100B-25 |
The effect of sodium chloride (NaCl) in nisin-containing film coating |
J. L. GROWER1, D. K. Cooksey1, and K. Getty2. (1) Dept. of Packaging Science, Clemson Univ., B-212 P&A Bldg., Box 340370, Clemson, SC 29634-0370, (2) Food Science Institute, Kansas State Univ., 148 Waters Hall, Manhattan, KS 66506 Low-density polyethylene (LDPE) films coated with nisin-containing solution containing commercially prepared nisin exhibited a cloudy, crystalline appearance. Commercially prepared nisin contains 2.5% nisin and is balanced with 77.5% NaCl, 18% milk solids and 2% moisture. The high concentration of NaCl may affect the inhibitory role of nisin. The first objective was to identify the crystalline structures in the nisin-containing film coating. Based on identification of the crystalline structures as NaCl, the second objective was to determine the role of NaCl in the film coating for inhibition of LM. The third objective was to study the mechanical and barrier properties of the nisin-coated films. Field emission scanning electron microscopy and energy-dispersive spectroscopy were used to analyze the film coatings. To test the effect of the NaCl portion of nisin on LM, solutions were made containing an equivalent amount of NaCl and milk solids found in 10,000 IU/cm2 commercially prepared nisin. A 10mL drop of solution was placed onto tryptic soy agar plates spiral plated with LM and zones of inhibition were measured (mm). Differences in film thickness, tensile strength and water vapor transmission rate (WVTR) were measured using ASTM procedures. Experiments were performed in triplicate. Crystalline structures on the film coating were identified as NaCl. A drop assay demonstrated that NaCl had no inhibitory effect on LM when used alone, indicating that nisin is the effective inhibitory agent when tested in peptone solution. Nisin and NaCl-containing film coatings increased the thickness of films due to the presence of NaCl crystals. The increased thickness of the film coatings affected the tensile strength of the films. The films have a "snowy" appearance when the coating contains nisin due to the high concentration of NaCl in commercially prepared nisin. The high concentration of NaCl may synergistically enhance the effectiveness of the nisin but alone is ineffective against LM in solution.
Session 100B, Food Packaging
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