**1. Introduction**

From the application in textiles, uses of natural dyes also extend to colouration of food and in other areas like medicines, cosmetics, and procession of leather products. Several sources of natural colorants used in the past have been reidentified today. Many are common and play a dual role in colouration of textiles as well as food products and drinks. Some dye-yielding plants contain compounds like curcumin, crocin, bixin, carthamin, punicalagin, nimbin that are known to have therapeutic properties and are used in various traditional medicinal therapies. Their inherent functional properties like antimicrobial, antifungal, deodorizing, UV protection, moth/insect-repellent, and others allow them to enhance the value of the dyed textiles, or the colored food products. This chapter deals with some selected natural colorants widely used in the textiles and food sectors and documents their chemistry, extraction process, application, usage and properties, separately, in relation to textiles and food. Few case studies on colourimetric measurements and analysis of functional properties of natural dyes on textiles and food are also discussed.

#### **2. Natural colorants for textile related application**

Natural dyes for textiles are dyes or colorants derived from plants, invertebrates, or minerals. From the plant source, colors are extracted from seeds, roots, stems, barks, leaves, flowers, berries, and fruits. In addition to the natural vegetable coloring matter, animal/insect coloring matter like tyrian purple, cochineal, lac and kermes, and mineral coloring matter derived from ocher, limestone, manganese, cinnabar, azurite, and malachite are also used to produce natural effects on the fabrics. With the advent of synthetic dyes, natural dyes faded into oblivion. But now with several advantages like fast and durable colors coupled with replaceable, biodegradable, and fairly nonpolluting nature over the synthetic ones, natural dyes are making a comeback.

Different natural dyes yield different colors–yellow (kamala seed pods, myrobolan fruit); mustard yellow (latex from the gamboge tree); yellow to orange (pomegranate rind, turmeric, and lichens); peach to brown (chestnut hulls); orange (gold lichen, carrot and onion skin); pink (berries, rose and beets); crimson to maroon (teak leaves and cochineal); orange, pink and red (madder root); red to brown (bamboo and hibiscus flower); brown (catechu bark and coffee beans); red to purple (red sumac berries, basil leaves, hibiscus flower, logwood, lac); purple (red cabbage and murex snails), blue (indigo leaves), green (sorrel roots, spinach, and peppermint leaves); yellow, gray to black (black berries, iris root, and walnut hulls) and sepia brown (octopus/cuttlefish).

Different compounds are present in natural dye sources that impart a variety of colors on textiles; indigotin (blue and purple), anthraquinones (shades of red), carthamin from safflower (red and yellow shades), naphthoquinone (orange, red, or reddish-brown shades), flavonoid dyes (yellow to greenish-yellow and brown colors), carotenoid (orange), tannins (different colors with different mordants) and curcumin (yellow shades).

#### **3. Natural colorants for food related application**

Color is the prime sensory attribute of foods and is often used by consumers as an indicator of food quality in terms of flavor, safety, and nutritional value. Food colors are dyes, pigments, or other substances that impart color when added to a food product or a drink. Such additives make the food more attractive, appealing, and appetizing; provide color to colorless foods or enhance their natural color; offset color that is lost on exposure to air, moisture, high temperature, light, and unfavorable storage conditions; and allows the consumers to identify products on sight. Thus, one of the main applications of food colorants is the modification or preservation of its visible appearance.

Food colors can be obtained naturally as extracts from natural sources, or they can be synthesized. Natural food colors are usually extracted from seeds, fruits, vegetables, leaves, insects, algae, etc., and are used both in domestic cooking and commercial food production and are available in many forms such as liquids, powders, gels, and pastes.

Among the natural food colorants, Asian spices like turmeric and saffron are used in everyday cooking; they lend an appeasing color to the food. Saffron, as a spice finds its use in biryanis and as colorants in dairy products. Caramel is mostly used to enhance flavor in deserts. Hibiscus is a commonly used bakery product and tea-based beverage to enhance the brown tint. Marigold does not have extensive use but the petals are sometimes used to enhance colors in salads. Beet juice has several applications in many beverages, dairy products, yoghurt ice cream, sauces, jams, jellies, and candies.

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

Different sources of natural colorants yield different colors; dark yellow is obtained from turmeric; yellow-orange from saffron; orange from carrots, red pepper/paprika, and sweet potato; pink from strawberries and raspberries; red from carrot, beets, and tomato; deep red from beetroot and red sandalwood; green from matcha and spinach; blue from red cabbage mixed with baking soda; purple from blueberries and purple sweet potato; brown from coffee, tea, and cocoa; and black from activated charcoal and squid ink.

