*5.2.3.5 Case study-8*

The solubility of bixin in oil and norbixin in water determines its usage. Annatto dye formulations suitable for dairy products like cheese and butter were developed and compared to their commercially available counterparts [55]. Three formulations were prepared; water-soluble solution using K2CO3, oil-soluble formulation using vegetable oil, and oil/water-soluble formulation using propylene glycol solution. The formulations were applied at different concentrations in cheese and butter. Lovibond Tintometer was used to measure the color of the commercial and experimental samples. Annatto dye oil/water soluble propylene glycol formulation was found to be the most effective formulation for imparting yellow color with good brightness to various dairy products (**Table 10**). Butter containing 3.75 mg/kg and 5 mg/kg of oil/water propylene glycol formulation closely resembled the commercial butter samples made using synthetic dyes. In the case of cheese, creamy yellow shade imparted by oil/water propylene glycol formulation at a concentration of 3.75 mg/kg looked very similar to the color of the commercial cheese sample.


#### **Table 10.**

*Lovibond tintometer readings of commercial and experimental test samples of butter and cheese.*

#### **5.3 Cochineal**

Cochineal is a natural dye made from the pulverized and dried corpses of a female sessile parasite found in tropical and subtropical South America and North America. Dyeing of cochineal extract is mainly practiced in Mexico and Peru. Cochineal extracts have been used over ages as colorant for food, textiles, cosmetics, pharmaceuticals, and plastic applications.

The dye has mostly been used in the dyeing of silk, wool, cotton, and natural pigments (lakes) obtained from cochineal insects were used for paintings, frescoes, and restoration processes [56]. It's the only natural red color that's been allowed by the FDA for use in food and cosmetics, and it's frequently used as a substitute for the infamous Red Dye #2.

**Genus**: Dactylopius | **Species**: coccus | **Family**: Dactylopiidae.

**Common name**: Cochineals | **Local name**: *Cochineal keet.*

**Part of the plant used for coloring:** Cochineal insects are found on the pads of prickly pear cacti in the genus *Opuntia* or *Nopalea* and are collected by brushing them off the plants, killed (by immersing in hot water or exposure to sunlight, steam, or dry heat of an oven), dried and powdered to get the dye. One pound of cochineal nectar requires 70,000 insects.

#### *5.3.1 Coloring pigment/component*

The important color producing components in cochineal extract are carminic acid, kermesic acid and flavokermesic acid [57–59]. Cochineal's coloring ability is due to cochinealin, or carminic acid (80–86%) with anthraquinone as the chromophore and –COOH, –OH, *>*C=O, and –CH3 as auxochromes. The bodies of female insects contain up to 25% of their dry weight of this pigment. Glyceryl myristate (a lipid) and coccerin (cochineal) are also found in cochineal. Carmine is formed by precipitating carminic acid onto an alumina hydrate substrate and dried to typically 50 percent concentration. Carmine is insoluble in water but is water-soluble when treated with a strong alkali [60]. Carminic acid showed a moderately strong correlation with chromatic values (a\*) from the pigment extract (**Table 11**). Also, there were no significant differences in the tint value of the samples containing different proportions of carminic acid [61].

#### *5.3.2 Application of annatto in textile coloration*

Cochineal was considered as one of the great treasures of the New World in the 16th–18th centuries, and along with alkanet, madder, kermes, and lac it formed a


#### **Table 11.**

*Variation in color values with respect to changing carminic acid n content in turmeric taken from difference different geographical origin.*

*Colorimetric Measurement and Functional Analysis of Selective Natural Colorants… DOI: http://dx.doi.org/10.5772/intechopen.102473*

source of natural red dye for textiles. Cochineal dyed textile fibers in intense red colors with excellent fastness and was the dyed textiles were highly prized. There are several studies on the use of cochineal for dyeing different fibers; cotton has been dyed with cochineal [62, 63] as also wool [4] and silk [64]. Cochineal extract was used to dye silk and wool by the simultaneous dyeing and mordanting process using 1 gpl and 5 gpl of the dye and 1.5 gpl potash alum and copper sulphate as mordants at pH 4 and 80°C for 90 minutes using liquor ratio 1:40 [65]. Polyamide fabric has been successfully dyed in a range of shades with cochineal using different mordants and mordanting methods [66].

#### *5.3.2.1 Color produced*

Cochineal produces scarlet, crimson, orange, and other range of fuchsias, reds, and purples on textiles. Different mordants produce different shades; blue-red/ reddish-purple color with alum, maroon-red with copper, purple with iron. The addition of cream of tartar into the dye bath during the dye process will shift the color from a reddish-purple to a vivid flag red color. A combination of mordants also produces different colors like rich red when tin and alum are combined, purplered when alum and iron are combined, and fuchsia to red shades with a combination of alum and cream of tartar. Over dyeing of cochineal with madder gives a good red, whilst cochineal over-dyed with indigo yields a range of light-fast violets and purples. Cochineal carmin has a maximum absorption wavelength (max) of 520 nm [67]. When carmin is esterified, the hydroxyl groups transform to carbonyl groups, lowering the electron cloud density and resulting in light shading effects [68].

