Demonstration: Blood stains are notoriously difficult to remove from fabric. Compare saliva with several cleaning products to see which ones remove blood stains more effectively. How does saliva compare with “mass-produced” detergents (Tide, Dawn, etc.) versus “natural” cleaning products (Mrs. Meyers, other “natural” soaps, etc.)?
Many dish soaps claim to contain enzymes that help digest and remove stuck-on food from dishes, just like the enzymes in saliva. Design an experiment to test how different dish soaps compare to saliva when it comes to digesting different kinds of foods (starchy foods, meats, cheese, fruit, etc.)