Transcript Slide 1

Food Spoilage:
“Stinkies”, “Slimies”
and Biofilms
-byJovana Kovačević
October 22, 2009
Outline
Spoilage of Food
o Spoilage Signs
o Meat, Fish, Dairy
o What do laboratory tests tell you about
spoilage?
Biofilms
o Properties and formation
o Why are they a problem?
How do we deal with spoilage and biofilms?
10/22/2009
2
Food Spoilage
Undesirable
deterioration of food
quality that may
result in changes in
odor, taste and
appearance of food.
10/22/2009
3
Food Spoilage
Types of spoilage:
 Microbial:
 Bacteria, yeasts, molds
 Non-microbial
 Foreign materials, enzymes
Changes not necessarily harmful
10/22/2009
4
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
10/22/2009
5
Spoilage organisms
Similar microflora emerge in different foods under
the same conditions
Affected by the:
o Type of food
o Processing
o Preservation
o Storage conditions
Domination of specific spoilage microbes:
10/22/2009
o Initial counts present
o Nutrient composition
o Chemical and physical parameters
6
Spoilage Signs
Odor:
 Breakdown of proteins
– putrefaction
e.g. “rotten egg” smell
Sliminess
Discoloration
10/22/2009
 Mold on bread, blue
and green mold on
citrus fruit and cheese
7
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
10/22/2009
8
Food Types: Based on rate of spoilage
1) Highly perishable





meat
fruit
milk
vegetables
eggs
WET
2) Semi perishable
 potatoes
 nuts
3) Stable
10/22/2009
 rice
 flour
 dry beans
DRY
9
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
10/22/2009
10
Meat Spoilage
10/22/2009
11
Meat spoilage…
Cutting board contamination
Conveyor belts
Temperature
Delay between storage and distribution
Fecal contamination from intestines
10/22/2009
12
Meat Spoilage Continued
Food
Types of
Spoilage
Spoilage Microorganisms
MEAT
Putrefaction
Clostridium, Pseudomonas, Proteus,
Alcaligenes, Chromobacterium
Souring
Chromobacterium, Lactobacillus,
Pseudomonas
Mouldy
Penicillium, Aspergillus, Rhizopus
Souring
Pseudomonas, Micrococcus, Bacillus
Greening
Lactobacillus spp., Streptococcus,
Pediococcus
Slimy
Leuconostoc
Souring
Greening
Lactobacillus, Carnobacterium,
Leuconostoc
Odor, Slime
Pseudomonas, Alcaligenes,
Xanthomonas
Fresh
Cured
Vacuum
Packed
Poultry
10/22/2009
13
Fish and Eggs Spoilage
10/22/2009
16
Fish and Eggs Spoilage Continued
Fish
Polluted waters
Transportation vehicles,
boxes
Poultry and Eggs
Human contact
Penetration by bacteria
Cracks
10/22/2009
TEMPERATURE
PHYSICAL DAMAGE
INTRINSIC FACTORS
17
Fish & Eggs Spoilage Continued
Food
FISH
EGGS
10/22/2009
Types of
Spoilage
Spoilage Microorganisms
Discoloration
Pseudomonas
Putrefaction
Chromobacterium,
Halobacterium, Micrococcus
Green rot
Pseudomonas
Colorless rot
Pseudomonas, Alcaligenes,
Chromobacterium
Black rot
Coliforms
Fungal rot
Proteus, Penicillium, Mucor
18
Spoilage of Milk and Dairy Products
10/22/2009
http://farm3.static.flickr.com/2313/2181694147_12ce5cd763.jpg
19
Spoilage of Milk and Dairy Products Continued
Food
Types of Spoilage
Spoilage Microorganisms
Bitterness
Pseudomonas spp.
Souring
Lactobacillus thermophilus
Sweet curdling
Bacillus cereus
Green discoloration
Penicillium
Green to black
discoloration
Cladosporium
Black discoloration
Candida
Sliminess (high pH)
Pseudomonas spp.
