Text

theses

The low processing temperature of cold smoked salmon poses several risk factors, one of which is the growth of the foodborne pathogen, Listeria monocytogenes. The desire for novel, naturally sourced antimicrobial agents is increasing with increased consumer demand and concern of antimicrobial resistance by foodborne pathogens. Photosensitizer curcumin (PSC) was prepared by suspending it in sterile distilled water. The absorption spectrum of PSC was evaluated using a spectrophotometer. A light unit of wavelength 430 nm was set up for the experiments. The antimicrobial efficacy of curcumin was evaluated on Listeria monocytogenes planktonic and solid system, followed by optimizing the PSC exposure time versus the light intensity combination. The first part of the study aimed to evaluate photosensitizer curcumin as a surface sanitizer on food contact surfaces typical of the cold-smoked fish industry. To form a Listeria monocytogenes biofilm, 1 mL of working culture of 106 CFU/mL was added to 9 mL of salmon exudate in which two 2x2 cm stainless steel (SS) coupons were placed for 72 hr. This was followed by 1 min exposure to 160 ppm curcumin and 76.59 kJ/m2 light dose. A control and 200 ppm of chlorine treatment were also performed for comparison. The PSC treatment with light exposure significantly decreased the population of L. monocytogenes similar to that of the 200 ppm chlorine treatment with a 3.45 log reduction. These results suggest potential application of the treatment method for control of the pathogen on stainless steel surfaces found frequently in the cold-smoked fish industry.
The second part of this study aimed to evaluate photosensitizer curcumin as a treatment method for cold smoked salmon. Salmon was sectioned into 3 cm x3 cm pieces with a thickness of 0.3 cm and inoculated with 100 L (108 CFU/mL) Listeria monocytogenes. The fish were treated with exposure to 320 ppm PSC for 1 min, followed by exposure to 76.59 kJ/m2 light dose. For comparison, a control with no treatment and treatment with exposure to 25 ppm of chlorine for 10 min was also performed. This was followed by brining, drying, and cold smoking. Another treatment was performed to gain perspective on exposing part of the previously PSC-treated salmon samples to an additional 76.59 kJ/m2 light dose post cold smoking. All the cold smoked salmon were vacuum packed and sampled on day 0, day 1, day 5, and day 10. Analyses of water phase salt, pH, moisture content, water activity, and color analyses of raw salmon, and smoked salmon on day 0 and day 10 were performed.
There was a consistent decrease in the Listeria monocytogenes population observed over time. The population of Listeria on the post smoking light treated salmon was significantly lower compared to control and chlorine treated salmon at each stage of treatment or storage except on day 5.

http://dissertations.umi.com/gsnb.rutgers:12314

M.S.

Includes bibliographical references

doi:10.7282/t3-4gzj-km06

The author owns the copyright to this work.