Week 3 Food lipids

Question 1

Lipids are..

Answer 1

Fats and oils

Burr & burr (1929) found that fats were essential

Compounds that are soluble in non-polar solvents and are insoluble in water

Question 2

Lipids are important for

Answer 2

1) Palatability - flavour, texture, feeling full
2) Nutrition - lipid bilayers essential for life,40% calories, essential fatty acids (linoleic), vitamin carrier
3) Processing - frying and lubrication in frying with oil

Question 3

Lipids classification

Answer 3

1) Simple - Fatty acids, waxes, mono/di/triglycerides
2) Compound - glycolipids, phosphoglycerides
3) Derived - sterols, fat soluble vitamins

Question 4

Simple lipids

Answer 4

1) Fatty acid
Chains of C and H atoms, with a terminal carboxyl group

2) Waxes
Esters of fatty acids and long-chain alcohols

3) Triglycerides
Fatty acid linked to glycerol (the major food lipid)

** ester link is: O-C=O **

Question 5

Compound lipids

Answer 5

Like triglycerides but more components

(e.g. phosphoglycerides, glycolipids)a

Question 6

Triglyceride

Answer 6

Simple

Glycerol + Fatty acid –> linked via ester bond

1 FA = monoglyceride
2 FA = diglyceride
3 FA = triglyceride

If R groups are same = Simple (triolein)
at least two different = mixed

Question 7

Phosphoglyceride

Answer 7

Compound

Made up of R1, R2, and X

R1 and R2 = fatty acids (Lipophilic- can dissolve in fats/non-polar solvents)

X= choline or ethanolamine (hydrophilic - as they are polar)

Question 8

Fatty acids

Answer 8

Chain of C and H atoms, with a terminal carboxyl group

Properties are derived from the structure of their FA. Small change = BIG effect on health

• Saturated (unhealthy, no double bonds). Named in accord of number of C atoms, including OOH group
• Unsaturated (healthy C=C). Double bonds usually methylene interrupted and conjugated
• Double bonds can be cis or trans.

Cis = alkyl group on the same side (big kink - weaker bonding because further away and more energy to break down)
Trans = on opposite sides (small kink)

Generally straight and even-numbered chains. C4-6
Unusual: branched or cyclopropene rings

Question 8

Fatty acid abbreviation systems

Answer 8

Trivial Names: No clues to structure, typically derive from a source: palmitic acid (palm), oleic acid (olive oil)

IUPAC Names: Follow the International Union of Pure and Applied Chemistry.
Carboxyl carbon is denoted No.1 Name derived from Greek numbering (hex, penta etc)
anoic denotes saturation, enoic denotes unsaturation- di, tri etc denotes the number of double bonds

The carboxyl-reference system: Indicates the no. of carbons and positions of double bonds using numbers: Carboxyl carbon is denoted No. 1

Omega labelling system: Greek letters are used to denote positions relative to the carboxyl carbon. The first carbon after the carboxyl carbon is the alpha carbon. The last carbon, furthest from the carboxyl group, is the omega carbon. Double bonds denoted in relation to omega carbon