Possible Routes of Contamina1on of Fresh Produce and Methods of Post- Harvest Sani1za1on

Transcription

1 Possible Routes of Contamina1on of Fresh Produce and Methods of Post- Harvest Sani1za1on Amanda Deering, Ph.D. Department of Food Science Indiana Hor1cultural Congress January 17 th, 2012

2 What s the Problem? The number of outbreaks associated with fresh produce has been increasing Spinach and Lettuce Tomatoes Sprouts - Mung Bean and Alfalfa Cantaloupe Pathogens Involved: E. coli O157:H7 Salmonella spp. Listeria monocytogenes hpp:// When Bad Things Come From Good Food January 2, 2007

3 Contamina1on of Plants/Produce Pathogenic bacteria can be introduced at any point during the growing, harvest, and post- harvest handling Plants can be a vehicle for transmission of bacteria to humans Passive contamina1on event Can some1mes be corrected by proper post- harvest sani1za1on methods Examples: Improperly composted manure Contaminated irriga1on water Breakdown in sani1za1on treatment

4 Introduc1on of Bacteria Through Wounds Cut or damaged surfaces (bruising) provides a point of entry for the bacteria into the plant Increases the risk of contamina1on Nutrients are released from the plant that provide food for the bacteria Excess trimming of produce should be avoided

5 Introduc1on of Bacteria Through Stomata are present on the plant surface Regulates gas exchange by opening and closing Bacteria can enter during washing using contaminated water or other contamina1on event Bacteria protected from sani1zers Natural Openings

6 Contamina1on of Plants What happens when the bacteria are not just associated with the outside of the plant? Can human pathogenic bacteria internalize within plant 1ssue? If so, can they move and persist within the plant? What routes of contamina.on are important in producing plants that can harbor internalized bacteria?

7 Where are Bacteria Internalized? EVERYWHERE: Vascular Tissue Epidermis Cortex Pith Leaves Fruits Roots Localiza1on to the vascular 1ssue means the bacteria have the ability to move throughout the plant Deering et. al., 2011

8 Importance of Seed Contamina1on How much water and/or bacteria can seeds take up? 485 seeds soaked in 10 7 E. coli O157:H7 culture in water for 12 hours at room temperature with rota1on Average % Weight Change = 116.2% Seeds retained an average 10 5 CFU/seed and retained these high levels over 12 days

9 Examining Routes of Contamina1on Can the bacteria persist and move within the plant? Contamina1on: Leaf - Wound to the leaf Soil Contaminated irriga.on water Seed Contaminated seed stock Tomato Varie1es (Dwarf): Micro- Tom Elfin Tommy Toe Sweet Quartz Red Currant BSL 2 Greenhouse, Purdue University

10 Bacteria Internalize in Tomato Fruit Seed and Leaf contaminated plants ( 50%) Never in soil contaminated plants Internalized bacteria protected from any sani1za1on treatment

11 Conclusions Routes of Contamina1on Cut, bruises, and natural openings can provide a point of entry into the plant and provide a carbon source to the bacteria Human pathogenic bacteria can internalize within plant 1ssue and move to ripe fruit Seed contamina1on most problema1c Lesser extent leaf and soil contamina1on These are greenhouse and laboratory studies Once contamina1on has occurred, bacteria can grow to high levels in the plant GAPs important Development of novel sani1zers necessary

12 Post Harvest Sanitization Methods and GAPs Partnership to improve food safety of fresh produce Test and develop novel sanitizers Develop sanitization testing methods Lettuce, spinach, blueberries

13 Researchers/growers have tested new sanitization methods: - Traditional: Chlorine - New: Ozone, Chlorine Dioxide Gas, Organic Acids No treatment completely eliminates all bacteria Importance of GAPs Post Harvest Sanitization Sanitizer must come in contact with the pathogen to be effective Internalization? Does the treatment effect the sensory qualities? Browning, off colors, off odors, changes in shelf-life of the product

14 Sanitization of Fresh Produce Chlorine is the most common sanitizer used - Concerns of residual chlorine present on the fresh produce - Concerns of residual chlorine by-products, such as trihalomethanes, that may be generated in the wastewater - Other sanitizers examined: Organic acid, ozone, chlorine dioxide gas, hydrogen peroxide, phosphoric acid Challenges with Leafy Greens: - Have soft tissues that can easily be damaged - Waxes (cuticle) on the surface can protect bacteria - Bacteria can internalize within the leaf tissue

15 GAPs Important for Growers Evaluate fields prior to planting - Only grow on fields that are found acceptable - Disc under and don t use fields or portions of fields where pathogens are present Have trained food safety staff and not harvest personnel doing pre-harvest checks on fields Train all field people as to WHY food safety is important Ø Field people are likely to see the problems first Ø They are trained to recognize and handle problems as they arise to maintain GAPs

16 Questions? Contact Information: Amanda Deering