Bread Makin

8/3/2019 Bread Makin

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Bread Making


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Systems of Bread-makingThe processes of yeast-leavened bread-

making may be divided into(a) Pre-fermentation (or sponge mixing): At this

stage a portion of the ingredients is mixed with

yeast and with or without flour to produce aninoculum. During this the yeast becomes adapted

to the growth conditions of the dough and

rapidly multiplies. Gluten development is not

sought at this stage.


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(b)Dough mixing: The balance of the ingredients ismixed together with the inoculum to form the

dough. This is the stage when maximum glutendevelopment is sought.

(c)Cutting and rounding: The dough formed above iscut into specific weights and rounded by

machines.(d)First (intermediate) proofing: The dough is

allowed to rest for about 15 minutes usually at

the same temperature as it has been previous tothis time i.e., at about 27C. This is done inequipment known as an overhead proofer.


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(e)Molding: The dough is flattened to a sheet and thenmoulded into a spherical body and placed in a bakingpan which will confer shape to the loaf.

(f)Second proofing: This consists of holding the dough forabout 1 hour at 35-43C and in an atmosphere of highhumidity (89-95C)

(g)Baking: During baking the proofed dough istransferred, still in the final pan, to the oven where it issubjected to an average temperature of 215-225C for17-23 minutes. Baking is the final of the variousbaking processes.


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(h)Cooling, slicing, and wrapping: The bread is

depanned, cooled to 4-5C sliced (optional in somecountries) and wrapped in waxed paper, or plastic

bags.


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Factors which effect the leavening action ofyeasts (i) The nature of the sugar available

(ii) Osmotic pressure (iii) Effect of nitrogen and other nutrients

(iv) Effect on fungal inhibitors

(v) Yeast concentration


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Factors which effect the leavening action of yeasts(i) The nature of the sugar available: When no sugar is added to the dough

such as in the traditional method of

bread-making, the yeast utilizes themaltose in the flour.

Such maltose is produced by the actionof the amylases of the wheat.


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When glucose, fructose, or sucrose are

added these are utilized in preference to

maltose.(ii) Osmotic pressure:

High osmotic pressures inhibit yeast action

Salt at levels beyond about 2% (based onflour weight) is inhibitory on yeasts. Indough the amount used is 2.0-2.5% and

this is inhibitory on yeasts. Salt istherefore added as late as possible inthe dough formation process.


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(iii) Effect of nitrogen and other nutrients:

Short fermentations require no nutrientsbut for longer fermentation, the additionof minerals and a nitrogen source

increases gas production.Ammonium normally added as yeast food is

rapidly utilized. Flour also supplies amino

acids and peptides and thiamine. Thiamineis required for the growth of yeasts.


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(iv) Effect on fungal inhibitors (antimycotic agents):

Anti-mycotics added to bread are allinhibitory to yeast.

(v) Yeast concentration:

A balance exists between the sugarconcentration, the length of thefermentation and the yeast

concentration.


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The Three Basic Systems of Bread-makingAll three are essentially similar and differ only in the

presence or absence of a pre-fermentation. Theformulation of the pre-ferment may consists of a

broth or it may be a sponge (i.e., includes flour). All

three basic types may be sponge i.e includes flour. Allthree basic types may also be batch or continuous.

a) Sponge doughs, b) The liquid ferment

system, c) The straight dough system


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(i) Sponge doughs:

most widely used worldwide

In the sponge-dough system of baking aportion (60-70%) of the flour is mixedwith water, yeast and yeast food in aslurry tank during the pre-fermentationto yield a spongy material due tobubbles caused by alcohol and CO2. If

enzymes are used they may be added atthis stage.


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The sponge is allowed to rest at about 27Cand a relative humidity of 75-80% for 3

to 5 hours. During this period the spongesrises five to six times because of thevolatile products released by this yeastand usually collapses spontaneously.

During the next stage the sponge is mixed

with the other ingredients.


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The heat of the oven causes themetabolic products of the yeast CO2,

alcohol, and water vapor to expand tothe final size of the loaf. The proteinbecomes denatured beginning fromabout 70C; the denatured proteinsoon sets, and imposes fixed sizes tothe air vesicles.


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The enzymes alpha and B amylases areactive for a while as the temperature

passes through their optimum temp,which are 55-65C and 65-70Crespectively.

At temperatures of about 10C beyondtheir optima, these two enzymesbecome denatured.


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At about 65-70C the yeasts arekilled. The higher outside temperature

leads to browning of the crust, a resultof reactions between the reducingsugars and the free amino acids in thedough.

The starch granules which havebecome hydrated are broken down onlyslightly by the amylolytic enzymes

before they become denatured todextrin and maltose by alpha amylaseand B amylase


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(ii) The liquid ferment system.

In this system water, yeast, malt, sugar,salt and, sometimes, milk are mixed

during the pre-fermentation at about30C and left for about 6 hours. Afterthat, flour and other ingredients areadded and mixed to form a dough. The

rest is as described above.


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(iii) The straight dough system: In this system, all the components are

mixed at the same time until a dough isformed.

The dough is then allowed to ferment atabout 28-30C for 2- 4 hours. During

this period the risen dough isoccasionally knocked down to cause it tocollapse.

Thereafter, it follows the same processas those already described. Thestraight dough is usually used for homebread making.


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Flavor development

During baking the lower boiling point

materials escape with the oven gases;and new compounds result from thechemical reactions taking place at the

high temperature. The flavor compound found in bread are

organic acids, esters, alcohols,

aldehydes, ketones and other carbonylcompounds.


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Baking

Bread is baked at a temperature of about

235C for 45

60 minutes. As the bakingprogresses and temperature rises gasproduction rises and various events occur

as below:a) At about 45C the undamaged starchgranules begin to gelatinize and are

attacked by alpha-amylase, yieldingfermentable sugars;


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b) Between 50 and 60C the yeast is killed;

c) At about 65C the beta-amylase isthermally inactivated;

d) At about 75C the fungal amylase isinactivated;

e) At about 87C the cereal alpha-amylase

is inactivated;


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f) Finally, the gluten is denatured andcoagulates, stabilizing the shape and sizeof the loaf.

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