1a. Objectives (from AD-416):
ARS is interested in integrated approaches to improve produce safety while maintaining quality. The Cooperator, University of Maryland, is interested in evaluating the produce surface characteristics and sanitizer efficacy on pathogen reduction. The Cooperator has the expertise and infrastructure to effectively conduct the proposed research activities.
1b. Approach (from AD-416):
ARS will acquire the basic knowledge of the factors influencing sanitizer degradation, pathogen attachment and internalization during leafy greens and tomato wash process. The Cooperator will provide the expertise in anti-microbial, surface adsorption, topography, and other characteristics in relation to sanitizer performance on pathogen reduction.
3. Progress Report:
Essential oils (EOs) have antimicrobial activities, but their insolubility in water and strong flavor restrict their application in fresh or fresh-cut produce. Metal-Organic Frameworks (MOFs) or porous coordination polymers (PCPs) are a new class of hybrid materials which can act as carriers for other molecules. In this study, MOFs were developed and applied for the first time to encapsulate thymol as a novel antimicrobial agent. MOFs in this study were synthesized using Zinc nitrate hexahydrate and 2-aminoterephthalic acid in N, N-dimethylformamide (DMF). Thymol was then loaded inside the MOFs at the loading rate of 3.95%. The structure of porous crystal MOFs was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Inhibition of E. coli O157:H7 was measured both in TSB medium and on TSA agar. An E. coli O157:H7 reduction of 4.4 log was achieved at a thymol concentration of 0.04%. An inhibition area of 223.73 mm2 was observed after a 12h incubation. Loading thymol into MOFs increases the thymol contact area, thus enabling improved antimicrobial activity in broth and slow-release activity on agar.