Introduction: (Initial Observation)
Minerals are among the important nutrients that our bodies need. Different fruits and foods contain different types and different amounts of minerals. In this project you will compare different foods or fruits for their mineral contents.
A question or another title for this project may be:
“Which fruits contain more dissolved minerals?”
You must collect food samples or fruit samples, juice them to extract a solution of minerals and then test them for the concentration of minerals. Some of the foods or fruits you may try are tomato, potato, carrot, lemon, orange.
Find out about minerals, their properties and their function in our bodies. Read books, magazines or ask professionals who might know in order to learn about the physical and chemical properties of minerals and the ways they can be tested. Keep track of where you got your information from.
Following are samples of information you may find:
Different types of minerals in food products
|Calcium||Calcium is vital for building strong bones and teeth. The time to build strong bones is during childhood and the teen years, so it’s very important to get enough calcium now to fight against bone loss later in life. Weak bones are susceptible to a condition called osteoporosis, which causes bones to break easily.||Milk and other dairy products such as yogurt, cheese, and cottage cheese are good sources of calcium. You’ll also find this mineral in broccoli and dark green, leafy vegetables like kale. Soy foods and foods fortified with calcium, including some kinds of orange juice and soy milk, are also good sources.||Teen guys and girls need 1,300 mg (milligrams) of calcium each day.|
|Iron||Iron helps red blood cells carry oxygen to all parts of the body. Symptoms of iron-deficiency anemia include weakness and fatigue, lightheadedness, and shortness of breath.||Iron-rich foods include red meat, pork, fish and shellfish, poultry, lentils, beans and soy foods, green leafy vegetables, and raisins. Some flours, cereals, and grain products are also fortified with iron.||Teen guys need 11 mg of iron a day and teen girls need 15 mg. Girls need higher amounts because they lose iron through blood during menstruation.|
|Magnesium||Magnesium helps muscles and nerves to function, steadies the heart rhythm, and keeps bones strong. It also helps the body to create energy and make proteins.||You get magnesium from whole grains and whole-grain breads, nuts and seeds, leafy green vegetables potatoes, beans, avocados, bananas, kiwifruits, broccoli, shrimp, and chocolate (yes, chocolate!).
||Teen guys need 410 mg of magnesium each day and girls need 360 mg.|
|Phosphorus||Phosphorus helps to form healthy bones and teeth. It also helps the body to make energy. It is part of every cell membrane, and every cell in the body needs phosphorus to function normally.||Phosphorus is found in most foods, but the best sources are dairy foods, meat, and fish.||Teen girls and guys should aim for 1,250 mg of phosphorus each day.|
|Potassium||Potassium helps with muscle and nervous system function. It also helps the body to maintain the balance of water in the blood and body tissues.||Potassium is found in broccoli, potatoes (with skins), leafy green vegetables, citrus fruits, bananas, dried fruits, and legumes such as peas and lima beans.||Teen girls and guys should aim for 2,000 mg of potassium each day.|
|Zinc||Zinc is important for normal growth, sexual development, strong immunity, and wound healing.||You’ll find zinc in red meat, poultry, oysters and other seafood, nuts, dried beans, soy foods, milk and other dairy products, whole grains, and fortified breakfast cereals.||Teen guys need 11 mg of zinc a day and teen girls need 9 mg.|
Picture in the right shows a sample of power juicer and a sample of blender. Juicing fruits and vegetables is a good way of getting the nutrients out of the fruit and have a nutritious fruit.
Initially the juice may not be clear. Floating solids will make the juice cloudy (like the beaker in the right). Filtration using a fine filter paper will produce a clear solution that may be colored depending on the type of the fruit (like the beaker on the left).
Also see the following links for some related information:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
Question is: Which fruits contain more dissolved minerals?
The purpose of this project is to compare different vegetables and fruits for their minerals concentration. Vegetables such as carrot, broccoli, onion, potato and celery may be tested. Fruits such as apple, orange, tomato, watermelon, and banana may be tested.
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable (also known as manipulated variable) is the fruit or vegetable. Possible values are carrot, broccoli, onion, potato, celery, apple, orange, tomato, watermelon, and banana. (Try at least 3 fruits or vegetables)
Dependent variable (also known as responding variable) is the concentration of dissolved minerals.
Constants are the experiment method and the amount of each fruit or vegetable juice to be tested.