A variety of compounds present in natural dye sources are responsible for different colors. Anthocyanins (flavonoids) found in fruits and vegetables are responsible for blue, purple, red, and orange colors. Carotenoids in fruits and vegetables are known for imparting red, orange, and yellow colors. Betalains present in most caryophyllales plants give a pink to red color. Curcumin is responsible for the yellow color of turmeric. Safflower gives an attractive yellow color. Chlorophylls from alfalfa (*Medicago sativa*) are responsible for the characteristic green color. Carminic acid in carmine from cochineal is responsible for dark purplishbrown or bright red or dark red color.

#### **4. Colorimetric measurement of natural colourants**

The appearance of a textile or food material is ascertained through its surface color and is the first sensation perceived by the consumer to judge its acceptability. The color of an opaque object is described by the reflectance of light as a function of its wavelength. The human eye is versatile and can detect light and light modification by the colorant and this is interpreted by the brain as color. For any color to be perceived by a human eye, a source of light, an object, and an observer is required.

Color measurement of products can be carried out in two ways; by visual evaluation or through instrumental analysis. The chromatic attributes and different geometric factors like texture, shape, etc. of foodstuffs can be assessed qualitatively by the human eye. In this process, the observer assesses the color of the sample under standard conditions of illumination, and after comparison with defined color standards; the assessment is defined in terms of some scores generally on a 9-point scale. One of the most popular scales is the 9-point Hedonic scale in which the products can be marked from 1 to 9 depending on the appearance and acceptability rate of the food product. A lower score indicates low and least acceptable color intensity; while a high score denotes high color intensity or acceptable appearance. Such visual assessment is subjective, relative, and is dependent on the observer and environmental conditions. On the other hand, the presence of color pigments can be also be quantitatively assessed using different types of equipment. But each instrument measures only one attribute at a time and so several instruments may be needed to measure various aspects of visual perception. Basically, there are three types of instruments that measure color or its attributes, colourimeter, spectrophotometer, and spectroradiometer.

Liquid chromatography is a method for separating, identifying, and quantifying the constituents of a mixture. The interaction of the sample with the mobile and stationary phases causes this separation. Because there are so many distinct stationary/mobile phase combinations that can be used to separate a mixture, chromatography is divided into various categories based on the physical states of those phases, liquid, and gas. Liquid–solid column chromatography is the most common chromatography technique that uses a liquid phase (mobile) that filters down through the solid stationary phase, bringing the separated components with it. To separate the components that make up a sample, high-pressure liquid chromatography (HPLC) uses pumps to push a pressurized liquid solvent containing the sample mixture

through a chromatography column loaded with solid absorbent materials. Each component in the sample interacts with the adsorbent material in a slightly different way, resulting in varying flow rates and separation of the components as they flow out of the column. The type of chromatography column employed determines how different chemicals are separated. Several different types of columns (size exclusion, ion exchange, normal phase, reverse phase) are used. Once the molecules make it through the column, they will be detected by a detector, which is typically a UV detector, but other detectors such as refractive index detectors, laser light scattering detectors, fluorescence detectors, and thermal conductivity detectors are also used. High-performance liquid chromatography (HPLC) is considered the 'gold standard' for measuring pigment concentrations in plant samples. A major drawback of this process is its high cost both in terms of time required for assessment, and the high cost of the testing equipment itself. Liquid chromatography can be combined with mass spectrometers (LC–MS) to analyze organic and inorganic compounds of biological origin. While liquid chromatography may separate mixtures with several components, mass spectrometry can identify the individual components'structural identity with high molecular specificity and detection sensitivity.

Colorimetric or spectrophotometric analysis is another technique to evaluate color in textiles or food. Because the amount and color of light absorbed or transmitted through a solution is dependent on the concentration of pigment particles present in it, such measurements rely on detecting the concentration of material (color/pigment) in a solution. Such color evaluation measures the change in the intensity of electromagnetic radiation in the visible wavelength area of the light spectrum after it is transmitted or reflected by the object or solution through which it passes. A colorimeter or spectrophotometer thus assesses the color in various sample solutions (dyes in textiles, or colorants in food) by absorbing a particular wavelength of light and denotes the assessment in the form of some values using the Beer–Lambert law. Under Beer's law of photometry, the amount of light absorbed is proportional to the solute concentration present in the solution. According to Lambert's law, the amount of light absorbed is proportional to the length as well as thickness of the solution taken for analysis or in other words, when light passes through a medium, its absorption is proportional to the intermediate convergence. Beer's law and Lambert's law are usually taken in combination as Beer–Lambert law which indicates the relationship of absorbance with both the path length of light inside the sample and the concentration of the sample.

