CAROTENOIDS

Prepared By :- Moksha Chib

Roll No :- 13 FET1003

Introduction

• Carotenoids are red , yellow & orange organic pigments , found in Chloroplast & Chromoplast of Plants & Photosynthetic bacteria.

• Carotenoids are the precursor of Vitamin A & are powerful antioxidants that helps in preventing some form of cancer and heart disease.

• Carotenoids are produced from fats & other basic organic metabolic building blocks found in Plants & Photosynthetic bacteria.

• Carotenoids cannot be manufactured by species in animal kingdom thus , needs to be obtained from the diet.

• Most Carotenoids are oil soluble.

Chemical Structure

• Carotenoids are tetraterpenoids i.e. they are produced from 8 isoprene molecules & contain 40 carbon atoms.

• All Carotenoids demonstrate a basic structure which consist of a hydrocarbon chain of varying length & varying types of end groups.

• Carotenoids contains a conjugated backbone composed of isoprene units, which are usually inverted at the center, imparting symmetry.

Structures of common Carotenoids

Lycopene, Acyclic, Red

‘α Carotene ( Bicyclic, Yellow)

‘β Carotene , Bicyclic, Orange

Colour

• Carotenoids gives colour ranging from pale yellow to bright orange to deep red.

• The C=C interacts with each other , thus forming conjugation which allows electrons in molecule to move freely. As this activity increase , the electrons have more room to move and require less energy to change states. The colour deepens as the conjugated system is extended.

• At least 7 conjugated dB are needed for a Carotenoid to impart colour.

• Cyclization causes some impediment , so α & β carotenes

are orange & red orange in colour respectively.

Classification of Carotenoids

CAROTENES

• Oxygen free Carotenoids which contains only carbon & Hydrogen.

• Readily soluble in petroleum Ether & hexane.

• Found in carrots, Apricots & gives bright orange colour.

• E.g Lycopene, β Carotene

XANTHOPHYLLS

• Contains 1 or more O2 atoms and functions like hydroxy, epoxy, keto, carboxy and methoxy groups.

• Dissolve best in Methanol & Ethanol.

• Generally yellow in colour.

• E.g Lutein, Zeaxanthin

Properties of

carotenoids

Quench singlet

electron

Lipophilic, insoluble in water

Bind to hydrophobic surfaces

Easily isomerizes & oxidized

Food Sources

• Carotenoids in food are mainly found in trans form.

• Major food sources are Carrots, Sweet Potato, Dark leafy greens especially broccoli & spinach , Tomato, Pumpkin, Palm oil & fruits like apricot, Papaya & Mango.

Food Sources - Green

• They contains hydroxycarotenoids, Epoxycarotenoids & Hydrocarboncarotenoid.

• Substantial amount of Chlorophyll is present which masks the orange yellow colour given by the Carotenoids.

• Carotenoids are present in the form of protein – Carotenoid complex.

• Major Carotenoids found in greens are β & α Carotene.

Food Sources – Yellow / Red

• These contains hydrocarbon Carotenoids.

• Apricot, Carrot , Pumpkin are major sources of β & α Carotene.

• Tomato , Watermelon are sources of Lycopene, Phytoenes.

• Carotenoids exists as crystals in these sources.

Food Sources – Yellow / Orange

• These contain Hydroxy Carotenoids, Epoxy Carotenoids which are esterified with straight chain fatty acid esters such as Lauric Acid & Mystic acid.

• These Carotenoids are present in the form of oil solution.

• Food sources are Mango, Papaya, Peach & Orange.

