Natural Pigment
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The document discusses the role of color in food acceptability, emphasizing that color is a critical factor alongside flavor and texture. It differentiates between natural pigments and artificial colorants, outlining their sources, properties, and implications for consumer health. Furthermore, it details the classification and chemical characteristics of various natural pigments, such as chlorophylls, carotenoids, and anthocyanins, as well as their functions in plants and food.
Natural Pigment
- 2. IntroductionIntroduction No matter how nutritious, flavorful, or well textured a food, it is unlikely to be eaten unless it has the right color. Factors which influence the acceptability of color in a certain food: No matter the biases or habits of a given area, certain food groups are acceptable only if they fall within a certain of color array Culture Geography Sociology
- 3. Color acceptability economic worth, i.e. in many raw food materials Color To denote the human eye’s perception of colored materials, part of the electromagnetic spectrum visible to the human eye and generally regarded as lying between 380 - 730 nm i.e. red, blue, or green. Together with flavor and texture, color plays an importantTogether with flavor and texture, color plays an important role in food acceptability.role in food acceptability. Color is mainly a matter of transmission of light for clearColor is mainly a matter of transmission of light for clear liquid foods, such as oils and beverages.liquid foods, such as oils and beverages. Color may provide an indication of chemical changes in aColor may provide an indication of chemical changes in a food, such as browning and caramelization.food, such as browning and caramelization. Pigment Normal constituents of cells or tissues (which iswhich is synthesized and accumulated in, or excreted from, livingsynthesized and accumulated in, or excreted from, living cells)cells) that impart color. It has other properties, i.e. energy receptor, carriers of O2, protectants against radiation
- 4. Dye Colorants used in textile industry, has no place in food usage. Lake A food colorant is synthetically made, absorbed on the surface of an inert carrier (i.e. alumina) and added to processed foods referred to as certified colors Colorant A general term referring to any chemical compound (synthetically made) that impart (communicate) color i.e. dye & lake
- 5. • The colors of foods are the result of natural pigments or of added colorants. • The natural pigments (non-certified colors) are a group of substances present in animal and vegetable products. • Four groups of natural pigments: – tetrapyrrole compounds: chlorophylls, hemes, and bilins – isoprenoid derivatives: carotenoids – benzopyran derivatives: anthocyanins and flavonoids – artefacts:: melanoidins, caramels
- 6. classificationclassification i. Plastid pigments: the pigments are found in plastids which are specialized masses of protoplasm lying in cytoplasm a. Leucoplasts:colourless plastids b. Chloroplasts: green plastids c. Chromoplasts: yellow or orange coloring matter i.e.Carotenoids ii. Sap pigments: the pigments are found in cell sap e.g.Anthocynins
- 7. Non-Certified Colors (natural colors)Non-Certified Colors (natural colors) – Beta-Apo-8’Carotenal – Beta carotene – Cochineal extract/carmine – Grape color extract – Grape skin extract – Fruit Juice
- 8. Non-Certified Colors (natural colors)Non-Certified Colors (natural colors) – Vegetable juice – Paprika oleoresin – Riboflavin – Titanium dioxide – Turmeric – Turmeric oleoresin
- 9. Artificial Color vs. Natural ColorArtificial Color vs. Natural Color • Artificial ColorsArtificial Colors – Obtained by chemical reactions – Relatively stable (in most cases) – Less costly to use – Health concerns • Allergens • Cancer risks? – Consumer acceptability: Questionable • Natural ColorsNatural Colors – Obtained from nature – Processed by physical means – May be less stable than synthetic ones – May be more costly to use. – No health concerns – Benefits to health _ Consumer acceptability: Good
- 10. Pigments Indigenous to FoodPigments Indigenous to Food A. Chlorophylls B. Myoglobin & Hemoglobin C. Antocyanins D. Carotenoids E. Flavonoids F. Proanthocyanidins G. Tannins H. Betalains I. Quinones & Xanthones J. Miscellaneous Natural Pigments
- 11. Green pigments involved in the photosynthesis of higher plants, incl. algae. Location in plants • In leaves, chlorophylls are located in plastid bodies, so called chloroplasts (5-10 long μm; 1-2 thick μm) within it are smaller particles, called grana ( Ф 0.2-2 μm) they are composed of lamellae (Ф 0.01-0.02 μm) chlorophylls molecule are surrounded by lamellae. • In foods, concern focused on chlorophylls a & b occur in approximate ratio of 3 : 1
- 12. Pyrrole pigments • The natural pyrrole pigments contain a complex stable structure formed of four pyrrole nuclei, these structures are known as porphyrins. • Porphyrins: it contain four pyrrole nuclei linked through the β-positions by means of four methylene groups NH N H HN H N Porphyrin
- 13. Synthesis of prophin • Prophin is parent compound of porphyrin NH N H HN H N Porphyrin N H 4CH2O CH3OH
- 14. Structure elucidation of porphyrins • From the IR spectra of porphyrins,functional group can be identified E.g. NH stech occures at 3300 cm-1 • In UV spectroscopy gives 4 absorption spectra at 625 nm, 570 nm, 530 nm, 500 nm. • NMR spectra of porphyrins following strech • Methyl hydrogen shows peak at 6.24 • Meso hydrogen shows peak at 1.22
- 15. Myoglobin is a complex muscle proteins Hemoglobin is the blood pigment • Hb contains 4 polypeptide chains & 4 heme groups, which are planar collection of atoms with the iron atom at the center. • Heme group function : to combine reversibly with a molecule of O2 carried by the blood from the lungs to the tissues. • Myoglobin a quarter its size compared to Hb; consists of a single polypeptide chain (±150 AA units) attached to a single Hb group; it is contained within the cell tissues & it acts as a temporary storehouse for the O2 brought by the Hb in blood. Hb considered the linking together of 4 myoglobins (the discussion of these pigments can be limited to myoglobin)
- 17. Physical properties • Oxygenation reaction Myoglobin + molecular O2 oxymyoglobin (O2Mb) forms bright red pigment • Myoglobin is part of sarcoplasmic proteins of muscle; soluble in water & dilute salt solution. Chemical Properties • Oxidation reaction Myoglobin oxidation metmyoglobin (MMb) forms brown color • Ferrous covalent complexes of myoglobin (purple) with : - Molecular O2 oxymyoglobin - Nitric oxide nitrosomyoglobin - Carbonmonoxide carboxymyoglobin
- 18. Effect of Handling, Processing & Storage • Cured Meat Pigment In commercial practice, sodium nitrite (NaNO2) is the source of nitrous acid: NaNO2 (salt cure) in water Na+ + NO2 - (nitrite ion) HNO2 (in the curing brine) Or using combustion gas (NO2) to smoke or gas-oven fresh meat: 2 NO2 (gas cure) + H2O (in meat) ---> HNO2 (nitrous acid) + HNO3 (nitric acid) Meat Curing:Meat Curing: HNO2 + Mb (myoglobin in meat) NOMb (pink cured meat pigment)
- 19. The formation of cured meat pigments viewed as 2 processes: (1) Biochemical reaction, which reduce nitrite nitric oxide; iron in heme the ferrous state (2) Thermal denaturation of globin heating at 66 C or higher & may involve the coprecipitation of the heme pigment with other protein in meat
- 20. • Packaging Because meat pigment easily reacts with oxygen to produce either an acceptable oxygenated products or unacceptable oxidized products • Carbon monoxide (CO) flushing It was done before sealing of fresh beef very effective for preserving & stabilizing color for 15 days Certain metallic ions (esp. Cu) extremely active in promoting autooxidation of O2Mb to MMb, while Fe, Zn, Al are less active
- 21. A group of reddish water-soluble pigments in plants which exist in the cell sap/juice, i.e. flowers, fruits, vegetables, • An anthocyanin pigment is composed of an aglycone (an anthocyanidin) esterified to 1 or more sugars. Only 5 type of sugars found in it, which are, in order of relative abundance : glucose, rhamnose, galactose, xylose, arabinose • Anthocyanins may also be “acylated” which adds a third component to the molecule, i.e. p-coumaric, ferulic, caffeic, malonic, vanillic, or acetic acids may be esterified to the sugar molecule. Fig. Anthocyanin aglycone
