Performing Department
(N/A)
Non Technical Summary
Antimicrobial packaging has attracted much attention from the food industry because of the increased food safety concerns and consumer demand for preservative-free food products. Current antimicrobial packaging solutions face challenges including high cost of antimicrobial agents, rapid exhaustion of antimicrobial agents, and the inability to inactivate a broad spectrum of microorganisms. This project aims to develop a low-cost and robust antimicrobial packaging films using single atom catalysts (SACs) that mimic natural enzymes to catalyze the disinfection of microorganisms via oxidation. This will be the first attempt to design and fabricate SACs-based packaging films that produce reactive oxygen species (ROS) to inactive spoilage and pathogenic bacteria attached on packaging film or contained on foods. The specific objectives are 1) Synthesize and evaluate SACs that possess a high oxidase-catalytic activity and antimicrobial properties, 2) Incorporate SACs into biopolymer films and structuralize the multilayer and/or composite systems using a series of bioplastics and other packaging materials, and 3) Validate the safety of film application in foods and determine the film's effectiveness in preserving food quality and suppress bacteria growth in real food matrices at different storage conditions. Upon completing the objectives, we will be well positioned to develop and manufacture the novel SACs-incorporated biopolymer packaging technologies to improve safety, quality, shelf-life of food. Thus, it is aligned with the Program Area Priority: Novel Foods and Innovative Manufacturing Technologies (A1364). Moreover, this project brings a unique collaboration between Virginia Tech and the George Washington University, an EPSCoR Institution.
Animal Health Component
30%
Research Effort Categories
Basic
30%
Applied
30%
Developmental
40%
Goals / Objectives
The overall goal of this proposal is to develop a low-cost and robust antimicrobial packaging films using carbon-supported SACs that mimic natural enzymes to catalyze the disinfection of microorganisms via oxidation.Objective 1: Synthesize and evaluate SACs that possess a high oxidase-catalytic activity and antimicrobial properties.Objective 2:Incorporate SACs into biopolymer films and structuralize the multilayer and/or composite systems using a series of bioplastics and other packaging materials.Objective 3:Validate the feasibility of film application in foods and determine the film's effectiveness in preserving food quality and suppress bacteria growth in real food matrices at different storage conditions.
Project Methods
Objective 1:Synthesize and evaluate SACs that possess a high oxidase-catalytic activity and antimicrobial properties.Task 1: Synthesize and characterize SACs microparticlesSACs will be first prepared via the thermal polycondensation of the mixture of metal salts and nitrogen-rich organic precursors.Monometal salts of Fe and Cu will be amended into dicyandiamide or melamine, and the SACs on a carbon nitride or nitrogen-doped carbon support will be synthesized by heating the mixture in the argon. SACs will also be synthesized from the calcination of metal organic frameworks.The structure, morphology, composition, and crystallinity of SACs will be assessed by scanning electron microscopy (SEM), transmission electron microscopy, atomic force microscopy, energy dispersive X-ray analysis, and X-ray powder diffraction. Surface area and porosity of catalysts will be analyzed by liquid N2adsorption. Functional groups and oxidation states of the elements in the catalysts will be characterized by Fourier transform infrared spectroscopy and XPS.Task 2: Evaluate SACs' capability to generate ROS and inactivate bacteriaThe prepared SACs will be evaluated for their capacity to generate ROS at different SACs concentrations. The synthesized SACs' bactericidal activity will be evaluated by performing plate bacterial killing assays.Leuconostoc lactisandL. monocytogeneswill be used as the representatives for Gram-positive bacteria, whilePseudomonas fluorescensandE. coliO157:H7 will be used as the representatives for Gram-negative bacteria.Objective 2: Incorporate SACs into biopolymer films and structuralize the multilayer and/or composite systems using a series of bioplastics and other packaging materials.Task 1. Design and fabricate SACs-incorporated bioplastic structuresProduction of flexible packaging films incorporating SACs: SACs will be incorporated into single bioplastic layer. For even distribution of SAC into polymeric matrix, we will adopt a solvent chemical pre-treatment.PHA will be ground and screened. SACs will be dispersed into isopropyl alcohol and ultra-sonicated andthe suspension will be sonicated.Both materials will be compounded using a twin-screw compounder,apelletizer will be employed to make the pellet-type samples.Blending of different bioplastics for composite structures incorporating SACs:In this study, we plan to blend PHAs with PLA, PBS, and PBAT, which are highly promising bioplastics in the view of commercialization due to their