ELECTRIC AND MAGNETIC FIELD-BASED SUPERCOOLING TECHNOLOGY TO ENSURE THE FRESHNESS IN THE FOOD SUPPLY CHAIN

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: AFRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 1024331
• Grant No.: 2021-67017-33338
• Cumulative Award Amt.: $481,960.00
• Proposal No.: 2020-03932
• Project Start Date: Jan 1, 2021
• Project End Date: Dec 31, 2024
• Grant Year: 2021
• Program Code: [A1364]- Novel Foods and Innovative Manufacturing Technologies

Recipient Organization
UNIV OF HAWAII
3190 MAILE WAY
HONOLULU,HI 96822

Performing Department
Human Nutri, Food & Anim Sci

Non Technical Summary
As the global population continues to rise, the ability to produce and maintain the quality of food has become an ever-increasing crucial issue that many animal scientists, agriculturists, and food scientists face. With all the resources allocated to the production and quality control of food, it is necessary to curtail the amount of food that is wasted. It is estimated that American households discard 211 kg of food waste per year, the majority of which are perishable foods, such as meats, which are often lost due to poor storage conditions. Another study claims that 10% of the food within American households is wasted annually, costing approximately $390 per capita; which translates nationally to a value of $165.6 billion in waste annually. In the USA, as well as other developed countries, minimizing food waste is one of the primary goals in achieving food security, and is of utmost importance. In particular, fish is one of the most perishable aquatic foods since it is easily bacteria spoiled and very tend to oxidation. Therefore, fish has a shelf life of only up to 4 days when stored in a typical refrigerator. The team has developed a proprietary supercooling technology that preserves perishable materials at below-freezing temperatures without formation of ice crystals using electric and magnetic fields. Since water in food is diamagnetic and also consists of dipole molecules which tend to realign and re-orientate, the applied electric and magnetic fields directly act upon water to prevent ice nucleation and promote supercooling during the freezing process. Supercooled foods can be maintained in their natural state for weeks with the same freshness factors they had before being supercooled. However, the current invention has technical and scalability limits in terms of sample and storage sizes because the electric field electrodes need direct contact with food materials. Therefore, the proposed project is intedned to develop and validate a radio frequency-based alternating electric field (AEF) wave having non-contact electrode units in conjunction with oscillating magnetic field (OMF) to preserve fresh food materials in larger scales. The proposed research work plan includes (1) design and optimization of the scaled-up supercooling device for the preservation of perishable foods such as sashimi grade fish fillets, (2) validation of the quality factors associated with the mid- and long-term supercooling process, and (3) implementation of the proposed supercooling technology for model food supply chain. Supercooling is expected to pose a great potential to add value to communities and businesses throughout the supply chain by extending the fresh quality of food and minimizing wastes.

Animal Health Component

40%

Research Effort Categories

Basic

20%

Applied

40%

Developmental

40%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
501	5010	2020	100%

Knowledge Area
501 - New and Improved Food Processing Technologies;

Subject Of Investigation
5010 - Food;

Field Of Science
2020 - Engineering;

Keywords

food supply chain

perishable

scale up

shelf life

subzero preservation

supercooling

Goals / Objectives
Objective 1. Design and optimize the proposed scaled-up supercooling device for the preservation of perishable foods such as fish. The task activities will include fabrication of a new high voltage AEF generator/electrode units, OMF module, and the development of the mathematical model of the supercooling device in terms of field distribution and thermodynamics.Objective 2. Test and validate the quality factors associated with the mid- and long-term supercooling process. The task activities will include validation of the newly designed and upscaled unit and test for freshness factors.Objective 3. Implement and validate the proposed supercooling technology for the model food supply chain. The task includes tests and reworks of the supercooling storage when exposed to adverse environmental factors such as temperature fluctuations and physical vibrations.

