Microbiology of food 1

Question 1

lactic acid bacteria is ?

Answer 1

Gram positive, aerotolerant anaerobe, rods or cocci

Question 2

Homofermentative

Answer 2

fermentation yields primarily lactic acid (prickles, saukraut)

Question 3

Heterofermentative

Answer 3

fermentation yields lactivist acid and a variety of flavourful coonhounds ( salami, milk)

Question 4

benefits of lactic acid?

Answer 4

increases food storage by reducing food spoilage

Question 5

why pasteurize before fermentation?

Answer 5

kill the natural microbiome of the food item

Question 6

Cheddar

Answer 6

lactic acid

Question 7

Swiss

Answer 7

lactic acid + propionibacteria

propionibacter produce propionic acid and acetic acid (flavour) and Co2 (bubbles)

Question 8

OKA

Answer 8

lactic acid bacteria + Geotrichum

- pressed curd is brined, surface is washed frequently. growth of Geotrichum

Question 9

Blue, roquefort

Answer 9

ripungi is mainly due to penicillium roquefortii
- spores from the mold are mixed with the milk (or curd)
small holes are drilled in the curd before wrapping - the mold grows in the holes and produces spores
- 3-6 months

Question 10

Camembert, brie

Answer 10

• unwrapped
  picture of Mold (penicillium) and bacteria ( Brevibacterium)
• 1-5 months ripening
  Proteases secreted by the microorganisms gives it the softness

Question 11

vinegar

Answer 11

acetic acid bacteria oxidize ethanol to acetic acid- strict aerobes, THIS IS NOT FERMENTATION
ethanol–> acetaldehyde–> acetic acid
Acetobacter: used in all commercial applications

Question 12

Wine made from

Answer 12

grape must (crushed grapes) + metabisulfite (NA2S2O5) (kills wild yeast)

Question 13

white wine vs red wine

Answer 13

white= skin removed
red= skin kept

Question 14

dry vs sweet wine

Answer 14

dry= all sugar fermented, sweet= sugar residual

Question 15

is yeast added to wine?

Answer 15

yes

Question 16

malting

Answer 16

grains that have been germinated, steeped and dried

production of amylase when grains begin to germinate

Question 17

mashing

Answer 17

Malth is soaked in warm water. during this time the amylase degrades starch–> fermentable sugars. ( glucose and maltose). Mash is then filtered= WORT

Question 18

why are hops added?

Answer 18

antimicrobial properties, flavour, bitterness

Question 19

boiling of wort

Answer 19

wort= filtered mash. gets sterile

Question 20

S. carlbergensis

Answer 20

botton yeast, for a lager, (14-23)

Question 21

lager use

Answer 21

S. carbergensis yeast (6-12 degrees)

Question 22

top yeast=

Answer 22

S. cervisiae, for an ale

Question 23

for an ale use

Answer 23

s.cervisiae

Question 24

how to make distilled alcoholic beverages?

Answer 24

malting, mashing, fermentation, distillation, aging and adding flavour

Question 25

scotch whiskies:

Answer 25

malt brew, wort is not boiled, mixed fermentation of lactic acid and yeast

Question 26

are lactic acid gram + or neg?

Answer 26

gram +

Question 27

is lactic acid anaerobic or aerobic?

Answer 27

areotoleraat anaerobe

Question 28

what shape are lactic acid?

Answer 28

rod or cocci

Question 29

Salami

Answer 29

mix with salt, sugar , spices and yeast - sometimes a scatter lactic acid is added - cure: preservation by addition of salt and drying

Question 30

yogurt (what is added?)

Answer 30

Streptococcus thermophilic and Lactobacillus bugaris- incubated at 42 Streptococci produce acids which favour the growth of lactobacillus which produces more acid (curdles the milk)

Question 31

2 methods to make Cheeses

Answer 31

1) starter culture is added to milk - ferment the lactose, produce lactic acid - curd develops 2) rennin can be added to culture which cleaves casein and results in curd forming

Question 32

longer ripening=

Answer 32

higher acidity and sharpness

Question 33

S. cerevisiae and S.ellipsoideus are resistant to what? and tolerant to what?

Answer 33

NA2S2O5 ( Metabisulfite) and tolerant to 12-14% alcohol

Question 34

Light beer?

Answer 34

yeasts and geneticaly manipulated so they can use all the sugar in the wort ( no sugar left over)

Question 35

polishing

Answer 35

filtration, carbonation , pasterization ect

Question 36

distilling compared to beer making?

Answer 36

``` hops not added. distil off the water- ethanol vapour is condensed and then collected. aged. different grains used. Vodka= wheat, rye, potatoes Gin= grains Rum: sugar cane Brandy= wine Whiskies= malt brews ```

Question 37

what is the scobby in kombucha?

Answer 37

symbiotic culture of bacteria and yeast | - Acetobacter and Saccharomyces

Question 38

Water activity

Answer 38

availability of water

Question 39

Xerophiles

Answer 39

dry environment, low osmolarity

Question 40

Osmophiles

Answer 40

high osmolarity, high sugar

Question 41

does cold food kill the microorganism

Answer 41

no

Question 42

most spoilage microorganisms can grow at a AW as low as

Answer 42

0.9

Question 43

less than ___ most bacteria and yeast cannot grow. can molds grow??

Answer 43

0.9, yes

Question 44

less than ___ only specialized microogrxs can grow

Answer 44

0.8

Question 45

hot food kept above? | cold below?

Answer 45

60 degrees | 4.5

Question 46

what do swollen packages indicate?

Answer 46

CO2 production and aerobic microorganisms

Question 47

natural microorganism in saurqraut

Answer 47

leuconostoc mesenteroides | lactobaccilus plantarum

Question 48

microorganisms added to yogurt

Answer 48

steptococcus thermophillus | lactobaccillus balgaris

Question 49

some of the ripening is caused by?

Answer 49

lactic acid, rennin and other enzymes present

Question 50

which cheese is with lactic acid only

Answer 50

cheddar

Question 51

longer ripening =

Answer 51

higher acidity and sharpness

Question 52

propionibacteria is involved in the ripening of

Answer 52

swiss cheese

Question 53

peniccilum roquforti is involved in the ripening of what cheese?

Answer 53

blue cheese

Question 54

penicillium and brevibacteria are spread on the surface of what cheese and are involved in ripening?

Answer 54

brie and camambert