Group+13



=__DIFFERENT ENVIRONMENTS AFFECTING YEAST GROWTH__ = =By: Group 13 (Victoria Kwee, Keisya Arya, Rachel Lucya, Martinus Linggo, Frederick Alvin, Vinsky Muthia) =

__**BIOLOGY**__

How does different content of dough with different sugar concentration affect the rising of the dough?
 * Research Question:**


 * Aim:** To investigate how the content of the dough with different sugar concentration affects its growth.


 * Hypothesis:** We think that the higher the sugar concentration is, the higher the dough will rise. This is due to the fact that yeasts feed of off sugar and hence we think that the more sugar is added into the dough, the more it will rise.

Content of the dough (sugar concentration): each beaker will have different content, one with yeast only (sugar: 0%), one with yeast and fruit juice (sugar: 43%) and another with yeast and teh botol (sugar: 21%). With different content hence different sugar concentrations, we will observe whether this will be a factor in affecting the rise of the dough. Height produced: the height of dough will be observed to show whether the content of dough is affecting its ability to rise or not. By observing the height, we can also determine its change of height from initial height and its CO2 production. Time: 15, 30, 45, 60 minutes. We will observe the dough rising in this set period of time. This is to observe the change in height over a set period of time. Amount of flour: 5gr of flour will be put into each of the beaker. The amount of it will be controlled to ensure fairness of results. Amount and temperature of hot water: 2 spoons of hot water (78 ˚C) will be put into each beaker. The temperature is controlled as it is the ideal temperature for dough in order for the yeast to grow. Amount of yeast: 1gr of yeast. Amount of fruit juice and teh botol: 2 spoons each. Flour Packaged Yeast Water Heater Fruit Juice Teh Botol 3 Beakers 3 Plastic spoons Mass Balance Stopwatch Ruler Cloth
 * Variables:**
 * Independent:**
 * Dependent:**
 * Controlled:**
 * Apparatus:**

All the apparatus are collected. Prepare 3 beakers and label them each A, B and C. Prepare the hot water by placing 250ml of tap water and heating it using heater (150 ˚C) for 4 minutes. In beaker A, add 5gr of flour, 1gr of packaged yeast and 2 spoons of hot water into it. In beaker B, add 5gr of flour, 1gr of packaged yeast, 2 spoons of fruit juice and 1 spoon of hot water into it. In beaker C, add 5gr of flour, 1gr of packaged yeast, 3 spoons of teh botol and 1 spoon of hot water into it. Mix each beaker with a separate spoon until all the flour is moistened. Be sure to check the bottom of the cup to make sure no dry flour remains. Continue to mix the dough for 2 to 3 minutes. Stop mixing when you see the mixture forming gluten “threads” as you pull it apart. Use the spoons to gently push the dough down to a relatively flat surface in each beaker. Mark the level of the dough on the side of the cups. Use a ruler to measure the approximate height in cm of the dough from the bottom of each of the beaker. Soak 3 cloths into the hot water and put them above each beaker. Observe what happens in 15 minutes. Record the height the dough has achieved from the initial height using the ruler. Do the same thing for the next 30, 45 and 60 minute. Repeat these steps for the 2nd, 3rd and 4th trial.
 * Method:**

Flour+ Yeast +Hot WaterFlour+ Yeast+ Hot Water+ Fruit Juice (Buavita)Flour+ Yeast+ Hot Water+ Teh Botol 0111111111111 15222242.51.52.52212 302.52.5224.53.5233322.5 453332.553.6343.232.53 6033335.3444.53.53.533
 * TIME**
 * (min)CONTENT**
 * HEIGHT (cm) (±0.05cm)**
 * TrialTrialTrial**
 * IIIIIIIVIIIIIIIVIIIIIIIV**
 * Raw Data**

__Calculation method:__ Data is gathered by finding the average values from the 4 trials done. The formula is: Average = (Trial 1+Trial 2+Trial 3+Trial 4)/4
 * Processed Data**