Thus, the principle of operation of a colorimeter is outlined as follows—in a colorimeter a beam of light of a given wavelength is directed toward a liquid sample (of the dyes in textiles, or colorants in food). While passing through a solution in the colorimeter, the beam of light travels through a series of lenses, and the photocell is able to detect the amount of light passing. The current produced by the photocell depends on the quantity of light striking on it; higher the concentration of the colorant/pigment in the solution, the higher is the absorption of light and consequently less transmission. Thus, less light passing through the solution would indicate the creation of less current by the photocell [1]. The colorimeter can qualitatively detect the presence of color pigment in a sample when the wavelength peak detected in the experimental sample matches with the peak (λmax) of the standard pigment.

The colorimeter can also measure the amount of pigment present in the sample. In this case, calibration curves can be made using the different concentrations of the standard solution of the pigment. With the help of a calibration curve, the amount of pigment present in the sample can be estimated. In case standard solutions are not present, then various equations can be formulated using extinction coefficients, molecular weight, etc. to ascertain the amount of dye pigment in the sample.

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

When items are viewed under different sources of light and illuminations, their colors are frequently diverse. The discrepancy is due to differences in the spectral power distribution of the illuminations as well as changes in the lighting. An illuminant is a specific spectral power distribution incident on the object viewed by the observer, whereas a source is a physical emitter of radiant energy, such as a lamp or the sun and sky. As a result, a single source of light can provide several illuminants. Illuminants can also have a variety of spectrum power distributions. Numerical specification of color was earlier visualized by chromaticity diagram and the three chromaticity coordinates (x, y, and z) were calculated by the use of the three tristimulus values that represent the amount of standard lights (red, green, and blue) required to reproduce a color.

Over time, a slew of alternative color appearance models have arisen, as well as a numerous new color measurement related terms. To represent the color of an item, several color coordinate systems can be employed, including RGB (red, green, and blue), Hunter Lab, Commission Internationale de l'Eclairage's (CIE) L\*a\*b\*, CIE XYZ, CIE L\*u\*v\*, CIE Yxy, and CIE LCH. Almost of modern color measurement is based on experimental observations in accordance with the CIE (International Commission on Illumination) color specification system. The human eye has three color receptors: red, green, and blue, according to CIE principles, and all colors are combinations of these.

Color evaluation methods such as the Hunter Lab L\*,a\*,b\* and the modified CIE system known as CIELAB are widely used in the food and textile industries. They were created as a result of investigations that correlated tristimulus values with visual perceptions of color in order to convert the X, Y, Z system (tristimulus values) to a visually uniform color-system. Each color can be considered equivalent to a member of the greyscale lying between black and white, according to L\*, which is an approximate measurement of brightness. As a result, the L value for each scale reflects the level of lightness or darkness, whereas the a and b values indicate redness or greenness, respectively. Hunter L, a, b is a color scale based on the opponent-color theory which states that color receptors in the human eye see color as pairs of opposites: light–dark, red-green, and yellow-blue. To fully define the color of an object, all three values are required. The scale consists of two color coordinates, a\* and b\*, as well as a psychometric index of lightness i.e. L\*. The parameter a\* is positive for reddish colors and negative for greenish colors, whereas the parameter b\* is positive for yellowish colors and negative for bluish colors. L\* is an approximate measurement of luminosity according to which each color can be considered as equivalent to a member of the greyscale lying between black and white. Thus, the L value for each scale, therefore, indicates the level of lightness or darkness; the values indicate redness or greenness, and the b values yellowness or blueness. The CIE 1976 L\*a\*b\* color or modified CIE system called CIELAB was recommended by the CIE in 1976 to improve on the 1966 version of the Hunter L, a, b. The CIELAB color scale, like the Hunter, expresses color as three values: L\* for perceived brightness, a\* and b\* for the four distinct hues of human vision: red, green, blue, and yellow. Under the two color scales, however, three values of L, a, and b are determined differently; the formulas for Hunter L, a, and b are square roots using CIE XYZ, whereas CIELAB uses cube roots of XYZ. The CIELAB color scales were designed to be a perceptually uniform space in which a given numerical change correlates to a corresponding perceived change in color, and so provides a better approximation to the visual judgment of color difference for very dark hues. Despite the fact that the LAB space is not genuinely perceptually uniform, it is valuable in the industry for detecting minute color changes. Because the CIE L\*a\*b\* scale, which was released in 1976, has gained popularity, the Hunter color scale is no longer as widely used as it once was. Although CIE measured the single color space, it was not truly uniform visually throughout the color space and could not define color-difference in a singular term i.e. two colors cannot be red and green at the same time or yellow and blue at the same time. It meant that equal color difference magnitude appear of different visual magnitudes in different regions of the color space. For this reason, the CMC equation (Color Measurement Committee) or color difference (ΔE\* or DE\*) formula which takes the non-uniformity of the color space into account is used to assess the difference between two colors and is more preferred in textiles color assessment today. The CMC equation corrects the CIELAB color scale's most significant flaw, which is chroma location dependency.

