Pigments:Food Colorants, Classification, Role and Extraction

Role and need of Food colorants: their classification, importance of Natural pigments and their classification, presence.

1. DOS&R IN ORGANIC CHEMISTRY TUMKUR UNIVERSITY By PRUTHVIRAJ K Faculty DOS&R in Organic Chemistry KPR. DOS&R in ORGANIC CHEMISTRY TUT

2. Food colourants Substances which add or restore colour in a food, that includes natural/synthetic constituents which are normally not consumed as foods as such ( FSSAI, 2011). Food colours can be classified into three groups; natural food colourants , which refer to ones that are synthesized naturally; nature-identical colorants , which although synthesized in industries, mime the natural ones and finally the artificial/synthetic colourants To restore the original food appearance. To intensify colours that are normally found in food and the consumer will associate this improved colour with food quality. To protect the flavour and light susceptible vitamins. To preserve the identity or character by which food is recognized KPR. DOS&R in ORGANIC CHEMISTRY TUT

3. Classification of food colourants Synthetic colours : These do not occur in nature and are produced by chemical synthesis. Seven synthetic colourants , belonging to four distinct chemical classes , are permitted by the FDA for use in foods and in orally ingested drugs and cosmetics: FD&C Red No. 40, FD&C Red No. 3, FD&C Yellow No. 5, FD&C Yellow No. 6, FD&C Blue No. 1, FD&C Blue No . 2 and FD&C Green No. 3. Citrus Red No. 2 is permitted only for colouring skins of oranges and Orange B for surfaces of casings of frankfurters and sausages . They share the common property of water solubility , being conferred by the presence of one or more sulphonic or carboxylic acid groups ( Parkinson and Brown, 1981) Nature-identical Colours : These colours are also manufactured by chemical synthesis , but do not require FDA certification and are considered chemically and functionally indistinguishable from the same colourant found in nature Natural Colours : Natural food colour is any dye, pigment or any other substance extracted using conventional methods, from vegetable, animal, mineral or other sources capable of colouring food drug, cosmetics or any part of the human body; colours come from a variety of sources such as seeds, fruits, vegetables , algae and insect. KPR. DOS&R in ORGANIC CHEMISTRY TUT

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6. Carotenoids Carotenoids are group of phytochemicals responsible for yellow, orange and red colours of foods and having an important role in the prevention of human diseases and maintaining good health. In addition to being potent antioxidants some carotenoids also contribute to dietary vitamin A. Although the chemistry of carotenoids has been studied extensively, their bioavailability, metabolism and biological functions are only now beginning to be investigated ( Rao and Rao , 2007). ß-Carotene, ß-apo-8-carotenal and canthaxanthin : These are the most commercially important of carotenoids. Beta-Carotene is the isomer of the naturally occurring carotenoid, carotene. Carotene is the pigment largely responsible for the colour of butter, cheese, carrots, alfalfa and cereal grains. The colourant is synthetically extracted with acetone, which results in the all-trans form. Both the synthetic and natural sources of ß-carotene are permitted colour additives ( Marmion , 1991) KPR. DOS&R in ORGANIC CHEMISTRY TUT

7. Betalains Betalains are a group of red and yellow colour water soluble pigments found in red beet, cactus fruits and in some flowers. They are stable to pH range 4-6 but degraded by thermal processing. The sensitivity of betalains to different factors suggests that their application as food colourants is limited. Based on these properties, betalains can be used in foods with a short shelf-life, produced by a minimum heat treatment, and packaged and marketed in a dry state under reduced levels of light, oxygen, and humidity Chlorophyll Chlorophylls have been the least studied of the food pigments. Chlorophylls (E 140) are vegetable pigments that occur naturally in plants and confer colour . Among the five different chlorophylls that exist, only two (a and b) are used in the food industry as colourants . Their complex structure is difficult to stabilize, being this the main drawback of their use in the industry, which has studied mechanisms of retaining or replacing the magnesium ion within the structure. The used commercial colourants of chlorophylls are extracted from alfalfa, and have been employed in dairy products, soups, drinks and sugar confections KPR. DOS&R in ORGANIC CHEMISTRY TUT

8. Anthoxanthins Anthoxanthin is a pigment and is similar to anthocyanin, but it exists in less oxidized state as the oxygen on the central group is uncharged. It is actually a composite of compounds known as flavones, flavonols and flavanones . Anthoxanthins are white, pale yellowish, water soluble pigments found in a plant’s cell sap. They contribute the cream and white colour of cauliflower, onions, white potatoes and turnips. Short cooking is desired. With prolonged heat, the pigment turns into a brownish grey colour . Lycopene Lycopene is the pigment principally responsible for the characteristic deep red colour of ripe tomato fruits and tomato products; it is also found in watermelon, papaya, pink grapefruit and pink guava. Processed tomato products are more available dietary sources of lycopene than fresh tomatoes. Lycopene is a member of the carotenoid family; it is a natural fat-soluble pigment found in certain plants and microorganisms, where it serves as an accessory lightgathering pigment and to protect these organisms against the toxic effects of oxygen and light. KPR. DOS&R in ORGANIC CHEMISTRY TUT