Project Methods
Task 1: Develop and optimize a scaled-up unit for food supercoolingController: The existing control unit's system level design has been broken into individual sub-system components isolated onto their own PCB boards. The existing PEF power supply and insulated-gate-bipolar-transistor (IGBT) board will be replaced with a new AEF module with the AC voltage having a frequency of the RF band as below.AEF wave in the RF region: The AEF wave generator in a frequency range of RF bands will be developed and implemented to exploit water dipole rotation within food matrices. The equipment deployed for the AEF function will consist of two fundamental components: a high voltage RF generator and applicators (electrode units). The food product to be supercooled is placed between a pair of electrodes, and an RF generator creates the AEF wave between the two electrodes.OMF system: Current system designs employ the use of Hiperco-50 as a ferric core material, an expensive alloy specifically engineered to amplify the magnetic field strength within electromagnets. For proof of concept, the proposed dimension of the scaled-up supercooling chamber will size 300 mm x 300 mm x 200 mm (LxWxH, sample space only). Depending upon the sample quantity and size, the storing space can be either a single or double layer system.Computational simulation: The PI's team will use the finite element software COMSOL Multiphysics (v. 5.5) to compute the numeric solutions for AEF electrode units and OMF electromagnets in engineered configurations and to optimize field emissions on food samples.Task 2: Test for supercooling and scaling up Test and validation of the newly designed and upscaled unit will take into account the suitable environmental and system operating parameters in maintaining large scaled food samples. A chosen sample is fish (local tuna purchased from Tamashiro Market, Honolulu, 1.5 - 2 kg).Sashimi grade tuna will have a wider range of fat contents so that the team can investigate the effect of AEF and OMF-based supercooling on both high fat and low fat fish fillets.The samples will be loaded within the chamber of the developed device and the monitoring of ambient, chamber, and sample temperatures conducted using T-type thermocouples. The experiments will be carried under a variety of cooling conditions, considering ambient temperature, cooling rate, and airflow characteristics to determine operational characteristics and ranges. Operational parameters (field intensity, working frequency, shapes of electrical signal waveforms, and treatment time) of the magnetic and electric fields will be tested and optimized. Quality factors of samples and controls will be analyzed at day 0, 7, 14, and 21 days.Task 3: Quality factor analysisAs key properties of fish samples, the team will test quality via microscopy, texture profile analysis, color analysis, and microbiological examination.1. Physical quality assessmentsHistological analysisThe light microscopic analysis will be conducted in evaluating the microstructure of fresh, refrigerated, supercooled, and frozen-thawed food products. For light microscopy observation, food samples will be sliced into approximately 5 mm thick sections. The sliced samples will be fixed with 4% paraformaldehyde in 0.1 M sodium cacodylate, pH 7.4, and stored in a refrigerator for 48 h. The fixed samples will be dehydrated in a graded ethanol series (30, 50, 70, and 100%) and embedded in paraffin. The food sample block will be sectioned at 10 μm with a microtome (Leica, SM 2000R, Germany) and then stained with hematoxylin and eosin. The images of the stained sections will be taken using a light microscope (Olympus BX 51, Japan) with a digital image capture system with a wide range of magnification.Measurement of thaw drip lossFood samples will be placed on a metallic rack at 3 cm distance from the bottom of a plastic vessel (20×20×10 cm) and closed with a pressure lid. A hole fitting the wire of the thermocouple probe on the vessel lid will allow connection to the temperature data logger. The plastic vessel will then be introduced in a thermostatically controlled chamber at 10°C to allow thermal equilibrium within 15 hrs. Drip loss will be measured by weighing the food sample during thawing.Texture profile analysis (TPA)Texture profile analysis will be performed using a Texture Analyzer TA.XT2 (Stable Micro Systems, Surrey, UK), equipped with a load cell of 250 N. Samples will be obtained by cutting out parallelepiped pieces (4.5 x 3 cm). The blade will be pressed into the sample at a constant speed of 0.8 mm s-1 until it reaches 50% of the sample height. Force-distance curves will be processed to obtain seven texture parameters: hardness, cohesiveness, adhesiveness, elasticity, gumminess, chewiness, and resilience.2. Degree of freshnessColor analysisThe color analysis will be carried out using a color meter (ColorTec PCM, Clinton, NJ, USA). The difference between Δa* and Δb* value will also be calculated by comparing the values of the thawed samples to the control.ATP-related compounds and K valueFor fish samples, the ATP-related compounds: adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine-5'-monophosphate (IMP), inosine (Ino), and hypoxanthine (Hx) will be assayed by HPLC with a few modifications. The concentrations of the ATP-related compounds from the HPLC results are used to calculate the K value for the tuna after each treatment.3. Microbiological analysisFood samples with different treatments (refrigerated, frozen-thawed, supercooled, 0 (fresh), 7, 14, & 21 days, 25 g) will be put in a sterile stomacher bag with sterile peptone water (225 mL) and homogenized immediately. After the sample is serially diluted, the number of CFU/g will be determined by the plate count method. Aerobic mesophilic and psychotropic counts will be determined using plate count agar (PCA, pH 7.0; Difco Laboratories, Detroit, MI, USA). In addition, yeasts and molds will also be counted on potato dextrose agar (PDA, pH 3.5; Difco Laboratories, Detroit, MI, USA). All microbiological analysis results will be presented as log CFU/g sample. 4. Sensory AnalysesSensory evaluation (conducted in our departmental Sensory Laboratory, which is connected to our Department of Health-certified kitchen) will identify differences and liking of supercooled vs. controls (fresh and frozen-thawed). Panelists (n=150) will be presented with three samples, each labeled with a unique 3-digit numerical code and asked to identify the sample that is different (triangle test). Following this, panelists will be presented with a second triangle test involving the supercooled sample and the second control. Subjects who correctly respond will be asked to rate the supercooled and two control samples on a 1-9 hedonic scale for flavor, juiciness, and overall liking. Difference and hedonic data will be analyzed via one-tailed (p = 1/3) hypothesis testing and one way ANOVA, respectively.Task 4: Test for model food supply chainTemperature management is a critical function for frozen and chilled food and other perishable food chains, especially when transportation or production cells or boats are involved as temperature changes are often unavoidable.The preliminary test will be performed in Dr. Jun's lab using the open chest freezer, based on (1) a typical cold chain temperature profile with programmed temperature abuse zones vs. (2) the proposed supercooling cold chain coinciding with the end of each step of the cold chain. Frozen control samples will be stored at -18°C for the designated number of hours/days for each step and +10°C for the pre-determined number of hours/days, indicating domestic storage at recommended and abuse temperature conditions, respectively. The model supercooling chain for fish preservation will maintain the temperature around -5°C.