The total color difference, ΔE, may also be calculated. A comparison of two colors is used to determine this color difference (ΔE\* or DE\*). One is designated as the standard (or target), and the other as the sample. ΔE is a single value that takes into account the differences between the L, a, and b of the sample and standard. The delta values (ΔL, Δa, and Δb) show how far a standard and sample differ in terms of L, a, and b. Different color difference formulae are used to calculate the numerical color difference between two colors.


Deltas for L\* (ΔL\*), a\* (Δa\*) and b\* (Δb\*) may be positive (+) or negative (�). Whether the sample is redder or greener than the standard is indicated by the sign of the delta value. For example, a sample will be redder than the standard if Δa is positive. The total difference, Delta E (ΔE\*) is always positive. For the delta values, tolerances can be established. Out-of-tolerance delta values indicate that the discrepancy between the standard and the sample is too great. If ΔE is out of tolerance, it is difficult to know the parameter that is out of tolerance. It can also be deceiving in situations when L, a, or b are out of tolerance but E is still within it.

Color values of textiles are also assessed in terms of K/S (Kubelka-Munk) values where higher values represent darker and more saturated colors. K/S values are usually calculated at the wavelength of maximum absorption of the color (λmax); however, a calculation over the visible region may also be employed. The Kubelka-Munk equation is as follows:

$$\mathbf{K}/\mathbf{S} = \frac{\left(\mathbf{1} - R\_{\lambda\text{max}}\right)^2}{2\mathbf{R}\lambda\_{\lambda\text{max}}} \tag{1}$$

Where K: is the constant related to light absorption of the dyed fabric; S: is the constant related to light scattering of the dyed fabric; R: is the reflectance of the colored fabric that is expressed in fractional form.

The objective measurement of color is thus dependent on the quantification of the light source (E), the object's reflectance (percent R), and the observer's color response functions r-g-b. In food products, color quality is either measured on a spectrophotometer and expressed in terms of the chromatic attributes (L\*, a\*, b\*) as proposed by CIE, or in terms of tint values measured using a tinctometer and interpreted as color ratio between yellow and red pigments (R and Y values). Colors on textiles can be characterized by hue (dominant shade); the amount of color

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

present or saturation; and by the degree of lightness or darkness of the particular color. Thus in textiles color values are generally expressed in terms of the color strength (K/S values), color difference (ΔE), chromatic attributes (L\*, a\*, b\*), as proposed by CIE and Metamerism Index (MI). Based on the respective magnitudes of ΔE, ΔC, ΔH, MI, a newer empirical index CDI (Color difference index) of assessing color for a binary mixture of dyes has also been postulated [2].

#### **5. Some selected colourants commonly used for colouration of textiles and foodstuffs**

#### **5.1 Turmeric**

Turmeric is derived from the tuberous rhizome of the Zingiberaceae family. *Curcuma longa*, the yellowish-brown rhizome from which the turmeric is derived develops beneath the ground and is cylindrical, tuberous, highly branched with a rough and segmented skin with a dull orange interior. The leaves are pointed and the flowers are funnel-shaped and yellow in color. *C. longa* is a perennial herbaceous plant that grows wild in tropical Asia. India is the largest producer, consumer, and exporter of turmeric in the world contributing 78% followed by China, Myanmar, Nigeria, and Bangladesh together contributing to 6% of the global production. Dried the turmeric rhizome gives yellow powder with a bitter, slightly acrid, but sweet flavor. *C. longa* is a medicinal plant that is used extensively in textile and food colouration. It is popularly used as a spice in South Asian and Middle Eastern cuisines as it lends a distinctive yellow color and flavor. *C. longa* also possesses antioxidant, anti-inflammatory, choleretic, antimicrobial, and carminative properties and has been used in traditional Indian ayurvedic medicine. The dye has been used to color fabrics in brilliant yellow colors. It can be used in combination with other plants like *Butea monosperma* flowers [3] or *Nyctanthes arbor-tristis* flowers [3] to give a range of yellow shades. It's typically used as a foundation color for indigo overdyeing to achieve a fast green.

**Genus***: Curcuma* | **Species**: *longa* | **Family**: Zingiberaceae. **Common name**: Turmeric | **Local name**: *Haldi.* **Part of the plant used for coloring**: Roots/rhizomes and leaves.

