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Dough Fermentation ( Lab Report )
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Purpose:

The purpose of this experiment was to monitoring the effect of ingredients and temperature of incubation and room for rising ability on dough.

Theory:

A prerequisite to a controlled fermentation is a fully hydrated, homogeneous dough, such as is obtained by correct mixing. The surface appearance of a sponge as fermentation progresses usually provides a reliable indication of the adequacy of its mixing. A properly mixed sponge will exhibit good gas retention that will make it rise and assume a well-rounded top. Retention of fermentation gasses allows loaves to develop properly and result in a light, well raised loaf after baking.

The surface of an under mixed sponge, on the other hand, will remain flat, which is indicative of an incomplete incorporation of the formula ingredients and an uneven fermentation. In straight doughs, mixing plays a much more critical role as the aim here is to obtain optimal physical dough development.

When a correctly mixed sponge or dough is fermented, two sets of forces come into play: gas production and gas retention. Gas production involves primarily the biological functioning of yeast on available fermentable carbohydrates, whereas gas retention is largely a measure of the mechanical and physicochemical modifications of the colloidal structure of the dough during mixing and during the course of fermentation.

The baker must control fermentation in such manner that the forces of gas production and gas retention are in proper balance. Thus, should gas production attain its maximum rate before the dough’s gas retention capacity is fully developed, then too much gas will be lost to bring about maximum aeration of the dough. On the other hand, if the gas retention capacity has peaked before gas production has reached its maximum rate, then again much of the gas is unable to perform its aerating function. Hence, the aim of fermentation control is to have gas production capacity and gas retention capacity coincide both as to rate and time. As Clark (in Pyler) has stated, “When both peaks are reached at the same time there frequently is combined in one loaf the largest volume together with the best grain, texture, crust color, and other loaf characteristics which the flour in question will produce.”

In the process of developing a bread dough, changes are brought about in the physical properties of the dough. In particular the dough’s ability to retain the carbon dioxide gas, which will later be generated by yeast fermentation, is improved in the process. This improvement in gas retention ability is particularly important when the dough pieces reach the oven. In the entry stages of baking, before the dough has set, yeast activity is at its greatest level, and large quantities of carbon dioxide gas are being generated and released from solution in the aqueous phase of the dough. The dough is only able to reclaim the gas formed if a gluten structure with the correct physical structure is created. The baker must coordinate the timing of the development of the gluten structure with gas production. It does little good, for example, to develop bread with high carbon dioxide release due to proper fermentation processes, but without the degree of extensibility necessary to provide good gas retention.

Can one measure gas retention and gas production? The answer is “Yes – but…” Instrumentation exists which can measure both in the same dough at the same time. It is probably not available to the vast majority of home bakers and perhaps even to most commercial bakers. It is the Chopin Rheofermentometer. This is a new instrument that simultaneously measures gas production and gas retention under realistic conditions. A piece of dough is placed in a sealed chamber under a weighted piston. As the dough rises piston movements is measured to determine the rate of expansion and the dough strength. At the same time, total gas production by yeast is measured along with the amount that escapes from the dough into the chamber. Subtracting the amount released from the total gives the amount retained. All of this is controlled by a microchip that calculates the results and produces a graph depicting “development of the Dough” and “Gaseous Release”. A retention coefficient is calculated by dividing the retained volume by the total volume. (Lallemand.)

Most of the desirable changes resulting from ‘optimum’ dough development, whatever the breadmaking process, are related to the ability of the dough to retain gas bubbles (air) and permit the uniform expansion of the dough piece under the influence of carbon dioxide gas from yeast fermentation during proof and baking.

Gas production refers to the generation of carbon dioxide gas as a natural consequence of yeast fermentation. Provided the yeast cells in the dough remain viable (alive) and sufficient substrate (food) for the yeast is available, then gas production will continue, but expansion of the dough can only occur if that carbon dioxide gas is retained in the dough. Not all of the gas generated during the processing, proof and baking will be retained within the dough before it finally sets in the oven.

What factors effect gas production and retention? These include the following that would seem to be of interest to most home bakers.

  • High Temperature: This increases gas production and decreases gas retention. Low temperatures give strong doughs that rise slowly, while high temperatures give weak doughs that rise quickly

  • Higher Water Absorption: This increases gas production and decreases gas retention. Diluted dissolved solids make yeast more active, but diluting gluten reduces the strength of the dough.

