“Colour is a measure of quality and nutrient content of foods”
Natural food colour is any dye, pigment or substance that imparts colour when it is added to food or drink. All individuals are sensitive to the colour of food, even appetites are influenced and stimulated by colour; colour may sometimes discourage eating certain foods and diminish the desire for particular foods. Sometimes, colours also suggest the flavour that is anticipated when eating or drinking. Both natural and artificial colours are widely used by food manufacturers.
At present, the demand for natural dyes is increasing worldwide due to the increased awareness of their therapeutic and medicinal properties and their benefits among public and because of the knowledge of profound toxicity of synthetic colours.
Natural dyes are derived from naturally occurring sources such as plants, insects, animals and minerals. Among all the natural dyes, plant-based pigments have medicinal values so are mostly preferred. Marketing strategies of food by major manufacturers are greatly influenced by colour. Today, the food industry and colour suppliers are constantly improving the technical and physical properties of colour preparations. Development of cost-effective, viable technology for preparation of a food colour and its application in foods is a challenge and the need of the day.
There are many natural colours but the basic four colours are comprised of carotenoids, chlorophyllin, anthocyanins and betanin. Other colorants or specialized derivatives of these core groups include annatto, caramel, carmine, elderberry, lycopene, paprika, turmeric, red cabbage, beetroot etc.
Natural food colours are predominantly used in the processing of:
- Packaged food;
- Confectionary and bakery items;
- Dairy products;
- Others (pet foods, condiments, functional foods, etc.).
Natural food colours have a dominant share in the global food colours market and for growth rate it is anticipated that its market share will increase further in the near future. Consumers around the world are choosing food products containing natural food colours over those that contain artificial food colour.
Food regulatory authorities around the world i.e. Food and Drug Administration (FDA), European Food Safety Authority (EFSA), FSSAI etc. have been closely regulating the use of artificial colours, which has further contributed to the demand for natural food colours. Highest demand is always met from the beverage industry. According to research conducted by Future Market Insights (FMI), the beverages segment will witness a CAGR of 7.2 percent through 2020 to reach a valuation of $374 mn.
The Packaged food industry’s reliance on natural food colours signifies that this segment also has huge potential. According to FMI’s Research Report on the global natural food colours market, this segment will witness a CAGR of 7 percent and will be worth $317 mn by 2020. The confectionary and bakery segment is projected to witness a CAGR of 6.9 percent with valuation of $304.6 mn, dairy products segment has 6 percent growth rate to reach a valuation of $230 mn and other segments like pet food, condiments and functional food, among others, will have the largest revenue valuation at $470.0 mn by 2020.
The simple extraction process used for naturally derived colouring is similar to that of concentrating fruit or vegetable juice. Manufacturing methods for converting natural sources into food colouring include extraction, heating, homogenization, milling, filtration, concentration and drying. Recent developments are very effective and productive i.e.
- Supercritical fluid extraction;
- Subcritical water extraction;
- Ultrasound assisted extraction;
- Mechanism of Microwave Extraction;
- Pulsed Electric Field.
Soxhlet: Plant parts are brought into a thistle of the soxhlet extractor and solvents like dichloromethane, dichloroethane, acetone, hexane or alcohol are used to extract the colour principles from various raw materials by column extraction either in hot or in cold conditions followed by the removal of solvents used. However, the use of organic solvents causes high energy costs and safety hazards.
Supercritical Fluid Extraction (SFE): SFE has found applications in the extraction of colour from natural sources. When a certain fluid is forced to a pressure and temperature higher than its critical point, it becomes a supercritical fluid. Under these conditions, diffusivity increased leads to higher extraction yields. It is a clean, safe, inexpensive, non-flammable, nontoxic, environmentally friendly, non-polluting solvent. Also, energy costs associated with SCFE are lower than conventional techniques.
Subcritical Water Extraction (SWE): Subcritical water extraction (SWE), i.e. extraction using hot water under pressure, has recently emerged as a useful tool to replace the traditional extraction methods and is among the more promising processes. Very high temperatures (over 400°C) and moderately high pressures are required to achieve the critical point of water. These extraction techniques provide higher selectivity, yield, an environmentally-clean process, and require shorter extraction times and do not use toxic organics.
Ultrasound Assisted Extraction (UAE): UAE is carried out by mixing dried and ground samples in methanol or any solvent in a flask, which is usually placed in an ultrasonic bath for 30-50 min. Temperature increases during extraction from 30ºC to 60ºC. The higher yield obtained in these UAE processes is of major interest from an industrial point of view, since the technology is an “add on” step to the existing process with minimum alteration, application in aqueous extraction where organic solvents can be replaced with generally recognized as safe (GRAS) solvents, reduction in solvent usage, and shortening the extraction time. The use of ultrasonic for extraction purposes in high-cost raw materials is an economical alternative to traditional extraction processes, which is an industry demand for a sustainable development.
Mechanism of Microwave Extraction: The extraction occurs as the result of changes in the cell structure caused by electromagnetic waves. Other techniques like microwave-assisted distillation, microwave hydro-diffusion, vacuum microwave hydro-distillation, microwave-integrated soxhlet extraction, solvent-free microwave extraction are proven to be efficient extraction technologies.
Enzyme Based Extraction: Various enzyme combinations are used to loosen the structural integrity of botanical material thereby enhancing the extraction of the desired colour components. Although the enzyme hydrolases such as lipases, proteases (chymotrypsin, subtilisin, thermolysin and papain) and esterases are used generally, some of the plant materials rich in colours which have been exploited for enzyme-assisted extraction are alfalfa, marigold, safflower, strawberry, aronia fruits, grapes, red cherries, and the results have shown positive effects.
Pulsed Electric field (PEF): PEF is reported to enhance mass transfer rates by basic principle of 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 and increase the extraction of valuable components.
Consumer awareness for health is leading the growth of natural colours. Many novel techniques have been evolved for better processing and higher yield of natural colour.
* Research Scholars at ICAR-National Dairy Research Institute, Bengaluru