Design of a Supercooling Device for Extended Shelf Life of Perishable Foods

DESIGN OF A SUPERCOOLING DEVICE FOR EXTENDED SHELF LIFE OF PERISHABLE FOODS

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

SMALL BUSINESS GRANT

Reporting Frequency

Annual

Accession No.

1009456

Grant No.

2016-33610-25447

Cumulative Award Amt.

$99,468.00

Proposal No.

2016-01027

Multistate No.

(N/A)

Project Start Date

Aug 15, 2016

Project End Date

Feb 14, 2017

Grant Year

2016

Program Code

[8.5]- Food Science & Nutrition

Recipient Organization
JUN INNOVATIONS LLC
1009 KAPIOLANI BLVD APT 806
HONOLULU,HI 96814

Performing Department
(N/A)

Non Technical Summary
In conventional refrigerators food items are frozen among ice crystals and their quality is compromised once they are thawed. The deterioration of quality may include generation of drips, protein denaturation and changes in the cellular structure of foods. The occurrence of ice crystallization can be prevented by the phenomenon called supercooling that involves temperature reduction below the freezing point of the sample.Supercooling involves cooling of biological samples below a phase transition temperature in a balanced state leading to prevention of their cellular activity. In this supercooled state, damage by freezing such as protein denaturation and cellular structure injuries can be avoided. This ability to preserve the biological samples such as cell culture, tissues and organs at subzero temperature is useful in pharmaceutical, biotechnological, food and other medical related industries. The research to sustain and maintain food and biological samples in a supercooled state is drawing major attention and promises to hold great potential in the near future.In order to enhance preservation technology over the existing art, the subject invention proposes a method and a device to preserve the quality of foods by treating them with a pulsed electric field and an oscillating magnetic field in combination. The proposed invention maintains perishable foods (such as beef and fish), in a supercooled state at around -4 ~ -6°C far below their equilibrium freezing points, and their original freshness is kept intact for transportation and storage purposes. Unlike other few supercooling methods based on the precision temperature control, our supercooling invention is insensitive to environmental disturbances causing ice nucleation, presumably due to 'memory effects' of magnetic field on water molecules. The invention may be extended to biomedical applications as well, such as preservation of cell cultures, proteins, and tissues and organs transport at subzero temperatures.

Animal Health Component

50%

Research Effort Categories

Basic

(N/A)

Applied

50%

Developmental

50%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
501	7299	2020	100%

Knowledge Area
501 - New and Improved Food Processing Technologies;

Subject Of Investigation
7299 - Research equipment and methods, general/other;

Field Of Science
2020 - Engineering;

Keywords

Goals / Objectives
The objective of this proposal is to develop a novel scaled up supercooling device to preserve perishable foods far below their freezing points while retaining their freshness. In order to establish the feasibility of supercooling, the following technical objectives are proposed:Objective 1: Design a scaled up supercooling unit for 'proof of concept'.Objective 2: Test the unit for extended shelf life of perishable food materials (beef and fish).Objective 3: Test for freshness factors (physical and chemical properties) of supercooled foods.

