Lipids
Introduction to Lipids
Function of lipids in food
1. Texture (mayo, chocolate)
2. Nutrition (energy supplier, antioxidant)
3. Flavour (flavour compounds dissolved in the fat)
Definitions of lipids
Lipids: a broad range of compounds that are soluble in organic solvents
- Lipids aren’t soluble in water (polar) due to their long hydrocarbon chains
Distinction between fat and oil
Fat solid state at room temperature
Oil liquid state at room temperature
Classification of lipids
Classification of lipids is based on;
- saponifiable and unsaponifiable lipids
Classification of fatty acids is based on;
- saturated and unsaturated fatty acids
Classification of lipids
Most lipids have a lot of saponifiable compounds and just a small amount of unsaponifiable
compounds
Saponifiable fraction
- Triacylglycerides (main fraction)
- Mono- and diacylglycerides
- Waxes
- Sterol-esters
- Phospholipids
- Glycolipids
,Unsaponifiable fraction
- Tocopherols
- Sterols
- Hydrocarbons, carotenoids etc
- Fat-soluble vitamins
- Hydrocarbons
- Some polyphenols
- Odour and taste compounds
Structural differences between saponifiable and unsaponifiable lipids
Saponifiable lipids contain ester bonds that can be saponified
Saponification: triglycerides are reacted with sodium or potassium hydroxide (lye) (NaOH or KOH) to
produce glycerol and a fatty acid salt, called "soap."
- NaOH/KOH hydrolyzes the ester bond
- Producing two unsaponifiable compounds; a sterol and a free fatty acid
EXAMPLE
The main compound: Triacylglycerides
Triacylglyceride: ester of glycerol and 3 fatty acids
Positions of fatty acids;
- Sn1: connected to first carbon
- Sn2: connected to second carbon
- Sn3: connected to third carbon
Saturated and unsaturated fatty acids
, Notation of fatty acids
C18:2= 18 carbon chain with 2 double bonds
- Counting the position of the FIRST double bond from the methyl group (CH3) on the
LEFT and indicated by ω
- Counting the position of the FIRST double bond from the acid group (COOH) on the
RIGHT and is indicated by Δ
Questions from slides
Fatty acid composition
All lipids have their own fatty acid composition
Division of oils and fats
Fats and oils are often characterized by determining the fatty acid composition of their triglycerides
Division can be made into 4 groups
1. Deposit fats from animals
o Contains primarily C16 and C18 fatty acids
o Relative high amount of saturated fatty acids
2. Milk fats
o Large variety in fat composition
o High amount of short chain fatty acids
o Trans-configuration of some unsaturated bonds
3. Fish oils
o Large variety in fatty acid composition
o High amount of unsaturated fatty acids with long chains
o Sensitive to oxidation reactions
4. Vegetable oils
o Contains primarily C16 and C18 fatty acids
o Mono- or polyunsaturated fatty acids
Introduction to Lipids
Function of lipids in food
1. Texture (mayo, chocolate)
2. Nutrition (energy supplier, antioxidant)
3. Flavour (flavour compounds dissolved in the fat)
Definitions of lipids
Lipids: a broad range of compounds that are soluble in organic solvents
- Lipids aren’t soluble in water (polar) due to their long hydrocarbon chains
Distinction between fat and oil
Fat solid state at room temperature
Oil liquid state at room temperature
Classification of lipids
Classification of lipids is based on;
- saponifiable and unsaponifiable lipids
Classification of fatty acids is based on;
- saturated and unsaturated fatty acids
Classification of lipids
Most lipids have a lot of saponifiable compounds and just a small amount of unsaponifiable
compounds
Saponifiable fraction
- Triacylglycerides (main fraction)
- Mono- and diacylglycerides
- Waxes
- Sterol-esters
- Phospholipids
- Glycolipids
,Unsaponifiable fraction
- Tocopherols
- Sterols
- Hydrocarbons, carotenoids etc
- Fat-soluble vitamins
- Hydrocarbons
- Some polyphenols
- Odour and taste compounds
Structural differences between saponifiable and unsaponifiable lipids
Saponifiable lipids contain ester bonds that can be saponified
Saponification: triglycerides are reacted with sodium or potassium hydroxide (lye) (NaOH or KOH) to
produce glycerol and a fatty acid salt, called "soap."
- NaOH/KOH hydrolyzes the ester bond
- Producing two unsaponifiable compounds; a sterol and a free fatty acid
EXAMPLE
The main compound: Triacylglycerides
Triacylglyceride: ester of glycerol and 3 fatty acids
Positions of fatty acids;
- Sn1: connected to first carbon
- Sn2: connected to second carbon
- Sn3: connected to third carbon
Saturated and unsaturated fatty acids
, Notation of fatty acids
C18:2= 18 carbon chain with 2 double bonds
- Counting the position of the FIRST double bond from the methyl group (CH3) on the
LEFT and indicated by ω
- Counting the position of the FIRST double bond from the acid group (COOH) on the
RIGHT and is indicated by Δ
Questions from slides
Fatty acid composition
All lipids have their own fatty acid composition
Division of oils and fats
Fats and oils are often characterized by determining the fatty acid composition of their triglycerides
Division can be made into 4 groups
1. Deposit fats from animals
o Contains primarily C16 and C18 fatty acids
o Relative high amount of saturated fatty acids
2. Milk fats
o Large variety in fat composition
o High amount of short chain fatty acids
o Trans-configuration of some unsaturated bonds
3. Fish oils
o Large variety in fatty acid composition
o High amount of unsaturated fatty acids with long chains
o Sensitive to oxidation reactions
4. Vegetable oils
o Contains primarily C16 and C18 fatty acids
o Mono- or polyunsaturated fatty acids
