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1. Fermentation of Bakery Products
DEPARTMENT OF MICROBIOLOGY
GOVERNMENT COLLEGE UNIVERSITY FAISALABAD
Iqbal Danish
m.Phil 2nd semester

2. Definition
The chemical breakdown of substance by bacteria, yeast
or other microorganisms typically involving effervescence
and the giving off heat is called fermentation.

3. Fermentation:
 Fermentation in bakery products occurs when yeast
converts the sugar, present in flour and dough, into
carbon dioxide and alcohol.
 CO2 enables the dough to rise and alcohol provides the
main flavor in bakery products.

4. HISTORY:
 Fermentation of bread by the action of yeast was known to
Egyptians as early as 2000 B.C.
 The practice was to use a little old dough “to start” the new
dough.
 These two dough were mixed together and allowed to ferment
for some hours before baking.
 They made approximately 50 varieties of bread.
 In 1860 Louis Pasteur discovered why bread rises and the role
of yeast in this process.

5. Bakery products:
 Buns and burgers
 Pizza
 Bread
 Donuts
 Cookies and biscuits

6. Leavening agent:
 A substance causing expansion of doughs and batters by the
release of gases such as CO2 within such mixtures, producing
baked products with porous structure.
 Such agents include air, steam, yeast, baking powder, and
baking soda.
 Sour dough uses lacto bacilli and wild yeast as leavening
agents.

7. Ingredients of bakery products:
FLOUR:
 It is the primary ingredient of most bakery foods.
 It comprises up to 95 % of all ingredients.
 It is made up of starch, proteins and minerals.
 Different types of flour are rye flour, bread flour , cake flour
etc.

8. Sugar:
 It provides sweetness and also supports the growth of yeast
 Also provides attractive brown color.
Water:
 It hydrates the flour and helps the yeast to multiply and rise the
bread by forming the by products

9. Eggs:
 Act as a leavening agent and maintain the texture of cake or baked
product. The also hold together the other ingredients.
Salt:
 It provides flavor, control yeast growth and makes dough more
elastic.
Yeast:
 Scientific name : Saccharomyces cerevisiae
 It is necessary for fermentation, unicellular fungi that feeds on
starch and sugar.
 It acts as a leavening agent by gas production
 pH requirement 4.5-6.0

10. TYPES OF YEAST
 Fresh Yeast:
 Soft solid in form
 Highest moisture content i.e. 67-72%
 Present in active state
 Shelf life is 2-3 weeks.
 Active dry yeast :
 Dry and granular form of yeast
 6-8% moisture content
 Must be rehydrated before use.
 Long shelf life, 2-12 months in refrigerator

11.  Instant yeast:
 Also in granular form
 4-6% moisture content
 Longest shelf life, more than a year
 Does not need to be rehydrated
 Can be added directly to the dough
 Hence it activates more quickly than active dry yeast

13. Chemistry of bread making:
Flour and water:
 Flour contains high levels of glutenin and gliadin proteins which are
collectively called gluten.
 When water is added, these proteins form a network held together by
hydrogen bond and disulfide cross links.
 Gluten trap the bubbles of gas.

14. Starch and sugar:
 Flour contains starch
 Amylase converts starch to maltose.
 Maltase in yeast converts this to glucose
 Glucose can be used by yeast for fermentation and in
providing flavor
Yeast and fermentation:
 Yeast help to convert sugars into carbon dioxide and ethanol.
 The bubbles of carbon dioxide formed cause the bread to rise.
 Alcohol contributes to the flavor as well as it also helps the
bread to rise.

15. Methods of bread making
1. Ingredient selection and scaling
2. Mixing
3. Primary Fermentation
4. Divide and pre-shape
5. Bench rest
6. Final shaping
7. Final fermentation
8. Scoring
9. Baking
10. Cooling

16. 1.Ingredient Selection & Scaling:
 Ingredients used are flour, water, salt and yeast
 We measure all of our ingredients in grams on scale.
2. Mixing:
 There are two stages to the mixing process: the first is to incorporate
ingredients.
 The second is to develop the gluten structure that is able to retain
gas produced during fermentation.
3. Primary Fermentation:
 This is done in covered container. Yeast converts sugars into CO2,
alcohol and organic acids.

17. 4. Divide and Pre-shape:
 When the dough is properly fermented, it is time to divide it to the
desired size and give the divided pieces a pre-shape.
5. Bench Rest:
 Bench rest is typically 15-20 minutes long and during that time, the
gluten network, which has been made more elastic through handling,
will relax and become more extensible.
6. Final Shaping:
 After shaping, the dough must be set somewhere to rest during its
final fermentation.