Alpha-Carotene Content of Selected Foods

Food Serving Alpha-Carotene (mg)

Pumpkin, canned 1 cup 11.7

Carrot juice, canned 1 cup (8 fl oz) 10.2

Carrots, cooked 1 cup 5.9

Carrots, raw 1 medium 2.1

Mixed vegetables, frozen, cooked

1 cup 1.8

Winter squash, baked 1 cup 1.4

Plantains, raw 1 medium 0.8

Collards, frozen, cooked 1 cup 0.2

Tomatoes, raw 1 medium 0.1

Tangerines, raw 1 medium 0.09

Peas, edible-podded, frozen, cooked

1 cup 0.09

Beta-Carotene Content of Selected Foods

Food Serving Beta-Carotene (mg)

Carrot juice, canned 1 cup (8 fl oz) 22.0

Pumpkin, canned 1 cup 17.0

Spinach, frozen, cooked 1 cup 13.8

Sweet potato, baked 1 medium 13.1

Carrots, cooked 1 cup 13.0

Collards, frozen, cooked 1 cup 11.6

Kale, frozen, cooked 1 cup 11.5

Turnip greens, frozen, cooked 1 cup 10.6

Pumpkin pie 1 piece 7.4

Winter squash, cooked 1 cup 5.7

Carrots, raw 1 medium 5.1

Dandelion greens, cooked 1 cup 4.1

Cantaloupe, raw 1 cup 3.2

Stability of Carotenoids

• Carotenoids generally have good heat stability as they can hanlde high temp & High pressure processing.

• They work best in pH above 3.5.

• They can be degraded by light , Low pH , Oxygen and enzymes.

• Carotenoids can undergo ISOMERISATION & OXIDATION , stimulated by Light. However, excessive stimulation may result in undesirable flavors & loss in colour due to formation of Volatile compounds.

Factors affecting Carotenoids content

• Maturation & Ripening• During ripening Chloroplasts are degraded & transformed into

Chromoplast , leading to synthesis of Carotenoids ( Alphonso Mango & Tomato ripening).

• Fruit & Vegetable structure• Carotenoids are reportedly more concentrated in the peel than in the pulp of the fruit. E.g. Tomato

• Other Factors• Exposure to the sun light & elevated temp in creases the

Carotenoids biosynthesis.

Effects of Home Processing & Cooking

• Cooking & Blanching• As a result of heat treatment during cooking , Carotenoids may

undergo oxidative degradation, Structural transformation or stereoisomerisation.

• Heating process results in chromplast disintegration, Carotenoids being dissolved in cellular lipids thus leading to a colour shift.

• Canning• Restoring temperature increase the cis isomerisation & reduces the

carotene content due to enhanced oxidation and isomerisation.

Effects of Home Processing & Cooking

• Dehydration• Dehydration results in severe degradation & isomerisation of

Carotenoids specially if the dried vegetables are kept unprotected from light & Air.

• Discoloration of Dried vegetable is promoted by high temperature.

Losses incurred during STORAGE

• Storage at 7-20°C for 16-43 days causes a substantial decrease in total carotenoid content even when fruits are ripened at optimal temperatures.

• Losses in α, β carotene and lutein increases in carrots as storage temp increases above 4°C.

• Both sweet pepper and parsley loose over 20% of their total carotenoid content at cold room storage (7°C) for 9 days.

• Indian Tuber shows irregular behaviour as its Carotenoids content increases with storage at 4°C & 25-30°C but decreases with 15-20°C.

Preservation

• Adeqaute modified atmospheres (MA) & controlled atmospheres (CA) i.e with low concentration of O2 are known to maintain carotenoid content.

• Samples are grown under N2 in the dark in the presence of carbonate sources like NACO3/NaHCO3 and an antioxidant (Pyragallol) which would ensure exclusion of oxygen.

• Avoiding high temperature and protection from light retains the carotenoid content.

• Chloroform, dichloromethane, tert-butylmethyl ether which are distilled solvents free from impurities are also used.

Analysis of Carotenoids

• Analysis of carotenoid can be performed spectrophotometrically such as identifying β carotene using its specific absorption coefficient at 450nm or by HPLC.

• Separations are performed on C18/C30 reversed phase HPLC columns using mixtures of acetonitrile, methanol, chloroform as mobile phases.

• Detection is performed using diode arrays or mass spectrometric detection.