Progress 01/01/21 to 12/31/24

Outputs
Target Audience:1. Food industries including fish and seafood 2. Cold chain, warehouse, and food distributors/retailers 3. Food preservation, commercial appliances, bio preservation, and medicine Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Supercooling technology keeps foods fresh below their freezing points without ice formation, offering promising preservation solutions. However, its thermodynamic instability poses practical challenges. This study investigates the impact of oscillating magnetic fields (OMF) on the stability of supercooled agar gel samples under mechanical and thermal stress conditions. Samples were treated with an OMF of 12 mT at 5 Hz and tested for supercooling stability over 24 hours at - 5.5°C. The OMF-treated samples exhibited a 95% probability of maintaining supercooling, compared to only 10% in untreated controls, based on a sample size of 50 trials. Under mechanical stress, the OMF effectively stabilized samples during moderate orbital vibrations. However, when vertical vibrations exceeded a peak force of 0.6 g, the supercooled state was lost, indicating that specific force thresholds play a critical role in triggering ice nucleation. In thermal stress tests, the supercooled state was maintained regardless of temperature fluctuations, with OMF-treated samples showing consistent resistance to ice nucleation across a range of ΔT values from 2°C to 8°C. The stability of supercooled agar gel samples during simulated transportation was influenced by driving speed and road conditions. The team chose four distinct road conditions, urban roads (A), highways (B), coastal routes (C), and mountainous roads/highways (D), that were analyzed to assess their impact on vibration intensity. Power spectral density (PSD) analysis indicated a relationship between vibration energy distribution and driving speeds. At 40 km/h, the lowest overall PSD values were recorded, indicating minimal mechanical disturbances. At 56 km/h, moderate PSD levels emerged, with energy peaks concentrated at mid-range frequencies. However, at 72 km/h, vibration intensity increased substantially, particularly at frequencies exceeding 0.1 Hz. These effects were further amplified on rougher surfaces, such as the coastal and mountainous routes (C and D), where irregularities in road curvature and surface roughness exacerbated mechanical disturbances.At -4°C, all tested conditions achieved a 100% success rate in maintaining the supercooled state, regardless of road type or speed limit. Route A (urban roads) with a speed limit of 40 km/h showed an average speed of 21.21 ± 1.71 km/h and a highest speed of 45.4 km/h. Routes B and C (highways and coastal routes) at a speed limit of 56 km/h exhibited average speeds of 44.72 ± 2.22 km/h and 37.16 ± 0.78 km/h, respectively, with highest speeds reaching 88.6 km/h and 75.2 km/h. Similarly, At -6°C, all tested conditions achieved a 100% success rate in maintaining the supercooled state, regardless of road type or speed limit. Route D (mountainous highways) with a speed limit of 72 km/h showed an average speed of 52.82 ± 3.41 km/h and a highest speed of 97.4 km/h. These results emphasize that higher average and maximum speeds, combined with road-induced vibrations, significantly influence the stability of the supercooled state, particularly at lower temperatures. These results confirm that all samples remained supercooled under the tested conditions, demonstrating the robustness of the supercooling technology across various vibration and thermal environments. The findings underscore that road-induced vibrations, even at elevated speeds and rougher surfaces, did not compromise the supercooled state within the tested temperature range. Sensory evaluations conducted with 54 panelists showed that supercooled sashimi-grade tuna samples maintained desirable attributes, especially in flavor and texture, for up to 7 days compared to conventional refrigeration. However, after extended storage, preferences shifted toward fresh samples. Statistically significant differences emphasize the comparative benefits of supercooling over refrigeration in preserving sensory quality, particularly in flavor and overall liking. These findings highlight the potential of supercooling as an alternative to both refrigeration and freezing for optimizing food quality during short- to medium-term storage. By effectively slowing down spoilage processes and preserving sensory attributes, supercooling could offer a promising method for extending the shelf life of perishable foods while maintaining consumer satisfaction.

