Use of Gamma Irradiation as an Intervention Treatment to Inactivate Escherichia coli O157:H7 in Freshly Extracted Apple Juice

<p><em>Escherichia coli </em>O157:H7 can contaminate dropped apples used for juicing via contact with manure or fecally tainted irrigation water and attach to the flesh of the apple through bruises and wounds where surface sanitizers are not effective. The goal of this project was to determine the efficacy of gamma irradiation at the maximum allowed dose of 1000 Gy to inactivate <em>Escherichia coli </em>O157: H7 in whole apples used for juicing. Whole apples were punctured to simulate wounds which were then inoculated with an outbreak strain of <em>E.coli </em>O157:H7 and subjected to gamma irradiation at doses upto 1000 Gy. The D-value of the <em>E.coli </em>O157:H7 strain was 334 Gy indicating that irradiation at 1000 Gy would result in a 3-log reduction of this pathogen. Contaminated apples were also stored for 3 weeks at refrigerated temperature during which time <em>E.coli </em>O157:H7 survived but did not grow. The inoculated apples were juiced, and the juice was stored up to 72 h. There was no change in counts of <em>E.coli </em>O157:H7 in the juice from the control apples, but irradiation at >600 Gy reduced counts by >3 logs, and survivors were not detected after 72 h storage. Sensory testing of juice treated at 652 Gy indicated consumers could tell the difference from control juice, due mostly to greater sweetness of the juice from irradiated apples. These results show that <em>E.coli </em>O157:H7 can easily survive in bruised apples and the juice made from them. Irradiation at 1000 Gy can provide significant lethality of <em>E.coli </em>O157:H7 in apples and juice conferring a greater level of safety without negative effects on sensory quality.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Food Science

Year dc:date.available

2019

Author dc:creator

• Fernandes, Dielle Aurelia

Contributors dc:contributor

• Dr. Anuradha Prakash
• Dr. Donna Williams-Hill
• Dr. Denise Foley
• Dr. Kirsten Hirneisen

• D-value
• sensory
• E.coli O157:H7
• irradiation
• apple juice
• Food Microbiology
• Food Science

Repository record dc:identifier

https://digitalcommons.chapman.edu/food_science_theses/6

OAI identifier oai:identifier

oai:digitalcommons.chapman.edu:food_science_theses-1006