Project Methods
Task 1. Design the supercooling unit for proof of conceptThe supercooling unit can be broken down into three essential components (1) the circuitry to control wave generation (2) electromagnets and electrodes for oscillating magnetic field generation and (3) sample chamber.Design of circuitryA pre-prototype PCB will be designed and optimized through two major revisions and small scale productions runs. The board accommodates an Atmel SAM3X8E 32bit MCU, a fully programmable microcontroller chosen for its ease of use and scalability for the project's needs. A built in high speed USB peripheral will be used for communication between an Agilent 34721A DAQ and LabView program for data acquisition and real time control, respectively. Waveform generation with the built in DAC will be used to drive the IRAMX20UP60A IGBT power module output at a specified bias voltage chosen by the user via on board potentiometers. The operational range of the PEF IGBT and OMF IGBT is 0-15 V and 0-90 V with a frequency range for both of 1 Hz - 20 KHz. The PCB layout has been tested and confirmed to output the desired waveform as chosen so by the user via software. The IGBT board and Power supply board will be developed to cut the number of equipment and cost of a prototype unit. Consolidated onto a single board are two IGBT power modules capable of driving both the OMF and PEF. Pursuing this avenue will allow for the elimination of several external equipment and redundancies, cutting the overall weight and cost of the prototype unit.The design of the electromagnets is crucial in maximizing magnetic field coverage. To better understand the physical characteristics of an electromagnet has on magnetic field density, FEM software COMSOL will be used to help visualize field intensity. Calculations will be based upon the Biot-Savart equation, modeled with a loss-less iron core and copper multi-turn coil. Parametric sweeps of wire diameter, turns, and core shapes reveal maximal field generation with 20-23 AWG wire, 1000-2000 turns and core geometry in the range of 30-50 mm diameter and length of 40-70 mm. Custom made electromagnets will be implemented based upon simulated parameters which showed a 1.5-2 times increase in field strength from previously used electromagnets.Task 2: Test the unit for an extended shelf lifeSamples of beef steak will be purchased at various retail stores. The day of purchase will be considered day 0 in this study. Fresh steak samples (200 g, 500 g, and 1000 g) will be cut to fit into a clear acrylic holder, equipped with a set of parallel electrodes (Fig. 6). Control samples of approximately equal shape and weight will be placed in acrylic holders without electrodes and set in either a refrigerator or freezer at 4 and -10°C, respectively. All samples and controls will be covered with polyethylene (PE) film to avoid dehydration during experiments. Quality factors of samples and controls will be analyzed at day 0, 7, 14, 21, and 28 days. All treatments will be done in duplicates.All data (temperature, voltage, and current) will be collected using a data acquisition unit (DAQ, Agilent 39704A, Agilent Technologies, Inc., Santa Clara, CA) at a scanning frequency of 10 sec. Temperatures of samples will be collected in real time using T-type thermocouple wire (TT-T-40-SLE, Omega Engineering, Inc., Stamford, CT).The degree of supercooling at which the beef sample was held during treatment will be controlled using a repeating sequence of three different duty cycles (0.8, 0.5, and 0.2) for the PEF. The time durations of duty cycles are 300 sec, 120 sec, and 120 sec. The duty cycle sequence will be repeated during the entire time the beef spent in the supercooled state. The input voltage will be set, through trial and error, to 5 Vrms with a frequency of 20 kHz in order to keep the internal