About bread production and its microbial spoilage. Useful for Food Microbiology.

1. By:
K.SANJAY(BP211525),
II M. Sc Applied Microbiology ,
Sacred Heart College(Autonomous),
Tirupattur.

2. Introduction:
• One of humanity's oldest foods.
• BREAD is a dietary product obtained from the fermentation
and the subsequent baking of a dough mainly made of cereal
flour and water, made in many different ways and sometimes
enriched with typical regional ingredients.

3.  Pita bread
 Roti
 Whole meal breads
 Brown breads
 White breads
 Rye breads
 Quick breads
 Gluten free breads
Types of Breads:

4.  Flour
 Salt
 Water
 Yeast
sugar Other ingredients:
 Enzymes : alpha and beta amylase , Proteolytic enzymes.
 Sugar: for flavor and color.
 Biological preservatives: mold inhibitors, includes potassium
acetate , sodium diacetate , sodium propionate and calcium propionate
Basic Ingredients Ingredients

5.  FLOUR is the bulking ingredient of bread, it forms the
structure of the product. It contain gluten. Gluten helps to form
an elastic stretchy dough.
YEAST is a raising agent.Yeast produce gases to make the
bread rise. Because it is living, correct conditions are needed for
growth – food, warmth, time and moisture.
 SALT is required to bring out flavour in the bread.This
ingredient is used in small quantities.Too much of this ingredient
will stop the yeast from growing.

6. SUGAR. yeast needs energy to grow. Sugar
provides the food for the yeast; it is needed to help the
yeast to grow.
 WATER is used to bind the flour together and helps
to form the structure of the bread.

7.  Weighing and mixing of ingredients
 Dough formation
Kneading
 Leavening
 Baking
Cooling
Slicing
Packaging
PROCESS:

8. Microbesand starter culture involved
• Most common starter culture is Saccharomyces cerevisiae
(Yeast)
• Yeast cells have a big role in raising the dough, its
development, flavor, aroma and texture.
• For bread making the amount of yeast used is 2-3 kg for 100
kilos of flour.
• There are two types of yeasts namely dry and wet. Different
forms of yeast used are: oFresh yeast - a firm, moist, cream-
coloured block oDried yeast - comes in small granules that are
first reconstituted with warm water and sugar and powdered

9. •IN 2 hours to 4 hours after yeast is added to the dough,
there is little growth or no growth.
•In 4 to 6 hours, there is decline in growth.
•When dough is introduced to oven, the temperature in oven
inactivates the yeast enzymes.
THE RATE OF GAS PRODUCTION BYTHEYEAST IS INCREASED BY
1. More yeast
2. 2. Sugar or amylase-bearing malt
3. 3. Yeast food within limits.

10. LEAVENING BY OTHER MICROORGANISM :
Leavening can be accomplished by gas-forming organisms other
than the bread yeast.
Heterofermentative lactic acid bacteria and Saccharolytic
anaerobes can take part in the leavening. •Salt-rising bread is
leavened by “salt-rising yeast”
IT IS DECREASED BY
1. The addition of too much salt
2. The addition of too much yeast food
3. The use of too high or too low
temperature.

11. •Yeast are reported to contribute flavor for bread. Some
workers believe that yeast add little or no flavor,
especially in bread made by rapid method.
•The bacteria growing in the dough can contribute the
most to flavors(according to the time provided for the
microorganism to grow).
•Most of the flavor in bakers’ bread comes from the
ingredients and chemical reaction that occur, such as
Maillard browing, during baking.
•Flavoring substances may include alcohol, diacetyl,
acetoin, isoalcohols, lactic, acetic, succinic acids and
their esters.
FLAVORPRODUCTION:

12. •The baking heat serves to kill the yeast, inactivate yeast
enzymes and those of the flour and malt, expand the gas
present, and set the structure of the loaf.
•It contributes desirable flavors.
•The heat also drives off most of the alcohol and other
volatile substances formed by the yeast but contributes
substance such as furfural, pyruvic and other aldehydes, and
other compounds that add to the flavor.
•Gelatinization of starch “set” of bread results from this
process, in which gluten gives structural support in the dough,
but starch supports the structure of baked bread.
THE BAKING PROCESS:

13.  Moisture = 12-14% (that is ideal for the prevention of the
bacterial growth). Fresh breads consists of around 40% of moisture
so in order to preserve it UV or fungicides are used
 pH= 4.5-6
 Temperature = 28-300C of dough after mixing and around 180-
3000C for baking
 water = water of medium hardness to be used as hard waters
retards fermentation and soft water is slightly acidic
Condition:

14.  Molds are the primary spoilage organisms in baked goods, with
Aspergillus, Penicillium, and Eurotium being the most commonly isolated
genera.
 Penicillium tends to be the more important in sourdough breads and in
breads stored at cooler temperature.
Freshly baked breads do not contain viable molds but soon become
contaminated upon exposure to air and surfaces.
 Bacillus spores are very heat resistant and can survive baking process and
start growing as the bread cools.
Microbial Spoilage: