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%
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.