temperature of the beef at approximately -4 ~ -6°C throughout the entire storage period. The applied voltage and frequency of the OMF are 95 Vrms and 1 Hz, respectively. The OMF is solely applied until the internal temperature of the beef reaches just below its freezing point (-2°C). The OMF treatment is referred to as phase 1, and the PEF and OMF combination treatment is referred to as phase 2 of the overall supercooling procedure. The same practice will be repeated for fish (tuna) samples.Shock-induced freezing will be tested on food samples during and after supercooling process. Two different tests will be performed for stimulation of the onset of ice nucleation: (1) physical vibrations (10- 15 times device shaking) and (2) on purpose fluctuations in ambient temperature. In our preliminary study with the pre-prototype device and water, we found that water (50 mL) exposed to magnetic and electric fields was able to maintain the supercooling status even at the shaking mode. The mechanical vibration of water molecules caused by external magnetic field seems to last for a considerable time, giving rise to claims for 'memory' effects. This finding needs further investigation.Task 3: Test freshness factors of supercooled foodsDrip lossThe drip loss of samples after storage will be measured with a commonly used method. Directly after cutting, fresh samples will be initially weighed and recorded. The samples weights will be again recorded after each treatment. Before weighing post treatment, excess drip will be removed with a paper towel. The frozen samples will be thawed at 4°C for 24 h before their final weights are recorded.Instrumental color measurementInstrumental color measurements will be recorded for Hunter L* (lightness; 0: black, 100: white), a* (redness/greenness; positive values: red, negative values: green), and b* (yellowness/blueness; positive values: yellow, negative values: blue) using a handheld color meter (ColorTec PCM, Clinton, NJ).Lipid oxidationMalondialdehyde (MDA) is one of the most commonly used markers of secondary products from lipid oxidation due to its ability to form a red colored complex with thiobarbituric acid (TBA) which can be measured using the spectrophotometry. The extent of lipid oxidation for each sample will be calculated using 1.56. 105 M-1cm-1 as the molar extinction coefficient is expressed as mg MDA per kg of meat. All measurements of lipid oxidation will be done in triplicate.pH measurementThe pH of each sample will be determined by homogenizing the sample with deionized water at room temperature. A pH meter (SevenEasy S20, Mettler Toledo, Columbus, OH) will be used to measure the pH of each sample. The pH of each sample will be calculated as an average of three measurements.Warner-Bratzler shearTreated and controlled sample muscles will be individually cooked, and the Warner-Bratzel shear test will be applied according to a previously described method with few adjustments. The samples will be placed in plastic bags (ZipLoc, SC Johnson, USA) and submerged in a water bath at 75°C. The internal temperature of the samples will be monitored using a K-type thermocouple wire, and cooking will be stopped when the temperature reaches 75°C. The samples will then be cooled until their internal temperature reaches 20°C. The maximum peak forces (N) for complete shear of the samples perpendicular to the direction of their muscle fibers will be measured using a Mecmesin Warner-Bratzler shear force machine (G-R Manufacturing Co., Manhattan, KS) with a cross-head speed of 5mm/sec. Four measurements will be done for each sample.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 as described by Ryder (1985) with a few modifications.The K value of fish has been used successfully in the past to evaluate quality as it positively correlates with the extent of spoilage.

