Preservatives (page 2)

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Author: Janice VanCleave

Try New Approaches

  1. How effective is calcium propionate in breads other than white bread? Repeat the experiment using different types of bread. such as wheat, rye, and potato. Science Fair Hint: Record results of the original as well as this experiment and display the data tables.
  2. Does temperature affect the effectiveness of the preservative calcium propionate? Repeat the original experiment using two sets of bread samples. Place one set in the refrigerator and place the second set in a warm area such as on top of a refrigerator. Science Fair Hint: Take photographs as each experiment progresses to show the changes in the food as a result of containing or not containing calcium propionate.

Design Your Own Experiment

Note: Avoid touching the food test samples. The food samples are not edible and should be discarded after the experiments.

  1. Drying foods was one of the earliest methods of food preservation. This method is based on the fact that the organisms known to spoil food do not grow and reproduce without water. Find out more about procedures for preserving food by drying. Place dried and fresh food samples in open dishes (beef jerky and strips of fresh beef make good samples). Examine the food samples daily for evidence of spoilage and determine the effectiveness of drying as a method of preserving.
    1. Table salt (sodium chloride) and vinegar (acetic acid) are used as preservatives. Test the effectiveness of these preservatives on inhibiting microbe growth. Dissolve one chicken bouillon cube in 1 cup of (250 ml) of hot water. Divide the solution equally between three clear glasses. Add 1 teaspoon (5 ml) of salt to one glass and 1 teaspoon (5 ml) of vinegar to the second glass. The third glass is the control. Label the glasses accordingly. Place the glasses in a warm place and examine their contents daily. Spoilage due to the presence of microbes results in a solution that looks cloudy, has an odor, and often contains gas bubbles.
    2. Does the amount of preservative added change the results? Repeat the experiment two times, first using one half as much salt and vinegar, and then using twice as much salt and vinegar.
  2. Many foods are spoiled by the growth of various fungi in the food. Favorable conditions such as moisture and warm temperature encourage rapid reproduction of fungi. Sugar is used as a preservative for fruits because it aids in removing moisture from the cells of the fruit. Fungi are less likely to grow in the dryer fruit. Demonstrate sugar's ability to dehydrate fruit cells by peeling an apple and cutting it into small pieces. Place the pieces into a jar and add 1/4 cup (62 ml) of granulated sugar and stir. Secure the lid on the jar. After about 24 hours, the apple pieces will be surrounded by a thick solution of the sugar dissolved in water from the fruit's cells. Use diagrams showing the changes in the jar to represent the dehydrating property of sugar. As part of a display, show pictures of products that use sugar as a preservative. Note: Salt also dehydrates and, like sugar, preserves by drying out food such as meat.
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