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Food Spoilage: “Stinkies”, “Slimies” and Biofilms

Food Spoilage: “Stinkies”, “Slimies” and Biofilms. -by- Jovana Kovačević. October 22, 2009. Outline. Spoilage of Food Spoilage Signs Meat, Fish, Dairy What do laboratory tests tell you about spoilage? Biofilms Properties and formation Why are they a problem?

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Food Spoilage: “Stinkies”, “Slimies” and Biofilms

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  1. Food Spoilage:“Stinkies”, “Slimies” and Biofilms -by- Jovana Kovačević October 22, 2009

  2. Outline • Spoilage of Food • Spoilage Signs • Meat, Fish, Dairy • What do laboratory tests tell you about spoilage? • Biofilms • Properties and formation • Why are they a problem? • How do we deal with spoilage and biofilms?

  3. Undesirable deterioration of food quality that may result in changes in odor, taste and appearance of food. Food Spoilage

  4. Food Spoilage • Types of spoilage: • Microbial: • Bacteria, yeasts, molds • Non-microbial • Foreign materials, enzymes • Changes not necessarily harmful

  5. Microbial Food Spoilage • Each food unique microbial environment • unique spoilage agents for each • Why do microorganisms spoil our food? • food composition ideal source of nutrients for microbes • availability of water and oxygen • suitable pH • Factors that affect spoilage: • Oxygen, temperature, pH, aw, humidity

  6. Spoilage organisms • Similar microflora emerge in different foods under the same conditions • Affected by the: • Type of food • Processing • Preservation • Storage conditions • Domination of specific spoilage microbes: • Initial counts present • Nutrient composition • Chemical and physical parameters

  7. Spoilage Signs • Odor: • Breakdown of proteins – putrefaction e.g. “rotten egg” smell • Sliminess • Discoloration • Mold on bread, blue and green mold on citrus fruit and cheese

  8. Spoilage Signs… • Souring • Production of acid e.g. sour milk from production of lactic acid • Gas formation • Meat becomes spongy • Swollen or bubbling packages and cans

  9. Food Types: Based on rate of spoilage 1) Highly perishable • meat • fruit • milk • vegetables • eggs 2) Semi perishable • potatoes • nuts 3) Stable • rice • flour • dry beans WET DRY

  10. Common Causes of Food Spoilage • Inadequate storage temperatures • Prolonged storage times • Improper ventilation • Cross contamination • Excessive delays between receiving and storing • Inadequate food safety standards

  11. Meat Spoilage

  12. Meat spoilage… • Cutting board contamination • Conveyor belts • Temperature • Delay between storage and distribution • Fecal contamination from intestines

  13. Meat Spoilage Continued

  14. Fish and Eggs Spoilage

  15. Fish Polluted waters Transportation vehicles, boxes Poultry and Eggs Human contact Penetration by bacteria Cracks Fish and Eggs Spoilage Continued TEMPERATURE PHYSICAL DAMAGE INTRINSIC FACTORS

  16. Fish & Eggs Spoilage Continued

  17. Spoilage of Milk and Dairy Products http://farm3.static.flickr.com/2313/2181694147_12ce5cd763.jpg

  18. Spoilage of Milk and Dairy Products Continued

  19. Spoilage of Fruits and Vegetables http://timelytidbits.wordpress.com/2008/07/28/the-word-of-god-as-rotting-fruit/

  20. Spoilage of Fruits and Vegetables

  21. Examples of Food Quality Tests • Meat & Fish: pH for vacuum packaging (< 6.0) • Visual inspection for leakage / color change • Faulty seals, pin-holes • Sensory test • Aerobic plate count at 30°C • Indication of hygiene at packaging • Expected refrigerated shelf-life • ↑ APC = improper cleaning of equipment, unacceptable time/temperature history of raw products

  22. Total Viable Count Enterobacteriacea Coliforms Escherichia coli Enterococci Staphilococcusaureus Bacillus spp. Clostridium perfringens Lactic acid bacteria Pseudomonas species Yeasts and molds Testing for Microbial Quality

  23. PHSA Lab

  24. Examples of Food Submission Forms

  25. Total Viable Count • Total Viable Count also known as: • Heterotrophic plate count (HPC) • Aerobic plate count (APC) • Total plate count (TPC) • Aerobic colony count (ACC) • Aerobic mesophilic count • Purpose: The aerobic plate count gives the total number of bacteria able to grow in an oxygenated or aerobic environment. • Cooked foods should have little to no bacteria present • Result provides a guide for shelf-life of foods • The higher the count: prolonged storage, and/or inadequate cooking. Note: Not a useful indicator for fermented foods or fresh ready-to-eat raw fruits and vegetables.