#### *5.1.1 Coloring pigment/component*

Turmeric has a volatile oil that contains turmerone, as well as other coloring compounds called curcuminoids mainly concentrated in the rhizome. Curcuminoids (1,7-bis 4-hydroxy-3-methoxyphenyl-1,6-heptadiene-3,5-dione) are natural antioxidants and curcumin is the principal curcuminoid present in turmeric. The other two curcuminoids are desmethoxycurcumin and bis-desmethoxycurcumin. Curcumin is a polyphenol and the principal coloring component of this yellow dye which has been also been classified as CI Natural Yellow 3 and considered a direct type of dye. Curcumin can be found in two different tautomeric forms: keto and enol. In the solidstate and in solution, the enol form is more energetically stable [4]. The chemical structure of curcumin is different under different pH and hence it can be used as an indicator. It remains yellow in an acidic medium, while when added to an alkaline medium above pH 8, the shift of the hydrogen atom causes the compound to change color giving a red hue. It is not soluble in water (acidic and neutral pH) at room temperature but is soluble in oil and alcohol. Curcumin also has fluorescence qualities, which extends the active life of these molecules and increases the chances of contact with oxygen in the air, making them more susceptible to photochemical

#### *Colorimetry*


#### **Table 1.**

*Variation in color values with respect to changing curcumin content in turmeric taken from difference sources.*

oxidation. [5]. A relationship exists between the curcumin content and the L\*a\*b\* values [6] and high curcumin content is associated with high L\* (lighter) and b\* (yellower) values, but with lower a\* (less red) value. Where a\* and b\* values are high, the resultant shades are red and yellow respectively, while when both a\* and b\*values are similar, the resultant shade is orange (**Table 1**).

#### *5.1.2 Application of turmeric in textile coloration*

Very few studies have been reported on dyeing of textiles with turmeric. Cotton was dyed with purified ethalonic extract of turmeric by the exhaust technique [7]. Enhancement of dye uptake and wash fastness of cotton was achieved through modification with enzymes and chitosan [8], irradiation with gamma rays [9], and microwaves [10] before dyeing. Silk was dyed with *Curcuma Longa L* rhizome in brilliant shades [11] and improved dye uptake and fastness were obtained on silk pre-irradiated with methanolic extract of *C. longa L* rhizome [12]. Nylon dyed with turmeric gave fast colors [13].

#### *5.1.2.1 Color produced*

Turmeric yields a warm gold color on undyed natural cotton fabrics, silk, and wool. It gives a wide range of yellows without mordants. With mordants (metal salts), it gives colors like golden yellow (tin), mustard yellow (copper and chromium), and olive green (iron). Its wavelength of maximum absorption (λmax) is 420 nm [14] or 450 nm [15] indicating that the dye can absorb color in the blue end of the spectrum. The wavelength of maximum absorption for turmeric is.

#### *5.1.2.2 Extraction*

Maximum yield (highest absorbance) of color from turmeric was obtained at pH - 6 at 100°C [16] indicating that the dye can be extracted under very mild acidic or neutral conditions. Also, maximum extraction occurs at high (boiling) temperatures [5]. The solvent extraction process gave maximum yield followed by aqueous extraction, but the purest form was obtained by spray drying [14].

#### *5.1.2.3 Dyeing conditions*

Color strength (K/S) value of the dyed fabric was maximum in pH 7 [7]. Good color strength was observed by dyeing fabric irradiated at 65°C for 40 min in dyeing bath having pH 6 [10]. Glauber's salt tends to neutralize or reduce the negative electric charge (zeta potential) of cotton fabric, thus facilitating the approach of the dye anions to the fabric within the range of formation of hydrogen and other bonds between the dye molecules and fabric and thus the color strength of cotton dyed with turmeric extract increases with increase in salt concentrations [5].

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

#### *5.1.2.4 Fastness*

In general, turmeric is a fugitive dye and bleeds easily. Turmeric exhibits poor washing fastness due to the phenolic groups present in curcumin which reacts with soda ash (in washing liquor) forming curcumin salt that is soluble in water and hence can be easily washed out from the dyed fabric. The poor light fastness of turmeric is attributed to the inherent susceptibility of its chromophore to photochemical oxidation. However, both the wash and light fastness of textiles dyed with turmeric can be improved through mordanting. The improvement in light fastness can be attributed to the reduced susceptibility of the turmeric dye chromophore to photochemical oxidation in the presence of mordant. Though dyeing with turmeric exhibits good fastness to rubbing, a decrease is noted both in the dry and wet rubbing fastness in the presence of the mordant.

