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FN 2232 > Lecture 18 > Flashcards

Lecture 18 Flashcards

1
Q

What is the purpose of yeast?

A

Leaven baked dough products

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2
Q

What are the essential ingredients in yeast breads?

A

Flour
Liquid
Yeast
Salt

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3
Q

What kind of food system are yeast products?

A

Foam food system

Gases dispersed in dough mix

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4
Q

What are examples of lean doughs?

A

French/italitan bread

Hard-Crust rolls

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5
Q

What is an example of rich doughs?

A

Brioche

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6
Q

What are examples of fish sweet doughs?

A

Croissant
Danish
Cinnamon Roll

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7
Q

What is a fried yeast dough?

A

Doughnut

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8
Q

What is the texture like with yeast breads?

A

White bread has fine crumb, thin cell wall, uniform grain

Shape of cells vary

Crumb is elastic, and springs back when touched

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9
Q

What kind of breads tend to be more dense and why?

A

Breads made with 50% whole wheat flour are more dense

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10
Q

What is the appearance of yeast breads?

A

White bread looks golden brown crust

Well shipped load as rounded top, side it smooth and even

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11
Q

What factors affect the shape and volume of dough?

A 
Stiffness of dough
Strength of dough
Fermentation
Proofing
Baking
Temp
Position in oven
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12
Q

What is the flavour of yeast breads like?

A

Yeasty

Other flavours are dependent on the type of bread

Sometimes sour taste due to time of fermentation

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13
Q

What is yeast?

A

Living unicellular organism
-a fungi

Can have many strains

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14
Q

What is the scientific name for bakers yeast?

A

Saccharomyces cerecisiae

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15
Q

Is yeast live when purchased?

A

Can be made formant after growth by drying or low temp

-can become active again once it is mixed into dough

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16
Q

What did people use before bakers yeast?

A

natural wild yeast

-equalt was flour and water was used to trap bacteria from the air and that’s what they use as the culture

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17
Q

Can yeast grow with or without O2?

A

Can to both

-begining stage is aerobic, later stage of baking is anaerobic

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18
Q

How does yeast work with bread?

A

Metabolizes fermentable sugars and ferments then anaerobically
-produces ethanol and CO2

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19
Q

What sugars can yeast readily metabolize?

A

Glucose
Fructose
Sucrose
Maltose

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20
Q

What happens to the alcohol (ethanol) when baked?

A

Evaporated and contributes to volume

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21
Q

What roles do acetic and succinct acids have on baking?

A

The acids impact gas holding capacity

CO2 trapped in flour gluten network

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22
Q

What does damaged starch turn into?

A

Hydrolyzed to maltose by alpha and beta amylase

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23
Q

What does yeast convert maltase and sucrase into?

A

The conversion hydrolyzes starch into maltose and sucrose

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24
Q

Why is sugar added to dough?

A

Speed up gas production

-but if its more than 10% sugar by wt then it will have a negative effect on yeast bread and can delay fermentation

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25
Q

What is the optimal fermentation temp and pH for yeast?

A

38C

4.8-5.5

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26
Q

What is the thermal health point of yeast?

A

54.4C

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27
Q

How is commercial yeast made?

A
  1. Healthy yeast are selected from he desired strain
  2. Yeast is placed with nutrients for budding to occur (multiplication)
  3. Culture is transferred to a medium called the wort
  4. After the yeast have multiplied, it is ready for fermentation
  5. After fermentation yeast is separated from wort
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28
Q

What are the nutrients in the wort?

A

Carbs
Vitamins
Minerals

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29
Q

What are the difference kinds of yeast you can find?

A 
Active dry yeast
Instant quick rising active yeast
Bread machine yeast
Inactive dry yeast
Compressed (cake) Yeast
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30
Q

What is active dry yeast?

A

Dried dormant live yeast cells

Activated by specific temp, hydration, food

Should not be added directly to dry ingredients

Mostly for home use

Larger cell

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31
Q

How long can yeast be stored?

A

1-2 years if unopened

-if unopened store in fridge

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32
Q

What destroys yeast cells?

A

Moisture

Warm Temps

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33
Q

What is instant quick rising active yeast?

A

Added directly to dry ingredients (no need to rehydrate)

50% reduction in dough rising time

High instability in air and must be packed with inert gas (O2) or vacuum

Smaller cell

Home or bakers

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34
Q

What is bread machine yeast?

A

Same as instant quick rising active yeast BUT with added:

-ascorbic acid (dough conditioner) to promote dough extensidbility (Stretching) during rising

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35
Q

What is inactive dry yeast?

A

Same as nutritional yeast

Dough conditioner, not a leavening agent

Inactivated by pasteurization during drying on steam heat roller dryers

Breaks gluten sulphide bonds (gluten reducing agent), resulting in a more extensible dough (optimizes CO2 retention)

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36
Q

What is inactive dry yeast a good source of nutrient wise?

