W13C1 : Food microbiology Flashcards
What are the two type of bacterial fermentation?
homofermentative
heterofermentative
What is a homofermentative fermentation?
yields primarly lactic acid
What are the two microorgnisms naturally present on the cabbage?
- leuconostoc mesenteroides
2. Lactobacillus plantarum
Which one of the predominant microorganisms naturally present on cabbage is responsible for the flavour compounds?
the leuconostoc mesenteroid
What are the microorganisms used in the pure culture of pickles ?
lactobaccillus plantarum and pediococcus cerevisae
What is the microorganisms used for the fermentation of salami?
lactobaccillus plantarum
What is curing ?
the preservation of food by the addition of salt and drying
T or F : milk naturally contain LAB
true
What are the microorganisms used for the yogurt making?
streptococcus thermophilus and lactobacillus bulgaris and bifidobacterium animalis
What temprature does yogourt is incubated at?
42˚C
What is the bacteria associated with flavor and CO2 bubbles in swiss cheese?
propionibacteria (produces acetic acid bacteria, CO2 and propionic acid)
What is the bacteria that grows on the surface of oka?
geotrichum
What is the mold associated with the blue and roquefort?
penecillum roquefortii
What is the kind of cheese that is a mixture of mold and bacteria?
camembert and brie
What is the bacteria associated with camembert and brie?
penicillium and brevibacterium spread on the surface of the cheese
What are the two yeast strains that a resistant to potassium metabisulfate
S. cerevisiae and S. ellipsoideus
T or F : vinegar is not a fermentation
t
The bacteria that transform the ethanol into acetic acid are strict ___aerobes or anareobes
aerobes
What is the final electron acceptor of the formation of acetic acid formation
oxygen
What is the yeast strain associated with lager?
saccaromyces carlsbergensis
What is the yeast strain associated with ale?
saccharomyces cerevisiae
What are the microorganisms in the SCOBY of kombucha?
acetobacter and saccharomyces
How long is kombucha fermented?
7-10 days
is spoiled food a safety hazard?
no it is not
What are the factors that affect the food spoilage?
- types of microorganism involved
- growth of the microorganisms
- moisture content of food
- temp
- pH
- oxygen availability
- chemical composition and physical state
- surface vs inside ex. grinding distributes the surface contaminant
which kind of microorganisms can grow at aw lower than 0.9?
molds
which microoorganisms evaluated in the labs can grow at a aw lower than 0.83?
staphylococcus aureus
What is the crucial factor influencing the spoilage?
the temperature
What is the difference between psychrophiles and psychrotroph?
psychrophiles grow best at low temperatures while psychrotrophs are able to grow at low T˚
What are the three microorganisms that can grow at temperatures lower than 4.5˚C?
- Yiersinia enterocolitica
- Listeria monocytogenes
- Clostridium botulinum
at what pH can LAB grow?
4 and under
What are the organisms responsible for the spoilage of food under 4.5 ?
molds and yeasts
What are the only microorganism that can’t grow without oxygen?
molds
What is the only microorganism that doesn’t have proteolytici properties?
yeasts
Can yeast grow at temperatures lower than 10˚C?
no, only bacteria and molds
What microorganism can grow at temperatures over 40˚C
bacteria
What is the only type of microorganism that can’t grow without oxygen?
molds
What is the only macromolecules that the yeasts can grow on?
carbohydrates
***what is the bacteria associated with cheddar cheese ripening
lactic acid bacteria
what are the cheeses associated with molds
blue cheese
brie and camembert
what are the two yeasts used in wine making
s.cerevisae and s.ellipsoideus
what are the steps involved in beer making
- germination of grains (malt)
- the malt is added of water (mashing)
- filtration to have wort
- wort is added of hops and boiled
- filtration + adding of yeasts
true or false : the beer have some LAB
false, the hops prevent growth of LAB
what are the microorganisms used in the making of whiskies
LAB and yeasts
what are xerophiles?
microorganism that can grow in a dry environment/low osmolarity
hot foods should be kept at ____ and cold food at ____
60 and 4.5˚C
what are the organisms responsible for spoilage in acidic food
molds and yeasts
t or f : molds can grow in anaerobic conditions
false, only some yeasts and bacteira
***under anaerobic conditions, the microorganisms will mostly be ____
bacteria (but some yeasts can grow)
