“factors affecting the rising of bread dough”...effect (version c) •adapting the task for...

Prescribed task: “Factors affecting the rising of

bread dough”

Ms Mancy Chan Pui Tak Canossian College

Prescribed task: “Factors affecting the rising of bread dough”

• Introducing the task (version A)

• Modifying the task to investigate temperature effect (version C)

• Adapting the task for school’s use

Introducing the task (version A)

Background

• CO2 expands the gluten network and causes the bread dough to rise

• depends on the growth and activity of the yeast

酵母的發酵作用

Observe and measure


• Factors affecting the rising of bread dough

– Temperature (Cup B)

– Additives

• Salt (Cup C)

• Sugar (Cup D)

• Vinegar (Cup E / optional)

– Control (Cup A)

Introducing the task (version A) Cup (Beaker)

Step 1 A B C D

Step 2

20 g bread flour

1 tsp yeast

20 g bread flour

1 tsp yeast

20 g bread flour

1 tsp yeast

20 g bread flour

1 tsp yeast

-- -- ¼ tsp salt ¼ tsp sugar

Stir the mixture

Step 3-6 30 ml distilled

water 30 ml cold

distilled water 30 ml distilled

water 30 ml distilled

water

Stir the mixture

Step 4-6 Measure and record the initial height of the dough (hi).

Wait for 25 minutes

Step 7 Record the final height of the dough (hf) in each cup. Note and record the texture of the dough in each cup.


Initial height of the dough (hi)

A C D E


Final height of the dough (hf)

A C

D

E B


Texture of the dough [Hint: You may indicate the “size of bubbles observed in the dough” using “+” signs.

The greater the number of “+” signs (maximum being 5), the larger is the size of bubbles observed in the dough.]

A C D E B


Results

Cup (Beaker)

Substance added

Fermentation temperature

(C)

Height of the dough Rise of

dough (cm) Appearance

hi (cm) hf (cm)

A -- ~25 1.7 4 2.3 +++ B -- ~4 1.7 2 0.3 / C salt ~25 1.8 2.5 0.7 + D sugar ~25 1.8 6 4.2 +++++ E vinegar ~25 1.8 3.6 1.8 ++

Another way of describing the appearance (will be mentioned by Eva)

Discussion

1. Based on the results of this experiment, state and explain which of the investigated factors favour(s) yeast fermentation.

2. Based on the results of this experiment, state and explain which of the investigated factors inhibit(s) yeast fermentation.

3. Discuss the applications of your findings in bread making.

Cup (Beaker)

Substance added

Fermentation temperature

(C)

Height of the dough Rise of dough (cm) Appearance

hi (cm) hf (cm)

A -- ~25 1.7 4 2.3 +++ B -- ~4 1.7 2 0.3 / C salt ~25 1.8 2.5 0.7 + D sugar ~25 1.8 6 4.2 +++++

Modifying the task to investigate temperature effect (version C)

Background • Similar to Version A • But “To study the effect of temperature on the

rising of bread dough”

• Different fermentation temperatures: – 25°C – 4-8°C – 40-65°C – 80-100°C


Cup (Beaker) Step 1 A B C D

Step 2 Measure and record the temperatures of the distilled water and the

cold distilled water

Step 3

20 g bread flour

1 tsp yeast ¼ tsp sugar

20 g bread flour


20 g bread flour


20 g bread flour


Stir the mixture

Step 4-8 30 ml distilled

water 30 ml cold

distilled water 30 ml distilled

water 30 ml distilled

water

Stir the mixture

Step 4-8 Measure and record the initial height of the dough (hi).

Room temperature 4°C 40-65°C 80-100°C

Wait for 25 minutes

Step 9 Record the final height of the dough (hf) in each cup.

Note and record the texture of the dough in each cup. Check the surrounding temperature of cup C and cup D every 5 minutes.


Results

A C D

B


Texture of the dough

[Hint: You may indicate the “size of bubbles observed in the dough” using “+” signs. The greater the number of “+” signs (maximum being 5), the larger is the size of bubbles observed in the dough.]