A

Protein

B vitamins

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37
Q

What is compressed (cake) yeast?

A

Blend of wet years cells, water, emulsifier and oil

Shorter shelf life of 10 days refrigerated due to 70% moisture

Softened in water (29C)

Powder will be 60% wt if compressed

Commercial bakeries

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38
Q

Which yeast is the most consistent in quality?

A

Compressed (Cake) yeast

-minimally processed

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39
Q

What will happen to compressed (cake) yeast if left out?

A

Will lose leavening power if left out at room temp for several hours

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40
Q

What does too much yeast cause?

A

Undesirable:

  • odor
  • Flavour
  • Coarse texture
  • Grey colour
  • Distorted shape in bread
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41
Q

What causes a sour flavour in bread?

A

Natural starters or Sours from wild yeast bacteria collected from the air

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42
Q

What does lactic bacteria do to bread?

A

Increase AA content due to the break down of protein and add more flavour
(Flour proteolysis)

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43
Q

What kind of flour has the highest gluten protein?

A

Bread flour

44
Q

Why do we need a stronger flour?

A

Weakening effect due to fermentation on the gluten

45
Q

What leads to cell rigidity?

A

Starch from the flour gelatinizes during backing f

46
Q

What is the role of pentosans?

A

They are gums in the flour and allow for increase water absorption
-leads to goof volume of loaf

47
Q

What kinds of flour has better hydration capacity?

A

Strong
High protein flours
-alter liquid addition

48
Q

When do you need to add more flour to dough?

A

When baking on a hot and humid day

49
Q

Why is liquid added to dough?

A

Water needed for yeast activation (40-46C)

Dissolves sugar and salt and binds water

Used for lean dough and crips crust

50
Q

What temp do liquids need to be heated to before being added to dry mix?

A

120-130F

51
Q

What kind of liquids can be added to dough?

A

Milk (scalded to denature protein)

Eggs

Cooked potato Starch
-provides gelatinized starch flavouring fermentation

Whey

52
Q

What does the addition of milk or eggs as liquid do to bread?

A 
More tender
Better dough handling
Crust colour
Flavour
Shelf life
53
Q

What happens when you have too much or too little liquid?

A

Much: Dilute gluten yielding decreased loaf volume

Little: dry, stiff, ineleastice, slow to rise, limited gluten development

54
Q

Why is salt added to dough?

A

Flavour enhancer
Firming effect on gluten structure
Slows fermentation
Increases time required for rising

55
Q

What happens if your dough has no salt or excessive salt?

A

No= crumbly

Excessive= .3% flour wt leads to stiff dough and difficult to work

56
Q

What does sugar do to dough?

A

Fermentation time increased
Yeast metabolizes sucrose before maltose
-sugar comes from flour and added

57
Q

What happens when you have too little or too much sugar?

A

Little: Rises quicker

Much: Delays action of yeast

58
Q

What does fat do to the dough?

A

Makes breads softer, increases shelf like

Improved dough handling

Increase gluten extensibility for increase load volume and better texture

Not an essential ingredient

59
Q

What does vital wheat gluten do?

A

Increases:

  • dough strength
  • water absorption
  • dough tolerance
  • loaf volume
  • crumb texture
60
Q

What do yeast nutrients to to dough?

A

Monocalcium phosphate or Calcium sulfate Supply nitrogen or phosphate for improved yeast growth

61
Q

What re pH regulators?

A

Help to lower pH for optimal yeast growth

  • Calcium carbonate
  • Calcium Sulfate
62
Q

Why are oxidizing agents sometimes added to dough?

A

Helps with gluten development

Stripping H atoms from sulfhydryl linkages, making sulphur available for disulphide bonding in gluten

Ascorbic is most popular

63
Q

Why are reducing agents sometimes added to dough?

A

Breaks disulphide bonds

Affects stretchability of dough

Can combine with oxidizing agent to optimize gluten development and increase volume

L-cyseine and inactive yeast act on gluten to increase extensibility while also shortening mix time

64
Q

What do emulsifiers do in dough?

A 
Enhance:
Stability
Soften hough for flexibility
Finer
Softer crumb
65
Q

What are some examples of emulsifiers?

A

Lecithin
Mono and diglycerides
Polysorbate 60

66
Q

Why are enzymes used in dough?

A

Slow staling
Enhance bread crust colour
Oven Spring
Softer crumb

67
Q

What is oven spring?

A

Final burst of rising after thee loaf has been put into the oven

68
Q

What are some examples of enzymes used?

A 
Alylases
Diastatic malt syrup
Malt Flour
Oxidase
Carbohydrase
Proteases
-mostly from fungi or bacteria
69
Q

Why is mixing important ?

A

Air is incorporated into the dough creating many small ag nuclei leading to gluten development

Helps moisture distribute throughout the dough

70
Q

Does yeast crease new nuclei in dough?