- 22. Stability in Food • The addition of sulfite, sulfite oxide rapid bleaching of the anthocyanins yellowish colors. i.e. in the making of jams, preserves such as dried fruits & vegetables • Anthocyanins show a marked change in color with changed in pH the higher the pH the faster the rate of destruction Chemical Reactions • The reaction with ascorbic acid the degradation of both compounds the intermediate, peroxide produces by ascorbic acid degradation i.e. Cranberry juice cocktail stored at room temperature: 0 days – 9 mg/100 g anthocyanins & 18 mg/100 g ascorbic acid 6 months – ascorbic acid degradation & 80% degradation of anthocyanin
- 23. anthocyanins • Group of anthocyanins: – Chalcone – Flavonones – Flavones – Flavonoids – Flavonols – Cathechins – Anthocyanidins
- 24. anthocyanins • Anthocyanidins which can be found in food (red violet spectrum): – Pelargonidin – Cynaidin – Delphinidin – Peonidin – Petunidin – Malvidin
- 25. Properties of anthocyanins • Anthocyanins are soluble in water • Anthocyanins are amphoteric in nature • Free anthocyanins are neutral are violet in colour,while acid salts of anthocyanins are red and alkali salts are blue • The anthocyanins have been characterized by two absorption bands band I at 475-460 nm(visible region) and band II at 275-280 nm(ultra violet region)
- 26. Identification test for anthocyanins • To extract of pigment in alcohol,add sodium acetate and small quantity of ferric chloride give a blue color • Diluted solution pigment in sodium hydroxide and shake in air so anthocyanindines are decolorised due to oxidation • Anthocyanins converts color from blue to violet when it is diluted in Sodium hydroxide while I sulphuric acid gives orrange
- 27. anthocyanins Isolation of anthocyanins: • The plant petals are dried and powdered. • Extraction with alcoholic HCl so anthocyanins are converted into soluble chloride • To above solution, ether is added to precipitate the pigment. The crude pigment is dissolved in HCl Functions of Anthocyanins: • The anthocyanins may cause an increase in osmotic pressure of cell sap • The beautiful colors of anthocyanins help in attracting the insect and thus assist the plants in cross pollination • Anthocyanins plays important role in photosynthesis and respiration • Anthocyanins may act as light filters,thus hinder decomposition of cholophyll against strong light
- 28. Constitution of anthocyanins • Hydrolysis: hydrolysis of anthocyanin with hydrochloric acid to yeild anthocyanidin and sugar residue • Structure of sugar: the sugar moiety is separated and identified by various chemical methods like benedicts method • Structure of anthocyanidin: • The number of hydroxyl groups in anthocyanidin is determined by employing acetylation and zerewitnoff’s method • The number of methoxy group are determined by zeisel’s method • In order to know the exact structure, when anthocyanidines are treated with KOH it gives Phloroglucinol. • Positions of sugar residues in anthocyanins: • Karrer’s method: Anthocyanin is methylated by dimethyl sulphonate and sodium hydroxide. Then methylated product is hydrolysed with 10% HCl to remove sugar residue.pressence of free hydroxyl group reveals the point of attachment of sugar moiety
- 29. A group of mainly lipid soluble compounds responsible of the yellow & red colors of plants & animal products (430 – 480 nm). • Most of produced carotenoids in nature is in form of fucoxanthin in various algae, in green leaves : lutein, violaxanthin, neoxanthin; β- carotene; lycopene in tomatoes; capxanthin in red peppers LUTEIN kiwi, egg yolk, corn, zucchini, red grapes, pumpkin Good for
- 31. General properties of carotenoids • Contain 40 carbon atom and having molecular formula of C40H56 • All carotenoids contain 7-8 conjugated double bonds in their molecules • In most of carotenoids the central portion of the molecule is composed of four isoprene units • In most of the natural carotenoids,double bonds are in the trans position • They are insoluble in water but soluble in chloroform • Many carotenoids are unstable in to air,heat.they are easily oxidised by atmospheric oxygen • The solution of carotenoids in ether or chloroform give intense blue color with conc.sulphuric acid
