Project Number: 2030-42000-053-007-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2021
End Date: Jul 31, 2023
Pathogenic and spoilage bacteria are noted for their association with food and water-linked outbreaks, with annual economic losses of more than $15 billion in the United States. Natural antibacterial agents ensuring food safety, quality, and nutritional and health properties are in high demand because of consumer desire for natural, ‘green’, and healthy foods. Many natural antibacterial agents have been reported in the recent years, but few of them could be practically used in the food industries due to their undesirable flavor and aroma, unsuitable physicochemical properties, and toxicity or other intrinsic safety concerns. One of the practical issues the fresh produce and processing industries face is the strong attachment and colonization of pathogenic bacteria on the surface of fresh produce. The removal and elimination of bacteria from these surfaces and inside the plant have been challenging due to the hydrophobic nature of the outer surface of the cell membrane. Common sanitizers, such as water-soluble chlorine compounds, are effective, but they have the risk of forming potential carcinogens and have been prohibited in some European Union countries. New strategies that can reach and penetrate through the hydrophobic surface without resulting in toxic residues that endanger human health and the environment are needed. The goal of this collaborative research is to discover and develop novel antibacterial agents, which are not only capable of improving food safety, but also have the potential to enhance food quality and shelf life. The specific objectives of this cooperative research agreement are: 1. Discovery and development of new natural antibacterial agents from edible materials including the by-products from agricultural and food processing for potential application in improving food safety and quality while enhancing agricultural food system sustainability and profitability. 2. Developing new ‘green’ formula including nano-encapsulations and the ‘green’ technologies, such as electrospinning, for targeted delivery and/or controlled release of the natural ‘green’ antibacterial agents onto and penetrating through the hydrophobic surface/membrane of vegetables. 3. Determining and demonstrating other potential human health benefits of the new ‘green’ antibacterial agents using in vitro assays. The health beneficial effects may include antioxidant/radical scavenging activities, potential anti-inflammatory capacities, and gut microbiota modulating properties. 4. Investigating the molecular structures and mechanisms involved in the actions of the novel antibacterial agents/formula to establish the scientific basis for their safe utilization in improving food safety, quality, and human health. The information should be also applicable to animal feeds and pet foods. 5. Demonstrating the effectiveness of the new ‘green’ antibacterial agents/formula in model food under mimicked commercial conditions and developing outreach materials to promote their utilizations in commercial food systems/industries.
A group of 40 selected edible materials, including by-products from agricultural and food processing (such as fruit seeds), edible botanicals with a historic utilization as food ingredients, herb medicines, secondary metabolites from probiotics (such as Enterococci, Bacillus sp., Lactobacillus acidophilus) and food components, such as phenolics, will be extracted and screened for their inhibitory ability against gram-positive (G+) and gram-negative (G-) bacteria at 3 or more doses. The active compounds in the extracts and fractions will be identified using an un-targeted HPLC-high resolution MS/MS (HRMS/MS) analysis. Further isolation and structure identification may be performed using column chromatography and preparative HPLC, and H1-NMR and C13-NMR, MS, FT-IR and UV spectra. The relationship between antibacterial activities and chemical structures will be analyzed. The antibacterial extract(s), their active fractions and the active component(s) will be investigated for further formulations, including nano-delivery systems, to improve water solubility, controlled release and targeted delivery to hydrophobic surfaces, stability, sensory impact and enhanced antibacterial activities for different food uses. Food polymers, such as zein and chitosan, will be used to develop the formulations and their efficacy will be examined. The antibacterial agents will also be examined for their antioxidant activities (scavenging capacities against DPPH and peroxyl radicals, reducing power, and chelating capacity), and the potential health benefits such as anti-inflammatory and gut microbiota modulating activities using laboratory protocols at University of Maryland. Molecular biology approaches, including proteomics and genomics approaches, will be used to investigate the biochemical mechanisms of the new antibacterial agents. The metabolism of the active compounds during treatments may also be examined by un-targeted HPLC-MS/MS analysis to understand the antibacterial mechanisms of the new agents/formula for further design and development of the next generations of the natural ‘green’ antibacterial agents. The top antibacterial agents and formula will be tested for their effectiveness in two leafy green food models (spinach and lettuce). The safety of the top active agents will be evaluated using MTT assay. More vegetable varieties or growing seasons may be involved to obtain representative results if necessary. The vegetables with and without the antibacterial treatments and inoculated bacteria will be taken at 0, 1, 2, 4 and 8 days of storage at refrigeration and ambient temperatures, and examined for their total bacterial counts, quality attributes (color, weight loss, and nutrients) and health properties (anti-inflammation) etc. Fact sheets will be developed based on the research results and will be published in extension newsletters and made available to colleagues in the food production and storage business.