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Sporeformers in Food
Transcript of Sporeformers in Food
Sporeformers in Food
What are sporeformers?
Spore Forming Bacteria
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.
• A group of bacteria which form an ENDOSPORE.
oval to spherical shaped cell,
formed at the intracellular site,
resistant to heat,
UV light, and desiccation.
Some predominant species of spore formers in nature and in foods are...
can either grow under mesophilic temperatures
aerobic to facultatively anaerobic .
some grow under thermophilic temperatures
causes botulism if ingested
can grow at both mesophilic and thermophilic temperatures.
Observation of Spores
. Endospores are not easily stained since they
are resistant to several dyes
but when stained,
difficult to decolorize.
stains the endospores green
to make breaks in the spores such that the stain can penetrate
stains the vegetative cells red
Detection of Ropiness
Detection of Flat-Sour Spores
Enumeration of Bacillus cereus
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
Dextrose Tryptone Agar (DTA)
Isolate food spoilage bacteria such as mesophilic aerobic sporeformers and thermophilic flat sour sporeformers
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
thermophilic bacteria that can cause flat-sour spoilage in low acid canned foods (flattening/deformation of cell)
Bromcresol Purple Agar
DTA + BP
Bromcresol Purple – pH indicator
purple – neutral
yellow – acidic
G. stearothermophilus (+)
Gram (+), has limited acid tolerance
Gram (+), Catalase (-)
dark opaque with yellow halo
(precipitate due to acid production,
insoluble lipids released by action of
lecithinase, an enzyme found in B. cereus )
Mannitol Yolk Polymyxin
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
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
Peptone and Beef Heart
- production of gas through the “splitting” of agar
- a “cheesy odor” or butyric smell can also be observed
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.
formerly classified as Clostridium nigrificans
causes spoilage in non-acid canned foods such as vegatabled and infant formula
(+) results: blackened spherical areas due to hydrogen sulfide production
-indicates the presence of Desulfotomaculum, nigrificans