- 32. Principal methods in elucidating the constitution of carotenoids 1. Determination of the number of double bonds:the number of double bonds in carotenoids is determined by addition reaction 2. Determination of hydroxyl group can be determined by zerewitnof’s method which consist in the action of Grignard reagents 3. Determination of methoxy group:methoxy group can be determined directly by Zeisel method 4. Determination of carbonyl group:by using of ammonium hydroxide 5. Determination of carbonyl groups: the carboxylic acid groups are determined by titration with alkalis. 6. Determination of side chain methyl group: carotenoids are oxidized by means of alkaline potassium permanganate 7. Determination of isopropylidene groups: the carotenoid is ozonolysed. During ozonolysis the isopropylidene group is converted into acetone which is estimated by iodometrically. 8. Degradation of carotenoids with potassium permanganate and ozone 9. Thermal degradation 10. Spectroscopic studies on carotenoids:IR,NMR and Mass spectroscopy for functional group identification
- 33. Functions of carotenoids 1. Carotenoids perform the role of light filters which protect chlorophyll against disintegration effect of light 2. It act as protector for sensitizing enzymes in the cell 3. Carotene and xanthophylls help in assimilation 4. Certain carotenoids plays important role in the reproduction of algae 5. Carotenoids also take part in redox reaction in plants. 6. They participate in photosynthesis by tranfering their excitation energy to chlorophyl
- 34. B-carotene • Occurs in green plants • Associated with cholophyl • Carrot is richest source of B-carotne • Isolation: the carrots are dried and then these are crushed to fine powder The dried powder is extracted with petroleum ether at room temperature and extract is concentrated at 30-40°c under reduced pressure Carbon disulfide is added to the extract and small of ethanol is added to this solution to remove colorless impurities and to get precipitate of B- carotene
- 35. Constitution of β-carotene • Molecular formula: from analytical date molecular weight of β-carotene was found to be C40H56 • Presence of 11-double bond: β-carotene consist 11-double bonds and it is confirmed by reduction of β-carotene with platinum hence product is obtained having molecular weight C40H78.means 22 hydrogens are added in β-carotene to form per hydro β-carotene • Presence of 5-conjugated double bonds: β-carotene adds five moles of maleic anhydride to form crystaline adduct, it indicates β-carotene contains 5-conjugated double bonds • β-carotene as bicyclic compound: as the molecular formula of fully saturated β-carotene is C40H78.This corrosponds to general formula for Bicyclic compounds like CnH2n-2. hence β-carotene contains two rings
- 36. Constitution of β-carotene • Presence of two Constitution of β-ionone units: when β- carotene is exposed to air, it develops odour of violets and this is characteristics of b-ionone • Presence of methyl side chain: when β-carotene in benzene solution is oxidised with cold aqueous permangnate it yields a mixture β-ionone, geronic acid, 2,2 dimthyl glutaric acid, it reveals that β- carotene consist of methyl side chain
- 37. • Carotenoids include a class of HC, called carotenes, and their oxygenated derivatives, called xanthophylls. • They consist of 8 isoprenoids units joined in such a manner that the arrangement of isoprenoid units is reversed in the center of the molecule. • Forms of carotenoids : (1) free state in plant tissues (crystals or amorphous solids) (2) solution in lipid media, i.e. capxanthin- lauric acid ester in paprika
- 38. • The association of carotenoids with proteins stabilised the pigment & also change the color, i.e. red carotenoid astaxanthin when complexed with protein blue colorant in lobster shells; ovoverdin, the green pigment in lobster eggs; carotenoid-protein complexes found in fruits, vegetables. • Carotenoids may occur in combination with reducing sugars via a glycosidic bond, i.e. CROCIN - containing 2 molecules of the sugar gentiobiose united with crocetin, found as the main pigment in SAFFRON Fig. Red pigment of astaxanthin Fig. LobsterFig. Mud crab
- 39. • Beta carotene is precursor of vitamin A, which yields 2 molecules of vitamin A by cleavage at the center of the molecule. • Stability of carotenoids depend on whether the pigment is in vivo or in vitro in environmental condition, i.e. lycopene in tomatoes is quite stable, but the extracted purified pigment is unstable. Chemical Reactions Provitamin A • Alpha carotene is precursor of one molecule of vitamin A; which is half identical to beta carotene. Oxidation reaction • Enzyme degraded carotenoids rapidly, i.e. lypoxygenase. • In processed food heat, light, presence of pro- and antioxidant influence carotenoids degradation.
