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Sporeformers in Food

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by

Rica Regine Regis

on 29 January 2014

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Transcript of Sporeformers in Food

EXERCISE 4
Sporeformers in Food

What are sporeformers?
Spore Forming Bacteria
Sidenote
For this particular exercise, white sugar and flour
were chosen as samples since they undergone heat
treatment during processing and yet sometimes contain substantial number of bacterial spores.
END
• A group of bacteria which form an ENDOSPORE.
Endospores
oval to spherical shaped cell,
formed at the intracellular site,
very refractile,
resistant to heat,
UV light, and desiccation.
small
Some predominant species of spore formers in nature and in foods are...
Bacillus
Clostridum
Bacillus species
rod-shaped bacteria
can either grow under mesophilic temperatures
aerobic to facultatively anaerobic .
some grow under thermophilic temperatures
Clostridium species
causes botulism if ingested
anaerobic bacteria
can grow at both mesophilic and thermophilic temperatures.
Observation of Spores
STAINING
. Endospores are not easily stained since they
are resistant to several dyes
but when stained,
they are
difficult to decolorize.
Schaeffer-Fulton Method
stains the endospores green
Malachite green
Steaming
to make breaks in the spores such that the stain can penetrate
counterstain
stains the vegetative cells red
Safranin
Detection of Ropiness
Detection of Flat-Sour Spores
Enumeration of Bacillus cereus
Detection of
Thermophilic Anaerobes
not
Producing Hydrogen
Sulfide (H2S)
Detection of
Sulfide-spoilage
Organisms
LABORATORY WORKFLOW
Bacterial Cultures
Spore Morphology
Position of endospores:
(1,4) central; (2,3,5) terminal; (6) lateral
Shapes of endospore
(1,2) Oval; (4,6) ellipsoidal; (3) club-shaped; (5)circular
Sticky, stringy consitency caused by bacterial production of long chained polysaccharides
Medium
Dextrose Tryptone Agar (DTA)
Isolate food spoilage bacteria such as mesophilic aerobic sporeformers and thermophilic flat sour sporeformers
Components:
Dextrose- CHO source
Tryptone- N source
Agar- solidifying agent
 grey-white, vesicle-like, dry, wrinkled
 (+) of ropiness
 Gram positive, catalase positive bacterium commonly found in soil
 could withstand high temperature of baking because it has the ability to form a tough, protective endospores
Test Organism:
Bacillus subtilis
thermophilic bacteria that can cause flat-sour spoilage in low acid canned foods (flattening/deformation of cell)
Flat-sour spores
Medium
Dextrose Tryptone
Bromcresol Purple Agar
DTBPA
DTA + BP
Bromcresol Purple – pH indicator
purple – neutral
yellow – acidic

Test Organisms:
G. stearothermophilus (+)
Gram (+), has limited acid tolerance
B. coagulans
Gram (+), Catalase (-)

round
dark opaque with yellow halo
(precipitate due to acid production,
insoluble lipids released by action of
lecithinase, an enzyme found in B. cereus )
Colonies
Mannitol Yolk Polymyxin
Agar
(MYPA)
Medium
or Cereus Selective Agar is a
good medium for the enumeration,
detection and isolation
of B. cereus on foods.
Selective and Diffrential Medium
Selective: MYPA favors growth of polymyxin resistant organisms (Gram + bacteria)
Differential: inability to ferment mannitol and presence of lecithinase
appears as rough, dry colonies
has a pink to purple base which are surrounded by a ring of dense precipitate
colonies
Bacillus cereus
Gram (+)
rod shaped
facultative anaerobic
Medium
Cooked Meat
Medium
useful as an enrichment broth for cultivating anaerobes that may be present in small numbers in a population and as a subculture medium for determination of proteolysis and spore formation of clostridium
Components
Peptone and Beef Heart
Dextrose
NaCl
- production of gas through the “splitting” of agar
- a “cheesy odor” or butyric smell can also be observed

Thermoanaerobacterium Thermosacchrarolyticum
Principle of Sulfide Spoilage
The H2S producing organisms reduce sulfite in the culture medium to sulfide when reacted wth iron to form black spherical colonies.
Test Organism
Desulfotomaculum nigrificans
formerly classified as Clostridium nigrificans
causes spoilage in non-acid canned foods such as vegatabled and infant formula
Medium
Sulfite Agar
Components:
Tryptone
Sodium sulfite
Iron nails
(+) results: blackened spherical areas due to hydrogen sulfide production
-indicates the presence of Desulfotomaculum, nigrificans
Bacillus coagulas
Bacillus
megaterium
Bacillus polymyxa
Bacillus subtilis
Bacillus cereus
Full transcript