lab activity ii - Liberty Union High School District

sweatertableBiotechnology

Dec 3, 2012 (4 years and 10 months ago)

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Name_______________________________________




Period __________


FOOD TECHNOLOGY LABS

Biotechnology is the application of principles of Biology for useful purposes. Currently,
Biotechnology includes the use of DNA for such diverse applications as forensic
s, organism classification,
and genetic engineering to change the genetic structure of an organism. Biotechnology also includes the
production of foods, cosmetics, pharmaceuticals, diagnostics, and purified macromolecules for use in
research and industry.
Any useful application of Biology is Biotechnology.

The basis of biotechnology is often fermentation biochemistry, as yeasts, molds, or bacteria must
be cultured in order to yield a high titer of the product desired. Ancient methods of food preservation
i
ncluded allowing the natural oxidation of sugars in order to preserve or produce a desired food for later
use. Grapes rot and turn to compost, milk is fresh for only a few hours without proper refrigeration, and
raw flour is useless to humans. Using the fe
rmentation technology, large genetic engineering,
pharmaceutical, agricultural, food and diagnostics companies are synthesizing their products in huge
quantities, heretofore unavailable without tremendous costs involved.

In each of these

experiments
, the
use of Biotechnology is demonstrated. In the first,

experiment
demonstrates denaturing protein in milk

to create yogurt and cheese.

In the 2
nd

experiment
yeasts will
anaerobically oxidize grape sugars to produce ethanol and carbon
dioxide. Lastly, in the 3
rd

experiment
we
will use yeast again for fermentation to leaven bread.


LAB ACTIVITY I:

LACTIC

ACID FERMENTATION


BACKGROUND:

After studying how microbes can cause food spoilage and in some cases
disease, you may find it hard to consider microbes as a po
sitive addition to food.
However, microbes are critical in the making of many foods and beverages,
including yogurt, cheese, bread, sauerkraut, pickles, olives, vinegar, coffee,
chocolate, wine and liquor, and beer.


How do microbes contribute to the makin
g and flavors of the foods listed
above? The secret is fermentation, a process by which organic compounds are
partially broken down in the absence of oxygen. During fermentation, the enzymes
produced by the cells of microbes convert organic compounds (such

as sugars) to
other organic compounds (alcohols, acids) and in some cases to carbon dioxide
(CO
2
). The microbes use the energy that is released during these conversions.
Three types of fermentation by microbes are especially important in food
production:
lactic acid, acetic acid and alcoholic fermentation.

The exact reaction or series of reaction involved depends on the particular microbes and the particular
food. In this lab we will investigate the process of lactic acid fermentation in dairy products.

F
ermented milk products such as yogurt, buttermilk, and especially cheese are a part of many people’s
diets. These products are all the result of lactic acid fermentation by certain species of acid
-
loving bacteria. The
following equation summarizes the conv
ersion that takes place in fermentation of dairy products.


C
12
H
22
O
11

+ H
2
O



3
H
6
O
3


Certain cultures of Mid
-
eastern peoples thrive on diets that include sour fermented milks. It is thought hat the
“friendly” bacteria found in these sour and fermented mi
lks colonize the human digestive tract. There the
bacteria ferment carbohydrates to form lactic acid, make B vitamins, and stimulate growth the other beneficial
intestinal microorganisms.

Today most fermented dairy products are made from cow’s milk. The b
acilli that ferment the milk are
responsible for the acidity, flavor, a
nd texture of the final product.

Two of the best known bacilli are
Lactobacillus bulgaris

and
Lactobacillus acidophilus
.

For this investigation you will focus on the fermentation of mi
lk to make yogurt. To make yogurt, you
must have some starter, consisting of either commercially made yogurt
or yogurt culture. The starter,
which
contains active bacteria, in added to warm milk and allowed to grow for several hours.


As a result of this
training lab you will:



Discover what makes milk curdle and thicken



Answer the question: “can a yogurt with active cultures make milk thicken?”



Be able to explain how active yogurt cultures curdle milk



PART I: WHAT CHARACTERISTIC IS SHARED BY LIQUIDS THAT

MAKE MILK CURDLE AND THICKEN?


MATERIALS:



Milk (40mL)






pH paper







4 cups





4 spoons



Vinegar (10mL)



Lemon Juice (10mL)




Diluted chocolate syrup (10 mL)




Tea (10 mL)



PROCEDURES:

1.

Put the vinegar, lemon juice, tea and chocolate syrup in their own sepa
rate cup
s
.

2.

Us the pH paper to measure the acidity of the vinegar, tea, lemon juice and chocolate syrup.

3.

Record the acidity of each solution

4.

Add 10 mL of milk to each of the solutions and stir.