Publications

• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2024 Citation: Lee, D., Tang, J., Lee, S. H., & Jun, S. (2024). Effect of oscillating magnetic fields (OMFs) and pulsed electric fields (PEFs) on supercooling preservation of atlantic salmon (Salmo salar L.) fillets. Foods, 13(16), 2525. [https://doi.org/10.3390/foods13162525]
• Type: Peer Reviewed Journal Articles Status: Published Year Published: 2025 Citation: Joya, A., Lee, D., Kang, T., Wall, M. M., & Jun, S. (2025). Effect of oscillating magnetic field (OMF) on the supercooling behavior of iron?oxide nanoparticle (IONP) agar model system. Journal of Food Science, 90(1), e17653.[https://doi.org/10.1111/1750-3841.17653]
• Type: Other Journal Articles Status: Submitted Year Published: 2025 Citation: Her, J., So, H. & Jun, S. (2024). Extension of the supercooled state within strawberry using the combination of pulsed electric field (PEF) and oscillating magnetic field (OMF).
• Type: Other Journal Articles Status: Awaiting Publication Year Published: 2025 Citation: So, H., & Jun, S. (2024). Application of Oscillating Magnetic Field-Based Supercooling Treatment for Solid Lipid Nanoparticles. Journal of the ASABE.
• Type: Other Journal Articles Status: Submitted Year Published: 2025 Citation: Lee, D., & Jun, S. (2025). Investigating the stability of supercooled states under external stress. Journal of Food Engineering
• Type: Theses/Dissertations Status: Published Year Published: 2024 Citation: Lee, D. (2024). Design, application, and stability of supercooled states in food preserved using engineered electric and magnetic fields. PhD dissertation, Molecular Biosciences and Bioengineering, University of Hawaii.
• Type: Theses/Dissertations Status: Published Year Published: 2023 Citation: Joya, A. (2023). Magnetic Field-Based Supercooling: Cell Viability Enhancement of Freeze-dried Lactobacillus spp. and Inhibitory Ice Nucleation of Iron-Oxide Nanoparticles in an Agar Model System. Master's thesis, University of Hawai'i at Manoa.
• Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Jun, S. (2024). Impact of supercooling storage on physical, chemical, and microbiological properties of fresh fish., FOOMA 2024, June 4-7, Tokyo, Japan
• Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Lee, D., & Jun, S. (2024). Investigating the stability of supercooled states under mechanical stress. CoFE 24, August 24-28, Seattle, WA
• Type: Conference Papers and Presentations Status: Published Year Published: 2024 Citation: Lee, D., & Jun, S. (2024). Effects of Pulsed Electric Field (PEF) and Oscillating Magnetic Field (OMF) on Supercooling Preservation of Salmon. International Association for Food Protection, July 14-17, Los Angeles, CA.
• Type: Other Journal Articles Status: Submitted Year Published: 2025 Citation: Lee, D., Beak, S.H., & Jun, S. (2025). Ensuring stability in supercooled food: a review of physical mechanisms and control approaches. Comprehensive Reviews in Food Science and Food Safety.

