Food tests: starch, glucose, protein

O/L Science · G.C.E. Ordinary Level · Grades 10–11

Aim

To test foods for starch, reducing sugar, protein and fat.

Apparatus

• Test tubes and a hot water bath
• Iodine, Benedict’s and Biuret solutions
• Food samples and paper

Method

1. Starch: add a few drops of iodine and look for blue-black.
2. Reducing sugar: add Benedict’s solution and heat.
3. Protein: add Biuret solution and look for violet.
4. Fat: rub on paper and look for a translucent spot.
5. Record the results in a table.

Conclusion

Iodine gives blue-black with starch, Benedict’s (heated) brick red with reducing sugar, Biuret violet with protein, and the paper test a grease spot with fat.