SEMI

• Fatty acid


  • Carboxylic group
  • Chains of carbons
  • Methyl group (CH3)
• Lipids


  • Category of compounds that includes triglycerides, sterols, and phospholipids
  • Contain carbon, oxygen, and hydrogen
  • Hydrophobic
  • The term "fat" is often used to refer to all the lipids
  • At times, solid lipid is called fat while its liquid form is termed oil
  • Are organic compounds that are soluble in fat solvents (alcohol, ether, acetone, benzene) but insoluble in water
  • Some lipids contain nitrogen, phosphorus and carbohydrates
  • Lipids release more energy compared to carbohydrates
• Lipid family


  • Triglycerides (Fats and Oils)
  • Phospholipids
  • Sterols
• Triglycerides


  • Glycerol- an alcohol compound composed of 3-carbon chain which serves as the backbone for triglyceride
  • Fatty Acids- an organic compound composed of a carbon chain with hydrogens attached and an acid group (COOH) at one end
• Types of fatty acids

  • Saturated (SFA)
  • Monounsaturated (MUFA)
  • Polyunsaturated (PUFA)
• Saturated fatty acid (SFA)


  A fatty acid carrying the maximum possible number of hydrogen atoms
• Monounsaturated fatty acid (MUFA)


  A fatty acid that lacks two hydrogen atoms and has double bond between carbons
• Polyunsaturated fatty acid (PUFA)


  A fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons
• Phospholipids


  Compounds similar to a triglyceride but they have a phosphate group and choline in place of one of the fatty acids
• Sterols


  Compounds composed of carbon, hydrogen, and oxygen atoms arranged in rings
• Dietary fats defined by fatty acid composition

  • Saturated fat
  • Monounsaturated fat
  • Polyunsaturated fat
• MUFA have one double bond between two carbons
• MUFA is predominantly in olive oil (oleic acid), avocado, almonds, peanuts, and margarine
• PUFA have two or more double bonds. Linoleic acid in corn oil, soybean oil, fish oil
• Fatty acids


  • Building blocks for triglycerides and phospholipids
  • Contains a carboxylic group, chains of carbons, and a methyl group (CH3)
  • Higher ratio of carbon and hydrogen to oxygen than in carbohydrates and protein
  • 20 different fatty acids with varied length, saturation, and shape
  • Different structures impart different characteristics
• Saturated fatty acids


  • All the carbons on the fatty acid are bound to hydrogen
  • Usually more solid at room temperature
  • Higher melting point
  • More stable
  • Have 0 double bonds between the carbons
  • Are found in animal products, hydrogenated vegetable fats, & tropical oils (palm & coconut oil)
  • Are solid at room temperature & unhealthy
• Unsaturated fatty acids


  • Some carbons form a double bond with each other instead of binding to hydrogen
• Monounsaturated fatty acid (MUFA)


  Has one carbon to carbon (C=C) double bond
• Polyunsaturated fatty acid


  • Has two or more carbon to carbon (C=C)double bonds
  • More liquid at room temperature
  • Lower melting point
  • Less stable
• Monounsaturated fatty acids


  • Have 1 double bond in the carbon chain
  • Are healthy
  • High levels are in olive oil, canola oil, almonds, & avocado
  • Become semisolid when refrigerated
  • Are liquid at room temperature
• Polyunsaturated fatty acids


  • Have >1 double bond in the carbon chain
  • Some are essential for the body
  • Are found in plant oils like corn, cottonseed, safflower, and sunflower oil
  • Are liquid at room temperature
  • Too much can promote cancer
• Fatty Acids Categories (Chain Length)

  • Short-chain fatty acids (Composed of 6 carbons or less, Liquid at room temperature)
  • Medium-chain fatty acids (Composed of 8-12 carbons)
  • Long-chain fatty acids (14 or more carbons, Most common type of fatty acid in foods)
• Fatty Acids: Categories (Essentiality)

  • Essential Fatty Acids (EFA) (fatty acids that cannot be synthesized in the body, thus, they must be supplied in the diet. These include linoleic acid (parent fatty acid of Omega-6 FA) and a-linolenic acid (parent fatty acid of omega-3 fatty acid))
  • Non essential fatty acid (fatty acids that can be synthesized in the body from essential amino acids. Arachidonic acid (linoleic acid serves as a precursor for its biosynthesis))
• Essential Fatty Acids


  • The body cannot make the essential fatty acids (EFAs)
  • Linoleic Acid & Alpha-Linolenic Acid
  • These EFAs are found in plant oils & plant foods
  • Deficiency characteristics develop when they are lacking in the diet
• Rancidity


  Spoiling of fats through oxidation
• Fats


  • The more double bonds there are, the more susceptible to oxidation and rancidity
• Ways to enhance stability of fatty acids and reduce rancidity

  1. Adding antioxidants

  2. Hydrogenation - addition of hydrogen to unsaturated fat
• Hydrogenation


  Makes fat more "solid" or firm, enhances stability and protects against oxidation, makes it more "shelf-stable"
• Foods where hydrogenated oils are widely used

  • Margarine
  • Shortening
  • Peanut butter
  • Baked goods
  • Snack food
• Benefits of hydrogenation

  • Makes food fats more stable, increasing shelf life
  • Makes fat more "solid" or firm
  • Changes the texture of the fat
  • Oils become more spreadable
  • Changes the characteristics of baked goods
• Risks of hydrogenation


  • Increases amount of trans fatty acids in foods with partially hydrogenated oils
  • Increases liver production of LDLs
  • Decreases liver production of HDLs
• Fatty acid composition of adipose tissue


  Mirrors the fatty acid composition of the diet
• Dietary protein and carbohydrate

  Converted to fatty acids in the liver through lipogenesis
• Phospholipids

  • Hydrophilic on one end; hydrophobic on the other
  • Make up the phospholipid bilayer in the cell membrane
  • Used as an emulsifier in foods
  • Synthesized by the liver
• Sterols


  • More complex than phospholipids or triglycerides
  • Four connecting rings of carbon and hydrogen
  • Do not provide energy
  • Cholesterol is the best known sterol; Not essential in diet
  • Part of cell membrane structure
  • Used to make bile, steroid hormones, provitamin D
• Phytosterols

  • Major plant sterols
  • Important part of sex hormones, vitamin D, bile, adrenal hormones, cholesterol
• Sources of Cholesterol

  • Exogenous: From outside the body. Cholesterol is made by animals. It is only found in animal foods & byproducts.
  • Endogenous: Made inside the human body.
• Exogenous sources of cholesterol

  • Egg yolk (275 mg per egg)
  • Organ meats & crustaceans such as crab, shrimp & lobster (190 mg per 3 ounces)
  • Smaller amounts in the fat portions of animal meats & products like milk
• Cholesterol is a very important molecule in the body
• Cholesterol is made inside the human body, primarily in the liver, from saturated fatty acids