Abstracts Biological Sciences

THE ANTIBACTERIAL ACTIVITY OF SELECTED SMALL MOLECULECOMPOUNDS AND THEIR EFFECT ON THE MORPHOLOGY AND MECHANICALPROPERTIES OF TAPIOCA STARCH FILMS

by Zilu Wan

Microbial contamination reduces the shelf life of foods and increases the risk of foodborne illnesses. This is a major worldwide public health concern. Antimicrobial therapy is an effective way to prevent and control foodborne diseases. By incorporating antimicrobial agents into packaging material, an active food packaging system can serve as a non-thermal method of controlling foodborne pathogens. The objectives of this study were to investigate the antibacterial activity of selected small molecules, and to investigate how these compound influence the barrier and mechanical properties of starch based film when incorporated into the material. Chapter 2 focuses on the antibacterial activity of the small molecule compounds. The study was initiated by dissolving the small molecules (JA-144, TH-4, and TH-8) in dimethyl sulfoxide (DMSO), and incorporating them into tapioca films. These were then evaluated against E.coli K12, Listeria innocua, Campylobacter jejuni and Campylobacter coli, respectively. The Minimum Inhibitory Concentrations (MIC) of JA-144, TH-4 and TH-8 were determined. The bacterial growth curves for E.coli K12, L.innocua, C.jejuni and C.coli after treatment with JA-144, TH-4 or TH-8 at the MICs were then quantitatively measured. Log reduction tests of the organisms exposed to the compounds in broth and incorporated into the films were followed by bacterial growth measurement tests to give an accurate evaluation of molecules’ efficacy when incorporated into the films. Results showed that the compounds incorporated into the tapioca films and in the broth produced =3 log reduction in the test organisms. Chapter 3 focuses on the effect of the small molecule compounds on the barrier and mechanical properties of the films. Specifically, thickness, moisture content, water activity, oxygen permeability coefficient (OPC), water vapor permeability (WVP), glass transition temperature, X-ray diffraction, melting temperature and storage/loss modulus were tested as function of the compound type. Results show that the JA-144 film had the highest moisture content, OPC and WVP. This meant that it had the lowest barrier properties and mechanical property due to the plasticizing and co-plasticizing effect of hydroxyl groups within its molecules. As for TH-4 and the TH-8 films, they had lower moisture content, OPC and WVP, which meant that they had better barrier properties, and higher mechanical strength due to the crosslinking effect of the sulfonamide group they contained. Results indicated that JA-144, TH-4 and TH-8 have great potential for antimicrobial packaging, but some modifications are still necessary for their optimal use in packaging material. Advisors/Committee Members: Melvin, Pascall (Committee Chair).