Digestion et Composants Alimentaires

Digestion

• Digestion is the breakdown of large molecules into smaller nutrients that can be absorbed into the blood.
• Digestion occurs in the mouth, esophagus, stomach, and small intestine.
• Two types of digestion:
  • Mechanical digestion: involves physical processes like chewing, churning, and mixing to break down food.
  • Chemical digestion: involves enzymes breaking down food into smaller molecules.
• Digestion in the mouth:
  • Mechanical: chewing (mastication)
  • Chemical: saliva (enzyme)
• Digestion in the esophagus: mechanical
• Digestion in the stomach: chemical (gastric juice)
• Digestion in the small intestine: mechanical and chemical (intestinal juice)
• Carbohydrates are sugars
• Proteins are made of amino-acids
• Fats are lipids
• Different tests can be used to identify the presence of different nutrients. Different tests are listed in subsequent sections.

Identifying Food Components

• Water: Heating a food sample and observing the droplets of water that form indicates water is present.
• Chlorides: Adding silver nitrate solution and observing a white precipitate confirms the presence of chlorides.
• Calcium: Adding ammonium oxalate to food, then observing a white precipitate, confirms the presence of calcium.
• Reducing sugars (like glucose): The Fehling test , where a brick-red precipitate forms after heating, indicates the presence of reducing sugars.
• Starch: Adding iodine solution and observing a blue-black color change confirms the presence of starch.
• Proteins: The Biuret test, where a violet color develops, confirms the presence of proteins.
• Lipids: The Sudan III test which produces a reddish-orange color confirms the presence of lipids.
• Coagulation: Observed for proteins. The test shows protein coagulation if the substance curdles (thickens) upon heating or acid addition confirming the presence of proteins.