#### *5.1.2.5 Functional properties of turmeric related to textile application*

Turmeric also has antibacterial and anti-inflammatory effects. Natural colorants extracted from turmeric exhibited excellent antimicrobial activities and related wound healing properties [17]. Silk fabrics dyed with an extract from *C. longa* rhizome using copper sulphate, ferrous sulphate, and potassium aluminum sulphate as pre-mordants possessed desirable antibacterial properties and 3% (owf) copper sulphate giving complete antibacterial activity against *Staphylococcus aureus* (Gram-positive) and *Escherichia coli* (Gram-negative) [11]. The study also indicated that an increase in the dye concentration leads to a more efficient antibacterial activity and 30% (owf) of turmeric gave the optimum level of antibacterial activity. Nylon fabric dyed with various concentrations of turmeric extract using different metallic mordants displayed excellent antibacterial activity in the presence of ferric sulphate, cupric sulphate, and potassium aluminum sulphate, and exhibited good and durable fastness properties [13]. Cotton yarns colored with turmeric and coated with chitosan provide high antibacterial action against bacteria (*E.coli* and *S.aureus*). Also, the yarn coated with chitosan dyed to a darker shade compared to uncoated yarn for the amount of the dye used [18]. Colorant from turmeric can have UV protection properties and can block almost 100% UV-rays when used to dye polyester. On coating the fabric with chitosan there was no change in UV protection property though the slight change in the shade was noted [19].

#### *5.1.2.6 Case study-1*

Turmeric (*C. longa L*.) extract was used to dye cotton using bio-mordants (*Citrus limon* and *Colocasia esculenta*), and for comparative purposes, metallic mordants (potassium dichromate and potash alum) were also used [20]. The samples were pre-mordanted (soaked) in the bio-mordant extract for different durations before dyeing; for the metallic mordants, they were boiled with the mordant solution at 80°C for 50 min followed by cooling for 60 min in the solution itself. The effect of mordanting time on the color strength was evaluated for the bio-mordants. The surface color strength (K/S) of bio-mordants (*Citrus limon* and *Colocasia esculenta*) pre-mordanted cotton increased with an increase in mordanting time for both the bio-mordants (**Table 2**). Cotton pre-mordanted with lemon containing significant amounts of tannins showed the highest surface color strength (K/S) among all mordants used. The effect of moisture absorption on the hue of the dyed fabric was also studied. For this, the dyed specimens were stretched and tied over the mouth of steel tubes containing 100 ml water each. The specimens were


#### **Table 2.**

*Surface color strength of cotton dyed with turmeric pre-mordanted with different mordants for different time duration.*

maintained under normal conditions of 25°C and 70% relative humidity for 24 h after which the face and rear side of the specimens were visually observed for any change in hue. Under acidic conditions (below pH 4), curcumin gave a yellow appearance, in alkaline pH, it changed its hue as the dyed cotton specimen absorbed moisture changing its pH and thus showing a significant change in hue on both side of the fabric. Furthermore, the visual uniformity of the dyed samples was found to be excellent for both bio-mordants. Due to the presence of citric acid, turmeric gave uniform color in low acidic conditions (around pH 4); at higher pH (pH 4 to 5) it showed a reddish color. Color fastness to rub (dry and wet), water (EN ISO 105 E01–2013), wash (ISO 105 C06), and perspiration (EN ISO 105 E04–2013) were found to be superior for the bio-mordanted cotton and the values ranged from 3 to 4–5 in most all cases.

#### *5.1.2.7 Case study-2*

Aqueous extract of turmeric was used to dye cotton fabric using aluminum sulphate as a mordant [15]. The effect of different mordanting techniques (per, post, and simultaneous) on the surface color strength of the fabric was evaluated (**Table 3**). Simultaneous dyeing and mordanting sequence gave maximum dye uptake probably due to the mordanting of cotton with aluminum sulphate mordant and formation of a complex between the color component of the dye curcumin and the metal mordant. Also, turmeric being a direct type of dye exhausted well in the presence of a salt-like alumnium sulphate (mordant) and hence simultaneous mordanting sequences gives better results (K/S).

New and uncommon compound shades were developed through combination dyeing of the cotton combination of turmeric (yellow dye) with using madder (red dye), and turmeric (yellow dye) with red sandalwood (red dye) in different


#### **Table 3.**

*Surface color strength (K/S) of cotton dyed with aqueous extract of turmeric using aluminum sulphate as a mordant by the different mordanting sequences.*


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

#### **Table 4.**

*Surface color strength (K/S) of cotton dyed with a mixture of dyes (turmeric with madder and turmeric with red sandalwood) in different proportion by the simultaneous mordanting and dyeing sequence using aluminum sulphate as a mordant.*

proportions by the different mordanting and dyeing process. A synergistic effect in the color interaction between the observed and calculated K/S values (calculated values were derived by adding the individual K/S value of the respective proportion of the two dye components on the fabric) was observed; the observed K/S values of the dyed cotton samples were always higher than the calculated or expected K/S values indicating the color value of the mixed dye system to be always higher. Also, an increased amount of turmeric in the mixture increased the dye uptake (K/S) values (**Table 4**).