 * Time (min)Average Height (cm) (±0.05cm)**
 * Flour + Yeast + Hot WaterFlour + Yeast + Hot Water + BuavitaFlour + Yeast + Hot Water + TehBotol**
 * 0111**
 * 152**2.631.75
 * 30**2.253.252.63
 * 45**2.883.882.93
 * 60**34.453.25


 * Graph**

In conclusion, based on our experiment, we can conclude that the higher the sugar concentration is, the higher the height of growth the dough will have. This is because yeast feeds on sugar thus, sugar speeds up the growth of yeast. When Teh Botol (sugar: 21%) was added, the dough rose from 1 cm to 3.25 cm in 60 minutes, but when fruit juice Buavita (sugar: 43%) was added to the content, the dough rose from 1 cm to 4.45 cm, and when nothing was added, the dough rose up to 3 cm only. It is then clearly evident that the higher the sugar concentration in the content of the dough, the higher the dough will rise. Buavita, which has a higher sugar concentration compared to Teh Botol, caused the dough to rise the highest. While the dough that had no sugar concentration at all, rose up to the lowest height. Not only sugar, the temperature of the water also affects the growth of yeast. In our experiment, we covered the dough with tablecloths soaked in hot water (78 ˚C). This temperature of moist dough is an ideal environment for yeast growth (http://www.streetdirectory.com/food_editorials/pastry/baking_tips/how_yeast_works.html) Yeast is dominant; it will grow quickly in a moist environment and will not grow at temperatures less than 78 ˚C. Furthermore, yeast converts starch in the flour to sugar for food. Without this ability, yeast would not grow. By observing the results gained, we were able to prove our hypothesis and it is evident that our hypothesis is correct.
 * Conclusion**


 * Evaluation**

The strength of our experiment was that we were able to gain sufficient data result. We ensured that our data was sufficient as we did 4 trials so that we were able to calculate its average height growth. We also followed the methods well. For each trial that we did, we followed the methods step by step and we also observed the height every 15 minutes. This helped us be efficient in time and in producing reliable data. The weaknesses of our experiment include how we didn't really measure the temperatures of the hot water thus affecting the results. Our measurements were also not fully accurate as we didn't always measure the weight of the flour inserted into the cup. We did not necessarily calculate it to exactly 5 gram but rather just put 5 spoons of flour to each beaker, and so that might actually have a negative result to our experiment, making it less reliable. That may have contributed to the results of our experiment. One of the improvements we could make in the future is ensuring the accuracy of our measurements by constantly checking the weight of the materials about to be inserted using mass balance rather than approximating it ourselves, which is a form of human error. Another improvement we could make is maintaining the temperature to keep it as a controlled variable. In conducting this experiment, we were very messy and our station was very cluttered. In the future, we hope to be more hygienic and to keep our table clean. The fourth improvement we could make is to be more prepared and organized. We had a slight trouble beforehand which was the materials that we had booked were not there when they should have been. This caused a delay in our experiment. From this incident, we've learned that we always need to double check everything. Lastly, an improvement we could make is to do a further research before conducting an experiment, so that we would get a basic understanding of the concept of our experiment. Overall we feel that our results are reliable enough to make a solid conclusion as there are no anomalous results.

__**CHEMISTRY**__


 * Aim:** To find out the effects of different environments (different pH level; acid, neutral and base) affecting yeast growth.


 * Topic question**: How does the pH (acidic, neutral, basic) of the solution affect yeast growth


 * Hypothesis**: We think that the neutral pH solution will allow the yeast to grow the most in a limited time span (20 minutes), and where the acidic and basic solutions would not grow that much. If the pH of the solution were too basic or acidic, it would make the enzyme denature and not work at all.


