Bread is an essential food in the world, from the most ancient times,because its tste is very delicious and it is easy to make it.I want to tell you how chemistry has a important role in the making bread.we need just flour and water to bake the bread.
Bread contains STARCH, a polymeric form of glucose, forming long molecular chains and PROTEINS, (10-12%, formed by GLUTEN) and SALT (0.5-1.0%). It can be prepared only with the flour of SOFT WHEAT and RYE, because only those cereals contain the gluten, a protein that allows and stabilizes the typical swelling of bread.
The initial phase is mixing of FLOUR and the 50% of its weight of TEPID WATER in which it has been dissolved the SALT and the BREWER'S YEAST, in an amount of about 1% of the flour weight. This yeast is made of colonies of a fungus, the SACCHAROMYCES CEREVISIAE, prepared on residuals of on residuals of beer industry.
In many countries are not used the yeast like Middle East, the bread remains flat and we obtain the UNLEAVENED BREAD.
The yeast, at a temperature of about 30-35C, finds its favourable environment to reproduce itself and decomposes the starch, by means of an enzyme, the ZIMASIS, in molecules of ETHANOL (CH3-CH2-OH) and CARBON BIOXIDE (CO2):
-(C6H12O6)n- -> 2n CH3-CH2-OH + 2n CO2
The alcohol and the CO2 diffuse in the mass of the pastry forming many little bubbles and causing its swelling during the RISING phase, lasting some hours, at a controlled temperature (30-35C), in a place protected by air currents. The rising time is directly proportional to the bread size.
Then, the pastry is slightly compressed,' it's given the desired form and it's put into the oven at 200-300 C, for a time of 20-45 min., according to the dimension of the pieces.
In the oven, the ethanol and the CO2 evaporate, leaving the mass very spongy . Inside the mass, where the temperature remains relatively low (about 100 C), the protein component (the gluten) coagulates and forms a protein skeleton or tridimensional network containing many starch granules, partially decomposed in starch-water and soluble amylo-dextrin. This swollen mass becomes stable and forms the CRUMB, soft and elastic, holding in much water.
In the exterior of the cooking bread, exposed to the highest temperature, water evaporates nearly totally, the starch decomposes into smaller molecules of maltose (C12H22011) and dextrin and it forms a partially caramelized sugar, with its typical blond or brown colour and its fragile consistence. This is the CRUST of bread.
The water retained by the crumb after the cooking is a measure of the YIELD of the bread; from 100 Kg of flour, 125-135 Kg of bread are normally obtained and the yield is the exceeding weight respect to the used flour.
This is the method of making bread and the chemical reactions which happen during it.
Bread contains STARCH, a polymeric form of glucose, forming long molecular chains and PROTEINS, (10-12%, formed by GLUTEN) and SALT (0.5-1.0%). It can be prepared only with the flour of SOFT WHEAT and RYE, because only those cereals contain the gluten, a protein that allows and stabilizes the typical swelling of bread.
The initial phase is mixing of FLOUR and the 50% of its weight of TEPID WATER in which it has been dissolved the SALT and the BREWER'S YEAST, in an amount of about 1% of the flour weight. This yeast is made of colonies of a fungus, the SACCHAROMYCES CEREVISIAE, prepared on residuals of on residuals of beer industry.
In many countries are not used the yeast like Middle East, the bread remains flat and we obtain the UNLEAVENED BREAD.
The yeast, at a temperature of about 30-35C, finds its favourable environment to reproduce itself and decomposes the starch, by means of an enzyme, the ZIMASIS, in molecules of ETHANOL (CH3-CH2-OH) and CARBON BIOXIDE (CO2):
-(C6H12O6)n- -> 2n CH3-CH2-OH + 2n CO2
The alcohol and the CO2 diffuse in the mass of the pastry forming many little bubbles and causing its swelling during the RISING phase, lasting some hours, at a controlled temperature (30-35C), in a place protected by air currents. The rising time is directly proportional to the bread size.
Then, the pastry is slightly compressed,' it's given the desired form and it's put into the oven at 200-300 C, for a time of 20-45 min., according to the dimension of the pieces.
In the oven, the ethanol and the CO2 evaporate, leaving the mass very spongy . Inside the mass, where the temperature remains relatively low (about 100 C), the protein component (the gluten) coagulates and forms a protein skeleton or tridimensional network containing many starch granules, partially decomposed in starch-water and soluble amylo-dextrin. This swollen mass becomes stable and forms the CRUMB, soft and elastic, holding in much water.
In the exterior of the cooking bread, exposed to the highest temperature, water evaporates nearly totally, the starch decomposes into smaller molecules of maltose (C12H22011) and dextrin and it forms a partially caramelized sugar, with its typical blond or brown colour and its fragile consistence. This is the CRUST of bread.
The water retained by the crumb after the cooking is a measure of the YIELD of the bread; from 100 Kg of flour, 125-135 Kg of bread are normally obtained and the yield is the exceeding weight respect to the used flour.
This is the method of making bread and the chemical reactions which happen during it.
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