#### *5.1.3 Application of turmeric in food coloration*

Curcumin is a polyphenol found naturally in turmeric rhizome that has antiinflammatory, antioxidant, anticancer, and immunosuppressive activities. It is used mainly in the development of dairy products as the presence of fat (triglycerides) enhances the solubility of curcumin [21]. While few studies have been carried out on colouration of food using turmeric, most of them focus on its functional aspects. Improvement in the sensory attribute and antioxidant potential of ghee has been reported by the addition of 160–350 ppm of curcumin [22]. The turmeric powder improved the oxidative stability and microbiological quality of soft cheese [23]. Turmeric extract rich in curcumin reduced the aging of fresh lamb sausages during modified atmospheric packaging by causing less generation of related volatile compounds due to its antioxidant capacity [24]. The addition of turmeric to the dough of biscuits and breads greatly improved the antioxidant potential and organoleptic properties of breads and biscuits [25].

#### *5.1.3.1 Color produced*

Turmeric when applied to food yields a bright orangish-yellow shade.

#### *5.1.3.2 Extraction & application conditions*

Curcumin is mainly dissolves in oils and alcohols. It is not stable at alkaline conditions especially at pH above 7.5 though it is quite stable in temperatures generally used for processing foods. Curcumin is complexed with aluminum ions as it is light sensitive.

#### *5.1.3.3 Functional properties related to food application*

Curcuminoids present in turmeric possesses anti analgesic, anticarcinogenic, antiinflammatory antioxidant, antiseptic properties. It also helps in the prevention, palliation, or treatment of various disorders such as diabetes, cholelithiasis, diabetes mellitus, foodborne illnesses, and circulatory disorders [26–28]. Moreover, it also acts as a potent food preservative as it slows down lipid oxidation and possesses antimicrobial activity.

#### *5.1.3.4 Case study-3*

The effect of heat treatment and conventional sun drying on the color of fresh turmeric rhizome was evaluated in terms of its hue, yellowness, and brightness (L\*, a\*, and b\* color coordinates) [29]. Turmeric rhizomes were subjected to heat treatment at varying temperatures (50–100°C) for different time periods (10– 60 minutes). The rhizomes were cooked at 100°C and then sun-dried for 15 days. The rhizomes were brightened (L\*) and yellowed (b\*) after being heated at 60-80° C. Heat treatment from 60 to 80°C increased the brightness (L\*) and yellowness (b\*) of the rhizomes; the values remained the same and did not change with further increase in temperature. The phenolic activity of oxidases in turmeric decreased with an increase in temperature and this led to a decrease in browning of the sample while inversely increasing its hue to a yellower shade and brightness. Though the heat treatment did not significantly decrease the concentration of curcuminoids, sun drying caused a significant reduction in curcuminoids (4–5%). Heat treatment thus enhanced the color of turmeric and maximum brightness was observed at 80°C for 30 minutes.

#### *5.1.3.5 Case study-4*

The impact of irradiation on the color stability of curcuminoids was examined and curcumin reagent (curcumin, DMC, and BMC; 79.4, 16.8, and 3.8% - w/w) was irradiated with fluorescent light (27 watt) for 24 hours using a household fluorescent lamp [30]. The color intensity was analyzed by measuring absorbance at 435 nm and curcuminoids before and after treatment were quantified using HPLC. Turmeric pigments (oleoresin and curcumin) were not stable under light, and their photo-degradation was lower when present in higher concentrations. An increase in concentrations of the sample (20–1000 μg/mL) resulted in a loss in color intensity of both oleoresin and curcuminoids in turmeric (**Table 5**).

#### **5.2 Annatto**

*Bixa orellana* is a perennial, tall shrub bearing bright white or pink flowers and red-brown fruits in the form of globular ovoid capsules or seed pods with delicate spines. The pods are grouped in clusters and each contains 30–45 cone-shaped seeds covered by a pericarp rich in the red-orange pigment, annatto. *B. orellana* is native

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


**Table 5.**

*Loss in color intensity of different pigments (i.e. oleoresin and curcuminoids) in turmeric due to light irradiation.*

and grows wild in northern South America and Central America. Later in the 16th and 17th centuries, *B. orellana* was distributed to the Caribbean, Hawaii, and South-Eastern North America, Southeast Asia, and Africa. It is cultivated primarily for its red seeds in India, Sri Lanka, and Java. In India, *B. orellana* is cultivated for its seed across Orissa, Andhra Pradesh, and Maharashtra. 70% of the world's coloring agents derived from natural sources come from annatto [31]. Its color is used in food, textile, paint, and cosmetic industries. Also called achiote or bijol it is used as a natural orange-red condiment/spice in the food industry and is used in the bleaching of dairy food products. It is soluble in lipids and is therefore used for imparting red to orange-yellow color to processed food. Annatto is also known as lipstick tree [32] and is used in cosmetics for the production of sunscreens [33], nail gloss, hair oil, and soap. Its medicinal value is associated with its antibacterial, antifungal, antioxidant, antibiotic, and antiinflammatory properties. It has shown anticancer, enhanced gastrointestinal motility, neuropharmacological, anticonvulsant, analgesic, and antidiarrheal activities and has been used as a laxative, cardiotonic, and expectorant, and for wound healing purposes. The dye is also used in the printing and dyeing of textiles like cotton, wool, and silk.

