Methods of Extraction of Pigments

Solvent extraction is the conventional method that is usually used to extract colors from plant materials:

  • • Thocyanin 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, whereas acetone may be used 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) (Naidu et al., 2012).

Advancements in pigments extraction from plant materials were necessary as the use of organic solvents is considered harmful both for human health and for the environment. The current advance techniques that are used in color extraction like high hydrostatic pressure (HHP), pulsed electric field (PEF), sonication-assisted extraction. HHP, PEF, and sonication belong to environment friendly and energy efficient technologies. They enhance mass transfer processes from plant or animal cellular tissues, increasing the permeability of cytoplasmic membranes, which, in turn, enhances the extraction yield of valuable cell components.

In substitution of solvent extraction some pretreatment techniques may be used: gamma irradiation for plant material, enzymatic extraction for pigments, antioxidants, flavors and phytochemicals. Enzyme pretreatment cannot be a complete substitute for conventional solvent extraction, but can result in increased yield of value-added cell components and reduction in extraction time, hence lowering solvent consumption. Based on this approach, enzymes have been explored as a means to enhance the extraction of carotenoids in marigold flowers.

A fast technique adopted by biotechnology and food industries for the concentration and separation of macro and micro molecules based on molecular size and shape in biotechnology and food is membrane technology. Advantages of membrane processing include improved product quality with higher yield, utilization of byproducts, and ease of extraction of temperature and pH sensitive products without alteration. Last but not least, membrane processing is environmental friendly, as no harmful chemicals are being used and less energy is consumed (Naidu et al., 2012).

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