Question

(a) Draw the structure of linoleic acid. Use this structure to indicate the meaning of; i. ii. iii. methylene interrupted double bonds, cis double bonds, the omega terminology. (b) Describe how you would measure an oils saponification value. Include a description of what the saponification tells you about an oil and how the saponification value of coconut oil would compare with the value for peanut oil. (c) Cocoa butters have a high proportion of triglycerides that can be described as symmetrical disaturated oleic glycerol esters. Draw an example of one of these triglycerides and explain how this structure relates to the characteristic sharp and high melting point of cocoa butter. (d) Discuss the 06:03 ratio in the human diet and account for differences in this ratio in the typical Japanese diet, Mediterranean diet and the Western diet. (e) Describe the glass transition and explain the role of aw and temperature in relation to the physical stability of a spray dried milk powder.

Answer 1

The structure of linoleic acid is

HOOC linoleic acid

1. Methylene interrupted bonds related to structural feature of polyunsaturated fatty acids- it actually means the two double bonds of cis-configuration present in linoleic acid that are separated by a single methylene group.

methylene interrupted bonds HOOC lineleierácid

2. Cis double bonds means the configuration of double bond is cis in linoleic acid. The cis configuration means the two hydrogens atoms adjacent to the double bond are on the same side of double bond

linoleic acid HOOC н н н и

3. Omega terminology: it is used in naming of double bonds present in fatty acids. The ω-x notation is used to indicate the position of the double bond which is closest to the −CH3 end in fatty acids

Linoleic acid have unbranched chain of carbon atoms, with a carboxyl group (–COOH) at one end, and a methyl group (–CH3) at the other end. The last atom is labeled as omega and x is the first atom of double bond under consideration.

6 . HOOC wer omega-9 omega-6 omega