18. 7. Final fermentation:
 For it dough pieces are placed in temperature and humidity control
cabinet in a proof-box. The dough gain its basic flavor and
leavening gases are generated.
8. Scoring:
 Most loaves will be scored, or cut, just before they are baked.
Scoring is typically done with a razor blade.

19. 9. Baking:
 Converts dough into edible product and gases also expand.
 It also aids moisture for proper crust development and caramelization
of starches to give brown color.
10. Cooling:
 Bread must be cooled before it is cut and it allows gluten strands to
cool and reconnect.
 It also evaporate gas and moisture.

20. Factors that affect yeast activity and the
degree of fermentation:
 Yeast activity is not limited to fermentation step
 It is activated when mixed with ingredients
 Its activity is ceased during final baking process
FACTORS:
 Fermentation time
 Fermentation temperature
 Specific ingredients in dough formulation
 Dough pH
 Yeast
 Presence of antimicrobial agents

21. .
FERMENTATION TIME:
 Time yeast get to act on sugars
 For distinctive flavor and texture
 Longer time, more fermentation
 Rate declines with time at constant temperature
 But does completely stops
FERMENTATION TEMPERATURE:
 Higher temperature, more activity
 Optimum temperature is 75F-85F
 1 degree rise in temperature results in 3-5 % increase in rate

22. .
 Fermentation generates heat
 Used to monitor degree of fermentation
LEVEL OF WATER:
 Stiffer dough take more time to ferment
 With additional water , osmotic pressure on yeast cell reduces
 Results in increase in rate and activity
LEVEL OF SUGAR AND SALTS:
 Fermentation is retarded in high conc. of sugar & salt
 Rate decreases if conc. exceeds 5%
 More with sucrose, glucose and fructose than with maltose
 Flour as primary source of sugars (0.5-1%)
 Fermented in 1-5 hours
 Salts inhibit yeast activity above level of 1%

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27. ADVANTAGES OF FERMENTATION OF
BAKERY PRODUCTS:
 Healthy Diet:
High in Carbohydrates so it is a healthy food to get energy, it contains
about 25g of Carbohydrates in 2 slices of bread.
 Add microbes to gut:
Fermented foods helps to get a supply of live good bacteria e.g. yogurt,
lactobacillus etc
 Food become more digestible:
Compounds converted to simpler forms. E.g.
Milk lactic acid, glucose and galactose, which makes products easy
to digest like in milky bread etc

28.  Changes taste:
Make food pleasantly sour, tangy, and develops flavor.
 Eliminates anti-nutrients:
The nutrients which interferes with absorption of other
nutrients can be destroyed by fermentation like Fe+2 and
Zn+2 decreases absorption. These broken down in
fermentation and minerals become available.
 Increase micronutrients:
Vitamin increase in food like vitamin B, iron, calcium,
vitamin D & A.

29.  Lower in fat:
No oil or deep frying is use in fermentation.
Very low amount of oiling is done at start for triggering the
process
 Decrease cooking time:
Foods that are indigestible or tough improved by
fermentation, decrease need of cooking and fuel like
cellulose converted to glucose

30. Disadvantages of fermentation:
 Possible Of Trans Fats Presence:
Plastic pack bakery products can contain trans fats by
manufacturer because they are inexpensive and extend
product life.
It is result of unhealthy cholesterol , increase heart
diseases, strokes and diabetes.
 Refined flour and sugar:
Refined flour have many of their nutrients removed
during processing.
Sugar is also no more good nutrient it leads to heart
disease

31.  Alcohol production:
Some fermented food products contain alcohol as a by product even
it is in small amount but effect cell of body cause damage to liver
and nerves.
 Ammonia production:
15% ammonia is also produced which is dangerous cause liver
damage.
 Vinegar present:
This acid used in food for sour and sharp taste in pizza etc.
It can cause teeth erosion due to its acidity.
It can cause caustic burn to stomach & oesophagus
 Lactic acid production:
Lactic produce in our muscle make them stiff so if it is present in
food and we intake it then it again make muscle stiff.

32.  Carbonic acid:
It is harmful, present in fermented food products and soft
drinks. It effect teeth, stomach and immune cells of our
body.
 Low in nutrition:
Sometimes microbes in product utilize nutrients for their
own growth and nutrient level depletes.
For example: B12 vitamin utilize by bacteria for their
own growth.
 Gastric cancer:
Fermented food increase the risk of developing gastric cancer
while diet in non fermented food reduce it. Fermented food
contain some time high amount of different acids, nitrites
nitrate & different salts which lead to gastric cancer