Antioxidants

“Enzymatic Browning” is the title given to the familiar process by which apples turn brown when cut or bruised. This occurs because slicing an apple damages its cell walls, thereby exposing the cells’ contents to oxygen. Polyphenol Oxidase (PPA, aka Tyrosinase) is the name of an enzyme available in apple chloroplasts that then catalyzes a reaction between this newly available oxygen and the apple’s naturally occurring phenolic compounds; whereby these polyphenols lose electrons while gaining oxygen, and are therefore said to have been “oxidized”. The colorless O-quinones, produced as a result of this oxidation, further react in a secondary process to form compounds with amino acids. These polymerized compounds are known as “melanin” and serve as an insoluble barrier with anti-bacterial properties to prevent the spread of infection/bruising in the apple’s tissue, as well as increase the plant’s resistance to climatic stress. Melanin is also responsible for lending the apple’s flesh it's signature brown color.

Supplies

1. Glass cups

2. Distilled Water

3. Apple slices

4. Variety of Antioxidants

Step 1: Hypothesis

I think that the solution with green tea will work the best, green tea is well known to be packed with vitamins and other nutrients, also, green tea is 60-80 percent catechins which are known as good antioxidants.

Step 2: Variables

Independent: Type of antioxidants, temperature, Ph levels, iron copper levels.

Dependent: Time until Oxidisation

Step 3: Background Research and Information

“Enzymatic Browning” is the title given to the familiar process by which apples turn brown when cut or bruised. This occurs because slicing an apple damages its cell walls, thereby exposing the cells’ contents to oxygen. Polyphenol Oxidase (PPA, aka Tyrosinase) is the name of an enzyme available in apple chloroplasts that then catalyzes a reaction between this newly available oxygen and the apple’s naturally occurring phenolic compounds; whereby these polyphenols lose electrons while gaining oxygen, and are therefore said to have been “oxidized”. The colorless O-quinones, produced as a result of this oxidation, further react in a secondary process to form compounds with amino acids. These polymerized compounds are known as “melanin” and serve as an insoluble barrier with anti-bacterial properties to prevent the spread of infection/bruising in the apple’s tissue, as well as increase the plant’s resistance to climatic stress. Melanin is also responsible for lending the apple’s flesh it's signature brown color.

Step 4: Procedure

1. Slice an apple into equal slices

2. Fill a cup with distilled water

3. At the antioxidants in the same volume (For capsules only 1 capsule was used)

4. Wait: observe and document the oxidization

5. Analyze Data

Step 5: Results / Data Analysis

90 minutes post-immersion:

No significant change across either scale for most samples. Apples immersed in water were slightly discolored (A: light brown, B: pale yellow) exclusively on the side exposed to air. Apples immersed in acerola cherry solution were slightly discolored (A: light brown, B: pale yellow) on BOTH sides.

9 hours post-immersion: Apples immersed in acerola solution were rated “worse” on both scales relative to the control slices immersed in water. The discoloration was evident on both immersed and exposed sides of these apples.

Apples immersed in blueberry solution were now discolored (A: pale yellow, B: light brown) on exposed half of flesh.

For Green Tea, Turmeric, and Acai; no significant change was noted across both samples A & B when compared to the time of slicing.

For all other solutions, pale yellow patches began on less than 25% of flesh.

22 hours post-immersion: No apples remain unaltered; but changes are very minimal in both samples A & B of apples immersed in Green Tea, Vitamin E, and Turmeric; and in sample A of Astaxanthin-dipped apples.

Apples immersed in Acerola remain “worse-off” in color when compared to those immersed in water; however extent of discoloration is now similar.

Apples immersed in Blueberry, Acai, Cacao are rated similar to those immersed in water on both scales.

38 hours post-immersion: Apples immersed in blueberry juice solution now similar in color to those immersed in acerola (both brown); although the extent of discoloration is lesser in blueberry-immersed slices. Both are slightly worse-off relative to control samples. No other significant changes reported.

46.5 hours post-immersion: No significant changes in any samples when compared to 38 hours post-immersion.

68 hours post-immersion: No significant changes across samples in both shade and extent of discoloration.

MOLD!

Most pervasive mold development on exposed half of both samples of Acai-immersed apples.

Some mold development on both samples of Cacao-immersed, and Acerola-immersed apples, as well as on sample (B) of blueberry-immersed apples.

Beginnings of mold on one sample of each of the following: water, green tea, astaxanthin.

No traces of mold on either of the Tumeric-immersed samples.

72 hours post-immersion:

Apple quarters were sliced in half to reveal inner flesh. The texture was surprisingly similar to that of fresh apples; still crunchy and hard at the core, with the exception of a few millimeters of “soaked” tissue along immersed edges.

Turmeric-immersed apples stood out as having the largest area of “white” inner flesh.

Step 6: Conclusion

Food substances commonly known to be rich in antioxidants, such as those used in our experiment, may reduce oxidation of apple slices; but do not necessarily do so. Apple slices immersed in acerola cherry, for example, consistently performed worse in both shade and extent of discoloration when compared to those immersed in filtered drinking water. Solutions of turmeric, green tea, vitamin e, and astaxanthin; however; proved to significantly reduce signs of both oxidation and mold development. Turmeric, specifically, stood out as being the top antioxidant amongst those tested.

Step 7: Application

An assumption that antioxidants tested on apple plant tissue would have a similar effect on human tissue leads us to promote high and regular intake of turmeric, green tea, vitamin E and astaxanthin. Caution may be warranted when consuming fructose-rich foods such as acerola cherries, despite their high vitamin C content; as fruit-based antioxidants (blueberry, acai, and acerola) consistently performed at a level equal to or worse than water in our experiment.