Defeating Oxidation in Apples By: Alexa Conzuelo Per. 6 Mr. Leingang

Question Which acidic fruit juices with different levels of pH best prevent an apple slice from becoming oxidized?

Hypothesis As I squeeze different acidic fruit juices then the lemon juice will best prevent the apple slice from becoming oxidized because it has the lowest pH level of all the fruits and the lower the pH the better it prevents oxidation in fruit. Also I believe that the orange juice will least prevent oxidation because it is the sweetest of all the fruit so it has a higher level of pH.

Background Information Oxidation is when two materials come into contact with each other and an electron is lost. This is both good and bad because it can cause things to rust such as metals. It can also make aluminum more durable, so its not such a bad thing. Oxidation does not weaken metal or copper when it rusts but it creates a patina, which is a film that develops on a material over a long period of time. This also affects fruits. There are some negative affects if something becomes oxidized. On a car the paint becomes dull over the years. A layer of wax protects the car and paint from oxidation. A bicycle left in the rain becomes rusty and unusable. Also a greenish coat settles on copper that has become oxidized over the years. Some metals don’t become oxidized because the steel is covered with a layer of metal that doesn’t cause a chemical reaction with oxygen. Fruits and vegetables turn brown and blemish, causing them to look inedible. Oxidation affects fruit and causes blemishes, or browning. This happens because when fruit is cut it comes into contact with oxygen. Then enzymes contained in the apple make a chemical reaction with the oxygen. This is what makes the fruit darken. Even if the vegetable or fruit is brown it is still edible, although it is best to cut those parts off. There are ways to prevent vegetables and fruit from becoming oxidized. One way is to cover the food item in plastic wrap. This prevents the cells and enzymes to interact with oxygen. Also you can slightly heat the fruit, which causes the destruction of the enzymes. Another method, which is the one I used, is to add citric acid to exposed parts of the fruit. This prevents oxidation because the juices have a very low pH and it interferes with the 3D structure of the enzymes. So it disrupts the structure, and prevents it from functioning. Now you may be thinking what pH is. Basically it’s the measure of a liquid’s acidity or basicity. You can measure this by using a pH indicator, which changes color to see the number of pH. The measure of pH isn’t absolute though, but close enough. Most values will range from zero to fourteen. Pure water at a lukewarm temperature is near seven, which is neutral. Less than seven is considered acidic, and more than seven is alkaline. An example is lime juice, which has a pH of two to 2.8, so its acidic. Baking powder is around 8.2. pH is important for food science, medicine, biology, chemistry, and other things.

Variables Manipulated variable: the different type of acidic fruit juice squeezed onto the apple slice Responding variable: the amount of browning on the apple slice that is recorded Controlled Variable: Type of apple, amount of juice squeezed onto apple, size of apple slice, amount of time apples are left to brown

Materials Two Fuji apples One lemon one lime one orange One grapefruit Stopwatch Knife Cutting board

Procedures 1. Cut four slices of apples around the same size and thickness, like in the diagram. Be careful when using the knife. 2. Cut a lemon in half and squeeze a tsp of juice. 3.Pour it on one side of apple slice # 1 4. Squeeze another tsp of juice and it on the other side. 5. Repeat steps 2-4 for the lime juice for slice # 2, orange juice for slice # 3 and grapefruit juice for slice # Put the apple slices on a plate. 7. Wait for two hours. Make sure the slices are not in the path of sunlight and at room temperature. 8. Record your observations. 9. Repeat steps 1-8 for one more trial.

Data table Trial 1 JuicesObservations of browning on applesDiagram Lime juiceSome browning on the top and bottom of apple slice. Lime juiceVery little browning on back, blemsih on the bank. Orange juiceSome browning over all of the apple Grapefruit juiceBrowning all over the apple, more on the top front side.

Data continued Trial 2 JuicesObservations of browning on apples Diagram Lemon juiceSlight amount of oxidation on front, little bit more on the back Lime juiceLeft part in the front large blemish, very little on back Orange juiceBrown on back and front Grapefruit juiceSlight oxidation on the front and back of apple slice

Conclusion I believed that the lemon juice would best prevent an apple lice from becoming oxidized, and the orange juice the worst. My hypothesis was correct because on both trials the apple slice covered in lemon had the least oxidation. The orange juice covered apple slice had the highest oxidation amount on both trials. The difference was that apple slice number one looked edible, while the apple slice number three didn’t. Therefore if I repeat my experiment the visible amount of oxidation on the lemon juice covered apple slice should not increase, and the orange juice covered slice should still have the most oxidation.

Abstract The purpose of my project was to see which acidic fruit juice best prevented an apple slice from becoming oxidized. I thought that the lemon juice would best prevent oxidation. To my knowledge there was no inconsistency in my experiment that could have affected my data. Upon completing my project I learned that both lemon and lime juice both work well against oxidation. Also orange juice isn’t very good as an anti-oxidative because its too sweet. There are some things I could have done differently and one of them was I could have left the apples exposed to air longer to see the fuller extent of how well the juices prevented oxidation.