  • Sugar: Gas production can be increased with sugar levels of about 5%, but reduced at higher levels because of osmotic pressure.

  • Salt: Salt decreases gas production even more than sugar.

  • Fiber Content: Higher fiber content or whole grain contents reduce gas retention and tolerance because the increased fiber interferes with the gluten structure.

Most flours possessing adequate baking properties pass through a stage in the course of fermentation during which gas production and gas retention are in optimum balance. The time range over which this is true may properly be designated as the flour’s fermentation tolerance. Since fermentation is subject to many influences that affect its course, it is evident that one and the same flour may have rather limited fermentation tolerance under one set of conditions, and good tolerance under a different set of conditions.

Materials and Apparatus:

  • mortar and pestle

  • graduated cylinder

  • rod

  • wheat flour

  • vegetable oil

  • sugar

  • salt

  • dry yeast

  • beaker

  • etuv

  • pipette

  • balance

  • Flask

  • Incubator

Procedure:

We worked as Group 2. Firstly; 1g dry yeast was dissolved together with 20 ml water. Secondly; it was added 80 ml water with 1 g sugar. Then; yeast solution and sugar solution were mixed each other. Next; 100 g flour was added into the prepared solution and mixture was mixed completely. After, dough was occurred. Graduated cylinders were oil. Dough was separated two equal parts and each other of their was put as 25 volume into two graduated cylinders. One of dough in graduated cylinders was incubated at 37 oC, another part dough was incubated at room temperature about 25 oC.

One times each 15 minute was measured to volume in Graduated cylinders. Lastly; volume graph of dough was drawn according to time.

RESULTS

          Volume of sponge at 25oC

           Volume of sponge at 37oC

time min

A1

A2

A3

A4

A5

A6

A7

A1

A2

A3

A4

A5

A6

A7

0

28

25

23

25

25

25

25

25

25

25

25

25

25

25

15

28,5

26

24

26

25

27

30

26

26

25

27

26

27

28

30

30

26

25

26,5

26

28

36

28

29

26

31

29

28

29

45

31

27

25

27,5

27

31

42

34

39

31

45

43

39

45

60

32

28,5

25

29

29

32

51

48,5

53

42

58

59

50

66

75

34

30,5

26

34

36

35

55

59

67

54

74

70

61

70

90

35

34

28

36

40

68

75

61

89

72

69

73

Dicussion:

In this experiment; properties of dough was studied. Dough was composed of flour, salt, sugar, vegetable oil and yeast and also soft water. In here;

Wheat flour is the key ingredient in most bread. Flour quality is particularly important in bread making as the quality of the flour will have a significant impact on the finished product. When flour is moistened and stirred, beaten or kneaded, gluten develops to give dough ‘stretch’. The elastic framework of gluten holds the gas produced by the fermentation action of yeast.

Yeast requires moisture, sugar and temperature for growth. When these requirements are satisfied, the yeast grows. Its function in bread making is to produce carbon dioxide gas to enable the dough to rise, form the cellular network found in bread crumb and give bread its characteristic aroma.

Salt is an essential ingredient in bread. It is used in very small amounts to give bread flavour. It also helps to control fermentation to produce bread of good volume and texture.

Water is used to produce the dough. It is important that the water is the correct temperature and quantity when making bread, because it affects the dispersal of the other ingredients.

            We examined dough at two different temperatures and at 37 oC dough was baking faster than at room temperature at 25 oC. Therefore, appropriate temperature provides more baking of dough. Besides, sugar content affects the growth of microorganisms, because sugar is substrate for microorganisms. Microorganism uses sugar and produce carbon dioxide gas. Carbon dioxide provides the baking of bread. Also; baking of bread depends on flour efficiency. In experiment depending on flour efficiency, first group’s dough volume was higher than other groups. In fact; second group’s dough volume must have been higher than other groups, however was not higher. First group’s flour efficiency can be higher than second group’s and other group’s flour efficiency.

During dough fermentation gluten maturation occurs, promoting extensibility and gas retention. These characteristics provide volume, texture, aroma, flavor and color to the dough. At our experiment was showed to effect of temperature onto dough which was fast rising at 37 oC but very low rising at 25 oC at room temperature.


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