Science Project Details:

Using fruit to preserve bread

Difficulty: Advanced 7
Cost ($): 20
Time required: < 2 weeks
1 hour to prepare, 10 days for the science project experiment
Availability of materials:
Bread may be purchased from a bakery or supermarket (eg. Wholefoods)
Required Skills: None
Safety concerns:

None

Abstract

This experiment was performed to compare how adding fruit paste to bread made it last longer without s. The tests were done using paste made from prunes, raisins and dates added to the bread before baking.

Hypothesis

Bread with fruit paste added lasts longer, compared to plain bread.

Background

Food preservation

Food additives are normally added as preservatives to food in order to prevent and inhibit the growth of bacteria, fungi and mold in the food. Some of the commonly used food preservatives include sodium nitrate, calcium propionate and sulfides.

Natural substances like salt, vinegar, alcohol and sugar have been used traditionally through the ages, to help preserve food. Pickling, smoking and salting are some of the methods that have been traditionally used to preserve food for later use. Certain enzymes that are found in fruits can also be used to preserve food. For example, ascorbic acid found in lemons can be used to prevent a cut apple from turning brown.

Baked foods like bread are very vulnerable to mold and bacterial growth. These microbes will thrive at pH levels between 6.5 and 7.5. Adding natural preservatives like prunes, raisins, vinegar and spices like cinnamon can help to control the growth of microbes on bread. Using citric fruits in the bread will help to reduce the pH level and increase its shelf life.

Scientific Terms

Food additives, preservatives, sodium nitrate, calcium propionate, sulfides, enzyme, ascorbic acid

Materials

The materials required for this science project:
- A loaf of plain bread
- A loaf of raisin paste-filled bread
- A loaf of prune paste-filled bread
- A loaf of dates paste-filled bread
- A magnifying glass
- A pair of plastic gloves
- A bottle of disinfected water
- A soap
- A clean towel

Procedure

1. For this experiment, the independent variable is the type of bread used – plain, prune paste-filled, raisin paste-filled and date paste-filled. The dependent variable is the number of days it takes for  mold to appear on the surface of the bread. This is determined by inspecting the bread with a magnifying glass. The constants (control variables) are the size of the bread, the hygiene level of the bakery and the type of packaging used for the bread.

2.  Plain bread, prune filled bread, raisin filled bread and date filled bread loaves are bought from a local bakery. They must be freshly baked in the bakery on the same day. This is to ensure that the source of water, other raw materials and the oven used to make the bread  are the same. The packing and handling method should also be the same for all 4  loaves of bread.

3. The 4  loaves of bread are then left in a cupboard. Before handling the bread, wash your hands with soap and  disinfected water. Wear  plastic gloves after drying your  hands with a towel.

4. The 4  loaves of bread  are inspected everyday with a magnifying glass for  signs of bacteria or mold growth. Do not remove the bread from the packaging. The observations are recorded in the table given below.

Observation

It  was observed that adding the paste made from raisins, prunes and dates into the bread, helped to increase the shelf life of the bread by 2 to 3 days.

Bread type

Shelf life of fruit filled brad and plain bread (days)

1

2

3

4

5

6

7

8

9

10

Plain bread

X

X

X

X

X

X

Prune bread

X

X

X

X

Raisin bread

X

X

X

Dates bread

X

X

X

X

√ - No mold or bacteria found, X - Mold or bacteria found

Conclusion

The hypothesis that  bread baked with fruit paste  will not spoil as quickly as plain bread, is proven to be true.

The use of synthetic preservatives and food additives to various types of foods, fruits and vegetables to make them last longer is a controversial topic that is often debated. Consumption of  synthetic preservatives has been shown to cause several health problems including respiratory difficulties. Even though natural preservatives may be  costlier, their use should be encouraged to avoid the side effects caused by synthetic preservatives.

Also consider

The experiment can also be done by adding cinnamon powder or pounded garlic to the bread.

Try to repeat the experiment under different room temperatures.

References

Preservative - http://en.wikipedia.org/wiki/Preservative

Keeping molds, bacteria at bay - http://baking-management.com/ingredients/bm_imp_7448/

Video(s)