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-by-Jovana Kovačević
Food Spoilage:“Stinkies”, “Slimies”
and Biofilms
October 22, 2009
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OutlineOutlineSpoilage of Food
o Spoilage Signso Meat, Fish, Dairyo What do laboratory tests tell you about
spoilage?
Biofilmso Properties and formationo Why are they a problem?
How do we deal with spoilage and biofilms?
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Food SpoilageFood Spoilage
Undesirable deterioration of food quality that may result in changes in odor, taste and appearance of food.
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Food SpoilageFood SpoilageTypes of spoilage:
Microbial: Bacteria, yeasts, molds
Non-microbial Foreign materials, enzymes
Changes not necessarily harmful
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Microbial Food SpoilageMicrobial Food SpoilageEach food unique microbial environmentunique spoilage agents for each
Why do microorganisms spoil our food?
food composition ideal source of nutrients for microbesavailability of water and oxygen suitable pH
Factors that affect spoilage: Oxygen, temperature, pH, aw, humidity
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Spoilage organismsSpoilage organismsSimilar microflora emerge in different foods under the same conditions
Affected by the:o Type of foodo Processingo Preservationo Storage conditions
Domination of specific spoilage microbes:o Initial counts presento Nutrient compositiono Chemical and physical parameters
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Spoilage SignsSpoilage SignsOdor: Breakdown of proteins
– putrefaction e.g. “rotten egg” smell
Sliminess
Discoloration Mold on bread, blue
and green mold on citrus fruit and cheese
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Spoilage Signs…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
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Food Types: Food Types: Based on rate of spoilageBased 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
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Inadequate storage temperaturesProlonged storage timesImproper ventilationCross contaminationExcessive delays between receiving and storingInadequate food safety standards
Common Causes of Food SpoilageCommon Causes of Food Spoilage
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Meat SpoilageMeat Spoilage
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Meat spoilage…
Cutting board contaminationConveyor beltsTemperatureDelay between storage and distributionFecal contamination from intestines
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Meat Spoilage ContinuedMeat Spoilage Continued
Food Types of Spoilage Spoilage Microorganisms
MEAT
FreshPutrefaction Clostridium, Pseudomonas, Proteus,
Alcaligenes, Chromobacterium
Souring Chromobacterium, Lactobacillus, Pseudomonas
Cured
Mouldy Penicillium, Aspergillus, Rhizopus
Souring Pseudomonas, Micrococcus, Bacillus
Greening Lactobacillus spp., Streptococcus, Pediococcus
Slimy Leuconostoc
Vacuum Packed
SouringGreening
Lactobacillus, Carnobacterium, Leuconostoc
Poultry Odor, SlimePseudomonas, Alcaligenes, Xanthomonas
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Fish and Eggs SpoilageFish and Eggs Spoilage
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Fish and Eggs Spoilage ContinuedFish and Eggs Spoilage ContinuedFishPolluted watersTransportation vehicles,
boxes
Poultry and EggsHuman contactPenetration by bacteriaCracks
TEMPERATURE
PHYSICAL DAMAGE
INTRINSIC FACTORS
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Fish & Eggs Spoilage ContinuedFish & Eggs Spoilage Continued
Food Types of Spoilage Spoilage Microorganisms
FISHDiscoloration Pseudomonas
PutrefactionChromobacterium,Halobacterium, Micrococcus
EGGS
Green rot Pseudomonas
Colorless rotPseudomonas, Alcaligenes,Chromobacterium
Black rot Coliforms
Fungal rot Proteus, Penicillium, Mucor
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Spoilage of Milk and Dairy ProductsSpoilage of Milk and Dairy Products
http://farm3.static.flickr.com/2313/2181694147_12ce5cd763.jpg
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Spoilage of Milk and Dairy Products ContinuedSpoilage of Milk and Dairy Products Continued
Food Types of Spoilage Spoilage Microorganisms
DAIRY
MILK(pasteurized)
Bitterness Pseudomonas spp.
Souring Lactobacillus thermophilus
Sweet curdling Bacillus cereus
CHEESE
Green discoloration Penicillium
Green to black discoloration
Cladosporium
Black discoloration Candida
Sliminess (high pH) Pseudomonas spp.
“Gassy” cheese Coliforms, LAB, Clostridia
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Spoilage of Fruits and VegetablesSpoilage of Fruits and Vegetables
http://timelytidbits.wordpress.com/2008/07/28/the-word-of-god-as-rotting-fruit/
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Spoilage of Fruits and VegetablesSpoilage of Fruits and Vegetables
Food Types of Spoilage Spoilage Microorganisms
FRESH FRUITS AND
VEGETABLES
Bacterial soft rot Erwinia carotovera, Pseudomonas spp.
Gray mould rot Botryitis cinerea
Rhizopus soft rot Rhizopus nigrican
Blue mould rot Penicillium italicum
Black mould rot Aspergillus niger, Alternaria
Sliminess andSouring Saprophytic bacteria
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Examples of Food Quality TestsExamples of Food Quality TestsMeat & 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 packagingExpected refrigerated shelf-life ↑ APC = improper cleaning of equipment,
unacceptable time/temperature history of raw products
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Testing for Microbial QualityTesting for Microbial Quality
Total Viable CountEnterobacteriaceaColiformsEscherichia coli
EnterococciStaphilococcus aureusBacillus spp.Clostridium perfringensLactic acid bacteriaPseudomonas speciesYeasts and molds
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Examples of Food Submission FormsExamples of Food Submission Forms
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Total Viable CountTotal Viable CountTotal 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 presentResult 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.
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EnterobacteriaceaeEnterobacteriaceaeA 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
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Coliforms and Coliforms and E. coliE. coliColiforms: Total coliforms Fecal coliforms:
o Found in human and animal intestinal wastes o More precise indicator of the presence of sewage
contamination than total coliforms Four groups of fecal coliforms:
o Enterobacter o Klebsiellao Escherichia o Citrobacter
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Escherichia coli
Best indicator of fecal sanitation problemsCharacterized by the fermentation of glucose and lactose
Found In the gut of warm blooded mammals In the gut of insects and reptilesAs natural soil microbial flora
Sanitary Quality Guidelines
Food GroupIndicator Test Result (CFU/g)
Satisfactory UnsatisfactoryAerobic Colony Count
Canned foods & Cooked hot-held food < 5 > 5
Cooked chilled food no handling < 100 > 1000
Cooked chilled food with handling &Preserved foods
< 100,000 > 1,000,000
Long shelf life fish products, meat products, fruitand vegetable products
< 1,000,000 > 100,000,000
Fermented foods & Fresh fruits and vegetables Not applicable Not applicable
Total Coliform Count
All foods except fresh fruits & vegetables,or foods containing them
<100 > 1000
Fecal Coliform Count
All foods except fresh fruits & vegetables, or foodscontaining them
< 3 > 3
Escherichia coli Count
All foods < 3 > 3
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Aerobic Plate Count: Environmental SwabsAerobic Plate Count: Environmental Swabs
Guidelines for interpretation of bacterial counts from swabs and sponges as means of monitoring the cleanliness of surfaces.
Interpretation
CFU Count Per Area Swabbed
Log Conversion
Counts on Surface* (based on 25 cm2 surface area sampled)
Clean < 45 CFU < 1.65 < 5 CFU / cm2
Contaminated 140 to 260 CFU 2.15 – 2.41 ~ 5 to 10 CFU / cm2
Very Contaminated > 260 CFU > 2.41 > 10 CFU / cm2
** 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.
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Common Spoilage MicroorganismsCommon Spoilage Microorganisms
Shewanella putrefaciensPseudomonas spp.
o Gram negativeo Rod shapedo Motileo Aerobico Non-spore formingo Biofilm formers
http://www.lille.inra.fr/lille_eng/unites_et_recherches/nos_unites/gpta/interfaces_bacteries_aliments_surfaces_solides
Pseudomonas aeruginosa
http://www.microbelibrary.org/asmonly/details.asp?id=545&Lang=
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BiofilmsBiofilms
“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/)
Biofilms ContinuedBiofilms ContinuedCommunities of bacteria adhering to:
Environmental surfaces Living tissues Indwelling medical devices Industrial or potable water
system piping Natural aquatic systems Food processing facilities:
o Floors, waste water pipes, bends in pipes, rubber seals, conveyor belts, stainless steel surfaces (Kumar and Anand, 1998)
FEMS Microbiology Letters. 228:203-210.
http://www.microbelibrary.org/
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Why do bacteria form biofilms?Why do bacteria form biofilms?
Protection from the environmento Sanitizers
o Antibiotics
Nutrient availability and metabolic cooperativity
Acquisition of new genetic traits
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Biofilm formation
http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/
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Control of Microbial SpoilageControl of Microbial SpoilageGood manufacturing practicesCleaning and sanitationProcessing environmentEquipment
Handling with minimal physical damage Washing (in some case) Proper storage temperatureRapid movement of food through processing plantTreatments…preservation
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Temperature based:o Chillingo Refrigerationo Freezingo Pasteurizationo Canning
Water activity reductiono Dehydrationo Addition of salts and sugars
IrradiationModified Atmosphere PackagingFermentationTreatment with chemicals
o Sorbic acid, phenylphenates, diphenyl and iodophors, fumigation with sulfur-containing dusts
Food preservationFood preservation
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ReferencesReferences1. 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
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Thank you!
