AP World History - PBL Component
Pasteurization is a process that kills bacteria by heating milk to a specific temperature for a set period of time. Louis Pasteur first invented pasteurization in 1864; he first began to examine why products like milk, wine, and beer sometimes went sour during the fermentation process. This led to his discovery that the souring was caused by certain unwanted strains of bacteria and yeast, or “germs”, as he called them. Pasteurization kills harmful organisms responsible for such diseases as listeriosis, typhoid fever, tuberculosis, diphtheria, and brucellosis. Pasteurized milk contains low levels of the type of nonpathogenic bacteria that can cause food spoilage, so it is very important to store your pasteurized milk in the refrigerator.
About the Color Changing Milk experiment, milk contains many things, but much of it is made up of water, proteins, and fats. So, when the “grease cutting” soap is added to the milk, the fat and protein chemical bonds are deteriorated and everything gets set loose. The fat and protein molecules practically explode in all directions. The molecules in the food coloring go all over as well, making it easy to see what’s happening. Changes in surface tension also contribute the water molecules in the milk zinging around. When Dawn soap is added, it reeks havoc on the milk and water tension, destroying the bonds that hold everything together. Just look at the colors fly!