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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