Does the Flexibility of Gelatin Depend Upon the Amount of Water?

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Author: Janice VanCleave

How Does the Amount of Water in a Gel Affect Its Flexibility?

Category: Biology—Food Science

Project Idea by: Benjamin Skrabanek

Gelatin is a substance made of animal protein. Proteins are nutrients made of one or more chains of chemicals. The protein chains forming gelatin are like long, tangled strands of sticky spaghetti. Gelatin is flavored and colored to make jiggly desserts and is also used in marshmallows and other foods.

When gelatin is mixed with hot water, the protein chains separate from one another and can freely move about. As the mixture cools, the proteins begin to recombine by forming bonds (the forces that hold chemicals together) between the chains. The chains connect in a haphazard way, forming a tangled web in which water in the mixture is trapped. This process is called gelling, and the semisolid that is formed is called a gel. The protein web of the gel gives it shape, and the trapped water causes it to be flexible (able to change its shape in response to a force, then recover its original shape when the force is removed); that is, the gel can jiggle. A project problem might be, "How does the amount of water in a gel affect its flexibility?"

Clues for Your Investigation

With adult help, follow the basic directions on a package of dessert gelatin. Make changes only in the amount of water mixed into the dry gelatin for each testing. Keep the amount of gelatin the same and vary only the amount of water for several different gels. Create a scale for testing the flexibility of the gels. For example, shake the gels after they have cooled, and determine on a scale of 1 to 10, with 1 being the least flexible, how easily they return to their original shape.

Independent Variable: Amount of water

Dependent Variable: Flexibility of gel

Controlled Variables: Type of dessert gelatin, amount of dry gelatin used, temperature of water, cooling time, testing procedure for flexibility

Control: Gel made with the median amount of water

Other Questions to Explore

  1. What effect do additives such as flavorings or sugar have on the flexibility of a gel?
  2. What effect does the addition of fresh fruit have on the ability of a gelatin to gel? Canned fruit? Types of fruit—citrus or noncitrus?

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