Notes on bread

DISCUSSION ON BREAD MAKING

Introduction

Baking is one of the most important discoveries of mankind. Bread is made by baking dough which has its main 4 ingredients wheat flour, water, yeast and salt. Other ingredients which may be added include flours of other cereals, milk and milk products, fruits, gluten,sugar etc. When these ingredients are mixed in correct proportions two processes commence: (i) the protein in flour begins to hydrate and forms a cohesive mass called as gluten (ii) evolution of carbon dioxide gas by action of the enzymes in the yeast upon the sugars.

The three main requirements in making bread from wheat flour are :- formation of gluten network, aeration of the mixture by incorporation of gas, and coagulation of the material by heating it in the oven.

 Essential ingredients and their functions in Bread Making : The ingredients required for bread making -

Flour

Flour is essential to the structure of dough and subsequently the bread. Gluten (Gliadin and Glutenin) is the principle functional protein of wheat flour. Thus the wheat flour is converted into cohesive, elastic, extensible dough. This viscous elastic three-dimensional gluten network retains gas formed by sugar fermentation and contributes to structure of dough and bread.

Starch plays important role in dough during baking. When heat is applied, gas cells expand gluten networks stretches, starch granules take up water and get partially gelatinized. This viscous paste sets to gel after baking.

Water

Water hydrates gluten proteins during mixing, gelatinizes starch during baking and serves as a dispersion medium for other ingredients such as yeast. Quality of water such as pH and hardness of water play important role in dough formation. Excessively alkaline water can retard the activity of yeast enzymes. Hard water containing calcium and magnesium ions, may have a tightening effect and soft water has loosening effect on dough.

Yeast

Yeast produces carbon dioxide and ethanol by fermentation of fermentable sugars. During fermentation it also helps in formation of flavour precursors. Rate of fermentation of dough by yeast is controlled by temperature, nutrient supply, water, pH, sugar concentration, salt and level and type of yeast. Generally two type of yeasts are used in baking: Compressed yeast and dried yeast. Both the types consist of living cells of Saccharomyces cerevisiae.

Salt

Salt acts as flavour enhancer and helps in control the fermentation by yeast. It also toughens the gluten and gives less sticky dough.

Principles Of Bread Making

Different steps in Bread making

Production of bread consists of number of  different steps.

There are different steps of bread making involves first sieving of flour to remove any foreign materials and coarse particles, and to aerate and make the flour more homogeneous.

The next step is dough mixing, which is accomplished by various methods of preparation of dough. Once the dough is formed, it is divided into pieces of requisite size. The divided dough is rounded to a ball shape and then passed through intermediate proofer, where the roughly stretched gluten fibre get time to recover their extensibility so that they can be moulded well without breaking the surface skin.

After intermediate proving, the dough is passed through a set of pairs of roller to form a sheet. The sheeted dough is now passed through pressure board to get moulded into cylindrical shape.

The moulded dough pieces are then placed into greased individual bread baking tins. The panned dough pieces are then passed through final prover under controlled temperature and humidity. After complete proofing, the dough tins are transferred to the baking oven. Once baking is completed, the breads are de-panned, cooled and then sliced. Sliced breads are then packaged in suitable packaging material, generally polypropylene pouches.

The following 12 steps in bread-making are as follows :  These steps are applied to all yeast products, with variations depending on a particular product.
These steps are--
1. Scaling of ingredients.
2. Mixing.
3. Fermentation.
4.Punching.
5 Scaling of the dough.
6.Rounding.
7.Intermediate proving/ Benching.
8.Moulding/ Panning.
9.Proofing.
10.Baking.
11.Cooling and,
12.Storing.

1.             Scaling of ingredients ----  All ingredients must be weighed accurately. Water, egg, milk must be measured by volume. Special care must be taken while measuring spices and other ingredients used in small quantities.

