Data Analysis Of Our Pizza

DATA ANALYSIS

Our experiment consisted pointing the differences of two types of yeast in a pizza: the dry and the fresh yeast. Letting the dough grow in a closed environment proved our hypothesis of anaerobic respiration, and also we could notice that the warm water and the sugar played an important part on the experiment.

Yeast is activated by warm water. If we use cold water, the dough will never grow and we would never see the difference between the fresh and the dry yeast. Sugar is going to be also the fuel of the yeast (in order for fermentation to take place, the yeast needed glucose), because the hot water may activate it, but the sugar is the one that is going to regulate how much the dough grow and how long is the yeast going to be active.

Respiration is important because it releases energy from glucose. It occurs in the mitochondria. Respiration is not necessarily of oxygen use, not in every case. When there is use of oxygen, we call it aerobic; and when there is no use of oxygen is called anaerobic which can lead to fermentation (bacteria) or lactic acid (eukaryotic).  Without respiration we wouldn't have any energy to perform necessary day to day functions. On the pizza dough when the dough grows, is the yeast doing anaerobic respiration.

If you leave the dough with the yeast in a closed environment (in this case we covered it with vinipel), it would make an anaerobic respiration which would lead to fermentation. The yeast would do oxygen-less respiration.

People take advantage of yeast in many different ways. Two of the most important or relevant uses are in the production of alcoholic beverages and baked products. Both of these take advantage of the products released by the yeast during fermentation. The ethanol released (C2H5OH) is what makes an alcoholic drink, well, alcoholic. And the carbon dioxide (CO2) is the gas that makes bread “bloom”. So yeah, yeast is a pretty good chef.

Some species of yeast are opportunistic pathogens that can cause infection in people with compromised immune systems. Cryptococcus neoformans and Cryptococcus gattii are significant pathogens of immunocompromised people. Yeasts of the Candida genus, another group of opportunistic pathogens, cause oral and vaginal infections in humans, known as candidiasis. Nonetheless, not all microorganisms cause us harm. As we have seen before, certain bacteria such as Lactobacillus Bulgaricus and Streptococcus Thermophilus are essential in the process of making yogurt. If we take advantage of our knowledge of microorganism and the life process that take place within them, we use these small organisms for our own purposes. Instead of considering yeast a nasty bacteria that could cause an infection, we should considerate as a small friend that will help us bake all types of bread, if the conditions are right.

In our experience, we could see that the dry yeast was softer than the fresh yeast. The dry yeast grew more and at the moment of tasting it, it was better than the fresh yeast. At the beginning even with the color and the texture of both pieces of dough, we could see a remarkable difference. The dry yeast was less hard and we were able to make the pizza shape easier, at the moment of cooking, it grew a lot more than the fresh yeast pizza. The fresh yeast was harder to shape and it grew less than the dry yeast.

The dry yeast is in a ‘sleepy´ mode before cooking; the fresh yeast is ´activated´ but its reaction lasts less than the dry yeast. If the dry yeast has a longer duration, the dough is going to grow more that the fresh yeast. Or also we could see more factors: like the amount of water and sugar, if it was enough or unequal.

From this experiment we proved how an anaerobic respiration works and how the biochemistry affects more that we can imagine in the kitchen. All processes have an explanation so we had to infer why the yeast on a pizza grows and how the types of yeast can make be different when cooking a pizza. Now we can really understand the fermentation processes, the goal was accomplished. 

SOURCES:

http://www.gourmettraveller.com.au/recipes/how-to/2008/2/can-i-swap-dried-yeast-for-fresh/
Amy Oliver, Can I swap dried yeast for fresh? (cited, march 2014)
http://www.genetics.org/site/misc/yeastbook.xhtml
Alan G. Hinnebusch, National Institutes of Health, Nov 2011, Yeastbook. (cited, march 2014)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785618/
World J Gastroenterol. Sep 28, 2013 (cited, march 2014)
http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=176765
Kurtzman Fell, Cletus Jack, Yeast Systematics and Phylogeny - Implications of Molecular Identification Methods for Studies in Ecology, Publication #176765, 2014 (cited, march 2014)

By: Valeria Arias, Laura Ibañez, Carolina Lopez, Juan Felipe Vasquez.

Pizza Lab

What did we do?