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14. Carotenoids Carotenoids are insoluble red, orange, or yellow & function as accessory pigments in plants: carotene (an orange pigment found in carrots ), lutein (a yellow pigment found in fruits and vegetables ), and lycopene(a red pigment in potatoes).antioxidants Carotenoids are lipophilic pigments that are not soluble in water . They are therefore not located in the vacuoles but in the mebrane structures of plastids (chloroplasts & exclusively in the chromoplasts of flower petals ). Common pigment in the many yellow flowers of the Asteraceae (also known as DYCs = damn yellow composites) KPR. DOS&R in ORGANIC CHEMISTRY TUT

15. The xanthopylls found in the bodies of animals are ultimately derived from plant sources in the diet . For example , the yellow color of chicken egg yolks, fat, and skin comes from ingested xanthophylls (primarily lutein, which is often added to chicken feed for this purpose ) Astaxanthin belongs to the xanthophyllbsubgroup of the carotenoids. Astaxanthin isbfound in microalgae, yeast, salmon, trout, krill,bshrimp,bcrayfish , crustaceans, and the feathersbof some birds. It provides the red color of salmon meat and cooked shellfish . Astaxanthin , unlike some carotenoids, is not converted to vitamin A (retinol) in the human body. While too much vitamin A is toxic, astaxanthin has low toxicity. It is one of the most desirable antioxidants. The primary natural source is the green alga Haematococcus pluvialis . Under high light & salt stress, it accumulates high levels of astaxanthin (up to 40 g of astaxanthin in one kg algae = 4 % dry weight The U.S. Food and Drug Administration (FDA) has approved astaxanthin as a food coloring (or color additive) for specific uses in animal and fish foods only. The European Commission considers it a natural food dye # E161. KPR. DOS&R in ORGANIC CHEMISTRY TUT

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19. KPR. DOS&R in ORGANIC CHEMISTRY TUT Anthocyanins

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31. KPR. DOS&R in ORGANIC CHEMISTRY TUT Tannins

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42. Extraction With solvents - extracted with nonpolar solvents. If the tissue is previously dried, then water-immiscible solvents are used such as petroleum or ethyl ether; with the fresh materials acetone or ethanol are used, which have two functions , extracting and dehydrating solvents. Solvents used in extraction must be pure (without oxygen, acids, halogens) to avoid degradation . Up to now, no solvent is optimal for the extraction of all carotenoids: carbon disulfide is the best solvent, but volatility, flammability, toxicity , and degradation limit its use. Chloride solvents are good, but they show high toxicity; free peroxide ether, despite its efficiency, is not used because of its flammability and volatility; other solvents such as hexane , heptane, and isooctane are not so good for extraction, but their other characteristics are favorable. On the other hand, it must be considered which compounds will be extracted: polar solvents ( such as acetone, methanol, ethanol) are good with xanthophylls but not with carotenes. As a general rule, the extraction process consists of the removal of hydrophobic carotenoids from an hydrophilic medium. The use of nonpolar solvents is not recommended because of penetration through the hydrophilic mass that surrounds pigments is limited, while slightly polar solvents dissolve poorly carotene in dried samples and solubility diminish in fresh samples. Thus, it was postulated that complete extraction can be reached by using samples with low moisture, and slightly polar plus nonpolar solvents. KPR. DOS&R in ORGANIC CHEMISTRY TUT

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44. Extraction Enzymatic and/or aqueous extraction. Food industries have used enzymatic methods to obtain a diversity of products: maize starch, gluten and starch of wheat, gelatin, deboned meat, among others . The main advantages of these procedures are specificity, moderated temperature and pH, treatments are mild, secondary products are scarce, and the final product is almost not affected. In enzymatic processing, enzymes with mixed activities are used because of cell wall complexity. Aqueous extraction has been proposed since 1950 as an alternative to organic solvent. This technology was implemented because of safety and the cheapness of the process, which is based on oil-water insolubility and phases are separated by differences in density. Saponification xanthophylls are usually esterified,279 which produces additional analyses complications, for example, a pigment with two hydroxyl groups can be without one or two positions esterified, which requires both separation and identification. Thus, saponification obtains less complex mixtures when only nonesterified pigments appear. Another advantage of saponification is chlorophyll destruction in the saponified samples. KPR. DOS&R in ORGANIC CHEMISTRY TUT