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Life Sciences Category 30. Which Washing Powder? Washing powders contain detergents, but biological washing powders also contain enzymes which break down larger molecules such as starch and protein into smaller molecules which can then be dissolved in water. The enzymes used are amylases used to break down starch, proteases used to break down protein and lipase used to break down grease and fats. The presence of these enzymes can be demonstrated by their action on starch, milk protein (casein) and fat. Have you ever wondered how biological detergents work and if there is any difference between the different brands available in the supermarket? You might like to: Design an experiment to investigate the effectiveness of a number of biological detergents and their ability to break down: • Starch • Protein • Fat Investigate if their effectiveness decreases: • Over time • With the temperature of the water
Possible Technique: Use a no. 6 cork borer to cut wells in starch/iodine agar, milk agar and mayonnaise agar in agar plates. Add 1% w/v of detergent and measure areas of clear zones. Starch agar: Mix 2 g soluble starch with cold water. Add to 100 cm3 boiling water. Mix 2 g agar powder with cold water. Add to boiling starch solution stirring continuously. Milk agar: Mix 2 g milk powder with 100 cm3 cold water. Heat until boiling. Mix 2 g agar powder with cold water. Add to boiling milk powder stirring continuously until dissolved. Mayonnaise agar: Mix heaped spoonful of mayonnaise with 100 cm3 cold water. Heat until boiling. Mix 2 g agar powder with cold water. Add to boiling mayonnaise stirring continuously until dissolved.
Research Links: https://cd1.edb.hkedcity.net/cd/science/biology/resources/l&t2/practical/Practical-16.pdf https://www.thoughtco.com/how-do-detergents-clean-607866 https://www.persil.com/uk/laundry/laundry-tips/washing-tips/difference-bio-non-bio-detergent.html
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