Objective

To compare the gel property of starch and xanthan gum at room temperature       

Background

Food ingredients can have unique behavior during processing based on their physical and chemical properties. This behavior is referred to as their functional property. Examples of functional properties are shown in the figure below. The physical property we will be observing in this lab is gelation. Some complex carbohydrates (polysaccharides) such as starch, pectin and gums (also called hydrocolloids) can affect the viscosity (thickness) of food by absorbing a large amount of water. Hence, they are used as thickening agents. Their ability to control the movement of water also allows them to function as stabilizers, preventing the growth of ice crystals which could damage food texture. For example, gums in ice-cream prevents ice-crystal growth, keeping the crystals small so that the texture remains smooth to the tongue when eating. Examples of gums used in food processing include xanthan gum, guar gum, locust bean, and carrageenan. Xanthan gum, the gum you will be working with in this lab is derived from the bacterium Xanthomonas campestris and is commonly used in gluten-free products to help add structure.

Materials and Equipment

  1. Starch
  2. Xanthan gum
  3. 250 ml measuring cylinder (or disposable plastic cup)
  4. Scale
  5. Stirring rod (or disposable plastic spoon)

Procedure

  1. Label two 250 ml measuring cylinders “starch” and “xanthan gum” respectively
  2. Weight 10 g of starch and xanthan gum and add to the respective beakers
  3. Measure and add 100 ml of water to the samples and mix vigorously for 2-3 minutes
  4. Observe differences

Lab Questions

  1. Describe the difference in viscosity between the starch and the xanthan gum mixtures (2 points)
  2. Did the starch form a gel? If not, what condition is required for starch to absorb water and gel? (1 point)
  3. Based on the differences you saw between the two carbohydrates, what would be a food product application for xanthan gum for which starch would not be suitable? Explain why. (3 points)

Courtney Simons
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Courtney Simons is a food science writer. He holds a BS degree in food science and a PhD in cereal science from North Dakota State University.
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