Progress 08/15/16 to 02/14/17

Outputs
Target Audience:This novel supercooling technology can positively impact the food preservation industry due to its ability to maintain perishable foods in a supercooled state while maintaining the foods cellular structure. The process of combining a pulsed electric field and an oscillating magnetic field to treat foods has proven to be far more advantageous than superchilling and freezing because it nature to decelerate the rate of spoilage without compromising the sensory quality and nutrient composition of foods. The developed supercooling device can be best applied to home appliance manufacturers, in particular the refrigerator and freezer industry. In addition, this device can be integrated into food storage and transportation processes anywhere starting from the point after harvest or manufacture, to distribution, down to the food retailer level. 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?The design, fabrication and validation was successfully demonstrated for LG Electronics. More in-site tech demonstrations will be scheduled for Samsung, and Haier this year. In addition, research will be presented at the Institute of Food Technologist 2017 Annual Meeting in Las Vegas, Nevada. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Despite the multitude of food preservation technologies on the market, every year, billions of dollars' worth of food is wasted due to bacterial or quality spoilage. The most commonly used household food preservation technologies are refrigeration and freezing. Refrigeration allows fresh food to maintain their texture, quality, and nutritional value; however, it can only maintain food for a relatively short period of time before spoilage occurs. In contrast, freezing maintains food at a much lower temperature, which slows down both cellular and microbial activity and allows food to be safely stored for much longer. However, formation of ice crystals during the freezing will cause irreversible textural damage to the food through volumetric expansion, moisture migration, and protein denaturation. Although freezing will preserve perishable foods for months, these disruptive changes decreases the consumer's perception of the food's quality. The occurrence of ice crystallization can be prevented by the phenomenon called supercooling that involves temperature reduction below the freezing point of the sample. Supercooling involves cooling of biological samples below a phase transition temperature in a balanced state leading to prevention of cellular activity. In this state, textural damage including protein denaturation and cellular structure injuries can be avoided. In this research, a novel supercooling device was developed to preserve the quality of foods by treating them with a combination of pulsed electric field and an oscillating magnetic field. The magnetic and electric fields keep water molecules vibrating to prevent the formation of ice crystals even as products drop to subzero temperatures. Therefore, under the subjected environment, supercooled foods do not need to undergo a thawing process, thus allowing them to maintain their quality, texture, and nutrients while extending their shelf life. The fabricated device maintains perishable foods in a supercooled state at around -4 ~ -6°C far below their equilibrium freezing points, and their original freshness is kept intact for transportation and storage purposes. Unlike other supercooling methods which are based on the precision temperature control, the developed invention is insensitive to environmental disturbances causing ice nucleation, presumably due to 'memory effects' of magnetic field on water molecules. Objective 1:Design a scaled up supercooling unit for 'proof of concept' In this research, a microcontroller based supercooling control unit was designed and fabricated to achieve a stable supercooled state a combination of pulsating electric fields and oscillating magnetic fields. The unit was designed with a power delivery system based upon an IGBT (insulated gate bipolar transistor) H-bridge with real-time voltage and current monitoring, data is processed via MCU for fault detection, temperature measurements, data logging, and power adjustments. The unit offers a wide range of operational modes to accommodate various foods. In addition, experimental parameters such as event detection, duration, or fault conditions can be defined. Current and voltage measurements were validated with comparison calibrations with respect to laboratory test equipment, maximum uncertainty of ±0.2% for current measurements and ±0.1% for voltage was determined. Objective 2:Test the unit for extended shelf life of perishable food materials (beef and fish). General performance of the supercooling unit was examined via supercooling beef steak (London broil) at an ambient freezer temperature range of -8±0.20°C to -10±0.20°C. An internal beef temperature of -4°C, approximately two degrees below its freezing point, was maintained for up to two weeks. A repeating sequence of three different duty cycles, 0.8, 0.5 and 0.2, were used for the PEF treatment with 20 kHz. During PEF with the duty cycle of 0.2, OMF with 1 Hz was applied to inhibit sudden ice nucleation. Objective 3:Test for freshness factors (physical and chemical properties) of supercooled foods. Quality assessment factors such as color, lipid oxidation, drip loss and texture of supercooled beef samples were evaluated and compared with those of refrigerated (at 4°C), frozen (at -10°C) and fresh samples. In samples stored for two weeks, supercooled beef samples maintained the original fresh qualities, as compared to other treated samples (refrigerated and frozen samples). After two weeks of storage, there were no significant difference in color parameter values of supercooled samples from those of the fresh beef samples (P > 0.05), except L* value. The TBARS value of supercooled samples after 14 d of storage was significantly lower (P < 0.05) than that of refrigerated and frozen samples. In addition, the major drip loss and tenderization due to cell damage which occurred during the freezing process was not seen in the supercooled samples. The results of from the freshness factors showed that the supercooled beef samples could maintain its original quality.

Publications

Type: Journal Articles Status: Submitted Year Published: 2017 Citation: Jin Hong Mok, Jae-Young Her, Taiyoung Kang, Raymond Hoptowit, Soojin Jun, 2016, Effects of pulsed electric field (PEF) and oscillating magnetic field (OMF) combination technology on the extension of supercooling for chicken breasts
Type: Journal Articles Status: Submitted Year Published: 2017 Citation: Her, J.Y., Shafel, T., Jun, S. 2017. Effect of extended supercooling state by using pulsed electric fields (PEF) and oscillating magnetic fields (OMF) on the quality of beef steak. Meat Science

Type: Journal Articles Status: Published Year Published: 2016 Citation: Jin Hong Mok, Jae-Young Her, Taiyoung Kang, Raymond Hoptowit, Soojin Jun, 2016, Effects of pulsed electric field (PEF) and oscillating magnetic field (OMF) combination technology on the extension of supercooling for chicken breasts