Progress 01/01/23 to 12/31/23

Outputs
Target Audience:1. Food industries including fish and seafood 2. Cold chain, warehouse, and food distributors/retailers 3. Food preservation, commercial appliances, bio preservation, and medicine Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?The PI and Co-PI successfully achieved the IRB approval for the proposed sensory analysis protocol for Human Subject Exempt Research at University of Hawaii. Sensory evaluation (conducted in the Department Sensory Laboratory, which is connected to our Department of Health-certified kitchen) will identify differences and liking of supercooled vs. controls (fresh and frozen-thawed fish). Panelists (n=30) will be presented with three samples, each labeled with a unique 3-digit numerical code and asked to identify the sample that is different (triangle test). Following this, panelists will be presented with a second triangle test involving the supercooled sample and the second control. Subjects who correctly respond will be asked to rate the supercooled and two control samples on a 1-9 hedonic scale for flavor, juiciness, and overall liking. Difference and hedonic data will be analyzed via one-tailed (p = 1/3) hypothesis testing and one-way ANOVA, respectively.

Impacts
What was accomplished under these goals? To ensure the quality and safety of perishable foods, the maintenance of a continuous cold chain through temperature control during transport and storage was deemed essential. Supercooling technology, which allows foods to remain fresh below freezing points without turning into ice, was identified as a potential solution to these challenges. The effectiveness of a supercooling preservation device was validated using a simulated food cold chain system. An open chest freezer was used to replicate typical cold chain temperature profiles. To simulate the physical disturbances associated with transportation, the supercooling unit and samples were subjected to mechanical vibrations on a custom-designed shaker platform. Furthermore, the study utilized 2% agar gels that were supercooled at -5°C and -8°C and exposed to vibrational forces to simulate the effects of ground transportation. Assessment of Supercooling Stability Under Mechanical Stress: Samples were exposed to varying mechanical stresses from 0 to 230 RPM under oscillating magnetic fields (OMF) over 24 hours inside an open chest freezer using a mechanical shaker (Talboy 3500 Orbital Shaker, Talboy Inc, Kingwood TX, USA). To estimate the effect of the shearing force on supercooled samples, the additional stress testing was conducted using a vibration table equipped with a stepping motor in consideration of Scotch Yoke mechanism (for lateral and longitudinal vibrations), and Cam and Follower mechanism (for vertical vibrations), of which all forces were controlled using Arduino programming. It was found that the instability of supercooling was more correlated with the intensity of vibration in the vertical direction rather than in the lateral and longitudinal directions. Additionally, the vibrations that vehicles often experience during transportation were measured using a specialized 3-axis sensor known as the AHRS IMU (WT901BLECL MPU9250). These measurements were then compared to the vibrations in a controlled experiment. The result showed that the range of vibrations experienced during transportation is within a magnitude range simulated in the laboratory. It was found that the level of in-vehicle vibration simulated in the test bed did rarely affect the supercooling stabilities.

Publications

• Type: Journal Articles Status: Published Year Published: 2023 Citation: Lee, D.Y., You, Y., Wall, M.M., Ho, K.H.Y., Li, Y., and Jun, S. 2023. Impact of supercooling storage on the physical and chemical properties of yellowfin tuna (Thunnus albacares). Journal of Food Engineering https://doi.org/10.1016/j.jfoodeng.2023.111818
• Type: Journal Articles Status: Submitted Year Published: 2024 Citation: So, H., and Jun, S. 2024. Application of Oscillating Magnetic Field-Based Supercooling Treatment for on Solid Lipid Nanoparticles. Journal of the ASABE. Submitted 2024.
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Lee, D. and Jun, S. 2023. Supercooling Preservation of Perishable Foods: Alternating Electric Field for Scaling Up. Institute of Food Technologists, July 16-19, Chicago, IL
• Type: Conference Papers and Presentations Status: Published Year Published: 2023 Citation: Lee, D. and Jun, S. 2023. Electric and magnetic field-based supercooling technology to ensure the freshness of yellowfin tuna (Thunnus albacares) June 20-23, ICEF 14, Nantes, France
• Type: Journal Articles Status: Submitted Year Published: 2024 Citation: Kang, T., Lee, D.Y. and Jun, S. 2024. An exterior chamber developed to explore oscillating magnetic field effects on supercooling of water. Journal of Food Science. Submitted 2024.