5.

Observe which mixtures curdle. Record your results.


PART II:
CAN A YOGURT WITH ACTIVE CULTURES MAKE MILK THICKEN?


MATERIALS:



P
lain yogurt with active culture




Baking soda



100 mL milk






Aluminum



Large beaker







2 teaspoons



Graduated cylinder





pH paper



2 cups

PROCEDURE:

1.

Heat the milk to 75 degrees Celsius and th
en cool to 45 degrees Celsius.

2.

Label one cup: baking soda. Label one cup: plain. Put your names and hour on each cup.

3.

Pour 50 mL of milk into each cup.

4.

Add a teaspoon of yogurt culture to each cup and stir.

5.

Add a teaspoon of baking soda to the cup labeled
“baking soda” and stir.

6.

Cover each cup with foil and place in the incubator.

7.

The next day, observe the mixture in each cup. Record your observations.


OBSERVATIONS AND RESULTS

1.

Which yogurt mixture got thicker overnight?

a.

What probably caused it to thicken?

2.

If neither mixture thickened, what might have happened?

ANALYSIS:

3.

What is coagulation mean?

4.

What is Casein?

Why does Casein clump when the pH is lowered?

5.

What relationship did you find between a mixture’s pH and whether lumps were formed?

6.

What are acids?

7.

How do acids react with milk to form clumps?

8.

Why did the substances that were not acids fail at forming clumps?

9.

Bacteria and enzymes in milk can interfere with the bacteria in yogurt. Why do you think it’s
important to use preheated milk in this test?

10.

Ther
e is no “acid” in yogurt’s list of ingredients. Could it be the active culture that adds acid to
thicken the milk? How?


11.

If an acid is thickening the milk, what would happen if you added a base (such as baking soda) to
the mixture?


12.

The same active culture
s were added to the baking soda cup as the one without. Why didn’t that
mixture thicken?


13.

Summarize in 2
-
3 paragraphs
“How active yogurt cultures curdle milk”
?

Part III
: THE ART OF
MAKING CHEESE


PROBLEM
:
What is the process that is used to make cheese?


BACKGROUND

Most people think of the relationship between food and bacteria
in a very negative way. People usually assume that bacteria make food
unappetizing, inedible, or even toxic. However, some bacteria help to
produce safe, nutritious, and tasty foods
, such as cheese and yogurt.

Fermentation is a process in which selected microorganisms
grown in a food and produce acids or alcohol. When milk products are
fermented, lactic acid is produced. The lactic acid coagulates the milk
protein so that the milk cu
rdles, forming a solid curd and a clear liquid
called whey. The curd is drained and aged to make cheese. Traditionally
the curd is drained through fine mesh known as cheesecloth. For instance, cottage cheese, the softest
cheese, is drained only slightly. T
he curd is then cut up into small pieces. Cottage cheese is not aged at all
so that it keeps most of the moisture of milk and has a very fresh taste with only a light tang of the whey.

The flavor and consistency of cheese depends on several factors, one fa
ctor that affects cheese
is the type of milk used to make it. Familiar cheeses are made from cow’s milk, goat’s milk, and sheep’s
milk. More exotic ones may be made from camel’s milk or mare’s milk. A second factor that affects cheese
is the type of bacter
ia used for fermentation. The most common bacteria used for cheese are
Streptococcus
,
Lactobacillus
, and
Leuconostoc
. Different species of each bacterium produce slightly
different cheese flavors and aromas. A third factor that affects cheese is the amount

of time given to each
stage of the cheese
-
making process.

In the past, people made cheese simply by letting the normal bacteria turn the milk sour. Various
bacteria used the milk sugar, lactose, to male lactic acid. If one batch produced a good cheese, a
small
amount of the cheese was saved to start the next batch. Today commercially produced cheese is started
with known cultures of selected bacteria. The bacteria are added to sterile milk and allowed to grow in a
controlled environment. In this activity y
ou will use buttermilk as a started culture.


OBJECTIVES



Prepare cheese from milk and buttermilk



Observe the biological processes involved in making cheese.


MATERIALS (PER GROUP
)



600
-
ml beaker




cheesecloth



500
-
ml whole milk



50
-
ml beaker




Scissors




50
-
ml
buttermilk




500
-
ml beaker





Salt (optional)



Hot plate




Cotton twine




Flavorings (optional)



Thermometer




Labels

Safety First

1.

Wear a laboratory apron and safety goggles.

2.

Be careful of breakage when using glassware.

3.

Be careful of burns when using the hot pla
te.

4.

Wash your hands thoroughly with soap and water before and after completing the laboratory.


PROCEDURE


Day 1

1.

Put on your laboratory apron and safety goggles. Make sure that all materials, equipment, and your
hands are as clean as possible.

2.

Pour 500mL
whose milk into a 600
-
mL beaker and 50mL buttermilk into a 50
-
mL beaker.

3.

Heat the whole milk in its beaker over a low
-
heat hot plate to 37ºC.

4.

Add the buttermilk to the warm whole milk and stir to mix well.

5.

Cover the beaker with a cloth or paper.

6.

Incubate
the mixture at warm room temperature, between 25 ºC and 35 ºC, for 48 hours or until a firm
curd has separated from the whey.

a.

This can be done in an incubator or solar oven.

b.

Observe the formation of curd.

Record your observations in the laboratory reco
rd sheet.


Day 2

1.

Make a square of cheesecloth two or three layers thick and 30 cm on a side

2.

Ask a student in your group to hold the square of cheesecloth like a loose net over a 500
-
mL beaker.

3.

Pour the curd into the cloth. Gather the edges of the cloth t
ogether and form a bag. Ask another student
to tie the top of the bag together leaving enough twine to hang the bag. Attach a label to bag with your
names and class period. Discard the liquid, called whey that passed through the cloth bag.

4.

Hang the bag whe
re your teacher tells you to hang it and allow the curd to drain (The teacher will put the
bag in the refrigerator overnight.)


Day 3

You can add flavoring to the cheese if desired. Carefully open the bag and mix in a small amount of the
flavoring of your
choice. Re
-
tie the bag and let it hang for at least 24 hours.


Day 4

For best flavor, remove the cheese from the refrigerator and let it warm to room temperature. Serve the
cheese on plain crackers. For comparison taste your own group’s cheese, some unflav
ored cheese, and
cheese made by other students.



On a separate piece of paper complete the following:


OBSERVATIONS:
Record what you observed at each step in the process of making cheese.


ANALYSES AND CONCLUSION

1.

Explain what causes milk to curdle.

2.

Explai
n why you added buttermilk to the plain milk to make cheese.

3.

Why was the milk heated? Explain your answer.

4.

Describe what took place in the milk as it turned to cheese.

a.

Describe the taste of the cheese you made.

b.

Did you like it?

c.

If you compared the taste o
f cheese made by other students, describe what you liked and
disliked about the other flavors.


GOING FURTHER

Describe another method besides fermentation for cheese production (2
-
3 paragraphs)









LAB ACTIVITY II: ANAEROBIC

RESPIRATION OF FRUCTOSE

B
ackground:


The natural occurrence of fermentation means it was probably
first observed long ago by humans. The earliest uses of the word
"Fermentation" in relation to winemaking was in reference to the
apparent "boiling" within the must that came from th
e anaerobic reaction
of the yeast to the sugars in the grape juice and the release of carbon
dioxide. The Latin
fervere

means, literally,
to boil
. In the mid
-
19th
century, Louis Pasteur

noted the connection between yeast and the
process of the fermentation

in which the yeast act as catalyst and
mediator through a series of a reaction that convert sugar into alcohol

The purpose of this experiment is to observe the results of
cellular respiration of yeasts, using grape sugar as a substrate and yielding carbon

dioxide and ethanol. In
the absence of oxygen, Glycolysis continues as fermentation, resulting in alcohol production. Sweet grapes
(20% sugar in the juice) produce 11% alcohol, after which the yeasts die, due to the high level of alcohol and
waste product

buildup. By carefully massing each ingredient, many quantitative experiments may be
performed, such as measuring the volume of gas produced, the percent alcohol produced, or the sugar
used.
(Students Should Not Taste Any Product).



MATERIALS



Vegetable b
aggies



Freezer Bag



Baker’s yeast



pH paper



150g of grapes



Incubator/oven (25


C
)
PROCEDURE:


1.

Use two self
-
locking plastic baggies, one which has perforations (for keeping
vegetables fresh), and the other a heavy
-
duty freezer bag.

2.

Mass 5 grams of dried ba
ker’s yeast (Saccharomyces) and place inside the heavy
-
duty freezer bag.

3.

Tape a pH indicator strip toward the top of the perforated bag (outside or
inside). Then insert the perforated baggie inside the heavy
-
duty bag.

4.

Mass 150 g of grapes, and, using a p
H indicator strip, squeeze one grape
to produce enough grape juice to test the pH of the grape.

5.

Record the pH.

6.

Into the perforated bag place all the grapes. Close the perforated bag.

7.

Carefully squeeze out any air in the bags. Close the heavy
-
duty baggie.


8.

Crush the grapes through the baggie, using fingers to crush each grape, to
release the grape juice.

9.

Mix the grape juice with the dry yeast, without opening the bag.

