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Principles of Food Science Exam Review > Chapter 17: Fermentation: Desirable Effects of Microorganisms > Flashcards

Chapter 17: Fermentation: Desirable Effects of Microorganisms Flashcards

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1
Q

Define microbiology.

A

the study of living organisms too small to be seen by the unaided human eye

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2
Q

Define microorganisms.

A

Organisms that are only visible through a microscope

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3
Q

What are the characteristics of microorganisms?

A

They multiply rapidly, and transfer easily from one surface to another (cross- contamination)

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4
Q

What is cross-contamination?

A

transfer easily from one surface to another (cross- contamination)

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5
Q

What are the microorganisms that have positive use in foods?

A

bacteria, yeasts, and molds

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6
Q

Bacterias are members of what kingdom? Yeasts and molds?

A

Bacteria: Monera

Yeasts + molds: Fungi

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7
Q

What do microorganisms depend on to grow and multiply?

A

Outside sources

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8
Q

Are bacteria single-celled or multiple-celled?

A

single-celled organisms

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9
Q

How does bacteria multiply?

A

Cell division

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10
Q

Describe the cells of bacteria?

A

Their cells have no nucleus and are filled with a gelatinous liquid called cytoplasm

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11
Q

How long is bacteria?

A

3 micrometers long

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12
Q

How is bacteria classified?

A

by shape, cell wall structure, and oxygen needs

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13
Q

Name the 3 basic shapes of bacteria.

A

– Bacilli have a rod shape
– Cocci have a spherical shape
– Spirilla have a spiral shape

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14
Q

Name the 2 types of cell wall structures of bacteria.

A
  • Gram-positive bacteria turn violet

- Gram-negative turn red

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15
Q

How are the cell wall structures of bacteria identified?

A

by the ability to be stained by a crystal violet dye, called Gram’s stain

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16
Q

Name the 3 categories of bacteria based on oxygen needs.

A

– Aerobic bacteria must have oxygen to function
– Anaerobic bacteria function best in an oxygen-free environment
– Facultative bacteria can function in either type of environment

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17
Q

What kind of bacteria spoils cabbage? What prevents the aerobic bacteria to grow?

A
  • Aerobic bacteria
  • submerging cabbage in salt water does not
    allow aerobic bacteria to grow
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18
Q

Aerobic bacteria in cabbage can multiply and develop what?

A

the flavor and texture of sauerkraut

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19
Q

What do bacterial growth rates depend on?

A

pH, air, temperature, and nutrients

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20
Q

Define fungus.

A

a plant that lacks chlorophyll

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21
Q

Are fungi single-celled? Do they have a nucleus?

A

– are not always single-celled

– have a nucleus in their cells

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22
Q

What is the function of fungus in nature?

A

widely distributed in nature and help organic matter decay

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23
Q

Give examples of fungus.

A

mushrooms, molds, mildew, rust, and yeast

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24
Q

How is fungi classified?

A

by their structure and reproduction methods

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25
Q

The basic structure of fungi is made of what?

A

made of filaments or tubes called hyphae

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26
Q

Describe the structure of hyphae.

A

have elongated cells or chains of cells that absorb nutrients from the environment

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27
Q

How is myecelium formed?

A

Hyphae intertwines and forms a branched network

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28
Q

How does myecelium reproduce?

A

by creating spores

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29
Q

Define spores.

A

the reproductive cells of fungi

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30
Q

How do spores develop?

A

in a sac- or balloon-like structure that explodes when full

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31
Q

How big are spores? What are they resistant to?

A

Spores are microscopic and resistant to harsh environments

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32
Q

Define molds.

A

fungi that form a mycelium structure with a fuzzy appearance

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33
Q

What do molds produce? What do they do?

A

Many produce antibiotics that kill bacteria likely to be growing in the same area

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34
Q

Define yeasts.

A

fungi with a single-celled structure

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35
Q

What do yeasts produce?

A

produce alcohol and carbon dioxide

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36
Q

What do yeasts form on soil or plants? What do they form in animals?

A

Soil or plants: mycelium structures

Animals: reproduce by budding

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37
Q

Name 4 common characteristics of microorganisms.

A

– grow rapidly and are good sources of edible
protein for animals
– can enhance or add to the nutritional value of food
– can enter a dormant or inactive state to protect themselves from a harsh environment
– reproduce when the environment supports growth needs

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38
Q

Define a pure culture.

A

a large volume of one type of microbe grown purposely

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39
Q

What are microorganisms used for in food processing plants?

A

development of such foods as pickles, cheese, and beverages

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40
Q

Define starter cultures.

