Fermentation of Bakery Products

1. Fermentation of Bakery Products
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2. 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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3. 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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4. 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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5. Bakery products
Buns & Burgers
Pizza
Bread
Donuts
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6. 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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7. 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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8. 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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9. 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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10. 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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11. 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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12. 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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13. 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

14. 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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15. Procedure
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