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Does Controlled Atmosphere Storage Affect the 
Malic Acid and Starch Levels in Apples?

Researched by Alyssa B.
2002-03



PURPOSE

The purpose of this experiment was to determine if controlled atmosphere apple storage would affect the amount of malic acid and starch levels in apples.
I became interested in this idea when one day I bit into an apple and it was crisp, mild, smooth and tart, while a week later the same batch was grainy and had a not-so-good taste. 
The information gained from this experiment may be useful for consumers and people in the apple industries.

 



HYPOTHESIS

My 1st hypothesis was that the malic acid content would decrease as the storage temperature increased.
I based my 1st hypothesis on the fact that apples ripen faster in warmer temperatures and malic acid content decreases after ripening.

My 2nd hypothesis was that the starch content would decrease as the storage temperature increased.
I based my 2nd hypothesis on a quote from a fruit storage article that said controlled temperature storage “slowed the ripening process.”

My 3rd hypothesis was that the longer the apples were stored the greater the malic acid content.
I based my 3rd hypothesis on the quote “The malic acid is pure in the apple just before it is ripe, but is less afterwards.”

My 4th hypothesis was that the longer the apples were stored the greater the affect on the starch content.
I based my 4th hypothesis on storage articles about temperature and its affect on ripening and sugar/starch content.

 



EXPERIMENT DESIGN

The constants in this study were:
§ Number of apples juiced
§ Amount of juice used for each test
§ Amount of water used for each test
§ Temperature of the 4º C room
§ Temperature of the 21º C room
§ Temperature of the 32º C room
§ Type of apple and harvest week
§ Number of apples used for starch test
§ Type of automatic titrater

The manipulated variables were the temperature the apples were stored at and the amount of time they were stored.
The responding variable was the amount of malic acid and starch in apples. 
To measure the responding variable I used a titrater to measure the amount of malic acid and an iodine solution to measure the starch. 

 


MATERIALS

QUANTITY ITEM DESCRIPTION

36                                  Red delicious apples
3                                    30x46x13cm cardboard box
1                                    clean paring knife
1                                    15x46x5cm cardboard box
1                                    5ml. Pipetteman pipette
13                                  sml.pipette tips
1                                   250mL. Beaker
3                                   400mL. pipette
1                                   Omega Fruit & Vegetable Juicer
100mL.                         Iodine spray (0.5% I2)
1                                    0.4732 Spray bottle
1                                   clean plastic  cutting  board
1                                   Schotts automatic titrater
1                                   stir bar
1                                   safety glasses
1                                   fume hood
1                                   100mL. Graduated cylinder
1300mL.                       Distilled water
1                                   4º  C storage room
1                                   21º C storage  room
1                                   32º C storage room
1                                   Adult supervisor

 


PROCEDURES

Time Zero
1. Set 3 apples aside for later use. 
2. Put 12 apples in each of 3 smaller boxes.
3. Label one A, one B, and one C.
4. Put box A in 4º C storage room.
5. Put box B in the 21º C storage room.
6. Put box C in the 32º C storage room.
7. Cut the three apples you set aside in half horizontally.
8. Put the bottom half in the shallow cardboard box and place under fume hood.  Label box in thirds A, B, and C.
9. Spray the tops of the bottom half with iodine solution.
10. Cut the top half in 1/8’s.
11. Put a beaker under spout of the juicer and push two pieces of apple into juicer.
12. Discard juice made from the pieces and put the beaker labeled A under the spout.
13. Push one piece of apple into the juicer at a time until all pieces are juiced.  Empty contents inside juicer (pulp) into garbage can.
14. Take juice and using the pipette, put 10 mL of juice into a beaker and add 100 mL of distilled water.
15. Put stir bar in and put under electrode of the titrator.  Insert sodium hydroxide ejector; turn the titrator and the stir bar on according to the supervisor.
16. Record malic acid and starch levels.
17. Clean juicer and supplies.
Procedures
1. Collect three apples from each room in buckets labeled A, B, and C.
2. Cut all the apples in the A bucket in half horizontally on the plastic cutting boards.
3. Put the bottom half in the shallow cardboard box and place under fume hood.
4. Spray the tops of the bottom half with iodine solution.
5. Cut the top half in 1/8’s.
6. Put a beaker under spout of the juicer and push two pieces of apple into juicer.
7. Discard juice made from the pieces and put the beaker labeled A under the spout.
8. Push one piece of apple into the juicer at a time until all pieces are juiced.  Empty contents inside juicer (pulp) into garbage can.
9. Set aside for later use.
10. Repeat steps 2-10 for apple buckets B and C.
11. Take juice and using the pipette, put 10 mL of juice into a beaker and add 100 mL of distilled water.
12. Put stir bar in and put under electrode of the titrator.  Insert sodium hydroxide ejector; turn the titrator and the stir bar on according to the supervisor.
13. Record malic acid and starch levels.
14. Clean juicer and supplies.
 