#### *5.3.2.2 Extraction*

The bodies of the insect, *Dactylopius coccus* contain 19–22 percent carminic acid, which can produce crimson and scarlet colors. To preserve the dye without rotting, the insects are dried to roughly 30 percent of their original body weight. The female cochineal insects are processed by immersing them in hot water or exposing them to sunshine, steam, or the dry heat of an oven to extract carminic acid. Each process generates a different color. The dried and powdered insect corpses are cooked in ammonia or sodium carbonate solution, the insoluble debris is removed by filtration, and alum is added to the clear salt solution to precipitate the red aluminum salt to make carmine, a more pure version of cochineal. Colorant extracted from cochineal in acid solubilized medium enhance the color characteristics of bio-mordanted silk fabric [64].

#### *5.3.2.3 Dyeing conditions*

pH of dye-bath has a great influence on shades obtained with cochineal though they do not impact the fastness properties of the dyed textiles.

Since the phenolic groups in cochineal are acidic, carminic acid is pale orange in low pH, but it changes to red in slightly acidic and neutral pH, and finally turns violet in alkaline solution [69]. Alkaline medium is favorable for dyeing cotton fabrics with cochineal extract and pre-mordanting cotton with alum and tannic acid mordant mixture improves the color yield [63]. Carminic acid also forms complexes with several metals ions, which act as acceptors to electron donors to form coordinate bonds with water-insoluble dye molecules. This complex formation between the dye and the mordant shifts the maximum absorption in the visible range to higher wavelengths with an apparent increase in color intensity. Tin-based mordanting gives a brighter, but higher lightness (L\*) value on wool dyed with

cochineal than other mordants [70]. The pre-mordanting method is preferred for aluminum and chromium salts, while the post-mordanting method is preferred for copper, tin, and iron salts in order to improve the color yield of wool dyed with cochineal extracts [71]. Catonization of cotton fabric [72] or its treatment with chitosan [70, 73] increases the color value of the cochineal dyed fabric. The optimum dyeing conditions for dyeing cotton with cochineal has been identified as temperature 60°C, time 60 min, MLR–1:40 liquor ratio [74].

#### *5.3.2.4 Fastness*

Cochineal generally dyes textiles with excellent light and wash fastness. It gave moderate to good fastness properties on cotton [74] and moderate (grade 3) to very good (grade 4–5) washing fastness, and moderate (grade 5) to excellent (grade 7–8) light fastness on wool yarns [75]. Excellent fastness properties have also been reported on wool dyed with cochineal under the influence of microwave treatment and bio-mordants like heena and pomegranate [4].

#### *5.3.2.5 Functional properties of cochineal related to textiles application*

Cochineal imparted antibacterial property to wool, silk, nylon, cotton, and viscose rayon fabrics [71, 76, 77]. Nylon yarn dyed with cochineal dye showed limited antibacterial activity, which increased on mordanting with copper and tin [76]. Excellent UV protection properties (UPF > 100) were observed on wool dyed with cochineal and this was higher for copper sulpate mordant compared to alum and also improved with the increase in dye concentration [65]. UPF values for silk dyed with cochineal was less than 50 at lower concentrations of the dye, but it was very good and in the acceptable range (UPF > 50) with a higher concentration of the dye and in the presence of copper sulphate mordant [65].

#### *5.3.2.6 Case study-9*

Woolen yarns were dyed with an aqueous extract of cochineal in presence of five different mordants (aluminum sulphate, stannous chloride, ferrous sulphate, citric acid, and cream of tartar i.e. potassium hydrogen tartarate), singly and in combination, using the pre-mordanting method as well as simultaneous mordanting methods [75]. During dyeing, the carbonyl group (>C=O) and alpha hydroxyl groups (–OH) in the anthraquinone moiety of carminic acid/kermesic acid of cochineal forms a coordinate complex with the metal cation of the mordant. The carboxylic acid group of the cochineal dye can also tautomerize and easily ionize into carboxylate anion (–COO) forming ionic bonding with –NH3<sup>+</sup> group of the wool fiber. In this way, metal-dye-fiber coordination complexes are formed between the mordant, dye, and the fiber. The anthraquinone-metal combination formed by cochineal and the metal mordant causes a red and blue shift in the visible region, i.e. between 460 and 570 nm, resulting in scarlet-red to purple colors [78]. Due to the H-substitution of the hydroxyl group bonded to C5 of the dye molecule by each metallic ligand, carminic acid present in the cochineal dye induces a bathochromic shift of the main hue to red when it interacts with metal cations during mordanting [79]. This happens when the bonding occurs between the 2 hydroxy group of dye molecule and metal cation [80]. But if bonding between dye and metal ion occurs in 7-hydroxy group, the complex could induce a small blue shift [80]. The bluish-purple color was obtained on unmordanted wool and a range of colors from scarlet-red to black on mordanting with the various mordants. In the *Colorimetric Measurement and Functional Analysis of Selective Natural Colorants… DOI: http://dx.doi.org/10.5772/intechopen.102473*