10.

Place the bags into a warm environment (25 degrees C), and observe for the next hour.

a.

Note the foam and gas filling the baggie.

11.

Allow some juice to touch the pH strip and record the pH.

a.

Record other observations.

12.

Open the bag and test the gas produced with a glowing splint or lighted match.

a.

What happens?

b.

After a day open the bag and all
ow air to reach the juice. Aft
er a few days, note the
smell

c.

Test pH with another indicator strip.

Analysis:


1.

What is fermentation?

2.

What is G
lycolysis
?

3.

What is the yeast using as food source?

4.

What is the pH of the juice when it is finished fermenting?

5.

Wh
at does the smell of the juice after being open to the air remind you of?

6.

What made the grape juice sour after a few days
?

7.

How does the
pH of the
j
uice

change
?

8.

What are some of the uses of the “sour juice”?

LAB ACTIVITY II
I: YEASTS & BREADMAKING: “GUESS WH
O’S GOT GAS”

BACKGROUND

Biotechnology is the application of principles of Biology for useful
purposes. Currently, Biotechnology includes the use of DNA for such diverse
applications as forensics, organism classification, and genetic engineering to
change
the genetic structure of an organism. Biotechnology also includes the
production of foods, cosmetics, pharmaceuticals, diagnostics, and purified
macromolecules for use in research and industry. Any useful application of
Biology is Biotechnology.

The basis

of biotechnology is often fermentation biochemistry, as
yeasts, molds, or bacteria must be cultured in order to yield a high titer of the
product desired. Ancient methods of food preservation included allowing the
natural oxidation of sugars in order to p
reserve or produce a desired food for
later use. Grapes rot and turn to compost, milk is fresh for only a few hours
without proper refrigeration, and raw flour is useless to humans. Using the fermentation technology, large
genetic engineering, pharmaceutic
al, agricultural, food and diagnostics companies are synthesizing their
products in huge quantities, heretofore unavailable without tremendous costs involved.

Yeast, a microscopic, one
-
celled organism belonging to the group of organisms called fungi. Ther
e are
many kinds of yeasts, some of them of great importance to humans. Yeast is necessary to make leavened
bread, beer, cheese, wine, and whiskey. It is rich in B vitamins; a form of yeast called brewer's yeast is used as
a diet supplement. Yeast is also
used in genetic engineering to produce large quantities of certain hormones
and enzymes, which are used for such medical purposes as healing wounds and reducing inflammation. Some
types of yeast, however, cause disease; candidiasis, a skin infection, is an

example.

Yeasts are found in the soil, in water, on the surface of plants, and on the skin of humans and other
animals. Like other fungi, yeasts obtain food from the organic matter around them; they secrete enzymes that
break down the organic matter into
nutrients they can absorb.

The yeast cell is oval or round and has a thin membrane. Under ideal conditions of moisture,
temperature, and food supply, it reproduces asexually, by budding. When a yeast cell reaches full growth, a
budlike swelling forms on it
s surface. Part of the parent cell's nucleus goes into this bud, and a wall is formed
between the parent cell and the bud, which then becomes a separate cell. This new cell may break off when it is
full grown. It may, however, remain attached as it produce
s another bud. In this way, chains or clusters of cells
are formed. Budding is a rapid process, requiring about 20 minutes to produce a new organism.
This
experiment, which can now safely, conveniently, and inexpensively be performed in a self
-
locking bagg
ie are
submitted. In each of these, the use of Biotechnology is demonstrated in this experiment by using yeasts for
fermentation.


PURPOSE:

This experiment is designed to observe the process of fermentation to capture the gas produced for
the useful purpo
se of Breadmaking.

Alcohol Fermentation Chemical Equation:

C
6
H
12
O
6

(sugar)
---
>
CO
2

(carbon dioxide) +
2CH
3
CH
2
OH

(ethanol)


PROCEDURE:

1.

Lightly grease the inside of a self
-
locking microwave
-
safe baggie.

2.

Add



150g all purpose flour



10g yeast



10g sugar



1g
salt



enough 40 °C water to mix


3.

Close the bag and m
ix by hand. Allow to rise,
knead through the bag once more and allow to rise again.

4.

Open the bag. Then cook the bread in the microwave, for approximately 2 minutes, turning once during
baking.


ANALYSI
S:

1.

What is the purpose of the sugar and flour in this lab?

2.

What are the two byproducts of this particular fermentation process?

3.

What do you think happens to the two byproducts in the process of cooking?

4.

What is the purpose of any leavener?

5.

What is the sci
entific name of baker’s yeast?

6.

Use Google to find one other Food Science area where yeast is used to make a food product.

a.

Summarize and attach the article