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how to test protein content in food
Proteins are an important source of energy. The average energy density of proteins is about 4 kcal/g or 17 kJ/g, which is comparable to carbohydrates. Proteins contain essential amino acids, such as lysine, tryptophan, methionine, leucine, isoleucine, and valine, which are essential to human health. Moreover, proteins play important roles in regulating human body functions, such as catalyze biological activities, and transport nutrients and other biochemical compounds across cellular membranes. In addition, proteins are major structural components of many natural foods, and can affect the texture, appearance, or stability of food products. Thus, it is important to develop methods for analysis of the identification, concentration, structure, and functional properties of proteins in foods, in order to meet labeling requirements for food quality controls.