Post 5: The Experiment

Introduction: In order for me to get a better understanding of how GMOs work, I conducted an experiment that would similarly relate to this topic. The company Arctic Apples is now introducing an apple that doesn’t turn brown. My goal for this project is to create an at-home experiment that can represent the same procedure and information this company used for their product.

Research: The big question here is why apples turn brown after being sliced. According to the Arctic Apples, “When an apple’s cells are damaged, such as when it’s bitten, sliced, or bruised, an enzyme called polyphenol oxidase (PPO) initiates a chemical reaction that results in the apple’s flesh turning brown.” After searching for liquids that prevent this browning from happening, lemon juice came as a number one pick. Lemon juice contains ascorbic acid (Vitamin C) and a low (acidic) pH level. When lemon juice is applied to a sliced apple, the ascorbic acid will react when the enzymes in the apple are exposed to oxygen. The pH in polyphenol reacts best when it is in the 5.0 to 7.0 range level. When the lemon (pH level of 2.0) interacts with the polyphenol, it prevents the polyphenol from reacting causing the prevention of browning.

Thesis/Hypothesis: My outcome expectation for this experiment is either the vinegar or lemon juice will prevent the apple from turning brown. Due to their acidity, the exposure these apples are facing prevents the apple from turning brown.

Experiment: For this experiment, I decided to use Gala Apples. There were five different mixtures being exposed to these apples: Lemon Juice, Vinegar, Water, Milk, and Baking Soda. There was an extra plate that contained no liquid, making this the controlled apple. All apples were placed in the solutions right after being sliced and left to sit for 2 hours at room temperature with some air exposure. All bowls contain two sliced apples; one exposed face up and the other facing down submerged into the liquid. The following images show the first photo taken of these apples at the beginning of the experiment and a table of each liquids pH levels.

Credit: Dacia Flores
Credit: Dacia Flores

Results: My hypothesis was only partially correct. The lemon juice did in fact prevent any kind of browning, but there were other liquids that prevented this as well like milk, water, and baking soda. The liquid that had the least effect was the vinegar, which is ironic because it was one of my picks. In the image below, I took a zoomed in image of the final results of each apple. The majority of the liquids helped keep the apple at a neutral stage, neither brown nor clear, but the vinegar liquid was the worst result.

Conclusion: Arctic Apples has confirmed that the cut down the PPO (polyphenol oxidase) in order to cause a low reaction when the apples are sliced and exposed to the oxygen. If the company wanted to use pH to prevent browning from occurring, they could add an acid to their apples as shown and proven to work in our experiment.

*Note: The apple slice on the right is the side that was submerged in the liquid.

Credit: Dacia Flores

Works Cited:

-Arctic Okanagan Specialty Fruits, 2017.