• Carotenoids the major pigments of carrot(Daucus car old).

• lipid soluble compounds responsible of the yellow and red colors.

• Carotenoids are pigments of C40

• There are over 600 carotenoids including beta-carotene.

• Carotenoids have been found to have antioxidative properties

Carotenoids are classified by

(A) their chemical structure

(1) carotenes that are constituted by carbon and

hydrogen

(2) oxycarotenoids or xanthophylls that have

carbon, hydrogen, and, additionally, oxygen.

(B) Clasification of carotenoids1. acyclic, ex: lycopene

2.monocyclic, ex: g-carotene

Bicyclic, ex: a-carotene (III) and b-carotene (IV)

•The relative amounts of different carotenoids are related to the characteristic color of some fruits.

•In the sequence of peach, apricot, and tomato, there is an increasing proportion of lycopene and increasing redness.

Cyclizations lead to the variety of carotenoidstructures

Carrots(Daucus carota)

Oxygenated carotenoids= xanthophylls(more common in fruits)

mango, persimmonmaizespinach

Capsicum(peppers)

brown

algae

Some common carotenoids with cyclic end structures:

crude palm oil has high of Carotenoids 673 mg/kg but it was destroyed by the normal processing and refining operations. gentler processes have been developed resulting a "red palm oil" that retains most of the carotenoids.

Crustaceans contain carotenoids bound to protein resulting in a blue or blue gray color. When crabs is immersed in boiling water (protein denaturationoccurred), the carotenoid-protein bond is broken and the orange color of free carotenoids appear.

• Stable in pH 2-7. At low pH color will change from red orange to orange-yellow due to the formation of alternate structure.•Stable up to 50°C and therefore color is not degraded by most forms of food processing.•C=C double bonds (unsaturated) mean that they are easily oxidized by oxygen in the air causing discoloration, loss of Vit A and off odors.•Metals from knives and cutting surfaces and UV light also catalyze the oxidation.•Food need to be kept wrapped, kept away from light and metal and kept in the refrigerator.

Stability of carotenoids

•Carotenoids in frozen or heat-sterilized foods are quite stable. •The stability of carotenoids in dehydrated foods is poor, should be packaged in inert gas, Ex : Dehydrated carrots fade rapidly

astaxanthin

blue-greenorange-red

cooking

lycopene

The increasing lycopene content of tomatoes during ripening

Lutein

A member of carotenoids

CORN•Corn contains about one-third of the total carotenoids as carotenes and two-thirds xanthophylls.•Compounds found in corn include zeaxanthin, cryptoxanthin, p-carotene, and lutein

Commercially available synthetic carotenoids used as food colorants,1.b-carotene,2.b-apo- 8'-carotenal (apocarotenal) 3. canthaxanthin.-good stability in food applications.

synthetic carotenoids

Conversion of Carotenoids to Retinoids

Enzymatic conversion of carotenoids occurs in liver or intestinal cells, forming retinal and retinoic acid

Provitamin A carotenoids Beta-carotene Alpha carotene Beta-cryptoxanthin

Other carotenoids Lutein Lycopene Zeaxanthin

Carotenoids can be as (1) primary antioxidants by trapping free radicals or (2) secondary antioxidants by quenching singlet

oxygen. -Carotenoids with nine or more conjugated double

bonds are very effective antioxidants. •Carotene, isozeaxanthin, and lutein are all effective singlet oxygen quenchers.

Lycopene and b-carotene are tetraterpenes calledcarotenoids

b-Carotene

Vitamin A

18

17 16

6

54

3

2 1 R R

12

3

45

6

1617

18

R12

3

45

6

1617

18

R2

3

45

61

1617

18

b-end group g-end groupe-end group

End-groups of Carotenoids

12

3

4

5

6

16

17

18

R

CH2R

1

2

3

4

5

616

17 18 R

18

17

16

6

54

3

21

k-end group c-end groupf-end group

End-groups of Carotenoids