2.               Mixing  ----  The objective of this step is-
1. To combine all ingredients into  uniform  smooth dough.
2. To distribute the yeast evenly in  the dough.
3. To develop gluten.
All the flour, yeast, water, yeast food is mixed sufficiently to make a homogenous mass. Fat should be added later, as it adversely affects water absorption and also in gluten development.
Quantity and quality of gluten will decide the length of mixing times. Strong flours will need longer mixing time. When the dough is properly mixed, the surface of the dough becomes smooth.
If the dough is over- mixed then the gluten structure will break down and rise during fermentation will be poor. The dough will heat up and sticky and will tend to flatten out during intermediate and final proving. Breads produced from excessively mixed doughs will have less volume and dark crumbly texture.
3.       Fermentation   ---- After the dough is correctly mixed it is fermented for pre-determined time .The yeast acts on the sugars and starches in dough to produce CO2 and alcohol and it raises the dough.

 There are three main sources of sugar in the fermenting dough--
---natural sugar present in flour.
---formula sugar
---sugar produced from starch by enzymes.
The gluten becomes more smoother and more elastic, so it stretches further and holds more gas.
An under-fermented dough will not develop proper volume and the texture of the product will be coarse.  An over-fermented dough is called an old dough. An over-fermented dough becomes sticky [ due to over action of enzyme protease and acids], hard to work and slightly sour .

4.   Knock-back-------
After 2/3rd of the fermented time is over , the dough is knocked back. Knock- back is not hitting the dough with your fist, but a method of deflating the dough, by extending the sides of the dough and putting it in the centre, so that the whole mass comes in contact with fresh air and the dough is virtually turned upside down.
                Knock-back helps to equalize the temperature, the temperature of the upper surface is lower than the temperature at the base of the dough, this causes a variation in the speed of fermentation.
              Knock-back helps the yeast to function efficiently, when the dough is fermented for some-time the yeast cells get surrounded by gas and other fermentation products which slow down their action, as it is drawn away from the food, so knock-back helps to expel the gas, so that the yeast can carry on its function properly. It  helps to redistribute the yeast for further growth.

5.   Scaling  -----  Using a baker's scale, divide the dough into pieces of the same weight, according to the product being made. Scaling should be done rapidly and efficiently to avoid over-fermenting of the dough.

6.       Rounding  -----   After scaling, the pieces of dough are shaped into a smooth  round balls. While dividing the dough by hand, it is desirable to cut the dough with a dough cutter. Pulling and breaking the dough should be avoided as it can disturb the gluten strands which can adversely affects the final texture of the product.

7.       Intermediate Proving  ----  Rounded portions of the dough are allowed to rest for 10-20 minutes. This relaxes the gluten to make the shaping of dough easier.

8.       Moulding/Panning  ----  The dough piece should soft and pliable, is moulded as per the desired shape. While moulding the pressure should be even throughout the dough piece. Uneven pressure will leave uneven gas pocket of uneven size in the final product. Moulding should not be too tight or too loose. Moulded pieces should be put into clean and well greased pans or trays. The pan size must be matched to the weight of the dough.

9.       Proofing  ---- Proofing is a continuation of the process of yeast fermentation that increases the volume of the shaped product. The bread is proofed under suitable conditions [27-30 degrees] and 70-80% humidity. Under proofing results in poor volume and dense texture. Over proofing results in coarse texture and loss of some flavour. French bread are given long proof to create its characteristic open texture, its strong gluten helps to withstand the long proof.
Rich doughs are slighly under proofed, because their weaker gluten structure does not withstand too much stretching.
During proofing operation the yeast should have sufficient food to affect a faster gas production. Therefore it is necessary that there is sufficient diastolic activity in the flour to produce fermentable sugars for the yeast to carry on its functions.
10.     Baking  ---  After the bread has acquired its full volume, it is baked. The temperature and the humidity of the oven should be well maintained in order to get good results.

