Title: Respiration in Yeast During Bread Making
Observation:
In your first attempt at baking bread, you mix cold water and yeast with sugar. You
then add this mixture to flour, salt, milk, and butter. Your bread turns out dry and
hard. Your friend says that he used warm water and his bread turned out soft, light,
and fluffy.
Hypothesis:
Using warm water instead of cold water will activate the yeast more effectively,
leading to better fermentation, which will result in bread that is soft, light, and fluffy.
Aim:
To investigate the effect of water temperature on yeast activation and bread
texture.
Materials:
Flour
Salt
Milk
Butter
Sugar
Yeast
Cold water
Warm water (approximately 37°C)
Mixing bowls
Measuring cups and spoons
Thermometer
Baking pan
Oven
Diagram of Apparatus:
Method:
Prepare the Ingredients:
Measure equal amounts of flour, salt, milk, butter, and sugar.
Divide the ingredients into two equal sets for two trials.
Yeast Activation:
Trial 1 (Cold Water): In a mixing bowl, combine yeast with sugar and cold water. Stir
and let sit for 5 minutes.
Trial 2 (Warm Water): In another mixing bowl, combine yeast with sugar and warm
water (approximately 37°C). Stir and let sit for 5 minutes.
Dough Preparation:
For each trial, add the activated yeast mixture to a separate set of flour, salt, milk,
and butter. Mix thoroughly to form dough.
Kneading:
Knead each dough for 10 minutes until smooth and elastic.
Proofing:
Place each dough in a lightly greased bowl, cover with a damp cloth, and let it rise
in a warm place for 1-2 hours or until doubled in size.
Baking:
Preheat the oven to 180°C (350°F).
Once risen, shape the dough into loaves and place them in baking pans.
Bake for 25-30 minutes or until golden brown.
Cooling:
Remove bread from the oven and allow it to cool on a wire rack before slicing.
Variables:
Controlled Variables:
Amount of flour, salt, milk, butter, and sugar used
Yeast brand and quantity
Proofing time and temperature
Baking temperature and time
Dependent Variable:
Texture and quality of the bread (softness, lightness, and fluffiness)
Independent Variable:
Temperature of the water used to activate the yeast
Expected Results:
It is expected that the bread made with warm water will be softer, lighter, and
fluffier compared to the bread made with cold water due to better yeast activation
and fermentation.
Limitations:
Variability in yeast activity due to environmental factors such as room temperature
and humidity.
Potential inconsistencies in measuring ingredient quantities.
Sources of Error:
Inaccurate measurement of water temperature.
Incomplete mixing or kneading of dough.
Uneven baking due to oven temperature fluctuations.
Assumptions:
Yeast used is fresh and active.
The thermometer is accurate and calibrated.
The oven maintains a consistent temperature throughout baking.
Precautions:
Ensure water temperature is precisely controlled to prevent yeast deactivation or
killing.
Avoid over-kneading, which can lead to tough bread.
Monitor the dough closely during proofing to prevent over-proofing.
Reflection:
This experiment highlights the importance of proper yeast activation in bread-
making, demonstrating how water temperature can significantly affect the quality of
the final product. It emphasizes the role of temperature in biological processes such
as fermentation and can be applied to other baking or culinary tasks where yeast is
used. Understanding these concepts helps improve baking skills and ensures
consistently good results.
