFs) in improving food freezing. To evaluate the potential role of superparamagnetic biogenic particles, we performed freezing experiments in a colloidal dispersion of <10-nm maghemite nanoparticles (MNPs) subjected or not to a 31.3-mT OMF at 50 Hz. Our results show that, at our experimental conditions, Néel mechanism governs the alignment of magnetic dipole moments and, therefore, no significant MNPs rotation, able to disturb the ordering of water molecules, should be expected during OMF experiments. Accordingly, no effects of the applied OMF were observed either on supercooling, ice nucleation, or on freezing kinetics even though heat removal was slightly increased during the precooling step. These results suggest that weak OMFs usually applied in commercial freezers should not produce any significant effect on superparamagnetic nanoparticles present in food that could improve the freezing process.

Energy reduction for commercial freezer by force convection cooling of heatsink

Commercial freezers are commonly used the outer wall as a heatsink. This heatsink needs surrounded ambient air for cooling, which is the natural convection mechanism. However, in theory the force convection provides more heat transfer than the natural convection. Therefore, energy consumption of the force convection is generally less than the natural convection. This study aims at testing and comparing the heat transfer between the natural convection and force convection of the heatsink of the commercial freezer. Moreover, this study investigated the potential of energy reduction of the freezer by using the natural convection and the force convection of the heatsink. In this study, the unmodified commercial freezer installed with the wind tunnel over the heatsink of the freezer was made. The necessary parameters such as heatsink surface temperature, cooling air temperature, ambient air temperature, velocity of cooling air, and power consumption of the freezer were collected. The testing conditions were varied the internal heat load of the freezer by using water as 0, 3, and 6 kg, and varied the cooling air velocity as 0, 1, 2, and 3 m/s. The results showed that the convection mechanism was significantly affected by energy consumption. Furthermore, it was clearly found that the heat transfer for the force convection was higher than the natural convection. Moreover, the use of force convection resulted in a lower energy consumption. In particular at the internal heat load of 6 kg, the energy consumption of the force convection decreased by 17.5%, 17.7%, and 20.5% as compared to the natural convection at the cooling air velocity of 1, 2, and 3 m/s, respectively. Based on the results obtained it can be concluded that the force convection for the freezer heatsink can be used to reduce energy consumption, which could be efficiently applied in the future works.

Heterogeneous hybrid extreme learning machine for temperature sensor accuracy improvement

High-accuracy temperature sensors usually come at a high cost, making them cost-ineffective solutions for mass-produced commercial products. The overall product cost can be one of the decisive factors for its success (e.g., commercial freezers). On the other hand, low-cost temperature sensors are viable options, but they suffer from accuracy issues. This paper presents a system aimed at improving the accuracy of a low-cost temperature sensor using a hybrid machine learning algorithm. The system utilizes a low-cost single-board computer connected to a series of sensors to collect data. These data are then used as an input vector to the proposed linear regression heterogeneous hybrid extreme learning machine (LR-HE-HyELM), a supervised learning algorithm responsible for increasing the sensors’ accuracy. The proposed linear regression heterogeneous extreme learning machine (LR-HE-HyELM) combines linear regression with the self-adaptive heterogeneous hybrid extreme learning machine (SA-He-HyELM) algorithm. SA-He-HyELM is an extreme learning machine (ELM) based algorithm that utilizes a genetic algorithm (GA) for the creation of an optimized single-layer neural network (SLNN) having different combinations of custom-created neurons at its hidden layer. The proposed training algorithm has all the advantages of SA-He-HyELM. These advantages include utilizing low-order and higher-order neurons in the same network while retaining ELM’s simplicity by making all GA parameters self-adaptive. The utilization of low-order and higher-order unit types in the same network resulted in optimized neural networks with better generalization ability than those with the same neuron types in their hidden layer. The creation of SA-He-HyELM was nature-inspired since the human brain contains different neuron types. The proposed system is tested with eight existing methods, with most of them having different neuron types in the hidden layer. The experimental results involved using a custom-created regression dataset having measurements taken from a commercial fridge. The proposed method managed to get the lowest mean square error (MSE) compared to the other eight methods.