The most important changes that take place are--
1. Oven spring, this is a rapid rise in the oven due to production and expansion of trapped gases as a result of the heat. The yeast is active at first but are killed as the temperature reaches 60 degrees inside the dough.
2. Coagulation of proteins and gelatinization of the starch. The product becomes firm and begins to hold shape.
3. Formation and browning of the crust.
Proofed breads are fragile, they should be handled carefully when being loaded into the oven.

11.     Cooling  -----  After baking the breads must be removed from mould and cooled on racks to allow the escape of excess moisture and alcohol created during fermentation.
If the moisture gets trapped between the bread and the surface of the mould , this will make the product soggy, known as sweating.
When bread is hot the starch granules are in a swollen state and are held unstably in a gluten framework. If bread is sliced in this state, the granules lump together giving a poor appearance to the slice.

12.   Storing------
Breads to be consumed within 8 hours may be left on the rack. For longer storage, wrap cooled bread in moisture-proof bags to preserve its freshness and to retard staling.

 Other different methods of bread making

1.      Straight Dough method

·         All the ingredients are mixed together, and the dough is fermented for a predetermined time.

·         The fermentation time of the straight dough depends on the strength of the flour. Strong flour requires more fermentation time to mature adequately.

·         Flours which require 2 to 3 hours for maturing should be used for making bread by straight method. Flours that take very long period for maturing should not be used because during prolonged fermentation periods it is very difficult to control the temperature of the dough and rise in temperature will cause acid taste and flavour in bread.

2.      No time dough method

·         Dough is fermented in the usual manner. It is just allowed a brief period (about 30 mins) for it to recover from the strains of mixing.

·         Since dough is not fermented, the two functions of fermentation (i. e production of gas and conditioning of gluten) are achieved to some extent by increasing the quantity of yeast ( 2 to 3 times of original quantity)and by making the dough little slacker and warmer.

·         Although it is possible to make fairly acceptable bread (during emergency) by using this method the product has poor keeping quality. Due to the absence of fermentation the gluten and starch are not conditioned sufficiently to retain the moisture.

3.      Salt delayed method

·         This a slight variation of straight method, where all the ingredients are mixed except salt and fat.

·         As a salt has a controlling effect on enzymatic action on yeast, the speed of fermentation of a salt less dough will be faster, and a reduction in total fermentation time will be faster.

·         The salt is added at a knock back stage. The method of adding salt at the later stage may be according to the convenience of individual baker. It may be sifted on the dough and mixed or it may be creamed with fat and salt.

·         Whatever way is chosen for mixing the salt, only three fourth (of actual mixing time) mixing should be given initially and one fourth mixing at the time of adding salt.

·         Due to absence of salt, the fermentation speed is enhanced and gluten is matured in a reasonably shorter time.

4.      Sponge and dough method

·         Strong flour take too long for conditioning and should not be used for making bread by straight dough method. For such flours sponge and dough method is more suitable where the problem of controlling the dough temperature time is not so acute.

·         Flour, proportionate amount of water, yeast and sugar are mixed together. Longer fermenting sponges may also contain some amount of as well. Mix all the ingredients evenly.

·         This sponge is fermented for a pre determined time. The ferment is carried out longest for almost 16 to 17 hours and minimum for an hour.

·         Scheduling flexibility - Sponges can usually be held longer than finished dough.

·         Increased flavor, developed by the long fermentation of the sponge

·         Less yeast is needed, because it multiplies during the sponge fermentation.

5.      Ferment and dough method

·         This is a variation of sponge and dough method.

·         All these formula ingredients will have a retarding effect on yeast activity.

·         If all the formula yeast, part of flour, yeast food and sufficient water are mixed together, the yeast gets initially an environment which is conducive to vigorous activity and at the end of fermentation time it is in a fit condition to take on extra load of fermentation in presence of milk, eggs, excessive fat etc.

·         Fermentation time of ferment depends on the formulation of the desired product but very often it becomes a matter of individual preference.

·         A ferment containing milk should be guarded against over fermentation as it will develop more than desired quantity of lactic acid which in turn will affect the flavor, taste and texture of the product. 