Progress 01/01/22 to 12/31/22

Outputs
Target Audience:1. Food industries including fish and seafood 2. Cold chain, warehouse, and food distributors/retailers 3. Food preservation, commercial appliances, bio preservation, and medicine Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?1. Implement the developed non-metallic 3D printed electrodes integrated with food containers in the supercooling preservation system combined with an oscillating magnetic field (OMF). This breakthrough approach is expected to enable the future development of an upscaled supercooling system, providing significant advantages to the customer by allowing for larger sample sizes and increased storage capacity. 2. Develop food packaging equipped with conductive non-metallic materials to deliver PEF current to food for effective supercooling preservation. 3. Validate the supercooling technology for the model food supply chain (supercooling stability against external temperature abuse and environmental shocks).

Impacts
What was accomplished under these goals? Design and optimize a scaled-up supercooling device for preserving perishable foods like fish (Objective 1). This will involve designing and fabricating 3D-printed conductive electrodes and non-contact electrodes, as well as developing a mathematical model of the field distribution and thermodynamics. The combination of conductive PLA filament and electrifi filament offers a promising approach for the design of non-metal electrodes for supercooling preservation. The conductive PLA filament used (Proto-pasta) has a resistivity of 30 Ω⋅cm along the X- and Y-axes and 115 Ω⋅cm along the Z-axis. The electrifi filament (Multi3D) has an average resistivity of 0.006 Ω cm, making it highly conductive. A food container was designed and printed using these conductive filaments, and it was powered with the high-frequency pulsed alternating current generated by an IGBT-based power supply. This allowed the container to provide an electric current during supercooling preservation without the need for traditional metal electrodes. The power supply was designed to generate square waveforms in the frequency range of 0 to 50 kHz and a duty cycle of 0 to 1. Also, to provide uniform current density through the sample a crossed orthogonal series of strip electrodes were used, and three different phases of electric current were driven by sequentially cycling each line pair above and below. In order to improve the understanding of the characteristics of MF and EF, a finite element method (FEM) software called COMSOL Multiphysics (version 5.5) was used to visualize and optimize the intensity and distribution of the fields. The 2D and 3D models were developed to simulate the current density and associated electrothermal characteristics of samples during supercooling. The material properties configured in the model shape, such as heat capacity, density, thermal conductivity, and electrical conductivity, were defined with the built-in material library properties of COMSOL Multiphysics (v.5.5) and actual measured values. Heat transfer in the food samples was governed by conduction, convection, and internal energy generation according to Joule's law. It was assumed that the heat loss at the boundary of the sample vessel was caused by the convective heat flux at a temperature of -5°C, and the convective heat loss was defined by Newton's law of cooling. The electric field distribution was expressed by Laplace's equation. Simulation results contributed to design and fabrication of the patterned electrodes to ensure that the fields were uniform and consistent across the supercooling chamber and sample. Food containers, containing flat and parallel electrodes, have been shown to have a uniform electric field across their geometry. Also, the pattern electrodes were designed to provide an adequate electric field and current density over the entire sample. The task is to test and validate the quality factors associated with mid- and long-term supercooling process (Objective 2). The experiment involves placing sashimi-grade tuna and salmon fillets in a single supercooling storage space and applying various strengths of electric and magnetic fields to improve the shelf life of samples. The focus is on the preservation of sashimi-grade fish fillets, particularly yellowfin tuna and farm-raised Atlantic salmon, and comparing it with refrigeration and freezing. The team monitored the temperature of the samples during the 10-day preservation period and found that supercooling at -3.5°C prevented deterioration and maintained the quality of the samples better than refrigeration and freezing. The supercooled tuna samples showed less discoloration, and the lipid oxidation (TVB-N) was significantly lower than the refrigerated tuna samples. The aerobic plate count (APC) was lower in supercooled tuna samples than in frozen and refrigerated samples, indicating that supercooling can prevent bacterial growth that can occur during thawing and refrigeration. The TBARS analysis showed that the refrigerated salmon fillet had a significantly higher level of oxidation compared to the supercooled and frozen samples, which could lead to off-flavor and color degradation.

