An official website of the United States government.

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Improving Microbial Safety of Northwest Fresh and Processed Berries

Zhao, Yanyun
Oregon State University
Start date
End date
  1. To determine the modes of contamination of Northwest fresh berries with specific examination of E. coli O157:H7 and Salmonella spp. at the point of harvest, and to evaluate the survival of E. coli O157:H7 and Salmonella spp. in unpasteurized berry juice and puree.
  2. To develop and validate effective disinfection methods, individually and in combination, for decontaminating berries harboring human pathogens.
  3. To develop and validate intervention treatments based on the hurdle principle that results in 5-log10-unit reduction in the number of E. coli O157:H7 and Salmonella spp. in unpasteurized berry juices and puree.
  4. To develop and deliver a new university course on food safety and sanitation which will be web based and available to other educational institutions. The food safety issues of fresh and processed berry products will receive particular attention.
  5. To develop and implement training and educational workshops for a targeted audience of berry growers, handlers, processors, distributors, inspectors, and regulators to reduce the hazards associated with fresh and processed berry products. HACCP training will be the main focus with the integration of GAP, GMPs, and SSOPs for the production of fresh berries and processing of berry products.
More information
Research, education and Extension will be implemented in performing this project.
  1. Berry samples from Oregon and Washington berry farms will be collected, packed in sterile plastic bags and shipped by overnight mail to the participating laboratories for microbiological examination on E. coli, Salmonella, coliforms, and total bacterial load. Unpasteurized berry juice and puree will be obtained from OR and WA juice/puree processors. Single strength juices and purees will be challenged with E. coli O157:H7 and Salmonella spp. The survival of pathogens in berry juices and purees at temperatures of -10, 4 and 20oC with 4 bacterial strains and 2 concentrations of bacteria (100/ml and 10,000/ml) will be determined at 1, 7 and 28 days or until there are no viable bacterial survivors.
  2. Six sanitizing treatments: chlorine, trisodium phosphate, lactic acid, acetic acid, ozone, and electrolyzed oxidizing water will be studied alone and in combinations to determine their antimicrobial efficacy against selected pathogens and fungi relevant to berries. Inoculated berries will each be sanitized with the disinfectants by immersing them in selected concentrations of disinfectant for varying lengths of time. Water-treated samples will serve as controls. The treated samples will be air-dried and stored at 4oC or 25oC for up to 6 weeks or until visible decay is observed. All berries subjected to disinfectation treatments will be visually evaluated for any color or texture loss.
  3. Intervention treatments for 5-log10 unit reduction in targeted pathogens on berry juice will be investigated. Separate and combined effects of short-term refrigerated/frozen storage, freezing/thawing, and high hydrostatic pressure on inactivation of E. coli O157:H7 and Salmonella spp. without the use of heat pasteurization will be determined. We will focus on single treatment and treatment combinations that result in a 5-log10 unit reduction in cell concentration without an adverse impact on visual quality.
  4. Food safety education and training for the university food science students will be provided. A course entitled "Food safety and sanitation" will be developed. The instructional materials will focus on food safety and sanitation in food processing plants and retail operations, with specific topics covering the issues associated with the safe production of berry products. The new 3-credit course will consist of lectures and structured plant visits where students will participate in development, implementation and validation of a sanitation and HACCP plan.
  5. Education and training programs will be developed to improve the food safety practices of berry growers and processors in the Northwest region. This will consist of three aspects: a) Development/adaptation of educational curriculum and materials for workshops; b) Forming of advisory committee to ensure a balanced and effective approach to development and presentation of a food safety program for Northwest berries production; and c) Delivery and implementation of outreach programs for farms/processors through workshops, consultations, and on-site visits.

Fresh Northwest berries and their juices and purees have challenged the belief that high acid foods cannot harbor viable pathogenic bacteria. They could also act as a vector for foodborne illness. This project is to enhance and ensure the safety of Northwest fresh and processed berries through integrated research, education and Extension efforts.

This project was started in Sept., 2002. We are now in the stage of preparing training materials for the workshops scheduled in Fall, 2003 on the microbial safety of Northwest berry and berry products with a focus on HACCP (Hazard Analysis and Critical Control Point), hiring two graduate students working on the research aspects of the project, and preparing the new "Food Safety and Sanitation" course that will be offered in Spring 2003 in the Department of Food Science and Technology, Oregon State University.

The following impacts are expected through the implementation of this project: 1) to improve the microbial safety of Northwest fresh berries and berry products, such as juice and puree; 2) to strengthen students' understanding in food safety, sanitation, and HACCP; and 3) to develop scientifically-based technologies for disinfecting fresh berries and achieving 5-log reduction in targeted pathogens in fruit juice and puree.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
Accession number
Education and Training
Escherichia coli
Bacterial Pathogens