At school, our assignment was to cook 2 pizzas. Pretty simple, right? Well, it's important to mention that the dough of these pizzas were very different. One of them had fresh yeast, while the other one contained dry or instant yeast. In this demonstration we observed (and tasted) the differences in the pizzas. We then analyzed our data to reach conclusions about how and why choosing different yeast affected the final outcome, taking into account our knowledge of fermentation processes. 

Here is a video of Valeria while we were preparing the dough:

After this, the yeast was added. One thing we noticed instantly was that the fresh yeast "bloomed" a lot quicker than the dry yeast. Why? It all comes down to the fermentation process that the yeast is performing.

Before being added to the pizza dough, the yeast was mixed with warm water and sugar and put in a glass jar covered with plastic.

The warm water was needed to "activate" the yeast, the sugar was added to give them energy, and the jar was covered to keep oxygen out of it. It sounds pretty cruel to "choke" the yeast by neglecting them oxygen, but it was necessary in order for them to initiate the fermentation process.

When yeast lack oxygen, they obtain energy by breaking down glucose into pyruvic acid and releasing ethanol and carbon dioxide. This CO2 being released is what makes the yeast "bloom", that is why it's used in many baked goods.After mixing the dough and yeast, we cooked the pizzas and we found some differences between them.The one made with dry yeast tasted better and was softer, while the fresh yeast had a bit of a harder crust.

PIZZA!

By: Valeria Arias, Laura Ibañez, Carolina Lopez, Juan Felipe Vasquez.

Alcoholic Fermentation

ALCOHOLIC FERMENTATION

Alcoholic Fermentation is a type of cellular respiration which does not involve oxygen (anaerobic respiration) and involves the breaking down of glucose to pyruvic acid and then finally ethanol.

Alcoholic fermentation is done by certain types of bacteria, including yeast. These microorganisms turn glucose into ethyl alcohol and carbon dioxide.This process begins after glucose enters the cell. The glucose is broken down into pyruvic acid. Afterwards, the pyruvic acid is converted into CO2, ethanol, and energy for the cell. We, humans have taken advantage of this process in the making of bread, beer and other alcoholic drinks. In the making of those products, the microorganism Saccharomyces Cerevisae [1] is used, also known as common yeast.

Yeast is used in the making of bread because of its bubble making powers (because of the CO2 being released), which makes the bread expand, which is kind of awesome. This process doesn't take too long, that's why not a lot of alcohol is released during the fermentation. That explains why you won't get charged with a DUI after eating bread! 

Bibliography:
[1] http://www.icr.org/article/glycolysis-alcoholic-fermentation/
Morton, J. S. 1980. Glycolysis and Alcoholic Fermentation. Acts & Facts. 9 (12). (cited, march 2014)
By: Valeria Arias, Laura Ibañez, Carolina Lopez, Juan Felipe Vasquez.

Fermentación Lactica

En nuestro proyecto de laboratorio, fue posible llegar a nuestro producto final, gracias a los procesos de fermentación láctica realizados por las bacterias presentes en el yogur, Lactobacilos búlgaros y Streptococcus thermophilus. 

¿Pero que es la fermentación?

• Recuerda: 

1. Anaerobico = No hay oxigeno
2. Aerobico = Si hay oxigeno

La fermentación láctica es un proceso celular anaeróbico donde se utiliza glucosa para obtener energía y donde el producto de desecho es el ácido láctico.

No solo las bacterias desarrollan este proceso de fermentación, tu también lo realizas. ¡Así es, tu también ejecutas este proceso! Cuando tus células necesitan energía, pero no están recibiendo suficiente oxigeno, recurren a la fermentación para la obtención de la energía necesaria. Sin embargo, el acido lactico puede generar fatiga muscular despues de un tiempo.

Es por esta razón, que cuando haces mucho ejercicio, sientes dolor o ardor en tus músculos, por el acido lactico siendo eliminado por tus celulas. 