  26. Enterobacteriaceae • A family of Gram-negative, facultatively anaerobic, rod-shaped bacteria that do not form endospores and ferment variety of sugars • Includes: • Pathogenic microbes: e.g. pathogenic E. coli, Proteus, Salmonella, Shigella, Yersinia, Enterobacter, Serratia, Klebsiella • Non-pathogenic microbes: e.g.Citrobacter, Erwinia, Hafnia

  27. Coliforms and E. coli • Coliforms: • Total coliforms • Fecal coliforms: • Found in human and animal intestinal wastes • More precise indicator of the presence of sewage contamination than total coliforms • Four groups of fecal coliforms: • Enterobacter • Klebsiella • Escherichia • Citrobacter

  28. Escherichia coli • Best indicator of fecal sanitation problems • Characterized by the fermentation of glucose and lactose • Found • In the gut of warm blooded mammals • In the gut of insects and reptiles • As natural soil microbial flora

  29. Sanitary Quality Guidelines

  30. Aerobic Plate Count: Environmental Swabs Guidelines for interpretation of bacterial counts from swabs and sponges as means of monitoring the cleanliness of surfaces. ** Values will vary depending on size of the surface area sampled. To calculate the number of bacteria per cm2 take the total CFU and divide by the surface area swabbed.

  31. Common Spoilage Microorganisms • Shewanella putrefaciens • Pseudomonas spp. • Gram negative • Rod shaped • Motile • Aerobic • Non-spore forming • Biofilm formers http://www.lille.inra.fr/lille_eng/unites_et_recherches/nos_unites/ gpta/interfaces_bacteries_aliments_surfaces_solides

  32. Pseudomonas aeruginosa http://www.microbelibrary.org/asmonly/details.asp?id=545&Lang=

  33. Biofilms “Variety of microorganisms arranged in a complex relationship to one another and embedded in a mass of extracellular polysaccharides of their own making” (http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/)

  34. Biofilms Continued • Communities of bacteria adhering to: • Environmental surfaces • Living tissues • Indwelling medical devices • Industrial or potable water system piping • Natural aquatic systems • Food processing facilities: • Floors, waste water pipes, bends in pipes, rubber seals, conveyor belts, stainless steel surfaces (Kumar and Anand, 1998) http://www.microbelibrary.org/ FEMS Microbiology Letters. 228:203-210.

  35. Why do bacteria form biofilms? • Protection from the environment • Sanitizers • Antibiotics • Nutrient availability and metabolic cooperativity • Acquisition of new genetic traits

  36. Biofilm formation http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/

  37. Control of Microbial Spoilage • Good manufacturing practices • Cleaning and sanitation • Processing environment • Equipment • Handling with minimal physical damage • Washing (in some case) • Proper storage temperature • Rapid movement of food through processing plant • Treatments… • preservation

  38. Food preservation • Temperature based: • Chilling • Refrigeration • Freezing • Pasteurization • Canning • Water activity reduction • Dehydration • Addition of salts and sugars • Irradiation • Modified Atmosphere Packaging • Fermentation • Treatment with chemicals • Sorbic acid, phenylphenates, diphenyl and iodophors, fumigation with sulfur-containing dusts

  39. References 1. Davey and O’Toole (2000). Microbial Biofilms: from ecology to molecular genetics. Microbiol. Molec. Bio. Rev. 64(4):847-867. 2. Forsythe, S.J, and P.R. Hayes. 1998. Food Hygiene Microbiology and HACCP. 3rd Ed. pp. 434. Aspen Publishers Inc., Maryland. 3. ICMSF. 2005. Microorganisms in Foods. Microbial Ecology of Food Commodities. 2nd Ed. pp. 763. Kluwer Academic/Plenum Publishers, New York, NY. 4. Marsh, E.J., H. Luo, H. Wang. 2003. A three-tiered approach to differentiate Listeria monocytogenes biofilm-forming abilities. FEMS Microbiology Letters. 228:203-210. 5. http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/ 6. http://www3.sympatico.ca/tania.nicolas/River%20Biofilm.jpg 7. http://www.lille.inra.fr/lille_eng/unites_et_recherches/nos_unites/ gpta/interfaces_bacteries_aliments_surfaces_solides 8. http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/ 9. http://www.microbelibrary.org/asmonly/details.asp?id=545&Lang= 10. http://timelytidbits.wordpress.com/2008/07/28/the-word-of-god-as-rotting-fruit/ 11. http://farm3.static.flickr.com/2313/2181694147_12ce5cd763.jpg

  40. Thank you!

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