Location: Food Quality Laboratory
Project Number: 8042-43440-006-012-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 22, 2023
End Date: Sep 19, 2025
The proposed project seeks to develop antimicrobial coatings to improve food quality of fruits and vegetables. Specifically, the parties will 1) develop and optimize an anti-microbial coating containing copper and biopolymers for improved reduction in microorganisms on seeds, fresh produce, and growth substrates; and 2) characterize the physiochemical properties of the coating materials and their effects on plant growth.
The growth of spoilage microorganism on fresh produce both pre- and post-harvest has been a major cause of loss of product yield, quality, and shelf life. The proposed study will improve food quality and security through the development and applications of novel anti-microbial coatings. Polymer composites consisting of alginate as matrix and Cu(II)-chelated chitin nanofiber (Cu(II)-ChNF) as 1D scaffolding filler will be developed for anti-microbial coating to improve food quality of fresh produce. Chitin nanofiber (ChNF) will be produced using phosphoric acid hydrolysis. Cu(II) ions will be chelated with ChNFs treated using aqueous alkaline solution. Controlled changes in mechanical properties, hydrophobicity, porosity, and gas permeation will be modulated for targeted substrates including seeds, plant growth surface, and fresh produce. For example, when high mechanical strength for seed protection is needed, high molecular weight alginate, as well as longer Cu(II)-ChNF will be used to produce bi-networking composite. On the other hand, if a programed break of the coating is desired (e.g., to facilitate germination), composites with a less degree of entanglement of the two components will be used. In addition to anti-microbial and mechanical properties, the coating needs to be permeable to allow efficient exchange of water, oxygen, and nutrients. Coating permeability can be adjusted by changing coating thickness, alginate molecular weight and Cu(II)-ChNF length, depending on the needs. Additionally, the coating developed can be highly hydrophilic with residual removal while tap water rinse. The main ingredients are from biomasses and are sustainable. Chitin is the second abundant biopolymer on the planet Earth, with an estimated yearly production of 100 billion tons, treated as biowaste. Alginate is derived from seaweed biomass, with a yearly production of >30 k tons. Cu(II) ions play a dual-role, as a broad-spectrum antimicrobial agent and cross-linkers with which, along with other factors such as alginate and ChNF concentrations, the mechanical properties of the coating film can be adjusted. Dope solutions of the polymer composite will be spray or dip applied to seeds, plants, and growth substrates. Physiochemical properties of the coatings, and their effects on seed germination, plant growth (e.g., leaf count, leaf area index, and photosynthetic efficiency), and inhibition on microbial proliferation will be assessed. Major testing parameters for coatings will include multi-scale structures (ranging from crystallographic packing, to nano-structures, and to macroscopic morphology), X-ray absorption fine structure, and porosity etc. Microbial growth will be monitored via culture-based methods with and without microbial inoculation. The organoleptic quality and phytonutrient concentrations will also be compared between the coated and control samples. The Cooperator will work closely with the USDA team, so that the coating formulation can be tailored according to the needs.