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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
Introducing the task (version A)
• 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.
Introducing the task (version A)
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
Introducing the task (version A)
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
Modifying the task to investigate temperature effect (version 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
1 tsp yeast ¼ tsp sugar
20 g bread flour
1 tsp yeast ¼ tsp sugar
20 g bread flour
1 tsp yeast ¼ tsp sugar
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.
Modifying the task to investigate temperature effect (version C)
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
Modifying the task to investigate temperature effect (version C)
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
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
Ways to maintain different temperatures
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)
Ways to maintain different temperatures
Steamer (40-65°C) Steamer (80-100°C)
Check the temperature
every 5 minutes.
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
Introducing the task
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.
Introducing the task
• 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.
Introducing the task
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
Introducing the task
Results (Apple balls)
Treatment Degree of browning at
0 min 5 min 10 min 15 min 20 min 25 min 30 min
No treatment + +++ +++ ++++ +++++ +++++ +++++
Immersed in lemon juice - - - - - - -
Immersed in 1% salt solution
- - - + + + +
Blanching - + + ++ ++ ++ ++
Introducing the task
Results (Apple slices)
0 min 5 min 10 min 15 min 20 min 25 min 30 min
No treatment
Lemon juice
1% salt solution
Blanching
Introducing the task
Results (Apple slices)
Treatment Degree of browning at
0 min 5 min 10 min 15 min 20 min 25 min 30 min
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.
Adapting the task for school’s use
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
Adapting the task for school’s use
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.