 * Variables:**
 * Independent Variable**:


 * Solutions:** Lemon juice, distilled water, NaOH (acid (2), neutral (7-8), basic (13))


 * Dependent Variable**:


 * The effect of yeast growth in different pH solutions:** To observe whether there is effect on the yeast, we measure the initial height compare to its final height after we control the time taken (20 mins).


 * Controlled Variables:**


 * Temperature:** We used an electrical heater and we can control the temperature to stay at 40 degree Celsius.


 * Volume of sugar:** Here, we used 1/2 teaspoon of sugar to allow the yeast to grow.


 * Volume of yeast:** Similarly, we used 1 teaspoon of yeast to control the volume.


 * Initial volume of solutions:** We made sure that the initial volume of the solutions are all the same. The height of the solution in the test tubes are 5cm at first all times.


 * Aluminum foil:** We use this to cover the test tubes so that the CO2 will not go out, therefore it minimize the chance of heat lost to the surroundings.


 * Time:** the time for the yeast to grow is only 20 minutes. The stopwatch helped us to control this.


 * pH:** we controlled the pH of the solutions using pH papers and by adding water, HCl (Hydrochloric acid), and NaOH (Sodium Hydroxide).


 * Materials:**

6 Test tubes NaOH solution (2 mol/dm3) Lemon juice pH papers Thermometer Stir Aluminum foil Stop watch Yeast Sugar Beaker 250ml Ruler


 * Method:**

First measure and put the different solutions in each test tube. For the lemon, squeeze for the juice. For the NaOH and the water, just measure the volume (5 cm initial height in test tube). Use the pH paper and make sure that the pH of the solutions are as the following (lemon juice 2, distilled water 7-8, NaOH 13). Put 1 teaspoon of yeast in each test tube. Put _ teaspoon of sugar in each test tube. Quickly put the aluminum foil to cover the test tubes. Fill the beaker around _ full and heat it to around 40 degree Celsius. Put all the test tubes in the beaker and start the timer. Wait for 20 minutes at try to control the temperature (40 degree Celsius) using the thermometer. After 20 minutes, measure the height of the solution. Observe any other effects if possible Repeat step 1-12 for 3 more times (total of 4 trials).


 * Raw Data:**

The end result of the yeast after encountered with different pH solutions.

516.5 cm8.5 cm5.5 cm 27.5 cm9.0 cm5.5 cm 37.0 cm8.5 cm5.5 cm 47.5 cm8.0 cm5.0 cm
 * Initial Height (cm)TrialsAcid (pH 2)Neutral (pH 7)Base (pH 13)**

We noticed that in neutral (pH 7) environment that the yest experiencing the rapid growth. The other environments (acid & base) also experienced growth in height of the yeast. However, the speed of both environments (acid & base) to grow the yeast was not as fast as in the neutral environments within 20 minutes.


 * Process data**

Finding the rate of the yeast growth given by its distance nd time

10.0750.1750.025 20.1250.2000.025 30.1000.1750.025 40.1250.1500
 * The rate of yeast growth given by its distance & time (cm/mins)**
 * TrialsAcid (pH 2)Neutral (pH 7)Base (pH 13)**
 * Rate of Yeast growth**0.1060.1753.75 x 10-3


 * Example:**

(0.075+0.125+0.100+0.125)/4 = 0.106


 * Rate: change in distance (cm)/change in time (mins)**


 * Example:**

(6.5-5)/20 = 0.075 cm/min


 * Presenting Process Data:**


 * Conclusion:**

After conducting the experiment, it indicates that our statement was right. As we mentioned in the hypothesis that the yeast will grow the most in neutral environment (pH 7). Whereas, in basic environment (pH 13) the yeast didn't grow much even in the 3rd trial the yeast didn't change or grow at all, it remained the same. In the hypothesis we also mentioned that the yeast in acidic environment (in this case was pH 2) won't grow at all, but in this experiment, the yeast did actually rise, although it wasn't as much as in neutral environment. After the experiment, we noticed that the optimum pH is around 5-8. Actually, yeast shouldn't have rise if the pH is too high (higher than 8) or too low (below pH4) but in our experiment, the yeast in the acid rise quite well. We conclude that the yeast grow best at neutral environment.