El proceso de la fermentación:
Las celulas necesitan la molécula de NAD+, y en situaciones de falta de oxigeno, la fermentacion responde para que la celula pueda producir NAD+. Durante el proceso de glucololisis, la molecula NAD+ es consumida mientras oxida la glucosa, convirtiendola en un compuesto de 3 atomos de carbono, llamado el acido piruvico. Como resultado se obtienen 2 moleculas de ATP, y las moleculas de NAD+ se ve reducidas a NADH. Para que las reacciones productoras de energia puedan tomar lugar es necesario reoxidar el NADH. Esto ocurre cuando el NADH cede dos electrones al acido piruvico y este se reduce a acido lactico. [1]

piruvato + NADH + H+-------> ácido láctico + NAD+ 

¿Como esto me ayuda a hacer yogur?

Cuando ciertas bacterias (Lactobacillus, Streptococcus), son expuestas a la leche, su operon lac (encontrado en el codigo genetico de la bacteria) es activado y produccion de  β-galactosidasa  puede tomar lugar. [2] Esta molecula descompone la lactosa y obtiene energia por medio de fermentacion. Un producto de la fermetentacion, como ya hemos mencionado, es el acido lactico. Este acido lactico resulta a un descenso en el pH de la leche, causando una precipitacion en las proteinas de la leche. Esto es lo que causa la coagulacion de la leche, dandonos yougur con sabor acido. 

Es por esto, que al destapar nuestra jarra, la sustancia que obtuvimos era espesa y tenia un sabor insípido y ácido, para disfrutar del yogur era esencial agregarle fruta y dulce.

¿Que factores afectan la fermentación?

La temperatura  y la exclusión del aire son los

principales factores que influencian el curso de la fermentación.

Temperatura

La temperatura juega un rol muy importante en este proceso, ya que las bacterias necesitan cierto ambiente y estar en las mejores condiciones para realizar el proceso de fermentación. La temperatura ideal para que la bacteria lactobacilos se desarrolle y realice la fermentación es de 30 grados centigrados. Sin embargo, hay un problema con esta temperatura, ya que el proceso de fermentación ocurre muy rápido y causa que el producto final tenga mal aroma. Es preferido mantener la temperatura entre 10 a 20 grados centigrados, para asegurar que el proceso de fermentación ocurra a un ritmo en donde la calidad no se pierda.

Por esta razón, debíamos cubrir nuestra jarra lo mejor posible, para que no perdiera calor, y las bacterias pudieran realizar la fermentación en optimas condiciones.

Exclusión de Aire

Las bacterias lácticas pueden sobrevivir en un ambiente que este en presencia o en ausencia de oxigeno, sin embargo, la fermentación, al ser un proceso anaerobio, no ocurre si se encuentra oxigeno. Si las bacterias tienen contacto con el aire, o con oxigeno, recurrirán a la respiración celular para la obtención de energía. Para llegar a nuestro resultado final (yogur) necesitábamos el ácido láctico, producto de la fermentación. Era necesario garantizar que las bacterias iban a realizar fermentación y no respiración celular, asegurarnos de que no iban a a tener contacto con oxigeno. 

Otra razón por la cual debemos sellar nuestro recipiente. Si el aire entra, pude afectar el proceso de fermentación. 

Bibliografia:
[1] Centro escolar LA ANUNCIATA IKASTETXEA: Investigacion Biotecnologate (cited 05/11/13)
http://www.laanunciataikerketa.com/trabajos/yogur/fermentacion.pdf

[2] JOHNNY CLORE: Lac Operon http://www.youtube.com/watch?v=2sMFswbOgKk (cited 05/11/13)

By: Valeria Arias, Laura Ibañez, Carolina Lopez, Juan Felipe Vasquez.

Our Report

This is our lab report where we summarized our process, results, analysis and conclusions, we also answered some questions to help us understand further this phenomenon. 

Results Obtained

RESULTS	IMAGE	EXPLANATION
Purified Milk		We obtained 1 liter of purified milk after boiling it.
Dense Liquid		Yogurt was added to the milk and the mixture was then covered; about 8 hours later we obtained a thick layer on top of the dense substance we could now call yogurt. It was a white substance with no strong smell.
Sweet and Tasty Yogurt		Because the yogurt had no flavor at all, sugar and strawberries were added to obtain a very sweet and tasty yogurt with soft texture.

Results: After obtaining a mixture of milk and yogurt, we then obtain a thick odorless and colorless substance, yogurt.  If we drank this sugar-less yogurt, it would be like drinking light yogurt. Sugar and fruits were added to give it a sweet and pleasant flavor.