 



RESULTS

The original purpose of this experiment was to determine if controlled atmosphere apple storage affects the amount of malic acid and starch in apples.

The results of the experiment were that the malic acid content decreased as the storage temperature increased and that the starch content decreased as the storage temperature increased.  The malic acid and starch content both decreased over time in storage.
 
 

See my table and graph.
 

 


CONCLUSION

My 1st hypothesis was that the malic acid content would decrease as the storage 
temperature increased. 

My 2nd hypothesis was that the starch content would decrease as the storage temperature increased.

My 3rd hypothesis was that the longer the apples were stored the greater the affect on the malic acid content.

My 4th hypothesis was that the longer the apples were stored the greater the affect on the starch content. 

The results indicate that all hypothesizes should be accepted.
Because of the results of this experiment, I wonder if the apple the apple dehydrates in warmer climate and makes a higher concentration of sugar and malic acid.
If I were to conduct this project again I would have had more apples to test. I also would have more frequent tests like every two days instead of once a week, also I would have replicated my entire experiment. 
 
 
RESEARCH REPORT

 

Apples

History of Apples

The apple or Malus sylevestris dates back to 6500 BC. It is not native to the United States but is native to southwest Asia. Julius Caesar planted the very first apple tree in England and the English brought seeds to the New World. The Massachusetts Bay Company planted the first tree. 
The apple is made-up of 85% water, vitamin A and C, potassium, pectin, and fiber. There is also malic acid in apples. The malic acid is what gives the apple its aroma, taste, and also healthfulness. There is also a lot of starch in an apple that is crunchy but is little in an apple that is mushy and grainy.

The Apple Tree

The apple tree is twenty to thirty feet tall when it is fully-grown. It belongs to the rose family because of its blossoms that eventually turn into apples. The tree has to mature for four years before it bears fruit, and bears fruit for forty years. The tree has head-spreading branches, which means the branches spread apart near the top of the tree. The trees grow when bees pollinate the stigma of the blossom. The small green cup that holds the blossom is called a calyx. The apple wood is used for engravings, carvings, saw handles, and ax handles.

Crops 

 Worldwide, we growers’ produce 2 billion bushels of apples a year. China produces 630 million bushels of apples annually the most in the world. The harvest time is late summer to fall depending on the variety. A fourth of the apples the world produces goes into cold storage. The United States ranks 2nd, with 260 bushels, of apples produced. Washington produces the most apples in the United States. France was third on this list.

Health 

Apples are very good for you. There are condensed tannins found in the juice of apples that help prevent plaque on the teeth. Apples also prevent periodontal or gum disease. Apples also have anti-adhesion properties. You can eat apples fresh to relieve constipation and diarrhea. An apple prevents urinary tract infection and reduces the risk of heart disease.
 