**Genus**: *Bixa* | **Species**: *orellana* | **Family**: Bixaceae. **Common name**: Achoite | **Local name**: *Latkan or sinduri.* **Part of the plant used for coloring**: Seeds.

#### *5.2.1 Coloring pigment/component*

Of the total carotenoid pigments present in annatto, 80% consists of the red pigment, bixin, and a yellow pigment, norbixin or orelline. Bixin is a yellowishorange-red dye that is high in carotenoid pigments and is derived from the thin seed coat of *B. orellana* seeds. Bixin occurs in nature as monomethyl ester of the dicarboxylic carotenoid compound [6,6<sup>0</sup> -diapo-ψ-ψ<sup>0</sup> -carotenedioic acid monomethyl ester] i.e. 16-*Z* (*cis*) form, but during extraction, it isomerizes to its 16-*E* (*trans*) form called isobixin. Norbixin is a naturally occurring demethylated derivative of bixin used for commercial purposes. Besides bixin and norbixin, other compounds such as beta-carotene, cryptoxanthin, lutein, zeaxanthin, orellin, bixein, bixol, crocetin, ishwarane, ellagic acid, salicylic acid, threonine, tomentosic acid, tryptophan, and phenylalanine are also found in the seeds of annatto. Bixin belongs to the direct/acid dye class [34]. Bixin content influences the color value of the annatto extract. With higher amounts of bixin, the L\* and b\* values decreased (darker and yellower) whereas a\* values increased (redder) under the Hunter measurement scale [35]. For Lovibond values, for the same dyes, the R-values increased with the increase in the concentration of bixin while the Y values remained the same. The low purity dye (CFTRI method) showed a higher b\*/a\* values as compared to the high purity dye (new patented process by CFTRI), whereas a reverse trend was


**Table 6.**

*Effect of bixin concentration on color values (hunter and Lovibond) [35].*

observed with respect to the Y/R values. However, a\* and R-values which corresponded to red color increased with an increase in concentration in both color measuring systems irrespective of dye purity [35]. With annatto giving orange shades (combination of yellow and red) b\*/a\* (degree of yellowness) values were also assessed. With an increase in the bixin concentration, the b\*/a\* decreased indicating a more yellow color. The study also indicated that the Lovibond color was more influenced by the source of dye and its purity as compared to the Hunter values (**Table 6**).

#### *5.2.2 Application of annatto in textile colouration*

Natural fibres like cotton [34, 36], silk [37] and wool [32] and also synthetic fibers like nylon and polyester [38] have been dyed with *B. orellana*. Leather has been dyed in the bright red shade with excellent rub fastness using bixa extract [39].

#### *5.2.2.1 Color produced*

Yellow and orange can be produced from *B. orellana*. Though annatto seed extract gives an orange-red color, the hue depends on the solvent used for extraction [40]. The wavelength of maximum absorption for annatto is 458 nm [41].

#### *5.2.2.2 Extraction*

Commercial preparations consist of solutions or suspensions of the pigment in vegetable oil or as a water-soluble form in dilute alkaline solution. Content of total phenols (TP) increases with an increase in pH and higher TP contents were obtained at an extraction time of 60 h and a solvent/seed ratio of 4 ml/g of the extract [42]. The primary pigment *cis*-bixin is partially transformed to the *trans* isomer and a degradation product when heated [43]. Microwave-assisted extraction using ethyl acetate solvent also gives good pigment yield [44]. Though the total dye yield (**Table 7**) on the extraction of annatto seeds by the new patented process by CFTRI, Mysore, 2004 was less than the dual solvent extraction method (CFTRI method), the more purer patented process gave higher bixin and nobixin yields (g/100 g) [35].

#### *5.2.2.3 Dyeing conditions*

*B. orellana* gives beautiful shades on cotton in alkaline medium using inorganic salts as mordants [45]. Woolen yarns can be dyed with bixa extract in acidic,

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


#### **Table 7.**

*Total yield of dye with bixin and norbixin content in Indian seeds of annatto extracted by different processes [35].*

neutral, and alkaline media using ferrous sulphate, stannous chloride and alum as mordants. Regardless of the presence or absence of mordants, dyeing silk and wool fabric with an aqueous extract of annatto seeds is best successful at pH 4 [41].