A

Yeast produces CO2 which increase the size of nuclei but does. not crease new gas cells

71
Q

What does fully kneaded dough look like?

A

Smooth
Not sticky
Can stretch to think film (windowpane test)

72
Q

What doe over mixed. dough look like?

A

Sticky
Excessively soft
-usually happens with mechanical mixer

73
Q

Why do we knead dough?

A

Aligning of gluten and gliadin molecules
-the swollen particles of both result in the alignment from the kneading

Starch granules for flour entrapped en developing gluten

74
Q

What happens during the fermented stage with eh first rising?

A

Dough is ripened

75
Q

What are the control factors for fermentation?

A 
Time
Temo
Environment
Atitude
Gluten Strength
Yeast
76
Q

What kind of fermentation doe sit start and finish as?

A

Begins as aerobic (20% O2 and 80% nitrogen) and then become anaerobic (only nitrogen remains)

77
Q

What does the run of glucose and yeast produce?

A

Ethanol and carbon dioxide

78
Q

What is also produced during fermentation that contributes to flavour?

A

Organic acids
AA
Others

79
Q

What is the purpose of Organic acids, AA andOther compounds produced during fermentation?

A

Decrease pH from 6-5 promoting fermentation nd amylase activity

Greater dispersion of gluten with loss of elasticity

80
Q

At what degree do you get the best flavour development?

A

26-32C

-become cold temp inhibits yeast activity

81
Q

What happens when dough is exposed to air and what should you do to prevent that?

A

Creates a film, and can lead to streaks and forms a hard crust

  • cover with damp cloth
  • Place in proofing cabinet
  • Grease surface of dough
82
Q

How long does it take for the Dough to double in size and what does it depend on?

A

1 hour

  • Yeast
  • Temo
  • Salt
  • Sugar
  • Dough stiffness
83
Q

What happens when you have over fermentation?

A

Weakened gluten strands (dense coarse grain)

Sour odor

84
Q

What happens when you have under fermentation?

A

Less tender

Small volume

85
Q

What is punching down dough?

A

Subdivide the gas cells to:

  • produce smaller cells
  • redistribute yeast cells
  • redistribute food substrate
  • Equalize temp
86
Q

When should you shape/mold the dough?

A

After letting dough relax for a bit after punching

87
Q

What happens when you shape the dough

A

Removes large gas bubbles on pans or baking sheets

88
Q

What is scaling?

A

When dough is divided into portions

89
Q

What is proofing?

A

The final rising stage in the pan

  • 30-35C and 85% humidity
  • size doubled after 30-60 mins
90
Q

What happens when you have an under or over proofed dough?

A

Under: Small and dense after baking

Over: collapse in oven

91
Q

When do you know a dough is ready to be baked?

A

When dough doesn’t spring back its done proofing and ready to bake

92
Q

What is oven spring?

A

Sharp rising of dough when it first goes in the oven from gas production and dough expands

93
Q

What happens if you have too hot of an oven?

A

Initially can set the bread before optimum oven spring occurs which reduces volume

94
Q

Why is steam injection good?

A

Is at the start of baking and allows crust to remain soft and expand giving a thin hard crust

No steam injected: crust formed early resulting in thicker and heavier crust

95
Q

What happens when temp of dough increases?

A

Yeast is killed
Enzymes inactivated
Fermentation stopped

96
Q

What temp should the dough reach to be done?

A

91-93C

-can reach 100

97
Q

Does mailer or caramelization take place in baking dough?

A

Both

98
Q

What is a high fibre dough?

A

Bran is detrimental to gluten and produces low volume dense bread

Pre soaking brann and finely grinding and adding shortening help overcome this effect on gluten

Vital wheat gluten and conditioners can help as well

99
Q

What are bagels?

A

Proofed, shaped, boiled and baked

Dense, chewy, tough

Boiling expands due to increased gas production and sets outer crust (partial gelatinization)

Baking browns the bagel

100
Q

What is staling?

A

Crust toughening

  • water migration rom crumb to crust
  • starch responsible for staling
101
Q

What happens when crumb firms?

A

Amylopectin retrogradation: starch molecules bind together in an ordered structure after gelatinization

Monoglycerides form a complex with amylose decreasing retrogradation and softening the crumb

Interaction with starch and gluten could be the cause of staling

102
Q

What prevents staling?

A

Fat
Emulsifiers
Amylase

103
Q

Can you reverse staling?

A

Yes, can toast or freeze

-fridge promotes staling

104
Q

How do you know when bread has spoiled?

A

Rope bacteria, their spores aren killed in baking

  • will have overripe melon odor
  • ropey inside
105
Q

Why does bread spoil?

A

Moisture and Temperature

106
Q

How can you prevent spoilage?

A

Calcium propionate as ate-molding additive

Calcium or sodium proionate

Acidify dough with vinegar or buttermilk

FN 2232 (20 decks)

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