A

pure cultures of microorganisms that are added to foods to begin a fermentation

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41
Q

Define microbial enzymes.

A

Enzymes produced by microorganisms

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42
Q

What is the source of most changes in food products?

A

Microbial enzymes

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43
Q

How do microbial enzymes act in the body?

A

– Microorganisms excrete digestive enzymes to break down large macromolecules for transport through the microbial cell wall
– Microorganisms can then absorb the fragments and use them for energy

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44
Q

How can microorganisms be classified

A

by the organic molecules they use as a food source

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45
Q

What are proteolytic microorganisms?

A

release proteases that change proteins into amino acids and are used to clot milk, tenderize meat, and remove pulp from cacao beans

46
Q

What are lipolytic microorganisms?

A

produce enzymes that digest fats and are used to flavor cheese, remove egg yolk, and clean up oil spills

47
Q

How are microorganisms classified in terms of their scientific names?

A

By 2 Latin names

  • The genus name
  • The species name
48
Q

What are characteristics of the genus name?

A

– is always capitalized

– indicates a family of organisms that have similar characteristics

49
Q

What are characteristics of the species name?

A

– is never capitalized

– identifies the type of microbe within the family

50
Q

Name the 4 factors that affect microbe growth.

A
  • Microorganisms need an energy supply
  • Microorganisms need water
  • Microorganisms grow at certain pH values
  • Microorganisms prefer a moderate temperature
51
Q

What are microorganisms composed of chemically?

A

composed of carbon, oxygen, nitrogen, and hydrogen

52
Q

What do microorganisms need to feed on?

A
  • C, O, N, H

- Minerals and vitamins to aid with enzyme activity

53
Q

Can microorganisms be dormant? In what conditions?

A

Some microorganisms can remain alive, but

dormant, in dried conditions

54
Q

What is a safe water activity for most food storage?

A

0.70 or lower

55
Q

How can water activity be lowered?

A

by removing water, adding solutes, or by freezing

56
Q

What are the 3 pH levels that microorganisms can live in?

A

Minimum, preferred, maximum

57
Q

What temperature do microorganisms prefer?

A

Modertate temp

58
Q

Why don’t microorganisms like freezing? And heating?

A

Freezing: slows enzyme activity and cell reproduction
Heating: can kill microorganisms

59
Q

When do microorganisms die if temperature is raised?

A

at 5 C to 12 C above the temperature for maximum growth

60
Q

Define fermentation.

A

enzymatically controlled change in a food product caused by the action of microorganisms

61
Q

The changes from fermentation result from what?

A

– digestive enzymes released by the
microorganisms
– the release of by-products, such as carbon dioxide, acetic and lactic acids, and ethanol

62
Q

What is the primary product of a microbial reaction?

A

Energy

63
Q

What can by-products of microbial reactions change in a food?

A

color, texture, flavor, aroma, and pH

64
Q

When does fermentation occur?

A

when nutrients broken down by digestive enzymes are absorbed by microorganisms for growth and energy

65
Q

What is yeast needed in?

A

all yeast breads, alcoholic beverages, and vinegars

66
Q

What is often used for yeast?

A

Saccharomyces cerevisiae

67
Q

What is the main source of energy of Saccharomyces cerevisiae?

A

– Sugar is its main source of energy

– It can utilize on honey, molasses, or corn syrup

68
Q

What steps is yeast affected by in the bread-making process?

A

– Warm liquid activates yeast
– Mixing distributes yeast evenly
– Kneading the dough develops the gluten
- Proofing

69
Q

What does proofing allow? What does it release?

A
  • Allows the yeast to produce enzymes that break down sugars

- Releasing alcohol and carbon dioxide

70
Q

What happens during the bread making process?

A

– carbon dioxide becomes trapped in pockets throughout the dough, gluten stretches, and the dough rises
– the dough continues to rise during baking and a crust forms

71
Q

What do bread products contain?

A

flour, yeast, salt, and water

72
Q

What is wine?

A

fermented juice of plant products such as grapes, honey, various fruits and dandelions

73
Q

What can be added to inhibit unwanted microbe growth?

A

Sulfur dioxide (SO2) or potassium metabisulfite

74
Q

How are wine juices kept? For how long?

A

held in anaerobic conditions for up to 4 weeks in oak barrels or stainless steel tanks

75
Q

When is wine fermentation complete?

A

when bubbling from CO2 production stops

76
Q

How is wine aged?

A

in barrels or vats to slowly develop the characteristic flavors

77
Q

Give examples of yeast fermentation in other alcoholic beverages.