Data Analysis

In our experiment we observed how the process of fermentation of lactose by different bacteria, known as “yogurt cultures”, produces lactic acid, which acts on the milk to give the yogurt its famous feel and texture. ^[1]

The first thing we did was to boil our milk. This was done to kill any undesirable bacteria that may affect the final product. We waited for a while for the milk to cool down, but while it was still warm, we poured our yogurt in. But, why didn’t we boil the yogurt as well? The yogurt has the bacteria we need for our process of fermentation. These include Lactobacillus Bulgaricus and Streptococcus Thermophilus. ^[2]

We then covered our jars of milk and yogurt with newspaper and tons of vinipel paper. The reason for this is the fact that the bacteria needed for the production of lactic acid reproduce and work better and higher temperatures ^[3], so we needed to make sure our containers would lose the minimum amount of heat.

After about 8 hours we uncover our containers. What we found was a thick, colorless, odorless substance. It had a dull and unpleasant taste. This was due to the lactic acid. We mixed large quantities of sugar and strawberries so our yogurt would taste better.

At the end, our result was a thick sweet yogurt; it had a very pleasant taste.

• What is happening on the microscopic level of our experiment?

The Lac Operon, found in prokaryotes, is responsible for the production of lactose in organisms. It is by default in the “off” position and is only turned on in the presence of lactose. When our bacteria were exposed to the lactose in the milk, their lac operon turned “on” and production of B-Galactosidase, Permease and Transacetylase began. These 3 compounds are responsible for the breaking down of lactose for the obtainment of energy. By breaking down the lactose and obtaining energy by fermentation, our bacteria release lactic acid, thus giving us yogurt. ^[4]

[1] CULTURES FOR HEALTH: What is Yogurt? http://www.culturesforhealth.com/what-is-yogurt-history (cited 05/11/13)

[2] NCBI: Molecular Analysis of Yogurt http://www.ncbi.nlm.nih.gov/pubmed/18175741 (cited 05/11/13)

[3] UK GOVERNMENT: What Bacteria Need To Grow http://archive.food.gov.uk/hea/1114/plainenglish/part2.html (cited 05/11/13)

[4] JOHNNY CLORE: Lac Operon http://www.youtube.com/watch?v=2sMFswbOgKk (cited 05/11/13)

CONCLUSIONS

•         Bacteria in the milk could have affected the final product, so that is why the milk had to be boiled.
•        The yogurt must NOT be boiled because it has some bacteria that were needed in the fermentation process, without these bacteria our final product would not have been yogurt.
•        We needed to cover our jar to prevent it from losing heat since we needed it to be warm for the bacteria to work at optimal conditions in the fermentation process.
•        In this experiment we learned that while working on these types of experiments we have to be careful, since any change, as insignificant as it may seem to us can affect the final product from a microscopic level.
•       We can take advantage of the Lac Operon found in bacteria for our own needs, as we can take advantage of many other chemical properties.
•        Sugar and other sweeteners are needed for the yogurt to have a pleasant taste, since the lactic acid gives us a tasteless substance.

QUESTIONS

1. What is pasteurization?

Pasteurization is a process that consists of heating food, for a determinate time and heat and immediately cooling it, this is usually for killing bacteria from liquids like milk. It is the most important step to prepare drinkable milk.

2. Compare your “home-made” yogurt to the “store-bought” variety. What effect do some of the other ingredients have on the “store-bought” yogurt?

Yogurts that are bought have more ingredients like probiotics to help your digestion, they may also contain preservatives that make this yogurt last longer. A homemade yogurt has nothing like this. It is simpler and has fewer chemicals.

3.  What are the 2 most common bacteria used in yogurt making? Which one did you use?

The kinds of bacteria that are in yogurt are Lactobacillus bulgaricus and streptococcus thermophilus. These bacteria are needed for the fermentation of milk to produce the product yogurt. Without these bacteria the milk and all lactose products would be impossible to make and wouldn’t exist. We used Lactobacillus Bulgaricus and Streptococcus Thermophilus..

E. FARNWORTH: Yogurt - A Milk Product with More http://www.medicinalfoodnews.com/vol02/issue5/yogurt (cited 05/11/13)


By: Valeria Arias, Laura Ibañez, Carolina Lopez, Juan Felipe Vasquez.

Now, Vale explains what we did in Spanish: