ROLE OF EACH INGREDIENT IN BREAD MAKING
The flour used for bread making should have a creamy white colour; it should feel slightly coarse when rubbed between the fingers. If squeezed into a lump in the hand, it should fall apart as soon as the hand is opened. The protein content s\of the flour should be high.
After flour, yeast is the next important ingredient for bread making.
Yeast is a unicellular microscopic plant. It consists of a cell wall, protoplasm and vacuole. It requires food, moisture and right temperature for its growth and reproduction. They reproduce by budding.
There is no organism known other than yeast which contains the same combination of enzymes in the same proportion. That is why there is no substitute for yeast as a fermenting enzyme.
(Enzymes are minute substances produced by living organisms which by its mere presence are capable of bringing bout or speeding up certain changes. The enzyme itself is neither destroyed nor changed.)
The most important enzymes which take part in the fermentation process are invertase, maltase, zymase and protease. (Fermentation is the process by which yeast acts on sugar and changes then into carbon dioxide gas and alcohol. The release of gas produces the leavening action. The alcohol evaporates completely during and immediately after baking.
The sugar in bread dough comes from two sources-
- It is added to the dough by the baker.
- It is produced from flour by the breakdown of starch into sugar by enzymes present in the flour. α and β amylase.
Invertase – Converts sucrose or cane sugar into simple sugar known as invert sugar which is a combination of dextrose (glucose) and fructose.
Maltase – It converts maltose sugar into dextrose (glucose) which is directly fermentable by yeast.
Zymase – It is actually the specific fermenting enzyme in yeast. Zymase attacks dextrose and is converted into carbon dioxide, alcohol and very small amounts of glycerin, lactic acid, and acetic acid. All these impart the particular flavor to bread.
Protease – this enzyme has a mellowing action on flour proteins, thus making he gluten strands more stretchable for bread to acquire volume and form structure.
As yeast is a living organism and is sensitive to temperatures.
Storage temperature - 1°C - 4°C Inactive
15°C - 20°C Slow action
20°C - 32°C Best growth
32°C Reaction slows down
60°C Yeast is killed
Sucrose Invertase Dextrose + Fructose
Maltose Maltase Dextrose + Dextrose
Dextrose Zymase Carbon dioxide + alcohol
(Glucose) Succinic + lactic + acetic acid + glycerin
Yeast is available in 3 forms:
- Fresh yeast / Compressed / wet yeast is moist and perishable.
- Active dry yeast is a dry granular form of yeast. It has to be activated before use, i.e. it has to be rehydrated in 4 times water its weight of warm water before use.
- Instant dry yeast is also a dry granular form of yeast, but it does not have to be dissolved in water before use. It can be added in its dry form because it absorbs water much more quickly than regular dry yeast.
Compressed yeast should be used 2-2.5 times more as compared to dry yeast.
The main function of sugar in bread making is to provide for yeast which in turn produces carbon dioxide. It helps in enhancing the flavor of bread. Being hygroscopic, sugar helps to retain moisture in bread.
It contributes to the golden brown outer crust colour of bread.
Apart from the sugar added in the formula, sugar is present in the fermenting dough as a result of the diastase activity. This sugar provides food for yeast at a certain time at the final stage of fermentation. It also imparts bloom to the bread.
Fat is used in bread making at the rate of 1-2%. Fat adds nutritive value to the bread. It acts as a lubricant on the gluten strands, thus improves the extensibility which enables the bread to acquire good volume. Fat also helps to retain moisture in the bread and thus its sliceability. Fat should be added during the last stages of mixing. If it is added in the beginning, it will have an adverse effect on water absorption power of the flour.
Sat imparts taste to the bread. It also helps in bringing out the flavour in bread. Is has a controlling effect on the yeast activity and thus keeps the speed of fermentation under check. Salt has a tightening action on flour proteins thus improving the gas retention power in the dough. Salt being hygroscopic, it helps to keep bread fresh and moist for a longer period of time. The colour of the crust is largely dependant on the amount of salt added while making the dough. That means if there is less salt in the dough, yeast action will be more than normal and there will be less sugar for caramelisation resulting in poor crust colour. On the other hand if more salt is present, there will be more sugar left at the time of baking due to the controlling effect of salt on yeast and the crust colour will be dark.
The amount of sugar in a bread recipe varies between 1.25% - 2.5% depending on the strength of the flour, length of fermentation time, etc.
Any water which is fit to drink can be used for bread making. Water binds together the insoluble proteins of flour to form gluten.
STEPS IN BREAD MAKING
All yeast products can be categorized into – lean dough products, rich dough products and rolled-in yeast dough products.
Lean Dough products are low in fat and sugar. E.g. bread rolls, French bread, brown bread, pizza, etc.
Rich Dough products are those that contain higher proportions of fat, sugar, eggs, etc. E.g. Brioche, sweet buns, etc.
Rolled-in dough products are those in which fat is incorporated into the dough in many layers by using a rolling and folding procedure. E.g. Crossaints, Danish pastry, etc.
There are 12 basic steps in the production of yeast breads. They are:-
- Scaling ingredients
- Intermediate proving
- Panning / make – up
All ingredients must be accurately weighed. Water, milk and eggs must be measured by volume. Special care must be taken while measuring spices, salt, etc.
Mixing the dough has three main purposes-
1. To combine all ingredients into a uniform smooth dough.
2. To distribute the yeast evenly throughout the dough
3. To develop gluten.
The dough could be made by hand or machine. When water is added while making the dough, gluten and gliadin join together to form gluten. Initially this gluten does not have much elasticity as it absorbs more water, along with proper kneading, the texture improves, the surface of the dough becomes smooth, the surface may show some round coin shaped gas bubbles trapped under a thin film of dough. A small piece of correctly mixed dough can be stretched between fingers into a thin translucent film.
Fermentation is a process by which yeast acts on the sugars and starches in the dough to produce carbon dioxide and alcohol.
Gluten becomes smoother and more elastic during fermentation.
The temperature should be between 28°C - 30°C and the relative humidity at 70% to 75% and time for fermentation is decided according to the strength of the flour and the recipe.
If the dough is allowed to over ferment (old dough), the dough becomes soft and sticky and the gluten strands will weaken.
An underfermented dough (green dough) will produce a bread with less volume and texture will be close and compact. The bread will dry out soon and will be crumbly due to insufficient conditioning of gluten.
4. Knock-back (Punching):-
After the dough is fermented for 2/3rd of its estimated time, it is knocked back.
Knock back helps to expel carbon dioxide, relaxes the gluten, redistributes the yeast for further growth and equalizes the temperature throughout the dough. It also exposes the yeast cells to fresh oxygen.
Punching is not hitting the dough with your fist, but deflating the dough.
5. Scaling / Dividing:-
Using a baker’s scale, divide the dough into pieces of the same weight according to the product being made.
During scaling allowance is made for weight loss due to evaporation of moisture in the oven. The weight loss is approximately 10% - 13% of the weight of the dough. Allow 50g – 65g per 500g.
Scaling should be done rapidly and efficiently to avoid overfermentation.
After scaling, the pieces of dough are shaped into smooth round balls. Rounding simplifies the later shaping of the dough and also helps to retain gases produced by the yeast (pulling and breaking of the dough should be avoided as it disturbs the trend of gluten strands thereby affecting the final texture of the product. It is desirable to cut the dough with a regular dough cutter).
7. Intermediate proving / Benching:-
Rounded portions of the dough are allowed to rest for 20-30 minutes. This relaxes the dough to make shaping of the dough easier. Fermentation continues during this period.
8. Moulding / Panning / Make-up:-
The dough, soft and pliable after the intermediate proving is moulded as per the desired shape.
Proper make up is of critical importance. All gas bubbles should be expelled during moulding. Bubbles left in the dough will result in large holes in the product. The dough should not be moulded too tight or too loose. Too tight moulding may tear off the surface and too loose moulding will open up the texture to an undesirable extent.
Proofing is a continuation of the process of yeast fermentation that increases the volume of the shaped dough. The temperature (27°C - 30°C) and 70% - 80% humidity of the proofing cabinet will help the dough to double in size without the formation of a crust.
After the bread has acquired full volume, it is baked. The temperature and humidity of the oven should be well maintained.
When bread is kept in the oven, is acquires heat gradually. Due to the increase in temperature, the yeast starts functioning vigorously producing gas which raises the volume of the product. The difference in the size of the product from the time it was kept in the oven to the time it is properly baked is known as oven-spring.
As baking proceeds, proteins coagulate and starch gets gelatinized. The product becomes firm and holds shape.
Finally, the product acquires crust colour.
After baking, bread must be removed from the moulds immediately and cooled on racks to allow the escape of excess moisture and alcohol.
Sweating takes place when moisture gets trapped between the bread and the surface of the mould which makes the bread soggy, technically known as sweating.
When the bread is hot, starch granules are in a swollen state and unstably held by the gluten network. If bread is sliced in this state, the starch granules will lump together giving a very poor appearance to the slice. As the bread cools down, the starch granules will shrink and stabilize in the gluten framework thus making it easy to slice the loaf.
Breads to be served within 8 hours may be left on the rack. For longer storage, breads are to be wrapped in moisture proof bags to retard staling. Breads must be thoroughly cooled before wrapping.