Senators strike deal for US phasedown of HFCs

Breaking a legislative deadlock that has extended through most of this year, key senators announced a deal for the US to phase down hydrofluorocarbon (HFC) production over the next 25 years. HFCs are refrigerants used in air conditioners and commercial freezers, among other applications. Chemical makers introduced them as replacements for stratospheric ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) . HFCs are potent greenhouse gases, and emissions of these chemicals are increasing worldwide. Sens. Tom Carper (D-DE) and John Kennedy (R-LA) an HFC phasedown. They ran into opposition from Sen. John Barrasso (R-WY), chairman of the Senate Environment and Public Works Committee, and other Republicans who raised concerns about possible adverse impacts on consumers and small businesses. In , Barrasso, Carper, and Kennedy agreed to HFC language that will be tacked onto that could progress in Congress in coming weeks. As Carper and Kennedy sought, the deal would require the US

US Congress considering HFC controls

Legislation to phase down—but not halt—US production of hydrofluorocarbons (HFCs) is gaining steam in Congress. H.R. 5544 in the House of Representatives and its Senate companion bill, S. 2754, have bipartisan support. Used as refrigerants in applications from air conditioners to commercial freezers, HFCs are potent greenhouse gases that have been widely used as substitutes for ozone-depleting chemicals such as chlorofluorocarbons (CFCs). HFC emissions are increasing. The House and Senate bills hew closely to provisions in the 1990 Clean Air Act Amendments that led the US to phase out production of ozone-depleting chemicals. The legislation would mandate the Environmental Protection Agency to create a system of allowances for HFC manufacture or import that companies could buy and sell. US production would phase down over 15 years, stopping at 15% of current production in 2036. If enacted, the legislation would boost the market for hydrofluoroolefins, a new generation of refrigerants. Currently

Assessment of Heterotrophic Bacterial Count (HPC) Associated with Commercial Freezers in Yenagoa Metropolis

Microorganism are known to be present anywhere they can proliferate, its presence dictates it pathogenicity or otherwise. The study was embarked to assess the enteric bacterial quality and potential risk of water at the bottom of selected commercial freezers in Yenagoa metropolis. Serial dilution was adopted for the assessment of Heterotrophic bacterial count (HPC). From the analysis, bacterial count ranged between 1.083±0.104×107cfu/mL and 2.0 ± 0.358×107cfu/mL. the highest was in sample 4 (S4) and least in sample 10 (S10), the study thus found the presence of heterotrophic bacteria in all samples. This research reveals that freezers S5, S3, S4 and S8 were seriously contaminated, having mean viable bacterial load of 2.47×107cfu/mL, 2.18×107cfu/mL, 2.00×107 cfu/mL and 2.00×107 cfu/mL, respectively; while freezer S1, S2, S6, S7, S9 and S10 had variably viable bacteria count, the occurrence of heterotrophic bacteria count (HPC) between sampled freezers was statistically very significant (P0.05, 0.01). Bacteria cells using morphological and biochemical characterization identified in the study include Escherichia coli (29.4%), which was the most frequently occurring organism, followed by Citrobacter spp (14.7%), Klebsella pneumonia (14.7%), Shigella spp (11.8%), Pseudomonas aeruginosa (11.8%), Yersinia spp (8.8%) and Campylobacter jejuni (8.8%). E coli were the most frequently isolated bacteria. E. coli and other Eneteric bacteria isolated from freezers are an indication that food items and water stored in these freezers are not safe from public health stand point. Susceptibility of isolates to antibiotics reveals 8(23.5%) were resistant and 26 (76.5%) were susceptible out of 34 cells identified. High resistance was seen in Klebsiella spp which had 2 (60%) and 100% susceptibility was seen among Citrobacter spp and Yersinia spp, on the other hand other isolate had varying drug resistant patterns. The importance of temperature control and regular efficient cleaning regimes need to be communicated to the public so that, effectual management and cleaning of freezers makes frozen food reliable and less likely to act as significant sources of human food and water borne diseases.

Experimental study on the selection of phase change materials for low temperature applications

Storage and transport of temperature sensitive products have become an important issue worldwide. The enhancement of thermal performance of cold application is under investigation and implementing thermal energy storage (TES) systems by using phase change materials (PCM) is one of the solutions to better storage. Hence, the selection of the suitable PCM for each specific application is an important matter. In this paper, a TES system using PCM for low temperature applications such as commercial freezers is studied. A set of PCM formulations based on ammonium chloride – water binary system were tested and analyzed to provide information useful for the selection of PCM with regards to their melting range, latent heat, stability under cycling, and cost. Thermal cycling was conducted to determine the thermal reliability of the PCM and the thermal properties were determined using differential scanning calorimetry (DSC) analysis.

Improving thermal performance of freezers using phase change materials

Food transport and storage at low temperatures is a matter worldwide due to changes of the dietary habits and the increasing of the population. The issue of improving food storage applies at different applications such as commercial freezers or refrigerated trucks. The aim of this work is to improve the thermal performance of commercial freezers using phase change materials (PCMs) under door openings and electrical power failure. A commercial PCM was selected (Climsel-18) with a melting temperature of −18 °C, which is contained in 10 mm thick stainless steel panels placed at different locations in the freezer. During 3 h of electrical power failure, the use of PCM maintained the freezer temperature 4–6 °C lower and that of the frozen products remains at acceptable levels for much longer time. With frequent door openings the benefit of the PCM is evident when the temperature of the cabinet is near the melting temperature of the PCM.

SEASONAL VARIATIONS IN CELL MEMBRANE PROPERTIES AND LONG-TERM QUALITY PRESERVATION OF SEMI-DRY 'MEDJOOL' DATE FRUIT

Semi-dry 'Medjool' date (Phoenix dactylifera L.) fruit (24-26% water content) has a prime economical value to the date industry in the Israeli southern Arava Valley. Excess fruit is customarily stored at -18°C for long periods with subsequent considerable damages to appearance. We have previously reported that long-term quality preservation of semi-dry 'Medjool' dates related to the level of fruit cell membrane integrity. The present study further explored the fruit cell membrane degradation process and the effects of seasonal variations on membrane integrity and fruit storage potential. High quality fruit were selected for cell membrane analysis and long-term storage studies. Cell membranes were isolated and the levels of total protein, lipid and phospholipid and of vanadate-sensitive ATPase activity were determined. Exposure of the fruit to -6 or -35°C for different periods of time confirmed the temperature dependence of membrane degradation rate. The development and extent of appearance damages paralleled membrane deterioration. Semi-dry 'Medjool' date fruit were collected on several dates along the harvest season. The levels of cell membrane constituents and activity were higher in fruit collected on early dates and declined with the progression in harvest season. Fruit storage potential was tested by placing the fruit in commercial freezers of -18 or -25°C and assessing fruit quality after a 9-months storage and a 3-weeks shelf life period. The quality of fruit harvested early in the season was maintained after storage at either -18 or -25°C, whereas, quality preservation in fruit collected late in the season was only achieved when stored at -25°C. The current study further establishes the role of fruit cell membrane integrity in quality preservation of semi-dry 'Medjool' date fruit during storage. The results suggest that the costs of quality preservation of semi-dry 'Medjool' dates can be reduced by adjusting long-term storage conducts to the physiological state of the fruit.

The effect of sub-zero temperatures on different lifestages of Lasioderma serricorne (F.) and Ephestia elutella (Hübner)

The effect of sub-zero temperatures on different lifestages of Lasioderma serricorne and Ephestia elutella was investigated as a means of disinfesting stored tobacco. Eggs, unacclimated cocoons and acclimated cocoons of L. serricorne were exposed to −10 °C, −15 °C and −20 °C in insulated boxes. There was no adult emergence from eggs or unacclimated cocoons following exposure to the respective temperatures for 4 h, 2 h and 1 h. With acclimated cocoons there was no adult emergence after 2 h at −15 °C and 1 h at −20 °C, but at −10 °C, there was adult emergence after 8, 12 and 24 h exposures. In field-scale experiments, cold acclimated fourth-instar larvae of L. serricorne were inserted into cases of leaf tobacco and boxes of finished product, put into commercial freezers and exposed to minimum temperatures of −10 °C, −18 °C or −25 °C. Critical temperatures were measured at the core of the commodity. No adults emerged from the commodity when exposed to at least −18 °C for periods ranging between 3.75 h and 39.25 h or when exposed to at least −25 °C for between 2.4 h and 3.7 h. At a minimum of −10 °C, 3 live adults emerged after 24 h exposure. With E. elutella, diapausing larvae were inserted into small scale tobacco bales and exposed to −10 °C, −13 °C, −15 °C or −20 °C. No emergence of adults and no larval survival was achieved after 21 d, 3 d and 2 h exposure at −10 °C, −15 °C and −20 °C respectively. At −13 °C, there was no adult emergence after 2 and 5 d exposure, but live larvae remained after 24 weeks incubation at 25 °C. Minimum conditions of −18 °C for 24 h and −25 °C for 4 h are recommended for the control of L. serricorne and −20 °C for 24 h for the control of E. elutella in stored tobacco (to fit with operational logistics).

Survival of Indianmeal Moth and Navel Orangeworm (Lepidoptera: Pyralidae) at Low Temperatures

Concerns over insect resistance, regulatory action, and the needs of organic processors have generated renewed interest in developing nonchemical alternative postharvest treatments to fumigants used on dried fruits and nuts. Low-temperature storage has been identified as one alternative for the Indianmeal moth, Plodia interpunctella (Hiibner), and navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), common postharvest pests in California dried fruits and nuts. The response of eggs, nondiapausing larvae, and pupae of both species to exposure to low temperatures (0, 5, and 10 degrees C) was evaluated. Eggs of both species were the least tolerant of low temperatures. At 0 and 5 degrees C, pupae were most tolerant, but at 10 degrees C, nondiapausing larvae of both species were most tolerant, with lethal time (LT)95 values of 127 and 100 d for Indianmeal moth and navel orangeworm, respectively. The response of diapausing Indianmeal moth larvae to subfreezing temperatures also was evaluated. Diapausing larvae were very cold tolerant at -10 degrees C, with LT95 values of 20 and 17 d for long-term laboratory and recently isolated cultures, respectively. Diapausing larvae were far less tolerant at lower temperatures. At -15 degrees C, LT95 values for both cultures were <23 h, and at -20 degrees C, LT95 values were <7 h. Refrigeration temperatures of 0-5 degrees C should be useful in disinfesting product contaminated with nondiapausing insects, with storage times of 3 wk needed for adequate control. Relatively brief storage in commercial freezers, provided that the temperature throughout the product was below -15 degrees C for at least 48 h, also shows potential as a disinfestation treatment, and it is necessary when diapausing Indianmeal moth larvae are present.

Computer Controlled Portable Frost Simulator for Field Studies of Frost Effects on Wild Blueberries

Two commercial freezers were modified to provide an inexpensive chamber system to investigate frost effects on wild, lowbush blueberries (Vaccinium angustifolium) under field conditions. A computer control system was developed with software written in Visual Basic 6.0 for MSWindows, which precisely controlled temperature in the plant canopy when the chambers were placed over blueberry plants in the field. Frost events (with temperatures ranging from -2 to -15 °C (28.4 to 5.0 °F)) were simulated by user input to control the cooling and warming rates, and minimum temperatures. The system records temperature set points, and current temperature in the plant canopy, or elsewhere in the plant environment, and provides a graphical display of key parameters. Trials have verified the reproducability of temperature profiles and the chambers have been used to provide preliminary information on the effects of frost at bloom on fruit set and development.