cost competency, availability, and functionality. The compounding process of different bioplastic polymers will be performed using a twin-screw compounder. Production parameters may include various screw speed, diameter of screw, back pressure, heating zone temperature profile, and diameter of die (2 to 5 mm).Production of multilayer structure with other packaging materials:To improve the efficiency of antimicrobial activity and cost competency for mass production, multilayer bioplastic packaging systems will be performed by a 2-step process.The first stepis to produce each layer: an outer top bioplastic thin film layer, a middle layer having SACs, and a molded fiber layer as a bottom layer. Parameters for compression process will be determined and optimized based on the raw fiber materials.The second stepis a lamination process, bioplastic layer incorporating SACs will be sandwiched by a molded fiber and a single layer bioplastic thin film by compression method using a hot-press as functions of compression pressure/time and molding temperature.Task 2. Evaluate the physical and mechanical properties of packaging systemsTensile and flexural tests will be carried out in accordance with the ASTM D695 and ASTM D790, respectively. Benchtop SEMwill be performed to investigate the morphological properties of composites.Melt flow rate will be obtained to compare flow properties between composites in accordance with the ASTM D1238 standard. Thermal mechanical analyzer (TMA) will be used to investigate the thermal decomposition temperature.The crystallization and melting behavior of specimens will be investigated with a differential scanning calorimeter.Objective 3: Validate the safety of film application in foods and determine the film's effectiveness in preserving food quality and suppress bacteria growth in real food matrices at different storage conditions.Task 1.Determine the toxicity/safetyof the filmWe will first evaluate the release of metal ions from SACs and the film containing SACs. The released metals will be analyzed by inductively coupled plasma mass spectrometry (ICP-MS).In addition, SACs could also release organics due to the self-oxidation by ROS, and the organics will be determined by the total organic carbon or liquid chromatography-mass spectrometry (LC-MS). Self-oxidation of SACs will also be evaluated by XPS to understand the introduction of oxygen functional groups to the catalysts. The leachate from SACs and the film will also be collected to evaluate their toxicity to human cells, such as Caco-2 cells that are epithelial cells of the colon tissue.Task 2. Determine the film's effectiveness in inactivating bacteria in a food matrixMeat and poultry will be used as representative foods because they are rich in nutrients and support microbial growth very well. They have been associated with multiple multistate outbreaks.Four bacteria (E. coliO157: H7, L. monocytogenes, P. fluorescensandL.lactis) will be involved in the assessment. Fully cooked chicken and raw beef will be studied as the first food matrix followed by raw beef steak. The enumeration of bacteria will be the same as mentioned above. We will adjust the distance between the film and the food samples to evaluate the effect of distance on the antimicrobial effects of the films.Task 3. Determine the packaging film's effectiveness in preserving food qualityNutritional profile and Color Measurement: Lipid profile, including total fat content, unsaturated fatty acids (MUFA and PUFA) and trans fats will be measured. α-tocopherol and β-carotene will be determined. Protein, amino acids profiles, zinc and iron will all be measured as a comprehensive set of nutritional panels for sampled beef/chicken. We will conduct experiments to slice the food samples into different layers from outmost to innermost and investigate the quality change of the slices.Flavor measurements. Gas chromatography equipped with mass spectrum and olfaction (GC-MS-O) will be utilized for aroma, especially off-aroma characterization.Volatile extraction will be performed by headspace solid-phasemicroextraction (HS-SPME) with a divinylbenzene/carboxen/polydimethylsiloxane (DCP, 50/30μm) fiber. Positive identification of volatiles will be based on their retention indices on polarity stationary phases (DB-Wax or DB-5 GC columns), mass spectrum, and odor attributes against authentic flavor standards. Quantitationtechniqueswill be performed by use of stable isotope dilution analysis (SIDA) or standard additionmethod (SAM), which has the ability to self-correct for the compound loss during sample workupand chromatography.Statistical AnalysisAll treatments in SACs production and characterization, packaging film fabrication and characterization, antimicrobial activity measurement, and food quality assessment will be performed in triplicate. Data will be expressed as mean ± standard deviation of all replicates. One-way analysis of variance (ANOVA) with Tukey's HSD will be applied to identify the significant difference between means in JMP software. For all analyses, values of p<0.05 will be considered statistically significant.?