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Fermentation Flashcards

1
Q

What is the definition of fermentation according to Louis Pasteur?

A

Life without air

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2
Q

What are some reasons to ferment products? (name 4)

A

Food safety
Shelf life extension
Nutritional value
Texture
Aroma
Taste
Appearance

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3
Q

What are the two non-food preservation related reasons to ferment food?

A

Abundant in human diet
Sustainable and natural

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4
Q

What are the three ingredients in a fermentation process?

A

Food components
Microorganisms
Water

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5
Q

What are the three types of operations when fermenting products?

A

Physical
Biological
Thermal

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6
Q

What are the five main types of fermentation?

A

Alcoholic
Lactic
Propionic
Alkaline
Acetic

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7
Q

What are the three most common workhorses in fermentation?

A

Lactic acid bacteria
Yeasts
Moulds

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8
Q

What type of intrinsic factors do enzyme activities add to fermented products?

A

Digestibility
Flavour
Taste
Acid formation

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9
Q

What are the four types of metabolites formed in fermented products?

A

Flavour compounds
Colouring substances
Vitamins
Antimicrobial compounds

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10
Q

What are the two ways to use microorganisms to ferment?

A

Natural fermentation or with defined starters

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11
Q

What are the pros and cons of natural fermentation?

A

Pros: Simple, small scale and low cost
Cons: unpredictable quality, failures (contamination with pathogens or spoilers), can be slow

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12
Q

What is back-slopping?

A

Grabbing microorganisms from the fermented food and adding it to the raw material

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13
Q

What are the pros and cons of fermenting with defined starters?

A

Pros: Predictable, constant and effective
Cons: expensive, only feasible at large scale

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14
Q

What are two products you can make with alcoholic fermentation?

A

Beer
Wine
Bread

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15
Q

Which m.o. is used for alcoholic fermentations?

A

Yeast

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16
Q

Which mechanism is used in the first step of alcoholic fermentation?

A

Common glycolysis

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17
Q

What is the end product of the first step of alcoholic fermentation?

A

Pyruvic acid

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18
Q

What is the final product of alcoholic fermentation?

A

Ethanol

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19
Q

What m.o. is used for lactic acid fermentations?

A

Lactic acid bacteria

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20
Q

What are the two types of lactic acid fermentation?

A

Homofermentative and heterofermentative

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21
Q

What are the two types of homofermentative lactic acid bacteria?

A

Homolactic fermentation
Mixed acid fermentation

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22
Q

What is the key enzyme in homo-fermentation?

A

Aldolase

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23
Q

What is the key enzyme in hetero-fermentation?

A

Phosphoketolase

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24
Q

What products are formed from mixed acid fermentation?

A

Lactate
Acetate
Formate
Ethanol

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25
Q

What yields more ATP? Homolactic or mixed acid fermentation?

A

Mixed acid fermentation

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26
Q

What does the strain of lactic acid bacteria determine?

A

Functionality
Aroma
Acidification

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27
Q

What is the m.o. involved in propionic fermentation?

A

Propionic acid bacteria

28
Q

What are the final products of propionic fermentation?

A

Propionic acid
Acetic acid
CO2

29
Q

What other m.o. is used (besides prionic acid) to make cheese?

A

Lactic acid bacteria

30
Q

What are the m.o.’s used for acetic fermentation?

A

Acetic acid bacteria and yeast

31
Q

What are the two stages of acetic fermentation?

A

Conversions of sugars into ethanol
Ethanol into acetic acid

32
Q

True or false: the second step of acetic fermentation is when the product is fermented?

33
Q

What is the intermediate product of acetic fermentation?

A

Acetaldehyde

34
Q

What are the steps in sauerkraut production?

A

Remove outer leaves
Shredding
Adding salt
Packing
Sealing
Main fermentation
Secondary fermentation

35
Q

Why is salt added to sauerkraut?

A

Selective effect on microbiota
Inhibits pectinolytic enzyme
Extracts cabbage juice

36
Q

What are the two types of fermentation that take place?

A

Hetero and homo fermentative fermentation

37
Q

What happens during heterofermentative fermentation?

A

Acids are formed and pH goes down

38
Q

What happens during homofermentative fermentation?

A

Acidity is increased and aroma compound formation

39
Q

What is the pH of sauerkraut?

40
Q

What are the potential production problems that can arise? What are the causes for these?

A

Pink/grey discoloration-> NaCl or temp too high, air leakage
Grey discoloration-> gram negative bacteria
Too soft-> not enough salt or too high pressure
Off taste-> temperature
Surface spoilage-> yeast through air leakage
Putrefaction-> presudomonas

41
Q

What is the difference in shelf life between not fermented and fermented meat?

A

Days to weeks to months

42
Q

What are the steps in the process of fermented sausage production?

A

Cutting
Tubing
Incubation
Smoking
Drying

43
Q

What are the steps of the actual fermentation of sausages?

A

Acidification
Maturation

44
Q

What is the role of Micrococcus in sausage fermentation?

A

Nitrite formation to prevent spoilage

45
Q

What is the role of LAB in sausage fermentation?

A

Acidification
Flavour

46
Q

What compound binds to myoglobin to make the meat stay red?

A

Nitrous Oxide (NO)

47
Q

What are the steps of beer production?

A

Malting
Brewing
Primary fermentation
Maturation lagering

48
Q

What is the role of malting barley in beer production?

A

Activate amylases and proteases

49
Q

What is the role of mashing malt in beer production?

A

Liberate fermentable sugars

50
Q

What is the product from primary fermentation in beer production?

51
Q

What is formed during maturation in beer production?

52
Q

What microorganism is used for beer making? What two sources can you get this from?

A

Yeast from freeze dried material or liquid suspension

53
Q

What ingredients and microorganisms are involved in kinema production?

A

Soybeans
Bacillus

54
Q

What are the advantages and disadvantages of using soybeans?

A

Pros: High in protein and favourable amino acid composition
Cons: Bitter, antinutritional factors

55
Q

What are the steps in the production process of kinema?

A

Soaking
Boiling
Crushing
Packaging
Incubation

56
Q

What type of fermentation is involved in kinema production?

A

Alkaline fermentation

57
Q

What is the key step in kinema production? Why?

A

Boiling
Enriches for spore formers-> bacilli abundance

58
Q

What ingredients and microorganisms are involved in tempeh production?

A

Soybeans and other beans + cereals
Rhizopus oligosporus

59
Q

What are the steps in tempeh production?

A

Soaking
Dehulling
Cooking
Draining
Inoculation
Packaging
Incubation

60
Q

What nutrients increase in concentration in tempeh production? what decreases?

A

Increases:
Nitrogen
Fatty acids
Fibre
Dry matter
Decreases: crude lipid

61
Q

What ingredients and microorganisms are involved in soy sauce production?

A

Soybeans and wheat
Aspergillys + yeast+LAB

62
Q

What are the steps in soy sauce production?

A

Koji stage and moromi stage

63
Q

What is the koji stage in soy sauce production?

A

Inoculation with koji moulds

64
Q

What is the moromi stage in soy sauce production?

A

Inoculation with LAB and yeasts

65
Q

Which are koji molds?

A

Aspergillus oryzae, Rhizopus spp.

Food Microbiology (4 decks)

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