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How Do You Keep Guacamole From Turning Brown?

based on 7 ratings
Author: Sharon Cooper
Type

Chemistry (Cooking)

Grade

Elementary School

Difficulty of Project

Easy

Cost

$10-$15 (depending on whether avocados are in season)

Safety Issues

None

Material Availability

Easily available!

Approximate Time Required to Complete the Project

A few days

Objective

  • To understand how to stop the oxidation process from occurring in guacamole.
  • To test different strategies for stopping this process. 

Materials and Equipment / Ingredients

  • Guacamole (homemade)
  • An avocado pit
  • Saran Wrap
  • Lemon juice 

Introduction

After creating a homemade guacamole, you might discover that the guacamole will quickly turn brown. Why does this occur? When avocados are cut open, it allows the enzyme polyphenole oxidase to react with the oxygen in the air. This creates a melanoidin pigment, which turns the guacamole brown. How does one ensure that the guacamole does not turn brown? 

Research Questions
  • Does leaving the avocado pit in the guacamole stop it from turning brown?
  • Does Saran Wrap stop guacamole from turning brown?
  • Does lemon juice stop guacamole from turning brown?
  • Which of these methods word the best? 
Terms, Concepts and Questions to Start Background Research
  • What causes guacamole to turn brown?
  • How does oxygen interact with avocados?
  • What are some proposed methods of preventing the guacamole from turning brown? 

Experimental Procedure

  1. Create four batches of homemade guacamole.
    a.
    Leave one batch alone. This is your control.
    b.
    In one batch, place an avocado pit on the top.
    c.
    In one batch, squeeze some lemon juice into the mixture.
    d.
    Spread Saran Wrap across the final batch.
  2. Leave the guacamole out on the counter, exposed to air.
  3. Observe how long each takes to brown. Once they are brown, feel free to throw them out. 

Bibliography

Hartel, Richard and AnnaKate. Food Bites: the Science of Foods We Eat. Springer Publishing, New York: 2008.

McGee, Harold. The Curious Cook: More Kitchen Science and Lore. Hungry Minds Inc, New York: 1990.

 

 

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