This chapter is designed to pull together some basic concepts of food chemistry that are of particular interest for engineering applications. In the simplified model, foods or nutrients that can be categorized chemically as lipids, proteins, carbohydrates, water, minerals, and vitamins along with oxygen, which is obtained from the air we breathe, are utilized by the body to support life. The analogy to a chemical factory can be carried one step further to focus on the manner in which foods are utilized. Foods such as carbohydrates and proteins are large macromolecules that must be reduced to smaller units to be useful in the metabolic processes. Using whole egg protein as a basis, the concept of chemical score for a protein food has been in use for some time. The key assumption in explaining the viscosity/sweetness interaction is that the chemical reactions occurring in taste buds are fast compared to rate of diffusion of sweetener through the carrier medium to taste buds.