“Gassy” cheese
Coliforms, LAB, Clostridia
DAIRY
MILK
(pasteurized)
CHEESE
10/22/2009
20
Spoilage of Fruits and Vegetables
10/22/2009
http://timelytidbits.wordpress.com/2008/07/28/the-word-of-god-as-rotting-fruit/
21
Spoilage of Fruits and Vegetables
Food
FRESH FRUITS
AND
VEGETABLES
10/22/2009
Types of
Spoilage
Spoilage Microorganisms
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 and
Souring
Saprophytic bacteria
22
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
10/22/2009
23
Testing for Microbial Quality
Total Viable Count
Enterobacteriacea
Coliforms
Escherichia coli
10/22/2009
Enterococci
Staphilococcus aureus
Bacillus spp.
Clostridium perfringens
Lactic acid bacteria
Pseudomonas species
Yeasts and molds
24
10/22/2009
25
Examples of Food Submission Forms
10/22/2009
26
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.
10/22/2009
27
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
10/22/2009
28
Coliforms and E. coli
Coliforms:
 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 Klebsiella
o Escherichia
o Citrobacter
10/22/2009
29
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
10/22/2009
30
Sanitary Quality Guidelines
Food Group
Indicator Test Result (CFU/g)
Satisfactory
Unsatisfactory
<5
>5
< 100
> 1000
< 100,000
> 1,000,000
Long shelf life fish products, meat products, fruit
and vegetable products
< 1,000,000
> 100,000,000
Fermented foods & Fresh fruits and vegetables
Not applicable
Not applicable
<100
> 1000
<3
>3
<3
>3
Aerobic Colony Count
Canned foods & Cooked hot-held food
Cooked chilled food no handling
Cooked chilled food with handling &
Preserved foods
Total Coliform Count
All foods except fresh fruits & vegetables,
or foods containing them
Fecal Coliform Count
All foods except fresh fruits & vegetables, or foods
containing them
Escherichia coli Count
All foods
Aerobic Plate Count: Environmental Swabs
Guidelines for interpretation of bacterial counts from swabs and sponges
as means of monitoring the cleanliness of surfaces.
Interpretation
Clean
Contaminated
Very Contaminated
CFU Count Per
Area Swabbed
Log
Conversion
< 45 CFU
< 1.65
140 to 260 CFU
2.15 – 2.41
> 260 CFU
> 2.41
Counts on
Surface* (based
on 25 cm2 surface
area sampled)
< 5 CFU / cm2
~ 5 to 10 CFU /
cm2
> 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.
10/22/2009
32
Common Spoilage Microorganisms
Shewanella putrefaciens
Pseudomonas spp.
o Gram negative
o Rod shaped
o Motile
o Aerobic
o Non-spore forming
o Biofilm formers
10/22/2009
http://www.lille.inra.fr/lille_eng/unites_et_recherches/nos_unites/
gpta/interfaces_bacteries_aliments_surfaces_solides
33
Pseudomonas aeruginosa
http://www.microbelibrary.org/asmonly/details.asp?id=545&Lang=
Biofilms
“Variety of microorganisms arranged
in a complex relationship to one
another and embedded in a mass of
extracellular polysaccharides of their
own making”
10/22/2009
(http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/)
35
Biofilms Continued
Communities of bacteria
adhering to:
http://www.microbelibrary.org/
 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.
Why do bacteria form biofilms?
Protection from the environment
o Sanitizers
o Antibiotics
Nutrient availability and metabolic
cooperativity
Acquisition of new genetic traits
10/22/2009
38
Biofilm formation
10/22/2009
http://www.personal.psu.edu/faculty/j/e/jel5/biofilms/
39
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
10/22/2009
41
Food preservation
Temperature based:
o
o
o
o
o
Chilling
Refrigeration
Freezing
Pasteurization
Canning
Water activity reduction
o Dehydration
o Addition of salts and sugars
Irradiation
Modified Atmosphere Packaging
Fermentation
Treatment with chemicals
o Sorbic acid, phenylphenates, diphenyl and iodophors, fumigation
with sulfur-containing dusts
10/22/2009
42
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
10/22/2009
43
Thank you!
10/22/2009
44