 * Evaluation:**

During our experiments, we have got some difficulties that we encountered. First difficulty that we encountered was to control the temperature, if we put the test tubes on the heater for a long time the temperature of 3 test tubes will increase to beyond 40_. Whereas, if the temperature is higher than 45_ the yeast will not rise, The optimum temperature of it was 40_, if the yeast is exposed to temperature beyond its optimum temperature the yeast will begin to fall which leads to no growth or very slow growth. When we did the experiment, we noticed that in the 4th trial the yeast in the basic solution (pH of 13), didn't change at all, the possibility of this eror is that when we was checking the pH of solutions (using pH strips) we accidentally mistaken read that it was pH 13 when it was not pH 12. Where some level of PH in the pH strips have similar colors to the other, therefore leading us to an error result. The other possibility was when we cover the test tubes with aluminum foil was not completely close therefore leading to the heat lost to the surroundings. To improve the experiment next time, we have to make sure that the test tubes are close properly so that there is no chance of heat losing to its surrounding and to be more accurate, we have to use water bath so that the temperature will be controlled.

__**PHYSICS**__

__**Aim:**__ to investigate the effect of different temperature to the rate of yeast growth

__**Hypothesis:**__ the higher the temperature of water the faster the rate of yeast growth because the higher the temperature means that there is higher kinetic energy in the molecules so collisions are more frequent. Therefore, rate of yeast growth is faster.

__**Variables:**__
 * Independent:** temperature of water (20.00±0.05_, 40.00±0.05_, 60.00±0.05_)
 * Dependent:** height of yeast in test tubes
 * Controlled:** set of equipment, content of yeast, initial height of test tube (7 cm)

__**Materials:**__ test tubes heater thermometer stopwatch yeast water sugar beaker mass balance

__**Procedure:**__ We weighed for 3 g of yeast in three different test tube We filled in 2 beakers with water and heat each to 40_ and 60_ We measured the water for 6 ml and pour it into another three test tube We put the yeast in the test tube with water **(control the content of yeast)** We put 2 teaspoon of sugar to each test tubes **(control initial height of test tube)** We put one test tube to the water with 40_ and another in 60_ and the other one in room temperature We start the stop watch We stopped it when 20 minutes has past We record the height of growth of yeast in the test tube We repeat steps 1-9 to get 4 trials

__**Data results:**__

Temperature (_ /± 0.5) Height after 20 minutes (cm / ± 0.05) Trial 1Trial 2Trial 3Trial 4 24 8.1 8 8 8.2
 * Raw Data**

409.19.299 607777

Temperature (_ /± 0.5)Height after 20 minutes (cm / ± 0.05) 24.08.10 40.09.10 60.0 7.00
 * Processed Data**

__Calculation method:__ Data is gathered by finding the average values from the 4 trials done. The formula is: Average = (Trial 1+Trial 2+Trial 3+Trial 4)/4

Temperature (_ / ± 0.5)Rate of yeast growth (cm/min) 24.00.055 40.00.105 60.00

__Calculation method:__ Data of the rate of yeast growth is calculated by subtracting the height after 20 minutes with the controlled initial height of 7 cm and then divide it with the time taken of 20 minutes. Formulaically, it can be written as: Rate of yeast growth = (height after 20 mintes-initial height)/20 For example when the temperature is 24_, then the rate of yeast growth can be calculated as: Rate of yeast growth = (8.1-7)/20 = 0.055 cm/min

__**Analysis:**__ The absolute error must be calculated to analyze systematic and random error. The calculation is as follows:

Uncertainty from thermometer: 0.5_ Uncertainty from ruler:0.5 cm or 0.005 m Uncertainty from mass balance: 0.01 g or 0.00001 kg Uncertainty from measuring cylinder: 0.1

Uncertainty from repetition is calculated with the standard deviation formula: Uncertainty=(max value - min value) ÷ 2

Uncertainty of 24_ temperature: 0.1 cm or 0.001 m Uncertainty of 40_ temperature: 0.1 cm or 0.001 m Uncertainty of 60_ temperature: 0

The absolute error from this experiment is 0.5 coming from the thermometer.

