ABSTRACT
Foods are produced and consumed in a wide variety of forms to provide the necessary nutrients and energy as well as sensory pleasure for humans. Food may be classified into various groups, according to their source of origin (i.e., plant based and animal based), structural or physical properties (solid, semisolid, and liquid), composition (fibrous, gelatinous, starchy, oleaginous, and crystalline), or postharvestprocessing procedure (raw or whole, minimally processed, processed culinary ingredients, and ultraprocessed). In the U.S. Department of Agriculture (USDA) Dietary Guidelines for Americans (www.choosemyplate.gov), foods are classified into five major classes: fruits, vegetables, grains, protein foods, and dairy. On the basis of the optical properties, food may also be classified into transparent (e.g., cooking oils and beverages), semitransparent or translucent (jelly, fruit juices), and turbid or opaque (fruits, vegetables, nuts, grains, meats, dairy, etc.). In transparent foods,
2.1 Introduction .................................................................................................... 19 2.2 Reflection and Transmission ........................................................................... 21
2.2.1 Fresnel Equations for Reflection and Transmission ........................... 21 2.2.2 Diffuse Reflection and Transmission .................................................24
