EFR

• Fats and oils


  Belong to a group called lipids

  
• Fats


  Solid at room temperature, derived from animal sources
• Oils


  Liquid at room temperature, derived predominantly from plants
• Three exceptions are coconut and palm oils, which are solid at room temperature; fish oils are liquid at room temperature

  
• Lipids


  Organic compounds composed of carbon, oxygen, and hydrogen, with relatively little oxygen present and hydrogen comprising a much larger proportion than in carbohydrates
• Lipids provide 9 kilocalories per gram compared with 4 kilocalories per gram for carbohydrates
• Simple Fats/Triglycerides


  The two key components are glycerol and fatty acids, which are linked together to form an ester

  
• Glycerol


  Has three hydroxyl (alcohol or -OH) groups, each of which can be esterified with a fatty acid, making the range of possible simple fat molecules extremely large

  
• There is no double bonds between carbons in saturated fatty acids while unsaturated fatty acids have 2 or more double bonds

  
• A double bond raises the melting point of a fatty acid
• Melting point


  The temperature at which a fatty acid is transformed from a solid to a liquid, requiring a lot of energy in the form of heat to convert a solid to a liquid, thus melting point is high
• When fats are hard (have high melting points) at room temperature, they may be poorly suited for specific preparations, such as creaming a shortened cake mixture
• Degree of unsaturation


  Affects the temperature at which fat melts - the more unsaturated the fat, the more liquid at room temperature, and the more saturated the fat, the firmer its consistency
• At double bonds, the configuration is either cis or trans. If the double bond is in the cis form, the melting point is appreciably lower than when the comparable molecule has a double bond in the trans form.
• Olive oil has more polyunsaturated fatty acids than lard does
• Fatty acids in foods

  • Most vegetables and fish oils are high in polyunsaturated fatty acids
  • Canola and olive oil are high in monounsaturated fatty acids
  • Animals, coconut oil and palm oils are high in saturated fatty acids

  
• Overall, animal origin contains 50:50 P/S ratio, while plant 85:15 P/S ratio
• Oxidative rancidity is accelerated by the presence of some water
• Hydrolytic rancidity requires oxygen
• Rancidity


  The chemical deterioration of the quality of a fat by either oxidative or hydrolytic chemical reactions

  
• Oxidative rancidity


  Involves the uptake of oxygen at a double bond in an unsaturated fatty acid in a fat, when fats are exposed to oxygen
• Reversion


  Another deteriorative change in fats that occurs with only a small amount of oxygen present, resulting in the development of off odors and off flavors, often described as "fishy" or "beany"
• Hydrolytic rancidity


  Begins when fat is broken down to glycerol and fatty acids, promoted by the action of enzymes like lipase, heat and moisture

  
• Water present in the food and increase in temperature will cause rancidity, and the rancid smell is due to the release of free fatty acids
• Oxidative rancidity


  Begins when a free radical forms, often initiated in a polyunsaturated fatty acid, and is facilitated by the presence of certain metals, light and/or warm temperatures
• Storage in tightly closed containers in a cool, dark place helps slow the onset and continued development of oxidative rancidity, but some oxygen still remains in the headspace of the closed container, and eventually oxidation will begin
• Antioxidants


  Can be added to products high in unsaturated fatty acids to delay the problems of oxidative rancidity, as these fats are particularly susceptible to oxidation

  
• The optimal frying temperature is 375F or 191C
• Optimal frying conditions are to avoid water, remove food particles to cool the frying fat
• Frying oils should be discarded when they become darker, more viscous, smoke easily, have a rancid odor, or impart off flavors in food
• Fats and oils produce smoke when they are heated to high temperatures and begin to degrade

  
• Smoke point


  The temperature at which fats and oils begin to degrade and a slight amount of smoke will appear, which varies with the substance being heated and its composition

  
• The higher the saturated fat and monounsaturated blends, the higher the smoke point

  
• Heating beyond the smoke point can affect taste, nutritional value and safety of food
• The approximate smoke point range for oils suitable for high-temperature cooking is 375°F to 450°F (190°C to 232°C)

  
• The type of food being cooked does not influence the smoke point of an oil
• The primary chemical process that occurs when an oil reaches its smoke point is oxidation
• Smoke point


  The temperature at which fat or oil begins to smoke, due to the release of free glycerol, followed by the breakdown of glycerol to acrolein

  
• Flash point


  The temperature at which tiny wisps of fire streak to the surface of a heated substance
• Fire point


  The temperature at which a heated substance bursts into flames and burns for at least 5 seconds