Download - Carotenoids
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CAROTENOIDS
Prepared By :- Moksha Chib
Roll No :- 13 FET1003
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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.
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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.
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Structures of common Carotenoids
Lycopene, Acyclic, Red
‘α Carotene ( Bicyclic, Yellow)
‘β Carotene , Bicyclic, Orange
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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.
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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
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Properties of
carotenoids
Quench singlet
electron
Lipophilic, insoluble in water
Bind to hydrophobic surfaces
Easily isomerizes & oxidized
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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.
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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.
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.