Title page for ETD etd-11142003-180132

Type of Document Master's Thesis
Author Piotrowski, Christine Lelia
Author's Email Address cpiotrow@vt.edu
URN etd-11142003-180132
Title Survival of Listeria monocytogenes in Fruit Juices During Refrigerated and Temperature-Abusive Storage
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Williams, Robert C. Committee Chair
Marcy, Joseph E. Committee Member
Sumner, Susan S. Committee Member
  • acid
  • juice
  • pH
  • cider
  • Listeria monocytogenes
Date of Defense 2003-10-10
Availability unrestricted
Survival of Listeria monocytogenes in apple, orange, red grape, and white grape juice was evaluated. A six-strain cocktail of L. monocytogenes was used to inoculate (approx. 7 log cfu/ml) fruit juices, which were stored at 4, 10 and 24°C for up to 61 days. Inoculated red grape juice was stored for up to 5 hours only. Samples were withdrawn at appropriate intervals, neutralized with 1.0 N NaOH, serially diluted in 0.1% peptone water, and surface plated onto Tryptic Soy Agar + 0.6% Yeast Extract (TSAYE) and Modified Oxford Agar (MOX), followed by incubation at 32°C for 48 hours. When L. monocytogenes was no longer detected by direct plating, samples were enriched for L. monocytogenes using Listeria Enrichment Broth (LEB), followed by isolation on MOX. L. monocytogenes remained viable in white grape, apple, and orange juices for up to 12, 24 and 61 days, respectively. Over time, recovery of Listeria on TSAYE versus MOX was not significantly different (P>0.05), indicating that limited acid-injury developed during storage. The results of this study demonstrate the ability of L. monocytogenes to survive in apple, orange, and white grape juices during refrigerated and abusive storage conditions. Therefore, measures to prevent or eliminate L. monocytogenes in the fruit juice-processing environment are necessary to ensure the safety of juice products for public consumption.

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