Pectin: structural properties

Question 1

Sources and uses of commercial pectin: Why it is used in all these products?

Answer 1

Sources: apple pomace and citrus peel.
Uses: juice concentrates, jams, ketchups, dressings, fruit drinks…
-Because of the gelling property that pectin has.

Question 2

Where do we find pectin ?

Answer 2

Pectin is present in all cell walls of plant material,in the:
• Middle lamella (mainly).
• Primary cell wall.
• Secondary cell wall (small amounts).

Question 3

Structural properties:

Answer 3

It has hairy regions and smooth regions and the hairy region.
The smooth region the polygalacturonan is the part of the main chain where we have the galacturonic acids (this is the part where the gelling is made with ). Has about 200-500 units. Main chain consist of alfa 1-4 linked galacturonic acids.

Question 4

What is a GALACTURONIC ACID ?

Answer 4

Uronic acids, they have an acid group COOH:
• Glycosidic bond of uronic acids is relatively strong.
• Building block of (heat) stable polysaccharides

Question 5

Name the three URONIC ACIDS and put and example of a polysaccharide that have it:

Answer 5

• D-galacturonic acid: pectin
• D- glucuronic acid: gum arabic
• D-manuronic acid: alginate
• L-guluronic acid: alginate

Question 6

Methyl-esterification of the pectin (DM: degree of methyl-esterification)

Answer 6

Few of the acid groups of the chain are methylated:

• High methylated: HM- pectin >50%
• Low methylated: LM-pectin <50%