Growth of Listeria monocytogenes, Salmonella typhimurium, and spoilage microorganisms on green beans affected by salt, antimicrobials, modified atmosphere packaging, and storage temperature

Author

Wei Tan

Date of Award

12-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Food Science and Technology

Major Professor

F. Ann Draughon

Committee Members

David A. Golden, Marjorie P. Penfield, John R. Mount, Luther R. Wilhelm

Abstract

Growth and survival of Listeria monocytogenes. Salmonella typhimurium, and spoilage microorganisms in minimally processed green beans as influenced by modified atmosphere packaging, storage temperature, salt treatment, and antimicrobial dips were investigated. Green beans were snipped, washed, dipped in a chlorine solution (200 ppm), and soaked in a 20% NaCl solution for 20 min. Green beans were inoculated with 10³-10⁴ CFU/g of L. monocytogenes Scott A or S. typhimurium, packaged in plastic bags under air or vacuum, and stored at 5,10, or 15°C. Growth of L. monocytogenes, S. typhimurium, and spoilage microorganisms (mesophilic aerobes, psychrotrophs, coliforms, lactic acid bacteria (LAB), yeasts, and molds) was monitored at 2- or 3-day intervals for 8 to 18 days depending on storage temperature.

Salt-treated green beans containing 2.32% NaCl had lower moisture content, water activity, and respiration rate than non-salt-treated samples. L. monocytogenes and S. typhimurium were not detected in uninoculated samples. In inoculated green beans, L. monocytogenes grew significantly (p<0.05) at all temperatures studied, and the population increased as temperature increased. Salt treatment and vacuum packaging reduced the population of L. monocytogenes at 15°C, but not at 5 and 10°C. S. typhimurium population increased significantly (p<0.05) in green beans at 15°C, but decreased at 5 and 10°C. Salt-treated green beans had higher counts of S. typhimurium than non-salt-treated beans regardless of storage temperature. Growth of spoilage microorganisms increased significantly (p<0.05) as temperature increased. Populations of mesophilic aerobes, psychrotrophs, and LAB were greater in salt-treated green beans than non-salt-treated samples at 10 or 15°C. Packaging system did not affect growth of S. typhimurium and spoilage microorganisms at any temperatures studied.

In the antimicrobial study, green beans were dipped into chlorine (200 ppm), potassium sorbate (2000 ppm), or Per/Lac 1911 (10,000 ppm) solutions and inoculated with L. monocytogenes Scott A or S. typhimurium. Green beans were packaged in plastic bags under air atmosphere and stored at 10°C for 12 days. Populations of L. monocytogenes on green beans was reduced by chlorine, but not by other chemical treatments. None of the antimicrobials had an influence on the population size and growth of S. typhimurium or spoilage microorganisms tested.

Recommended Citation

Tan, Wei, "Growth of Listeria monocytogenes, Salmonella typhimurium, and spoilage microorganisms on green beans affected by salt, antimicrobials, modified atmosphere packaging, and storage temperature. " PhD diss., University of Tennessee, 1995.
https://trace.tennessee.edu/utk_graddiss/7524