Natalie+Kerr+and+Courtney+Stolba

Accuracy in Expiration Dates on Bread Yeast **BACKGROUND** Imagine having nothing to eat but the ingredients for bread. But wait! Tragedy! The yeast has expired! I know, I know, this got a rise out of us too. __//Will you still be able to make your bread?//__ You don't know, and this is a loaf or death situation! Luckily, this experiment will tell you if you knead to have fresh yeast on hand to bake your bread. When you buy something, you always look at the expiration date to see if it is still good. Usually, if the expiration date has past, then you don't use it under the assumption that it is bad or wont work as well. Since yeast is a dormant, or time delayed, bacteria, they are designed to react after a certain amount of time. (Bread-Making) We wanted to test how true this was. We are doing this experiment to find out if expired yeast will work just as well as new yeast. We decided that we didn't have enough knowledge and would have to perform an experiment. This would save money when baking bread and be informative to bakers everywhere. This information is kneaded by any home baker. To test this, we plan on baking three loaves of bread. One with yeast that has already expired, one with yeast in its expiration month and one with yeast that is brand new. Yeast grows under favorable conditions, (warmth) and eats sugar. This is why to activate the yeast you mix it in a cup 105-115 degree Fahrenheit water, (Bread Making) with 1 tablespoon of sugar, (Phosphates And Yeast In Baking) and let it sit for 6 minutes (Yeast). Our Hypothesis is that the brand new yeast will work better. We agree with the food companies, and think that the new yeast will have more foam, rise higher, bake quicker and taste better!
 * BREAD RECIPE** [|__http://www.food.com/recipe/simple-white-bread-5477__]

**HYPOTHESIS** If we bake three different loafs of bread, one with yeast that has already expired, one with yeast in its expiration month and one with yeast that is brand new, then the yeast that is brand new will have more foam, rise higher, and bake quicker as well as taste better! IV: expiration date of yeast DV: 1st and 2nd rising height, amount of foam yeast produces, time it takes for the bread to cook, quality (based off of testers results) Constants: bread recipe, water temperature, amount of yeast, other ingredients, time before measuring the foam, all dry and active yeast
 * VARIABLES**

**SUPPLIES**

Bread Pans

Measuring cups - Dry

Measuring cups - Liquid

Measuring spoons

Thermometer

Bowls - one graduated cylinder - one Oven

Scale 1 1/4 cups water, at 109 degrees, F

1 (1/4 ounce) packages yeast

1 tablespoons sugar

1 teaspoons salt

1 tablespoons vegetable oil

3 1/4 cups flour Crisco

**Experimental values: //(what to do during the ISP)//**

Measure height of foam after 6 min,

measure height of dough before rising

Measure height of dough after 1st rising

Measure height of dough after 2nd rising

**PROCEDURE**

1. Mix the water, yeast, and sugar together in a small bowl. Record the temperature of the water and the diameter of the cylinder that you use. After 6 minutes, measure and record the height of the foam and record the circumference of the container.

2. Add the salt to 2 3/4 cups of the flour in a large bowl.

3. Set the other half cup of flour aside. Mix the liquid and the dry together and then add the oil.

4. Mix until it comes away from the sides of the bowl, sprinkle some of the last cup of flour on a wooden surface, and knead until the dough gets sticky again.

5. Keep adding more flour and keep kneading.

6. Push forward, fold over, push forward, fold over.

7. Put a little oil in the bread pan and add the kneaded dough. Cover,let stand for about 1 hour in a warm place. Measure and record the height of the dough. Punch down and roll it out, Roll it up, tuck in the ends and place back in the pan.

8. let it rise again for 45 minutes.

9. Measure and record the height of the dough again. Use a sharp knife to put a few slashes in the top, brush with a little beaten egg or milk, and put into a pre-heated 375 (f) oven for 30 minutes.