On the Applicability of a Plug Flow Immersion Freezer: Theoretical Considerations

The most promising means of fast-freezing is the immersion of the product in a liquid of appropriately low temperature. The direct contact of a product with low temperature freezing mediums can, however, cause several problems, the most usual being the burning of its surface or even its rupture, due to the thermal shock it undergoes. It is possible to overcome these problems with the application of a plug flow immersion freezer. The aim of this paper is to investigate the applicability of a plug flow immersion freezer on a theoretical basis. For this purpose, a theoretical model was developed and tested for the freezing of squid. The results of this model indicate that the use of the proposed freezer is quite attractive for products of small thicknesses, up to 1 cm. A rather high value of the heat transfer coefficient can be achieved, while it is possible to set the temperature range of the freezing medium between −10 and −30°C, significantly higher than the ones found in most commercial freezers.

DONOR BLOOD FROZEN AND STORED BETWEEN -20°C AND -25°C WITH 35-DAY POST-THAW SHELF LIFE

With standard blood bank facilities and interconnected plastic bags donor erythrocytes can be frozen and stored in commercial freezers at temperatures of -20° to - 25°C for at least 6 months. The cryoprotectant, a mixture of glycerol and dextrose, is washed off in a closed-circuit system. After being thawed and reconstituted with an additive solution, the pack of red cells can be stored in liquid form for up to 35 days at 4°-6°C. The system lends itself to routine clinical blood transfusion practice.

The Use of Redesigned and Mechanically Modified Commercial Freezers to Dry Waterwetted Books and Exterminate Insects

Comment modifier un congelateur ordinaire et l'utiliser pour eliminer les insectes et secher les levres mouilles

A low cost program device for automatic control of laboratory refrigerators

Summary A flexible, yet precise, automatic control system has been adapted for use with one or more commercial freezers. The system permits rapid or gradual fluctuations in temperature over a 60°C range. Temperatures as low as −120°C can be programmed if the freezing unit has adequate capacity. The system operates on a modified Wheatstone bridge which includes a series of preselected resistors corresponding to desired temperatures and a Pt resistance thermometer located in the freezer. When the temperature in the freezer differs from the programmed temperature the bridge circuit becomes imbalanced. The resulting signal is relayed through a control unit which switches the freezer on and off. Programming, construction, and performance of the system are discussed. Results from an experiment are presented to illustrate the system's performance as well as some of the problems encountered with test material of varying size and water content. Variation in the heat exchange capacity of samples can be compensated for by making preliminary tests. The reliability of the system has been demonstrated over a 3-year period, representing 15,000 hrs of operation. Based upon this experience, we can recommend the application of this system to a wide variety of cryobiological investigations.

Studies on the Quality of Newfoundland Cod. 10. Effect of Some Commercial Freezing Rates on the Frozen and Stored Quality of Trap Cod

Time–temperature curves are reported for points at the centre, one-quarter depth, and at the surface of blocks of dressed cod, and blocks and packages of cod fillets, frozen in commercial plate freezers. Freezing rates at the centres varied by a factor of about 4 where thickness of the pack was the only variable. The same factor applied to the fastest- and slowest-frozen fish in [Formula: see text]-inch-thick blocks. Using a special arrangement, dressed trap-caught cod and cod fillets were then frozen, some at the fast rate and some at the slow rates normally encountered at the centre of [Formula: see text]- and [Formula: see text]-inch-thick commercial packs, respectively (0.7 and 2.7 hr through the temperature range of 32 to 5°F (0 to −15 °C)). The frozen and stored (at −10°F) samples were of similar quality for periods up to 22 weeks, based on taste panel assessment.

The Relation of Refrigerated Lockers to Conservation of Fishery Products

Abstract The use of refrigerated lockers by the housewife as a method of preservation of foods has recently become of considerable importance, and hundreds of such locker plants are now available. The use of such facilities for storage of fish can be of benefit to the sports fisherman to preserve his catch, to the frugal housewife in putting up a supply of fish when there is a surplus and prices are low, and to the commercial fishery industry as a means of distributing frozen fish in small communities where large commercial cold storage plants are not located. As is the case in the commercial cold storage of fish, considerable care must be taken in provision of adequate storage methods for fishery products which are to be stored in refrigerated lockers in order to prevent development of such undesirable changes as freezer burn, rancidity, and discoloration of the products. Methods which are satisfactory for use in commercial freezers may not be suitable for use by the refrigerated locker patron. Freezing ...