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Testing High Carbohydrate Foods

By Muhammad Sahnan SPd, Teacher at SMP Al-Azhar Medan, North Sumatra

Testing High Carbohydrate Foods
The students report on the findings of their experiment to find the highest carbohydrate

MEDAN, NORTH SUMATERA – The nutritional content of foodstuffs can be discovered by using a food test or reagent indicators. The following experiment was carried out during a Grade VII lesson. The reagent used to test for carbohydrate content is called Benedict's reagent which is orange. After samples are tested with droplets of Benedict, the reagent changes color.

The objective of this lesson was for students to test for carbohydrate and find the levels of carbohydrate in foodstuffs. The equipment used to do these tests were a bunsen burner, toothpicks, a spoon, a knife/cutter, mortar, test tubes and a pipette.

The materials needed were the solution of Benedict's reagent, fresh vegetables, tubers, and fruits. For this experiment, each group tested different foodstuffs. The cereals group conducted its experiment on raisins, dates, and cereals. The vegetables group conducted its experiment on mushrooms, broccoli, and cauliflower. The teacher then explained what carbohydrate testing was, and the steps that must be carried out when conducting a test. "Now, please go ahead and find out what foods are highest in carbohydrates" he said.

The steps of the carbohydrate test were outlined on the worksheet. "Blend the ingredients together using a mortar and add a little water. Put some bits of this blended material into a test tube and add droplets of Benedict's reagent at a ratio of 1: 1. Then watch its color change," said one of the students as she read out the steps of the carbohydrate test. The classmates in her group carried out the instructions.

The experiment was not yet complete. The material that had been mixed in a test tube was then heated with a bunsen burner. The results of the experiment by the cereals group were that dates that were initially a brownish yellow color became turquoise after a few droplets of Benedict's reagent were added and after they were heated they became a brick red color which indicated a high carbohydrate content. Raisins that were at first light brown, after a few droplets of Benedict's reagent, became dark green, and after they were heated turned a yellowish brown color, which indicated moderate levels of carbohydrate. Cereal that was milky white, changed color to light blue after a few droplets of Benedict's reagent were added, and after they were heated they turned into an aquamarine blue color which indicated a low carbohydrate content. This group concluded that dates have a higher carbohydrate content than raisins and cereal.

It was similar for the vegetable group that tested mushrooms, broccoli, and cauliflower. Mushrooms have a lower carbohydrate content, broccoli contains a moderate level, and cauliflower have a higher level. This experiment by the vegetable group disproved their initial hypothesis which posited that green leafy vegetables have low carbohydrate content. Each group wrote a report and then presented it to the class and the other groups responded.


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