Publications

• Type: Journal Articles Status: Published Year Published: 2022 Citation: Kang, T., Lee, D., Ko, Y., & Jun, S. (2022). Effects of pulsed electric field (PEF) and oscillating magnetic field (OMF) on supercooling preservation of beef at different fat levels. International Journal of Refrigeration, 136, 36-45. https://doi.org/10.1016/j.ijrefrig.2022.01.004
• Type: Journal Articles Status: Submitted Year Published: 2023 Citation: Lee, D., You, Y., Ho, K., Li, Y., & Jun, S. Impact of Supercooling Storage on Physical and Chemical Properties of Yellowfin Tuna (Thunnus albacares). Journal of Food Engineering
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Lee, D., You, Y. and Jun, S. 2022 Impact of supercooling storage on the physical and chemical properties of yellowfin tuna (Thunnus albacares). Institute of Food Technologists, June 10-13, Chicago, IL
• Type: Conference Papers and Presentations Status: Published Year Published: 2022 Citation: Tang, J., Kang, H. and Jun, S. 2022 Effect of pulsed electric field (PEF) and oscillating magnetic field (OMF) on supercooling preservation of salmon. Institute of Food Technologists, June 10-13, Chicago, IL
• Type: Conference Papers and Presentations Status: Submitted Year Published: 2023 Citation: Lee, D and Jun, S. 2023 Supercooling preservation of perishable foods: Alternating electric field for scaling up, Institute of Food Technologists, July 16-19, Chicago, IL

Progress 01/01/21 to 12/31/21

Outputs
Target Audience:1. Food industries including fish and seafood 2. Cold chain, warehouse, and food distributors/retailers 3. Food preservation, commercial appliances, bio preservation, and medicine Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?The PI is in collaboration with the identified vendor for fabrication of a new high voltage AEF generator/electrode units integrated with the proposed OMF module.

Impacts
What was accomplished under these goals? The developed test was focused on the investigation of physiochemical changes in tuna subjected to a novel supercooling preservation, which was assisted using a combination of pulsed electric fields (PEF) and oscillating magnetic fields (OMF). Fresh tuna fillets were stored without freezing at -3.2°C for 8 days. The electrochemical impedance spectroscopy (EIS) parameter indicated that there was a significant difference between the frozen-thawed samples (36.3%), and fresh (46.6%) and supercooled (45.9%) samples, indicating that cell damage from ice crystal growth did not occur in the supercooled tuna sample. The microstructure observation and drip loss measurement further confirmed that the ice crystal damage was present in frozen tuna, whereas no cellular damage was found in the supercooled samples. The EIS proved its ability to distinguish between tuna samples that were frozen or chilled (i.e., refrigerated and supercooled) during storage; however, less sensitive to detect the extent of spoilage. Instead, the K-value was used to evaluate tuna freshness, and the measured K-values of the refrigerated, supercooled, and frozen tuna samples after 8 days of storage were 74.3%, 26.4%, and 19.9%, respectively, suggesting that the supercooling treatment significantly preserved the tuna fillets fresh with the improved shelf-life, compared to conventional refrigeration.

Publications

• Type: Journal Articles Status: Under Review Year Published: 2021 Citation: Kang, T. Lee, D., Ko, Y., and. Jun, S. 2021. Effects of pulsed electric field (PEF) and oscillating magnetic field (OMF) on supercooling preservation of beef at different fat levels. International Journal of Refrigeration
• Type: Journal Articles Status: Accepted Year Published: 2021 Citation: You, Y., Muci, L., Kang, T., Ko, Y., Kim, S. Lee, S., and Jun, S. 2021. Application of supercooling for enhanced shelf life of asparagus (Asparagus officinalis, L.). Foods 10.3390/foods10102361