Chapter 1 Proteins

Chapter 1 - Proteins

Learning Outcomes

• Chemical elements in protein molecules.

• Products of protein digestion: amino acids.

• Definitions and examples:

  • Essential amino acids

  • Non-essential amino acids

  • High biological value proteins

  • Low biological value proteins

  • Complementary proteins

• Food sources of proteins.

• Functions of proteins in the body.

• Cooking processes: denaturation, foaming, coagulation, Maillard browning, gluten development.

Chemical Elements of Proteins

• Proteins are mainly composed of:

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

  • Oxygen (O)

• These elements form basic units called amino acids.

Formation of Protein Molecules

• Formed by joining many amino acids through chemical bonds.

Digestion of Proteins

• Begins in the stomach, with partial digestion.

• Further broken down into amino acids in the small intestine.

Amino Acids

• Essential Amino Acids: 9 required from food (e.g., lysine, valine, leucine).

• Non-essential Amino Acids: 11 produced by the body.

• Total: 20 different amino acids.

Types of Proteins

Biological Values

• High Biological Value Proteins:

  • Complete proteins with all essential amino acids.

• Low Biological Value Proteins:

  • Incomplete proteins lacking one or more essential amino acids.

Complementary Proteins

• Formed by combining two low biological value proteins (e.g., pulses with grains).

Protein Food Sources

• High Biological Value Sources:

  • Animal products (beef, chicken, eggs, dairy, fish).

• Low Biological Value Sources:

  • Plant-based sources (beans, nuts, seeds).

Functions of Proteins

• Growth and Repair: Supports growth and replaces worn-out cells.

• Structural Role: Components in skin, muscles, tendons.

• Transportation: Carries nutrients and gases (e.g., hemoglobin).

• Enzyme Formation: Proteins make enzymes for digestion.

• Immunity: Antibodies protect against harmful microorganisms.

• Energy Reserve: Used when carbs and fats are insufficient.

• Body Movement: Integral to muscle composition.

Reactions Involving Proteins

• Denaturation: Alteration of protein structure due to heat/pH changes.

• Foaming: Proteins trap air when beaten (e.g., egg whites for meringues).

• Coagulation: Solidifying of proteins (e.g., frying eggs).

• Gluten Development: Formation of a protein network in wheat flour mixed with water.