10. Take temperature readings starting at 25 minutes, and every 2 minutes after that. The bread is done when an instant read thermometer reads 190 (f). Record how long it takes to reach the 190 degrees. We will Use the above process on each loaf of bread, starting with the expired yeast from April, 2012. We measured the sides of the bread pan and found it to be 21 x 11.5 cm (length x width). These measurements remained the same as nothing impacted the size of the glass pan. Then we put the dough into the pan and pressed it flat. We measured the height of this dough (4.5 cm) and multiplied this by the length and width of the pan. This gave us the volume of the dough, ( V= length X width X height). As you can see in the graph below, this gave us a volume of 1086.75 cm for the original dough volume. We then took the dough out, punched it down and put it back in the pan. We covered it and left it on the counter for an hour. After that hour, we measured the height (10.5 cm) and repeated the process to find the volume of 2535.75 cm. Following this intense mathematical equation we proceeded to knead the dough. Placing it back in the pan we waited for 45 minutes before measuring the height again. We found it to have risen to the same 10.5 cm. Crust be praised, this meant that the volume was the same and we didn't knead to repeat the mathematical equation! We then had to find the volume of the foam from the yeast. Since it had grown inside a cylinder, we were able to use the equation (using 3.14 for pi) V=3.14(r)squared(h). The radius was 50 mm and the foam was 5 mm tall. This gave us a volume of 785 mm which we converted to 78.5 cm. Once the bread was done and the baking time had been recorded, we measured the height ( 13.5 cm) and used the same process as before to find the volume of 3260.25 cm. We repeated the procedure with the yeast that expired in Dec. 2013. We found our results using the same methods as before, however, this time the foam had a height of .8 cm. The dough, 3 cm initially, 8.3 cm after the first rising, 9 cm after the second rising, and 10.5 cm after baking for 29 minutes. All findings can be found in the chart. Following these steps, we again repeated the experiment with the the newest yeast, which will expire in Aug. 2015. We used the same methods as we had used for the past two breads. This time, the foam had a hight of .6 cm. The dough had a hight of 3 cm initially, 8 cm after the first rising, 8.5 after the second rising, and 10 cm after baking. All breads were baked in December, 2013. ((Read more: http://www.food.com/recipe/simple-white-bread-5477?oc=linkback))

**ANALYSIS:** We looked at our datea and it followed our hypothesis in the taste department. The new yeast tasted the best. However, the oldest yeast provided the most bread, even if it had the worst taste. As you can see in our graph, Bread 3, with the newest yeast, is the average best. It has no extremes between foam and bread volume and has the best taste. The farther in the future the expiration dat is, the fewer extremes you will have. We also found that although Bread 2 and 3 had different amounts of foam, they had the same initial dough volume and the rising dough volume were directly proportional. Our water temperature was consistantly 109 degrees F for all breads. Each bread also took two more minutes than the previous bread to reach 190 degrees F. The expired yeast also had the same dough volume after the first and second rising, showing it wasn't working as well. The other two yeasts conisstantly rose after each time period, showing that they worked better. The mass of the first bread's dough (the expired yeast) was orriginally greater, which makes sense for the greater ending volume. THis means there was some mechanical error along the way, since they should have all had the same volume. 1/3 of our bread was rated 5 out or 5 stars. **CONCLUSION:** Over the course of our experiment, we have concluded that our hypothesis is correct. when we baked 3 different loafs of bread with expired yeast, yeast in its expiration date, and yeast that is brand new, we discovered that the bread with the new yeast did work the best out of the three. This bread was not only best in the area of taste, but also in the fact that it had the best balance between the volume of the yeast's foam and volume of the baked bread. The farther away your yeast was from expiring, the less extreme these ratios of yeast to bread value became. However, throughout our experiments there were also many areas that could stand to be improved. One thing we could change when repeating this experiment would be to bake all of the breads on the same day, rather than different days. This would eliminate humidity, room temperature and other variables outside of our control. Also, we do not have any information on how the yeast is handled in the factory before being shipped to the stores. Any slight change in factory conditions could change up the results as well. To further develop our research we could make multiple types of each bread catagory (old, present and new yeast) so we had more data to compare. WE also could have tested different brands of yeast, or the sam brand with a different activity rating. As you can see from our information gathered,there is no need to fear if you must bake bread with expired yeast. However, for the best bread, we recommend using the newest yeast you can find. **RESEARCH:**
 * || Red Star (expired April 2012) || Red Star (expired December 2013) || Brand New Red Star Yeast (expires August 2015) ||
 * Original Dough Volume || 1086.75 cm, cubed || 724.5 cm, cubed || 724.5 cm, cubed ||
 * First Rising Volume || 2535.75 cm || 2052.75 cm, cubed || 1932 cm, cubed ||
 * Second Rising Volume || 2535.75 cm || 2173.5 cm, cubed || 2052.75 cm, cubed ||
 * Water Temperature || 109 degrees F. || 109 degrees F. || 109 degrees F. ||
 * Volume of Foam after 6 Minutes || 78.5 cm || 62.8 cm, squared || 47.2 cm, cubed ||
 * Time for bread to reach 190 (F) || 27 min || 29 min || 31 min ||
 * Baked loaf volume || 3260.25 cm || 2173.5 cm, cubed || 2415 cm, cubed ||
 * Quality || 3 || 4 || 5 ||