A

– Beers are made from fermented barley
– Bourbon is made from corn
– Rum is made from sugar cane or molasses
– Brandy is distilled wine or fermented fruit juice
– Liqueurs have a brandy base with sugar and flavorings added

78
Q

Name the 3 main types of bacterial fermentation.

A

1) Lactic acid fermentation
2) Proteolytic
3) Acetic acid fermentation

79
Q

What is lactic acid fermentation?

A

Fermented foods produced by bacteria whose by-product is lactic acid
Produces the other by-products of acetic acid, formic acid and carbon dioxide

80
Q

What does sauerkraut result from?

A

the lactic acid bacterial fermentation of cabbage submerged in brine, a salt and water solution

81
Q

What does brine do in sauerkraut?

A

The salt controls water activity and pulls water with dissolved sugar and nutrients to the surface

82
Q

What does bacteria do in sauerkraut?

A

Bacteria utilize the sugar and release carbon dioxide and lactic acid into the brine

83
Q

How are cucumbers turned into pickles?

A

heating them in a spiced vinegar solution, refrigerating in an acid brine, or fermenting them with lactic acid bacteria

84
Q

What does commercial pickling involve?

A

– washing the cucumbers in a chlorine solution

– placing them in a brine with a pure culture of Lactobacillus (starter culture)

85
Q

Which other foods can be pickled?

A

vegetables such as watermelon rinds, beets, cauliflower, okra, and onions, and even eggs

86
Q

How can lactic acid fermentation be used in meats?

A

to make dry and semidry sausages

87
Q

What does lactic acid fermentation provide in meats?

A

– Increased acid tenderizes the meat and adds a tart flavor

– Fermentation, smoking, and drying prevent spoilage

88
Q

How does cheese form curds?

A

Milk is pasteurized, then rennin and lactic acid bacteria are added to form curds

89
Q

How is the whey separated from the curd?

A

– Curds are cut into small cubes and heated to help the whey separate from them
– Whey is drained off and collected for use as an additive in other processed foods

90
Q

What can cheese curds turn into?

A

– mixed with cream to make cottage cheese

– put in presses to squeeze out excess moisture for making aged cheese

91
Q

What happens during aging or ripening of cheeses?

A

cheeses wrapped with wax are placed in curing rooms

92
Q

What is responsible for the characteristic flavour of cheeses?

A

Different bacteria or molds

93
Q

What does the sharpness of cheese refer to?

A

refers to the strength of flavor and aroma

94
Q

How does the sharpness of cheeses develop?

A

Develops as cheese ages

95
Q

Cheeses that age longer tend to what?

A

– have firmer consistency
– have more crumbly textures
– melt into sauces more readily

96
Q

What by-products do molds create?

A

antibiotics, flavor compounds, and enzymes

97
Q

Name some examples of fermented foods often used in Asian cuisine.

A

– soy sauce, a fermented mix of soybeans and wheat
– tempeh, a soybean cake of cooked, mashed soybeans pressed into blocks, inoculated with Rhizopus molds, and wrapped in banana leaves

98
Q

What is two-step fermentation?

A

uses bacteria as well as fungi to produce the product

99
Q

Describe the two-step fermentation process of cheeses?

A

lactic acid bacteria is needed to form the product, then other microorganisms develop the flavors and textures

100
Q

Describe the two-step fermentation process of sourdough bread?

A

lactic acid bacteria ferments the product, and then a yeast starter proceeds to ferment the product

101
Q

east releases alcohol as they break down sugars, what follows yeast fermentation?

A

Acetic acid fermentation

102
Q

What does Acetobacter bacteria use as energy? What does it release?

A
  • Alcohol

- Releases acetic acid

103
Q

What is produced by acetic acid fermentation?

A

Vinegar

104
Q

How is acetic acid fermentation used in baked goods?

A

produces candied citron from citron lemons

105
Q

How is acetic acid fermentation used in chocolate?

A

turns cacao beans into chocolate

106
Q

Name 2 benefits of fermentation.

A
  • Microorganisms help preserve some foods

* Fermentation offers a wider range of food options

107
Q

How do microorganisms help preserve some foods?

A

Fermented foods tend to have a low pH and can be stored for longer periods (especially at refrigerated temperatures)

108
Q

What does the variability of nutritional changes in fermented foods depend on?

A

– microorganisms used
– other ingredients added
– impact of fermentation on bioavailability

109
Q

The concentrations of which nutrients are higher in cheese than in milk?

A

Fat and calcium

110
Q

At what pH are bacteria killed? At what pH are molds killed?

A

Bacteria: 4.6
Molds: 1.5

Principles of Food Science Exam Review (20 decks)

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