Masters Theses

Date of Award

12-1984

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

P. Michael Davidson

Committee Members

Hugh O. Jaynes, John R. Mount

Abstract

Polyvinyl chloride films are widely used packaging materials. These films are used to package food, pharmaceutical, and medical products. Since the occurrence of microbial growth on a PVC film could result in contamination of the product, this study was conducted to determine if a PVC film could support growth of fungi and to define chemical methods of inhibiting growth.

Polyvinyl chloride film was subjected to nine species of fungi in three separate growth studies to determine if the film could serve as a nutrient source. All mold species were found to be capable of utilizing the film for carbon or nitrogen when the other nutrient was supplied. Only two species, Aspergillus fischeri and Paecilomycessp., were found to be capable of utilizing the film without added nutrient. The film components found to be utilized by the fungi as carbon sources included the epoxidized oil (plasticizer-stabilizer) and the Ca-Zn stearate (heat stabilizer). As a nitrogen source, the stearamide (lubricant) was not found to be an available nutrient source in the component study, but was found to be available in the PVC film.

To inhibit growth of the fungi on the PVC film, an initial screening test was conducted in vitro to determine the susceptibility of the fungi to the following antimicrobials: BHA (butylated hydroxyanisole), methyl paraben, propyl paraben, and potassium sorbate. The fungi were found to be inhibited by all of the preservatives except potassium sorbate at low concentrations. However, when the preservatives were applied to the film the concentrations which inhibited growth in the in vitro study were not effective in inhibiting fungal growth on the film. Therefore, increased concentrations of the inhibitors were applied to the film. Potassium sorbate at 4000 ug/ml (0.4%) was found to totally inhibit growth of Fusarium sp. while BHA at 2000 ug/ml (0.2%) inhibited growth of Paecilomycessp.

In conclusion, polyvinyl chloride films were found to be susceptible to microbial attack. The composition of the film, the microorganisms present, and the environmental conditions were shown to be determinants in the utilization of the film as a nutrient source. Therefore, it is important to determine if a PVC film can support growth of microorganisms under actual use conditions. If the film is susceptible, then appropriate methods such as controlling environmental conditions, reformulation of the film, or application of an antimicrobial agent can be used to prevent growth.

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