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
This is a sample hypothesis:
Among potato, tomato and cucumber, potato is the one that has the highest amount of minerals. My hypothesis is based on my gathered information about plant growth and the way plant roots absorb nutrients from the soil. Since potato is really a root, it most likely has the most amount of minerals.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment: Extracting minerals from fruits or vegetables
Introduction: To extract water soluble minerals, we may wash them away from fruit and then concentrate and crystallize them. This process must be done with extra care because most minerals are inside the plant cells; so somehow the cell membrane must brake open to release the cell content. We may not use heat in this process because many fruits and vegetables will form a gel when heated. Formation of gel makes the process more complex because we will need to do filtration of hot liquids. For the vegetables or fruits you test, you must decide if you want to test the entire fruit including seeds and skin or you just want to test the edible portion of the fruit.
- Get about 1 kilogram of the fruit or vegetable you want to test. Wash and dry them before going to the next step. Measure and record the exact weight of your fruit sample. (It would be more scientific if I would say “Measure and record the exact mass of your fruit sample.”, but I am trying the make it more user friendly. Some students may not know what is the difference between the weight and the mass. A simple answer is that weight will change depending on your location. For example you weigh less on the top of Everest mountain or on the moon, but your mass will remain the same. Mass is the same as weight at sea level.)
- Cut the fruit to small pieces and run them through a power juicer. Collect all the juice. Then remove all the collected pulp (that may still contain some minerals), mix the pulp with one cup of water and transfer pulp-water mixture to a blender and mix them at high speed for a few minutes. The blades of the blender will brake open more cells and release more minerals in water.
- Use a fine filter paper to filter the juice and the pulp mix. Add additional distilled water to the mixture if it helps the filtration process. You must get a clear solution before going to the next step. The filtered juice of some fruits and vegetables may contain some color; however, it must be clear.
- Transfer the clear juice to a heat resistant glass container, heat it up slowly until all the water evaporates. (This is a slow process. Using excess heat to accelerate the drying process will cause the liquid to splash around at the last few moments and ruin your experiment.)
- Scrape the remaining dry minerals and collect them in a small container. Measure and record the mass of collected minerals.
Repeat the above procedures for every additional fruit or vegetable you want to test. Your results table may look like this:
|Fruit or vegetable||Initial mass
|Ratio of minerals|
Ratio of minerals is calculated by dividing the mass of extracted minerals by the initial mass of fruit or vegetable used for test.
Note: Fruits with high content of sugar, oils and other organic substances may form a gummy substance after heating. More heat is required to evaporate or burn this gummy substance. This part of heating must be done outside in an open space or under a well ventilated hood.
Make a graph:
When your results table is ready, use the data in table to draw a graph for visual presentation of your experiment results.
Make a bar graph with one vertical bar for each fruit or vegetable you choose to test. The height of each bar shows the ratio of the minerals in fruit or vegetable it represents. Use 5 centimeters for each one percent of minerals; so, the height of 20 centimeters indicates 4% minerals.
Are there other methods for measuring the amount of minerals in food?
Yes There are.
- In chemistry laboratories devices such as flame photometers are used to identify and measure the amount of metal ions such as Sodium, Potassium, Iron and Zinc in the clear filtered juices.
- When an organic substance such as a fruit is placed in extreme heat; all the organic matter will burn, evaporate and decompose. What remains is a mixture of different minerals. This method is also known as calcination.
None of the above two methods are recommended for young children due to expensive equipment and the risks associated with excessive amounts of heat.
Materials and Equipment:
This is a sample list of materials:
- Power juicer
- Distilled water
- Beakers or Pyrex glass cups, pots or pans
- Filter paper MiniScience Part # P601
- Other kitchenware and plastic containers.
- Hi precision jewelry scale or laboratory scale with ability to measure 0.01 gram or better.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Your results may vary depending on the type and the source of fruits you test. It is important to report your own results even if it is very different from results provided by others. Sample results indicates that an average size apple has about 185 milligram minerals (1 gram = 1000 milligrams). A medium banana has 546 milligrams of minerals*.
* Compiled from data available at:
Make sure you write your calculations in this part of your report.
Summery of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
It may not be possible to find a book or other type of publication that is discussing the exact subject of this project “Minerals in foods”; however, you may find many books that discuss food chemistry, general chemistry, analytical chemistry and biology that are all somehow related to this project. Find such books; review them for related information and list them as your references or bibliography.