Lab Report Template Enzymatic Browning Of Fruit 6xj36

Lab Report Enzymatic Browning of Fruit Name ___Elizabeth Mamros_________________________________________ Pd __1__ Date _4/16/2015_ Learning Objectives:  Test various preservatives for their effectiveness at preventing apple slices from turning brown  Learn about enzymatic browning in fruits and vegetables

Describe Enzymatic Browning. When and how can it be beneficial and also when is it detrimental? Enzymatic Browning is an oxidation reaction that occurs when the enzymes that create malanins and benzoquinone, such as polyphenol oxidase and catechol oxidase, come into with the oxygen in the air. These enzymes catalyze the oxidation of phenols to form quinones. The polymerized quinones become melanins which appear brown. Enzymatic browning is beneficial when brewing tea or flavoring dried fruit. This chemical process is detrimental to fresh foods such as fruit, vegetables, and seafood.

Pre-Lab: Apple slices turn brown very quickly when left in the air. This is caused by an oxidation reaction when the apple reacts with oxygen in the air. A particular enzyme in apples, called polyphenoloxidase, speeds up the oxidation of apples. In this activity, you will determine which preservatives are effective at preventing the oxidation (the browning) of apples. 1. What chemicals produced from the polyphenoloxidase are responsible for the brown color when fruit slices sit in air? A good resource is: http://www.food-info.net/uk/colour/enzymaticbrowning.htm Quinones and malanins 2.

List some ways to prevent enzymatic browning. Blanching, refrigeration, freezing, change pH, dehydration, irradiation, high pressure treatment, addition of inhibitors

3. What are ascorbic acid and citric acid? What are some of their uses? Ascorbic Acid: reducing agent that removes oxygen, used to replenish vitamin C, treat scurvy Citric Acid: acidulant that reduces pH, used as a food preservative, cleaner, chemical in photography development

Data: Peters Township High School

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Lab Report Enzymatic Browning of Fruit Record your observation using the following scale: 0 1 2 Not brown Apple Slice 15 minutes 30 minutes In air (control) 0 1 Ascorbic acid 0 0 Citric acid 0 0 Vegetable oil 0 1 Plastic Wrap 0 1 Sugar 0 1 Sodium Chloride 0 0

3

4 1 hour 3 0 1 3 4 2 0

5 Very brown 1 day 5 0 1 3 4 3 0

Post-Lab: 1. Which substances were effective in preventing browning of apple slices? Ascorbic acid, citric acid, sodium chloride 2. Did some of the treatments alter the smell, texture, or appearance of the slices? Which ones and how? yes, vegetable oil made the apple slice slimey, the plastic wrap made the slice soggy and very brown, the in air slice turned leathery and very brown, the citric acid slice smelled slightly of oranges 3. Is the treatment necessarily a good choice for a preservative just because it prevented browning? Why or why not? No, some of these treatments, like the citric acid, changed the pH of the apple and made it more acidic. I would not want to digest an even more acidic than normal apple. Also, some of these treatments altered the smell and texture of the apples which would change our perception of their taste probably for the worse. 4. Can you relate the experiment to real world products sold for this purpose? Fruit Fresh, Eat Cleaner, Rubber Bands, Apple Saver Evidence: Time Stamp: 0 min.

Time Stamp: 15 min.

Peters Township High School

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Lab Report Enzymatic Browning of Fruit

Time Stamp: 30 min.

Time Stamp: 1 hr.

Time Stamp: 1 day

Peters Township High School

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Lab Report Enzymatic Browning of Fruit

Peters Township High School

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