Hugh Lockhart

Development of a Food Packaging Coating Material with Antimicrobial Properties

Antimicrobial films may provide an effective way to control food-borne pathogens and spoilage microorganisms to thus enhance food safety and decrease product spoilage. Antimicrobial films can be produced by incorporation of chemical preservatives or antimicrobial agents into a plastic film. The agents can then diffuse into the food to control target microorganisms. In this work, antimicrobial coatings were developed by incorporation of nisin, lactoferrin (an antimicrobial peptide derived from bovine lactoferrin in cow’s milk), sodium diacetate, sorbic acid, and potassium sorbate into a coating material. Saran® F-310 resin, a copolymer of vinylidene chloride, was used to produce the base coating using a solvent casting method. The antimicrobial activity of these films was verified on laboratory media against the food-borne pathogen Listeria monocytogenes. Films containing nisin, sorbic acid, and potassium sorbate inhibited L. monocytogenes strain CWD 95. The lowest level of nisin, sorbic acid, and potassium sorbate that had antimicrobial activity was 1, 1.5, and 2% w/v respectively. Films containing sorbic acid were the most compatible with the resin solution and had the best physical appearance. The water vapor barrier of films containing sorbic acid was almost unchanged compared to the control film (no antimicrobial agent). The three-dimensional structure of the films was observed using Scanning Electron Microscope (SEM). The results show that films containing sorbic acid were the most homogenous of the sample films.

Predicting the Strongest Peelable Seal for ‘Easy-Open’ Packaging Applications:

The effect of heat sealing temperature, time, and pressure on the heat sealing strength of five commercially available packaging films has been evaluated in order to obtain the strongest peelable seal for ‘easy-open’ packaging applications. The mechanical and physical properties of the seal are evaluated. An innovative method and technique to measure the heat sealing properties of different packaging materials is outlined. Inflection points on the temperature-time sealing profile were obtained and determined to be equivalent to the fusion temperature. The fusion temperatures correlated well with the highest peel strength of seals made at the experimentally determined temperatures. The highest peel seal strength has been achieved at a temperature near the fusion point, but below the melting point. The seals made above the fusion point result in weld seals. The pressure has limited effect on the sealing properties of the sealed films in the range tested for this work. The method has been found to be applicable to design of peelable heat seals for many packaging materials and seems to have promise as a method of process measurement and validation for heat seal processes. The project foresees the potential use of this method into other widely used packaging materials, and the method can be useful in the Hazard Analysis and Critical Control Point (HACCP) system for heat sealing processes.

A New Methodology for Whole-Package Microbial Challenge Testing for Medical Device Trays

It is critical that packages containing sterile medical devices maintain a sterile barrier until the device is used. In 1995, a study conducted by the Health Industry Manufacturers Association (HIMA) compared a whole-package microbial challenge test to physical integrity testing [1]; published results indicated the superiority of physical tests. This paper discusses the problems with the classic approach to whole-package microbial challenge, outlines a new whole-package microbial challenge test, and details the work done to begin to illustrate its effectiveness. The project aim is the creation of a new methodology for microbial challenge testing of medical device packages that reduces the chance of false positives that were commonly observed with the previous technique. The proposed method involves aseptically filling sterile, sealed packages with growth media, challenging them with microbes, incubating the package, and then conducting colony counts to determine package contamination. Results suggest that the proposed technique does not have the false positives that were associated with historical microbial challenge testing. False positives are a serious problem, as they indicate that a package has not maintained its sterile barrier when, indeed, it has. This can lead manufacturers to false assumptions about production and the package, potentially resulting in increased costs for healthcare providers and patients. Research presented here represents the first step in creating a standardized methodology for whole-package microbial challenge testing. Currently, such a test does not exist. While there are numerous physical integrity tests that a manufacturer of medical devices can employ to verify the integrity of packages before release to the market, a need exists for a standardized whole-package microbial challenge test that overcomes the difficulties associated with those of the past.