The chemistry of trans fats

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• The chemistry of trans fats

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Role of lipids in foods

• Texture
• Cooking medium
• Color
• Flavor
• Rancidity
• Nutrition

Dependent on levelof unsaturation
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Impact of unsaturation on melting point
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Impact on saturation at the molecular level
Linoleic Acid
Stearic Acid
Melting Point 70ºC Solid
Melting Point -5ºC Liquid
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Physical and chemical properties of desirable
food lipids

• Has proper melting properties
• Mouth Feel
• Baking
• Has good oxidative stability
• Has good nutritional attributes

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Formation of trans fatty acids by biohydrogenation

• Ruminants (extra stomach) contain microflora that
  aid in food digestion
• Ruminant microflora contain enzymes that
  hydrogenate unsaturated fatty acids
• This biohydrogenation has a number of
  intermediates that have trans fatty acids

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Chemical hydrogenation

• Chemical hydrogenation was first used on food
  oils in the early 1900s to use cottonseed oil as
  a lard replacement (Crisco)
• The use of hydrogenated oils increased during
  WWII as margarines were substituted for butter
• Today, hydrogenation is used to both make liquid
  oils solid, and to increase the oxidative
  stability of oils

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Chemical hydrogenation begins with oil refining

• Solvent extracted seed oils contain many
  components that negatively alter the properties
  of foods and oils
• Phospholipids
• Water absorption and browning
• Off-colors
• Free fatty acids
• Rancidity, flavor and smoke point
• Off-flavors

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Physical vs chemical refining

• Chemical refining uses two steps
• Neutralization
• Remove free fatty acids
• Deodorization
• Volatile off-flavors
• Physical refining uses one distillation step that
  removes both free fatty acids and off-flavors
• Requires higher temperatures
• Has higher oil recovery

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Differences between trans fatty acids in bio- and
chemical hydrogenation
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Alternatives to hydrogenation without increasing
saturated fatty acids

• Frying oils oxidative stability
• Oils naturally low in 183 (corn, cottonseed and
  GMO)
• High oleic/low linoleneic oils (breeding or GMO)
• Baking plastic range
• Fractionation
• Blends
• Interesterification

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Nutritional implications of interesterified lipids

• Saturated fatty acids are more bioavailable at
  the sn2 position of triacylglycerols
• Triacylglycerols with high sn2 saturated fatty
  acids can have more of an impact on increasing
  LDL cholesterol
• Interesterification could either increase or
  decrease the concentration of saturated fatty
  acids at sn2 depending on starting lipids and
  technique used

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Conclusions

• Food oils need to have the proper melting
  characteristics and good oxidative stability
• Use of hydrogenation to accomplish these goals is
  hampered by the formation of nutritionally
  unfavorable trans fatty acids
• Alternatives exist to replace hydrogenated fatty
  acids by utilizing oils with desirable fatty acid
  compositions via blending, breeding and genetic
  modification
• However, it will be difficult to remove all trans
  fatty acids since they are formed during oil
  refining

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