Food Colour : Importance and Extraction

 Food Colour

Color is an appearance property attributable to the spectral distribution of light. The human eyes are sensitive only to electromagnetic vibrations in the wavelength range of 400 (380) to 760 nm this region of spectrum is known as visible region. The mixture of all colors of different wavelengths in the visible region is known as white light. The approximate wavelength range of different colors are illustrated in below figure.

Importance of Food Colors

Marketing strategy of food by major manufacturers are greatly influenced by color. Color affects almost everything one does in life is the statement given by Downham and Collins i.e., from purchasing items for one’s home, his/her clothing, or their food, decisions are made while giving color the at most importance. Their hypothesis is that all individuals are sensitive to the color of food. Appetites are also influenced and stimulated by color; color may sometimes discourage eating certain foods and diminish the desire for that food.

Colors also suggest the flavors that are anticipated when eating or drinking. Bright orange colored drinks imply the flavor of orange. Simillarly, a bright red colored drink may hint at strawberry or cherry or beetroot flavor. Dull colors of orange or red drinks may indicate a lesser quality of nutrients and so are not as appealing. From past 20 to 30 years many food industry are being processed to create visually appealing food that tastes good that can be used by common man. This briefs out the importance of color to food choices.

 

v  Color is added to food for the following reasons:

a)        To Replace Color Lost During Processing,

b)        To Enhance Color Already Present,

c)        To Minimize Batch-To Batch Variations, And

d)       To Color Otherwise Uncolored Food.

 

v  Food colors are divided into four categories:

1)        Natural Colors:Natural colors are pigments made by living organisms. Usually, pigments made by modification of materials from living organisms, such as caramel, vegetable carbon and Cu-chlorophyllin, are also considered natural though they are in fact (except for carbon) not found in nature.

2)        NatureIdenticalColors:Nature-identical colors are man-made pigments which are also found in nature. Examples are β-carotene, canthaxanthin and riboflavin. 

3)        Synthetic Colors:Synthetic colors are man-made colors which are not found in nature., these are often azo-dyes.

4)        Inorganic Colors: Examples of inorganic colors are titanium dioxide, gold and silver

 

v  Sources of Natural Colour (Pigments)

Pigments are found widespread in nature from the simplest prokaryotic organisms like cyanobacteria and throughout the kingdoms of fungi, plants and animals. Most natural food colorants come from the division Magnoliophyta (flowering plants) of the plant kingdom. However, natural colorants from other sources such as scale insects (cochineal and lac), fungi (Blakeslea trispora and Monascus spp.), and cyanobacteria (Arthrospira spp.) are used today for coloring food.

 

Table : Natural color and their E number

Class	Color	E -number
Chlorophyll	Olive green	E 140
Anthocyanins	Red, purple, blue, pink, magenta	E 163
Carotenoids	Red, orange, yellow	E 160
Betalains	Red, yellow	E 162

 

 

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Methods of Extraction of Food Colour (Pigments)

Solvent extraction is the conventional method that is usually followed to extract colors from plant materials. Anthocyanin and betalain pigments, which are water soluble, are extracted from the raw material with water and sometimes with aqueous methanol. For carotenoids extraction, hexane is the solvent of choice and acetone is good choice of solvent for the initial extraction of pigment from the plant material. After thorough extraction of the plant material, the extract is concentrated and subjected to purification steps by using column chromatography. Identification and quantification of the pigment is performed by Spectrophotometry or by high pressure liquid chromatography (HPLC).

 

The current advance techniques that are followed in color extraction are as follows:

1)        High Hydrostatic Pressure (HHP),

2)        Pulsed Electric Field (PEF),

3)        Sonication assisted Extraction,

4)        Gamma Irradiation,

5)        Enzymatic Extraction,

6)        Membrane Technology.

 

High Hydrostatic Pressure (HHP) and Pulsed Electric Field:

Are environment friendly and energy efficient technologies that enhance mass transfer processes within plant or animal cellular tissues, as the permeability of cytoplasmatic membranes can be increased which in turn enhances extraction of valuable cell components. In addition, the decrease in the dielectric constant of water under HHP combined with temperature leads to a decrease in the polarity of the media, contributing to the higher yield of total phenolics and other antioxidants. PEF is reported to enhance mass transfer rates by electroporation of plant cell membranes, improving tissue softness and thus influencing the textural properties. PEF is reported to be an ideal method to enhance juice production, increase the extraction of valuable components better than the yields obtained by enzymatic maceration.

Sonication assisted extraction

Sonication assisted Extraction is one of the most commonly used methods to enhance mass transfer phenomena by cavitation forces, where bubbles in the liquid/solid extraction can explosively collapse and generate localized pressure, causing plant tissue rupture and improving the release of intracellular substances into the solvent.. Its feasibility for the extraction of secondary metabolites such as tea, mint, chamomile and ginseng has been highlighted in many studies.

Gamma Irradiation:

Gamma-irradiation, as a pre-treatment to a plant material, increases cell wall permeabilization, resulting in enhanced extraction of cell constituents in higher yield.

Enzymatic Extraction:

Enzyme assisted extraction of worthy products from plant materials viz., pigments, antioxidants, flavours and phytochemicals is another new technology. Enzyme pre-treatment cannot be a complete substitute for conventional solvent extraction, but can result in increased yield of value added cell components and a reduction in time of extraction and reduction in amount of solvent consumption.

Membrane Technology:

Membrane processing is a fast and emerging technique for the concentration and separation of macro and micro molecules based on molecular size and shape in biotechnology and food processing industries. Advantages of membrane processing are many which include improved product quality with higher yield, utilization of by-products, temperature and pH sensitive products can easily be extracted without alteration and lastly is environmental friendly as no harmful chemicals are being used and less energy is consumed.

Future Perspectives:

The choice of appropriate color to food is very challenging and wrong selection of color may lead to lot of problems viz., lack of consumer appeal and the failure of product. Color suppliers are facing challenges of producing cost effective, good stability, easy to handle, technology for the production of colors. In this aspect, new technologies are welcome with improved benefits over existing technologies.