Malic Acid

Malic acid is an important ingredient in apples, therefore it is also known as apple acid. Malic acid is a colorless crystalline compound that is a metabolite in the Krebs Cycle that produces 90% of the energy within its cells. Malic acid binds to aluminum. It removes the aluminum from the enzyme tubulin-which protects and maintains nerves-then is removed from the body through urine. There is roughly 0.2-1.0 gram of malic acid in an average apple (the part that you can eat). Malic acid is what makes the saying “An apple a day keeps the doctor away” true!

Health 

You cannot become deficient in malic acid because the body produces malic acid itself. Malic acid also helps prevent many diseases and conditions. Fibromyalgia is a disease that is in the muscles and malic acid is a very popular remedy to decrease pain related to it. Malic acid also is a remedy for hypoxia-related conditions which is respiratory or circulatory insufficiency, or when you don’t get enough oxygen. Some scientists believe that malic acid can also reduce the risk of Alzheimer’s disease. Malic acid also helps the body make ATP more efficiently. ATP is the energy currency that runs the body, from food.
 

Starch

Starch is a biopolymer system including mainly Amylose and Amylopectin. Starch is used for pressing clothes and making foam packing (because it is biodegradable). Starch is made up of glucose, or other sugar, in repeated units, which your body can burn for energy. A way to test for starch is to use an iodine solution on the object and it will turn a blue-black color if it has starch in it. This happens because the starch chemically reacts to the iodine solution.

Heath

One third of the total weight of food intake is starch. You can find starch in many different foods including potatoes, grains like corn and wheat, and apples. Red Delicious apples should have a 1.5 - 2.0 rating on the starch scale to be perfect. You get most of the energy you use from starch. 

Controlled Atmosphere

Controlled atmosphere is a non-chemical storage process that uses an airtight room. The oxygen is reduced in the room, by adding nitrogen. The oxygen drops from about 21% in the regular air that we breathe to one or two percent. The temperature in the room is kept at32 to 36 degrees Fahrenheit. The humidity in the room is kept at about 95%. The carbon dioxide level is also controlled. They change the conditions of the rooms depending upon the variety of the apple. Machines and computers help keep the conditions stable and constant.

History

Controlled atmosphere started in England before World War _ when some farmers discovered that there produce lasted longer if it was stored in an airtight room. The scientists had to figure out why they lasted longer. Researches in Washington have been among the leaders in controlled atmospheres. Controlled Atmosphere started in the United States in 1960, Washington now has the most controlled atmosphere storage of any growing region.

How it Works

Apples “breathe” just like humans, in with oxygen and out with carbon dioxide, as the starch turns to sugar. In the airtight rooms, the oxygen turns into carbon dioxide, which slows the ripening process. 
 

BIBLIOGRAPHY

“Malic Acid” Malic Acid 11/21/02 http://www.hollandandbarrettt.com/Supp/Malic_Acid.htm 

“Morphologic Change of Starch Granules in the Apple cv. Mutsu  During Ripening and Storage” Scanning 11/21/02
 http://www.scanning-fams.org/scanabstracts/SCANNING99/21326

Washington State Apple Commission. “Controlled Atmosphere Storage (CA)” Core Facts 1/30/03 http://www.bestapples.com/facts/controlled.html 

Washington State Apple Commission. ”Keep Your Family Healthy” Health & Nutrition 10/10/02 http://www.bestapples.com/healthy/index.html

“What is Starch” What is Starch 1/29/03
http://www.poco.phy.cam.ac.uk/research/starch/whatis.htm 

Washington Apple Maturity Program Handbook.1986.Washington Apple Maturity Program,Wenatchee,WA.

Washington State University,Tree Fruit Research and Extension Center. “Postharvest Information Network” 1/29/03 http://postharvest.tfrec.wsu.edu/index.html 
 
 

ACKNOWLEDGEMENTS

I would like to thank my Supervisor from TreeTop for helping me learn to use all the materials. I would also like to my advanced science teacher for guiding me through the project and making sure I did all the steps required of me. 
 
 

 


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