Water Content in Fruits and Vegetables

Grade Level: 5th - 7th; Type: Life Science

Objective:

This project is about determining the water content of fruits and vegetables and determining whether it is related to the nutritional value of the food. The goal is to get students thinking about the properties of healthy foods.

Research Questions:

• What is the water content of fruits and vegetables?
• Does the water content of in a single serving of produce relate to the total protein content in a serving of that food?
• Does the water content of a single serving of produce relate to the total mineral content? What about the total vitamin content?

In varying degrees, the fruit and vegetables that we eat are composed of water. While high water content is loosely associated with higher values of macronutrients such as protein, it is not necessary associated with vitamin and mineral content.

Materials:

• Orange, pineapple, watermelon, fresh peas, tomato or broccoli
• Dehydrator
• Good scale sufficient for measuring mg. (triple beam or electronic)
• Calculator
• Internet access

Materials are available from the kitchen and the grocery story. The dehydrator is available at good kitchenware stores. The scale balance can be found in a lab. If such a scale is not available, look into using a very good kitchen scale.

Experimental Procedure:

1. Weigh each fruit and vegetable separately and note its weight. For some fruits (such as a watermelon), weighing a serving size of the fruit will be more appropriate.
2. Cut the produce up into thin slices and put it into the dehydrator. You may have to dehydrate each item separately. Just make sure that you dehydrate all of the pieces of a fruit together.
3. Weight the dehydrated produce.
4. Calculate what percentage of the fruit or vegetable is water by subtracting the dehydrated weight from the hydrated weight. Divide this value by the entire weight of the fruit and multiplying by 100.
5. Make a chart comparing the water content of the fruits and veggies.
6. Go to the USDA web site (found in the Bibliography) and find the nutrient value of each food.
7. If the student has time, repeat this experiment with other foods.

Terms/Concepts: Water content; Dehydration; Protein; Carbohydrates; Vitamin D; B vitamins; Macro-nutrients; Micro-nutrients

References:

Books

Bauer, Joy. The Complete Idiot’s Guide to Total Nutrition (Fourth Edition), 2005.

Rockwell, Lizzy. Good Enough to Eat: A Kid’s Guide to Food and Nutrition, 2009.

Websites

USDA Nutrient Data Laboratory

http://www.nal.usda.gov/fnic/foodcomp/search/