BREAD PRODUCTION AND ITS SPOILAGE

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

1. Bread production from yeast and its spoilage 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. Microbes and 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 More yeast 2 . Sugar or amylase-bearing malt 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. FLAVOR PRODUCTION:

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: