W13C1 : Food microbiology

Question 1

What are the two type of bacterial fermentation?

Answer 1

homofermentative

heterofermentative

Question 2

What is a homofermentative fermentation?

Answer 2

yields primarly lactic acid

Question 3

What are the two microorgnisms naturally present on the cabbage?

Answer 3

1. leuconostoc mesenteroides

2. Lactobacillus plantarum

Question 4

Which one of the predominant microorganisms naturally present on cabbage is responsible for the flavour compounds?

Answer 4

the leuconostoc mesenteroid

Question 5

What are the microorganisms used in the pure culture of pickles ?

Answer 5

lactobaccillus plantarum and pediococcus cerevisae

Question 6

What is the microorganisms used for the fermentation of salami?

Answer 6

lactobaccillus plantarum

Question 7

What is curing ?

Answer 7

the preservation of food by the addition of salt and drying

Question 8

T or F : milk naturally contain LAB

Answer 8

true

Question 9

What are the microorganisms used for the yogurt making?

Answer 9

streptococcus thermophilus and lactobacillus bulgaris and bifidobacterium animalis

Question 10

What temprature does yogourt is incubated at?

Answer 10

42˚C

Question 11

What is the bacteria associated with flavor and CO2 bubbles in swiss cheese?

Answer 11

propionibacteria (produces acetic acid bacteria, CO2 and propionic acid)

Question 12

What is the bacteria that grows on the surface of oka?

Answer 12

geotrichum

Question 13

What is the mold associated with the blue and roquefort?

Answer 13

penecillum roquefortii

Question 14

What is the kind of cheese that is a mixture of mold and bacteria?

Answer 14

camembert and brie

Question 15

What is the bacteria associated with camembert and brie?

Answer 15

penicillium and brevibacterium spread on the surface of the cheese

Question 16

What are the two yeast strains that a resistant to potassium metabisulfate

Answer 16

S. cerevisiae and S. ellipsoideus

Question 17

T or F : vinegar is not a fermentation

Answer 17

t

Question 18

The bacteria that transform the ethanol into acetic acid are strict ___aerobes or anareobes

Answer 18

aerobes

Question 19

What is the final electron acceptor of the formation of acetic acid formation

Answer 19

oxygen

Question 20

What is the yeast strain associated with lager?

Answer 20

saccaromyces carlsbergensis

Question 21

What is the yeast strain associated with ale?

Answer 21

saccharomyces cerevisiae

Question 22

What are the microorganisms in the SCOBY of kombucha?

Answer 22

acetobacter and saccharomyces

Question 23

How long is kombucha fermented?

Answer 23

7-10 days

Question 24

is spoiled food a safety hazard?

Answer 24

no it is not

Question 25

What are the factors that affect the food spoilage?

Answer 25

1. types of microorganism involved
2. growth of the microorganisms
3. moisture content of food
4. temp
5. pH
6. oxygen availability
7. chemical composition and physical state
8. surface vs inside ex. grinding distributes the surface contaminant

Question 26

which kind of microorganisms can grow at aw lower than 0.9?

Answer 26

molds

Question 27

which microoorganisms evaluated in the labs can grow at a aw lower than 0.83?

Answer 27

staphylococcus aureus

Question 28

What is the crucial factor influencing the spoilage?

Answer 28

the temperature

Question 29

What is the difference between psychrophiles and psychrotroph?

Answer 29

psychrophiles grow best at low temperatures while psychrotrophs are able to grow at low T˚

Question 30

What are the three microorganisms that can grow at temperatures lower than 4.5˚C?

Answer 30

1. Yiersinia enterocolitica
2. Listeria monocytogenes
3. Clostridium botulinum

Question 31

at what pH can LAB grow?

Answer 31

4 and under

Question 32

What are the organisms responsible for the spoilage of food under 4.5 ?

Answer 32

molds and yeasts

Question 33

What are the only microorganism that can’t grow without oxygen?

Answer 33

molds

Question 34

What is the only microorganism that doesn’t have proteolytici properties?

Answer 34

yeasts

Question 35

Can yeast grow at temperatures lower than 10˚C?

Answer 35

no, only bacteria and molds

Question 36

What microorganism can grow at temperatures over 40˚C

Answer 36

bacteria

Question 37

What is the only type of microorganism that can’t grow without oxygen?

Answer 37

molds

Question 38

What is the only macromolecules that the yeasts can grow on?

Answer 38

carbohydrates

Question 39

***what is the bacteria associated with cheddar cheese ripening

Answer 39

lactic acid bacteria

Question 40

what are the cheeses associated with molds

Answer 40

blue cheese

brie and camembert

Question 41

what are the two yeasts used in wine making

Answer 41

s.cerevisae and s.ellipsoideus

Question 42

what are the steps involved in beer making

Answer 42

1. germination of grains (malt)
2. the malt is added of water (mashing)
3. filtration to have wort
4. wort is added of hops and boiled
5. filtration + adding of yeasts

Question 43

true or false : the beer have some LAB

Answer 43

false, the hops prevent growth of LAB

Question 44

what are the microorganisms used in the making of whiskies

Answer 44

LAB and yeasts

Question 45

what are xerophiles?

Answer 45

microorganism that can grow in a dry environment/low osmolarity

Question 46

hot foods should be kept at ____ and cold food at ____

Answer 46

60 and 4.5˚C

Question 47

what are the organisms responsible for spoilage in acidic food

Answer 47

molds and yeasts

Question 48

t or f : molds can grow in anaerobic conditions

Answer 48

false, only some yeasts and bacteira

Question 49

***under anaerobic conditions, the microorganisms will mostly be ____

Answer 49

bacteria (but some yeasts can grow)