case when mordants were used in combination, the final color depended on the chelating property of the dominant mordant, which forms more coordination complexes with the cochineal dye than the other mordants. Thus, ferrous mordant combinations gave grayish chrome; stannous mordant combinations gave reddish chrome and aluminum mordant combinations gave purple chrome. The redness/ greenness (a\* values) values of dyed samples from both the pre-mordanting method and simultaneous mordanting procedures were positive, indicating that all colors obtained using cochineal dye were in the red-purplish range. All dyed samples irrespective of the mordanting procedures showed an increase in yellowness (b\* values) after mordanting and consequently, the color of dyed samples shifted from bluish (higher negative b\* values) to yellowish (lower negative or positive b\* values). In the pre-mordanting method, the metal cation of the mordant probably diffused well inside the fiber matrix-forming ionic bonding with functional groups of wool fiber before dyeing. During this dyeing process, this metal cation fixed on the fiber probably formed coordinate bonding with the cochineal dye molecule resulting in more aggregation of the dye molecules with the metal cation and formation of dye-fiber-metal complex inside the fiber. Contrarily in the simultaneous dyeing and mordanting method, the coordinate complex between the metal cation and the cochineal dye molecule was probably formed both in the dye-bath as well as inside the fiber matrix leading to lesser aggregation of dye-metal complex inside the wool fiber. Thus darker shades were obtained by the pre-mordanting process and the lightness (L\*) of dyed was found to be higher in the case of simultaneous dyeing and mordanting process.

#### *5.3.2.7 Case study-10*

Wool was dyed in purple shades with cochineal and metal mordant (aluminum sulphate) and bio-mordant (chitosan) using the pre-mordanting process [81]. Results show that K/S value of wool mordanted with chitosan was higher than when mordanted with aluminum sulphate. Dye uptake increased with an increase in the concentration of the bio-mordant but beyond 1000 mg/L concentration, the K/S decreased. The decrease in dye absorption at higher bio-mordant concentrations may be due to the aggregation of bio-mordant on the wool surface reducing the area for dye adsorption as some dye sites already occupied by the bio-mordant become inaccessible to dye molecules. Thus, by using chitosan as mordant for dyeing wool with cochineal, not only the ill effects of a metal mordant is eliminated, but appreciable depth of color is obtained with lower amounts of dye. Low dye absorption was observed for unmordanted wool at pH 7 which increases at pH 4 indicating acidic pH to be favorable for dyeing wool with this dye. Dye absorption for wool fiber is primarily controlled by ion-exchange reactions between the carboxyl group of dye and amino groups of wool. Below its isoelectric point (pH 4.2), wool, is positively charged, whereas above that point the carboxyl groups present in it render a net negative charge. As a result, at pH 6, the amino groups in wool will always be protonated (carboxylate anions). The pKa value for the carboxyl group of carminic acid in cochineal dye is 2.81, indicating that carminic acid will exist in carboxylate anion form at pH 4. As a result of its increased affinity, the weak carboxylate anion of dye substitutes that of the acid at pH 4. The anion of dye has a complicated character, and when it is bound on wool, it undergoes additional interactions with ionic forces, increasing wool's dyeability. However, dye absorption in wool pre-treated with chitosan followed an unanticipated pattern and showed higher dye absorption at pH 7. Generally, at pH 4, bio-mordant like chitosan acts as a cationic polyelectrolyte due to protonation of its amine groups

thereby significantly increasing the dye absorption capacity of treated wool and at pH 7 it has a very low positive charge. However, the reaction between cochineal and chitosan treated wool was contrary to this indicating that the contact forces them are not solely electrostatic. Hydrogen bonding formation of carminic acid with several hydroxyl and carbonyl groups reduced in the acidic media due to protonation and loss of pair electrons of amine groups of the bio-mordant, resulting in better dye absorption in neutral medium. L\* (lightness/darkness) decreased on mordanting indicating darker shades on chitosn pre-mordanted wool dyed with cochineal extract. The a\* values were positive indicating redder shades, which decreases on mordanting with chitosan. The b\* value of wool dyed with cochineal without any mordant was negative indicating bluer tone. These values were positive and the yellowness of the shades increased (decrease in blueness) when wool was pre-mordanted with chitosan before dyeing with cochineal extract.