- 40. Vegetable juice • Coloring components – Anthocyanins • Solubility: water • Stability: – Light: good – Heat: fair – pH: color changes heavily as pH changes (the lower the pH is, the more condense the color is) • Acidic: red • Neutral: purple • Alkaline: Blue
- 41. Red Radish Color • One of the most stable anthocyanin colors • red in acidic solution • Low odor version available • Both liquid and powder forms available
- 42. Red Radish Color • Keeps red at higher pH up to 6 • Wide applications – Beverage – Tomato paste – Pizza topping – Fruit preparations – Snack foods – Dairy – Confectionery 0038-ralb in a model rice beverage, pH 6.0
- 43. Paprika Oleoresin • Source: – Extracted from red pepper • Solubility: – Oil soluble –ACRC made itACRC made it water dispersiblewater dispersible
- 44. Paprika Oleoresin • Stability – Light: Fair. – Heat: good • Applications: – Seasoning – Snack – Salad dressing – Popcorn – Beverage – Confectionery – Others
- 45. Turmeric Oleoresin (Curcumin) • Source: – Extracted from curcuma longa L., a member of ginger family. • Coloring component: – Curcumin and curcuminoids • Solubility – Fat and alcohol soluble – Cold water insoluble – Commercially dissolve curcumin in polysorbate- 80 or –60 to make it water dispersible
- 46. Turmeric Oleoresin (Curcumin) • Stability: – Heat: good – Light: poor – pH: color hue change with pH • Greenish in acidic pH • Orange yellow in neutral pH • More stable in acidic pH than in neutral or alkaline pH • Color hue: Bright yellow in acidic solution
- 47. Turmeric Oleoresin (Curcumin) • Applications: – Pickle – Bakery – Confectionery – Others – Snack – Pudding – Gelatin – Gummy bear – Yogurt – Popcorn – Finger foods
- 48. Lutein • A member of carotenoids • Solubility: – Oil soluble – We made it water-dispersible • Reasons to use lutein – Extended studies have proved the importance of lutein to eye health – Antioxidant--a free radical scavenger
- 49. Lutein • Applications – As a nutritional supplement can be added to all foods (plain in taste and flavor) – As a natural colorant: can be added to all food (a bright yellow color in water solution)
- 50. Lycopene • Sources: – Synthetic – Extracted from nature, plants or microorganisms • A member of carotenoids
- 51. Lycopene • Solubility • Oil soluble by nature • ACRC has made stabilized and water- dispersible lycopene — for beverage and other food applications
- 52. Isolation of lycopene • Typically, lycopene can be isolated from the juice of tomatoes. • First, tomato pulp is obtained by centrifugation and the resulting pulp is then dissolved in methanol, with additions of calcium carbonate and celite as filtering agents. • After centrifugation, the colored supernatant is filtered. • The colored filter papers are resuspended in the acetone/hexane solvent to redissolve the lycopene. • The lycopene is then partitioned using an aqueous acetone/hexane mixture. • The organic phase containing lycopene can be dried with anhydrous Na2SO4 to remove any residual water.
- 53. Lycopene • Properties – Benefit to prevent prostate cancer – An antioxidant—free radical scavenger – Beautiful orange color in beverage • Applications – As a nutritional supplement, It can fortify every food. – As a natural colorant, it can color every food
- 54. Constitution of lycopene • Molecular formula: C40H56 • Reduction with platinum, lycopene is converted to perhydrolycopene( C40H86). This reactions reveals lycopene contains thirteen double bonds • Ozonolysis of lycopene is carried out, it gives acetone and levulonic acid this reaction reveals that terminal residue of lycopene contains methylheptenone • When oxidation of lycopene is carried out with chromic acid, it yields eight molecules of acetic acid, thereby suggesting that there are six –c(CH3)= groups present in the chain
- 55. • Plants containing betalaines have colors similar to plants containing anthocyanins. • The presence of betalaines in plants is mutually exclusive of the occurrence of anthocyanins. • They consist of red-violet betacyanins (λmax∼540 nm) and yellow betaxanthins (λmax∼480 nm). • Their color is not affected by pH, contrary to the behavior of anthocyanins. E. Betalains
- 56. • Betalains are water soluble and exist as internal salts (zwitterions) in the vacuoles of plant cells. • Plants containing these pigments are restricted to 10 families of the order Centrospermae, e. g., in red beet and also in some mushrooms (the red cap of fly amanita). • The general structure of betalains:
- 57. • About 50 betalains have been identified. The majority have an acylated sugar moiety. • The acids involved are sulfuric, malonic, caffeic, sinapic, citric and p-coumaric acids. • All betacyanins are derived from two aglycones: betanidin isobetanidin
- 58. Betanin • Betanin is the main pigment of red beet. It is a betanidin 5-0-β-glucoside.
Editor's Notes
- #6: Tetrapyrroles are compounds containing four pyrrole rings. The four pyrrole rings are interconnected through one-carbon (methine or methylene) bridges, in either a linear or a cyclic fashion. Because of their ability to form metal complexes, these compounds are particularly important in biological systems.