A C D B


Results

Cup

(Beaker) Temperature of

distilled water (C) Fermentation

temperature (C)

Height of the dough Rise of

dough (cm) Appearance

hi (cm) hf (cm)

A ~25 (27C) ~25 (27C) 1.8 4.5 2.7 +++

B 4 – 8 4 – 8 1.9 1.9 0 /

C ~25 40 – 65 1.7 4.5 2.8 ++

(Shrink after few minutes)

D ~25 80 – 100 1.9 2.8 0.9 +

(fully cooked)

Cup (Beaker)

Temperature of distilled water (C)

Fermentation temperature (C)

Height of the dough

Rise of dough (cm)

Appearance

hi (cm) hf (cm) A ~25 (27C) ~25 (27C) 1.8 4.5 2.7 +++ B 4 – 8 4 – 8 1.9 1.9 0 /

C ~25 40 – 65 1.7 4.5 2.8 ++

(Shrink after few minutes)

D ~25 80 – 100 1.9 2.8 0.9 +

(fully cooked)

Discussion

1. Based on the results of this experiment, state and explain which temperature(s) favour(s) yeast fermentation.

2. Based on the results of this experiment, state and explain which temperature(s) inhibit(s) yeast fermentation.

3. Discuss the applications of your findings in bread making.

Adapting the task for school’s use

• List of ingredients

• Choice of cups

– Plastic cups

– 250ml Beakers / Glass cups

• Ways to maintain different temperatures

List of ingredients

Strong flour Yeast (Small pack)

List of ingredients

Distilled water

Choice of cups (Plastic cups)

Choice of cups (Plastic cups)

Requirements:

• Volume (~250ml)

• Cylindrical cup

• Heat resistance (for Version C)

Choice of cups

Plastic cups (285ml) Beakers (250ml)

Cheap ($32 for 25) Expensive (~@$15) (Can be borrowed from Science Lab)

Reusable Reusable

A little bit fragile (broken 10 out of 25 after student trial)

Need to handle with care (But students are aware of it)

Cannot be used in Version C Can be used in all 3 versions

Ways to maintain different temperatures

Water bath

Dangerous when students pour in

or out hot water

Oven (Electric)

Need to have an oven thermometer to

monitor the temperature inside the

oven


Result

Cup (Beaker)

Temperature of distilled water (C)

Fermentation temperature (C)

Height of the dough

Rise of dough (cm)

Appearance

hi (cm) hf (cm)

D ~25 80 – 100

(Steamer with lid) 1.9 2.8 0.9

+ (fully cooked)

D2 ~25 80 – 100

(Electric oven) 1.9 3.1 1.2

+ (fully cooked)


Steamer (40-65°C) Steamer (80-100°C)

Check the temperature

every 5 minutes.

Prescribed task: “Investigating Ways to Prevent

Enzymatic Browning”

Prescribed task:“Investigating Ways to Prevent Enzymatic Browning”

• Introducing the task

• Adapting the task for school’s use

Introducing the task

• Investigate the effectiveness of three ways of preventing enzymatic browning:

– immersing the food in lemon juice

– 1% salt solution

– blanching for a short period of time


Procedures

• Steps 1-3

– Making lemon juice, 1% salt solution and boiling water

• Step 4

– Making apple slices or balls

(will be mentioned later)

Dissolve 1 g of salt completely

in 100 ml distilled water.


• Steps 5-6

– Different treatments of apple slices or balls

• No treatment

• Immersed in lemon juice for 30 seconds

• Immersed in 1% salt solution for 30 seconds

• Blanching (Immersed in boiling water for 30 seconds and cool it in icy distilled water)

• Step 7

– Determine and record the degree of browning every 5 minutes for 30 minutes. Tabulate the results.


Results (Apple balls)

No treatment

Lemon juice

1% salt solution

Blanching

0 min 5 min 10 min 15 min 20 min 25 min 30 min


Results (Apple balls)

Treatment Degree of browning at


No treatment + +++ +++ ++++ +++++ +++++ +++++

Immersed in lemon juice - - - - - - -

Immersed in 1% salt solution

- - - + + + +

Blanching - + + ++ ++ ++ ++


Results (Apple slices)


No treatment

Lemon juice

1% salt solution

Blanching


Results (Apple slices)

Treatment Degree of browning at


No treatment + ++ ++ +++ ++++ ++++ +++++

Immersed in lemon juice - - - - - - -

Immersed in 1% salt solution

- - - - - - + (edge)

Blanching - + + +

+

+

+

Remarks

Prefer to use Red Delicious Apple

(Medium to large size)

• Red Delicious apple is easier to undergo browning. • More obvious results can be obtained.


Using the corer:

1. Push an apple corer down into the flesh of the apple.

2. Twist the corer.

3. Remove the apple flesh from the corer.

4. Cut the cylindrical apple flesh into 0.5cm thick slices.

Apple corer


Using melon baller :

1. Cut the apple into half.

2. Use the melon baller

to scoop out the balls.

Melon baller

More obvious results can be obtained.

* Easier to turn brown.


• White tiles

(Bought it from 磁磚店)

• White plates

“factors affecting the rising of bread dough”...effect (version c) •adapting the task for...

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