__Random error analysis__ Random error in this experiment mainly comes from human error. Firstly, when the sugar is poured from the teaspoon to the test tube, many did not get inside the test tubes. The measuring cylinder is also very small so it is very hard to put in exactly 6 ml to the cylinder. This contributes to random error because the volume may vary inconsistently.

__Systematic error analysis__ Systematic error comes from the temperature as the one being heated and is the beaker and not the test tube with yeast content. Parallax error when reading the thermometer and also when measuring the height of the test tube after 20 minutes may contribute to systematic error.

__**Graph:**__

As seen from the graph, the relationship between the temperature and rate of yeast growth is directly proportional until the maximum point where it has an inversely proportional relationship. The optimum temperature for yeast growth, from the graph, is seen to be around 40_. From room temperature to around 40_, the rate of yeast growth increases with temperature. After this temperature, yeast will still grow but at a slower rate. Until it reaches around 60_, yeast cells become stressed and its content damages. This explains why the graph after around 40_ has an inversely proportional relationship with the rate of yeast growth.

__**Conclusion:**__ In conclusion, the optimum temperature for yeast growth in which it has a fast rate of yeast growth is around 40_. Below this temperature, yeast will grow but at a slower rate. Above this temperature, the rate of growth of yeast will also slow down. Until to about 60_, yeast cells die. This is why from the experiment, we did not observe any growth in yeast. Our hypothesis was partly right. As the temperature increases, the rate of yeast growth will also increase but only to a certain temperature. Beyond this, the rate will slow back down due to thermal death point of about 60_. From a web source http://www.newton.dep.anl.gov/askasci/bio99/bio99693.htm we found out that the temperature with an optimal growth for yeast is 30_ or 37_ and death of yeast above 50_. This is similar to the results derived from our experiment.

__**Evaluation:**__ The strength of our experiment procedure is shown from the data reliability. This is due to the mass of yeast successfully controlled and the time taken of 20 minutes. However, we still need to improve many aspects. Firstly, we did not measure the amount of sugar accurately because we use teaspoon to measure. When pouring it to the test tubes, much of the sugar did not get into the test tube. To improve, we can measure the mass of sugar using mass balance and slowly pouring it to the test tube. Secondly, the 6 ml of water is not very accurate. The measuring cylinder was too small to get an accurate volume. To improve this, we can use the pipette to fill the measuring cylinder. Thirdly, we heat the water in the beaker instead of the water mixed with the yeast. This means that the heat given to the water in the beaker may not be the same amount given to the test tube. To improve, we can heat up the water mixed with the yeast. Fourth, we were not able to control the temperature to be constant throughout the 40_ and 60_ experiment. To improve, we can use a water bath to control the temperature.


 * Relation to environment:**
 * Economical:** Because we know the optimum temperature and pH, we can save time and money because we know what we need to do.
 * Ethical:** Putting too much sugar to the dough can speed up yeast growth; however, it can endanger people's health as people cannot have too much sugar in their blood system, especially people who have diabetes.
 * Moral:** Bakers may be tempted to include more sugar into the dough than they're supposed to in order for the yeast to grow faster so they can sell more products. The bakers' morality is questioned, whether the consumers' health or their business is more important to them.
 * Environmental:** The fermentation of the dough can be predicted as we know when to store it and until a period of time it can be kept.
 * Social:** Bread is a staple food to some countries. In relation to the moral issue, if the bakers think that their business is more important than the people's health, then the people may be consuming more sugar from the bread than they think they are.