Title page for ETD etd-051199-181646


Type of Document Master's Thesis
Author Wright, Jim
Author's Email Address jiwright@vt.edu
URN etd-051199-181646
Title Utilization OF Apple Wash Treatments And Ultraviolet Light For The Elimination Of Escherichia coli O157:H7 In Apple Cider
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Sumner, Susan S. Committee Chair
Hackney, Cameron Raj Committee Member
Pierson, Merle D. Committee Member
Zoecklein, Bruce W. Committee Member
Keywords
  • Escherichia coli O157:H7
  • Apple Cider
  • Sanitizers
  • Apples
  • Ultraviolet Light
Date of Defense 1999-02-12
Availability restricted
Abstract
Three studies regarding Escherichia coli O157:H7 in apple cider were conducted. The objectives were: to evaluate the effectiveness of wash and sanitizers for removing E. coli O157:H7 from apples; to survey cider producer practices; and to determine the efficacy of ultraviolet light for reducing E. coli O157:H7 in cider.

Apples with a five-strain acid resistant mixture of E. coli O157:H7 were treated with 200 ppm hypochlorite, a phosphoric acid-based fruit wash, 5% acetic acid, 5% acetic acid followed by 3% hydrogen peroxide, a peroxyacetic acid-based solution, and distilled water. The water wash caused insignificant reductions. All other treatments caused significant reductions. Acetic acid and peroxyacetic acid were the most effective with reductions of 3.1 and 2.6 logs, respectively.

The survey determined that most producers are small, seasonal operations. Most use sound orchard management practices, clean and sanitize daily, sort and wash apples, use refrigeration, and try to prevent contamination. However, some use drop and damaged apples. Few use chemical sanitizers on apples, preservatives, pasteurize cider, or have HACCP programs.

Cider inoculated with the same mixture of E. coli O157:H7 was processed using a thin- film ultraviolet disinfection unit operating at 254 nm. Dosages ranged from 9,402 to 61,005 æW- sec/cm2. Treatment significantly reduced E. coli O157:H7 (pó 0.0001) with a mean reduction of 3.81 log CFU/ml. Reduction was also affected by the level of background microflora in cider. Results indicate that ultraviolet light can reduce this pathogen in cider. However, additional reduction measures are necessary to achieve the required 5 log reduction.

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