Lipids Flashcards
What are the major food lipid components?
triacylglycerols TAG
What is the most important minor lipid components?
phospholipids
What is a saponifiable lipid?
Saponifiable components have an ester functional group that can be hydrolysed by a reaction with a base
What are EFAs Give 2 examples.
essential FAs: not synthesized in body but can be obtained through diet rich in vegetable oils, seeds and nuts
e.g. linoleic acid and α-linoleic acid
What is a TAG
triacylglycerol = glycerol esterified with 3 FAs
What are the 4 main isomeric forms of TAGs?
- sn-positional isomers: contain same FAs in their structure but at different sn position (PP)
- Chain length isomers: contain same amount of carbons but divided between different types of FAs
- Double positional isomers: contain the same amount of double bonds but with at least one of them at a different position
- cis-trans conformational isomers: they differ by the conformation of their double bond
Which minor lipid components are amphiphilic?
mono and diacylglycerols and lecithin
Which minor lipid component has antioxidant activity and yellow to red pigmentation?
hydrocarbons (has both)
(tocopherols have AO activity)
What are example of fat soluble vitamins?
Vitamins A, D, K and E (tocopherols and tocotrienols)
What does the Iodine Value tell you?
Iodine reacts with double bonded C-C. The higher the IV, the higher the degree of unsaturation
How do you determine FA composition by GC?
- convert FAs to FAMEs
- dissolve FAMEs in an organic solvent and inject it to a FID or MS
On what does the retention time of FAMEs in the GC depend on?
- The length of the chain: smaller FAs move faster than longer FAs
- The presence of no, one or more double bonds: more unsaturated FAs have a longer rt
- The position of the double bonds: the lower the ω, the longer the rt
- The configuration of the double bonds: trans fatty acids elute faster than cis fatty acids
What are the 3 main steps in crystal formation?
supercooling, nucleation and crystal growth
What is polymorphism of fat crystals?
Polymorphism of fats refers to the arrangement of the fat crystals
Three types: alpha, beta’ and beta
Slide 15 for structural differences
What are the properties of alpha, beta’ and beta crystals? Give example of foods they’re found in?
Table slide 16
How can transitions between polymorphs occur?
Transitions occur always towards the formation of more stable polymorphs
This is done by increasing the T above the Tm and allowing the crystals to recrystallize
What is the effect of TAG composition on crystallization?
- Saturated FAs have a higher melting point than unsaturated FAs
- Longer chain FAs have a higher melting point that shorter chain FAs
- The position and configuration (cis/trans) of the fouble bond can also influence the crystallization behavior
- TAGs with similar FA chains tend to form more stable crystals than TAGs with mixed FA chains
What is Solid Fat Content analysis
corresponds to the mass fraction of solid (%) present at a certain T
In Differential Scanning Calorimetry, what is endothermic and what is exothermic?
Melting = endothermic
Crystallization = exothermic
Explain initiation, propagation and termination reactions in lipid oxidation
slide 21
How are epoxides formed?
oxygen attacks near double bond creating the 3 membered epoxide ring
What are the main sources of fat?
vegetable sources: soybean and palm
animal: milk, lard, tallow and fatty fish
What are the differences between seed and pulp oils?
Seed oils are extracted from seeds and pulp oils are extracted from mesocarp (fruity flesh surrounding the seed)
What are the steps in seed oil extraction?