 * Yeast is a living, single-celled type of fungus that feeds on sugar and grows only under favorable conditions.
 * A process known as fermentation is used in the preparation of bread. During fermentation, yeast breaks down sugar (that is added to flour) into carbon dioxide and alcohol. Carbon dioxide, the gas that soda bubbly, makes the dough fluffy, while alcohol flavors the bread.
 * Yeast: A microorganism of the fungus family that promotes alcoholic fermentation, and is also used as a leavening (an agent that makes dough rise) in baking.

1) Reaction Rate: There are basically three types of reaction rate: fast, time-delayed and heat-triggered. Fast leavening agents provide nucleation during mixing and help establish the grain of the final product. In high-temperature baking, these agents can be very important in providing rapid early expansion. Time-delayed leavening acids provide bench or floor time. They are designed to react after a certain period of time. This is particularly important in operations where there are large batches or where a dough or batter will be processed over an extended period of time. Heat-triggered leavening agents undergo the majority of their reaction after an activation temperature has been reached. In general, activation temperatures are greater than 100lE "This delay based on temperature activation provides the ultimate in bench tolerance or floor time," (states Heidolph).

2) Yeasts secrete enzymes that break down carbohydrates (through fermentation) to yield carbon dioxide and alcohol. The source of carbohydrates are either living hosts or non-living hosts such as rotting vegetation, or the moist body cavities of animals. Yeasts are considered by some scientists to be closely related to the algae, lacking only in photosynthetic capability— perhaps as a result of an evolutionary trend toward a lifestyle dependent upon host nutrition. they thrive in warm and moist places high in oxygen and low in carbon dioxide

3) Bakers yeast (Saccharomyces cerevisiae), when added to baker’s dough, produces carbon dioxide pockets that make bread rise. Let the yeast mixture sit for 5 or 6 minutes, 2 to 3 for it to become thoroughly dissolved and 2 or 3 more for it to begin to grow and show signs of life

1) "Bread-Making." Biotechnology: Changing Life Through Science. Vol. 2: Agriculture. Detroit: U*X*L, 2007. 354-358. Gale Virtual Reference Library. Web. 6 Dec. 2013.
 * BIBLIOGRAPHY:**

2) "Phosphates And Yeasts In Baking." Prepared Foods 176.8 (2007): 47-54. OmniFile Full Text Select (H.W. Wilson). Web. 6 Dec. 2013.

3) "Yeast." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Vol. 6. Detroit: Gale, 2008. 4737-4738. Gale Virtual Reference Library. Web. 6 Dec. 2013.


 * COMMENTS & PEER REVIEWS: **
 * Key: **✓ = Corrected according to peer review

✓ I can't find a hypothesis for your ISP, what are you trying to test, exactly? -Lily Holmes ✓ Just a side note nothing huge, you might want to add a hypothesis and a background. But I like it so far.- Your favorite Noah Hahn It was so informative and then I reach this. Anyways you're doing a great job but I'd probably take that out above. - Jess Earl ✓ Rather than putting the URLs down you should probably do a bibliography to make it look better and give proper credit. - Jess Earl ✓ I think that having a hypothesis will help the reader understand what you are trying to find with the experiment -Monica Dentino ✓ Could you guys also add oven temperature or how long it bakes as a dependent variable? -Emily Kastl - Yes! ✓ How do you plan to measure quality of bread? Are you going to have taste testers? -Lily Holmes - a scale of 1-10 with tasters ✓ How many bowls? -Your favorite Noah Hahn

✓ I think to get more conclusive results, you should make multiple loafs of bread with the same type of yeast, measure what you need to measure on each loaf, then at the end average your results out. -Emily Kastl Great idea!! I love how important and informative it is!!!!! I also like how you try to have fun with it, science can be boring if you don't have fun- Abby Shute I also like how you are telling me the information from each site, right? I am assuming that is what the paragraph is.- Abby Shute

✓ I think the research will flow better if you make a bibliography without the URLs but the research is really helpful! -Monica Dentino ✓ I don't see your hypothesis. You might want to add one.-Liz Foster ✓ You should probably site the background information instead of just putting the URLs.-Liz Foster