 

FEW DIFFERENT TYPES OF YEAST BREAD :-

There are four types of yeast bread, which are described below :-

1. Batter bread - The dough for batter bread is not kneaded. Batter bread is coarser in shape and texture than bread prepared with kneaded dough. It has a higher ratio of liquid to the flour and other dry ingredients.  Beat the batter, few minutes develops the gluten, though not as much as a kneaded bread. The dough rises only once, in the bread pan. Batter bread generally does not rise as high as kneaded bread.

2.Kneaded bread - Kneaded bread offers many options for bakers, especially in regards to shaping. The dough is allowed to rise before shaping, then it is shaped and allowed to rise again. Finally, the bread is baked in electric bread machines are also kneaded bread.  Examples of kneaded bread include loaf bread, baguettes, pan rolls, and crescent rolls etc.

3.LEAN / SIMPLE YEASTED BREAD:- Bread dough containing less sugar, egg and fats is lean yeast bread: Example – French bread, white milk bread, Irish soda bread.

4.RICH YEASTED BREAD :-  Bread dough, rich in sugar, yeast, eggs, and fats is rich yeasted bread.  Example – Savarin, panettone, brioche, etc.

Baking Temperature & Its Importance

Baking temperature causes physical transitions and chemical reactions to take place in the dough/batter. The following stages are temperature-dependent and participate in the sequential transformation of bread dough.

1. Development (also known as oven spring)

As temperature increases, the free water/alcohol mixture in the product vaporizes, fermentation gases (CO2) dissolved in the liquid dough phase become less soluble, and are released into the cells, causing them to expand in response to the rise in pressure.

As a result, cells increase in volume by retaining gases due to their deformable nature as these are surrounded by the continuous gluten/starch soft matrix. This results in a large reduction in the density of the dough as the product gradually develops an aerated structure. Note that the size to which the gas bubbles can grow is limited by the ability of the gluten/starch film surrounding them to stretch without rupturing.

In this stage, the product undergoes a series of irreversible chemical and physical transformations. Oven spring is accompanied by the following changes and conditions:

·         The killing of yeast cells at 50–60°C (122–140°F)

·         Maximum enzymatic activity at 60°C (140°F). The enzyme-driven reactions that convert starch into sugars and break proteins into amino acids increase with heat, so they increase most near the dough surface.

·         Starch gelatinization. It starts at 55–65°C (130–150°F) as granules become fully swollen with local free water.

·         Denaturation of gluten proteins at 50°C (122°F) and coagulation at 70–80°C (160–180°F). As a consequence, gluten becomes increasingly tough and stiff as it irreversibly forms a gel.

·         Above 85°C (185°F), starch looks glassy, and gluten looks rubbery. This is the start of the dough-crumb transition process.

·         Inactivation of naturally-occurring and added enzymes inside the dough (70–85°C) (160–185°F).

2. Drying (reduction of dough/batter moisture)

·         Under the action of the heat transfer mechanisms, high temperatures develop inside the baking chamber (200–300°C) (390–570°F), and water molecules at the dough surface absorb latent heat and start to evaporate.

·         Due to the low humidity of the air inside the baking chamber, a water vapor pressure (air moisture concentration) gradient is created. Liquid-state water starts to diffuse and migrates from the product core to the surface, where it evaporates and is lost to the oven atmosphere.

·         The loss of moisture from the dough piece is dependent on the baking chamber temperature. 3. Color formation

The external surface of the product is exposed directly to the high temperatures of the oven and readily absorbs the heat from the energy sources. These high temperatures trigger non-enzymatic reactions that give rise to the desirable brown crust:

·         Mallard browning takes place above approximately 105°C (220°F) and requires the presence of reducing sugar (glucose, maltose, or lactose) together with an amino acid, the type of which determines color and flavor.

·         Sugars caramelize at 160°C (320°F). This reaction will happen only in the presence of water.