Date of Award

Summer 8-2019

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Jennifer Perry

Second Committee Member

Balu Nayak

Third Committee Member

Robson Machado

Additional Committee Members

Brian Perkins

Abstract

In the last decade, outbreaks linked to the consumption of contaminated fresh produce have increased mitigation efforts to minimize the risks associated with these products. Due to the lack of a kill step during processing of ready-to-eat (RTE) foods, good manufacturing practices (GMP’s), and sanitization are the key prevention areas most commonly used to control these risks. Many factors must be considered by processors for successful intervention such as sanitizer type, method of application, duration of application, and concentration. Additionally, product considerations such as water content, pH, and bacterial harborage sites can contribute greatly to how effective an applied treatment may be. The goal of this research was to evaluate alternative sanitization methods at the pilot scale to combat Listeria innocua and native microflora on fresh cut cantaloupe and wild blueberries. Parameters chosen for these studies aimed to mimic current processing conditions to provide a better understanding of what you likely would see in a large-scale processing environment.

To carry out this research, a bench scale study was completed to determine which treatment combinations to use at the pilot scale. Sequential applications of chlorine (200ppm), peracetic acid (PAA, 80ppm), and electrolyzed water (200ppm active chlorine constituents) were compared to a water control. The combination of sanitizer treatments were applied via dip or spray singly, or sequential application of dip then spray, or duplicate spray.

At the pilot scale, sanitizer combination treatments were evaluated for 3 minutes of contact time followed by freezing for up to two weeks (wild blueberries) or refrigerated storage for 48 hours (fresh cut cantaloupe). Microbial populations were evaluated at each stage to determine the efficacy of each treatment. For fresh cut cantaloupe we found that none of the treatments investigated were effective at reducing Listeria innocua populations at the pilot scale and observed an increase in population following refrigerated storage. Similarly, for wild blueberries none of the treatments investigated significantly reduced Listeria innocua populations and after two weeks of freezing Listeria innocua was detected in the product. Our results demonstrate the complex interaction of the treatment applied and product type, volume of product, and application method. Understanding these interactions can help processors to make informed decisions for potential food safety interventions and the applicability of current research at the pilot scale. Further investigation into the effects of growing practices on microbial communities and other potential pathogen inactivation methods need to be evaluated.

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