fermentation of bakery products
TRANSCRIPT
Fermentation of Bakery Products
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Fermentation
Fermentation is a metabolic process that
converts carbohydrates into acids, gases, and alcohol
C6H12O6 → 2 C2H5OH + 2 CO2
Occur in yeast and bacteria
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Fermentation of Bakery Products
Yeast produces
Carbon dioxide and alcohol - enables dough to rise and modify its
physical properties
Volatile compounds - involved in the original taste and flavor
In the process of baking, most volatile compounds and all of
the alcohol evaporate
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Stages of fermentation
• Ferments sugars naturally present in flour
• 1.5% of the flour weight
• Gases releaseFirst stage
• Fermentation of maltose
• Maltose – comes from action of the amylases
• Maltase (yeast enzyme)- splits maltose to glucose
• If sucrose is added – invertase transformed it into glucose and fructose
Second stage
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Bakery products
Buns & Burgers
Pizza
Bread
Donuts
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Yeast
Saccharomyces cerevisiae
Dormant at 40°F (4.4 oC)
Die at 130°F (54.4 oC ) during baking
A standard amount of 2.5 g of baker’s yeast for 100 g of flour
provides 25 billion yeast cells
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Types of yeast
Fresh yeast
Compressed yeast
Highest moisture content
Active state
Spoil and die faster than other types, giving it a short shelf-life
Not more than two weeks
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Active dry yeast
Dry, granular form of yeast
Must be rehydrated in warm water before use
Longest shelf-life
In a sealed container, in the fridge it will keep for years
Many of the yeast cells are dead in processing
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Instant yeast
Does not have to be dissolved in water before use
Activates more quickly than active dry
Can be added directly to dough
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Factors that affect yeast activity and the
degree of fermentation
Fermentation time
Fermentation temperature
Specific ingredients in dough formulation
Level of water, sugar and salt
Dough pH
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Fermentation time
Longer the fermentation time, the higher the degree of
fermentation
Rate of fermentation declines with time at a constant
temperature, it does not completely stop
Fermentation temperature
Higher fermentation temperatures increase yeast activity
Optimum temperature : 75°F-85°F (23 -29 oC)
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Specific ingredients in dough formulation
Level of water
o Stiffer dough take long time to ferment
o With additional water - osmotic pressure on the yeast cells is reduced
o Increase yeast activity and the overall rate of fermentation
Level of sugar and salt
o Fermentation is retarded in the presence of high concentrations of
sugar and salt
Dough pH
o Yeast activity is fairly constant : pH range of 4-6
o At the onset of fermentation : 5.5-5.8
o During fermentation -:decreases to 5
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Goals of fermentation
Improves dough handling characteristics
Intermediate compounds - soften gluten protein structure
present in dough
Long fermentation - complete hydration of the gluten proteins,
which also aids in its softening
The softened protein matrix improves the dough handling
Enhances gas retention in doughs
Gluten softening - the dough protein matrix hold more carbon
dioxide 13
Enhances finished product texture
Soft and smooth texture
Provides desirable fermentation flavor
Volatile and non-volatile flavor precursors - unique fermentation
flavor
Extends shelf-life of final product
Action of amylases on broken starch causes the shelf-life
extension
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Procedure
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