1 Introduction

Any food product is instinctively scrutinized from a visual sense before deciding on purchasing or consumption. Color remains one of the most prominent visual cues contributing to the sensory aspect of foodstuff. There is significant research underscoring that the color of the food psychologically manipulates impelling the expectation of flavor generated in our brain before tasting the food (Velasco et al. 2015, 2016). Consumers’ inclination to a particular food item is primarily visual specific to the color of the food which aids the consumers to predict the flavor and taste of the food. Interestingly, the perception of colour is deep-rooted and comes intuitively to human beings. For ages, the colour of fruits, vegetables, and meat has remained a determinant factor to distinguish raw from ripe and fresh from old or spoilt.

The implication attached to colour to the food impacted the decision of worldwide food manufacturers to add in a variety of colour additives. The natural colorants derived from natural sources including plants and microbes were used to impart colour to food which was later replaced by synthetic colorants. Natural colorants are of two categories: organic (derived from living sources) and inorganic (gold, silver). Synthetic food colorants are chemicals processed from coal tar compounds and most of them contain dyes from the azo group (Dey and Nagababu 2022). Moreover, natural identical man-made colours like riboflavin are also available (Sezgin and Ayyildiz 2018).

A considerable hike in demand for packaged food fostered the massive use of food colorants. Henceforth, food colorants are added to every packaged and processed food product sold on the markets and almost every food item sold or manufactured by a food industry or a food selling outlet. Additionally, prepared food, e.g. in restaurants and other small food-selling outlets, contains food colouring agents to enhance their visual appeal to entice consumers. However, health hazards reported predominantly in children triggered by these fascinating synthetic colours need to be addressed (Arnold et al. 2012). The colossal use of permitted and non-permitted food colorants, their toxicities, and associated adulterations are global concerns with varying gravity in different countries.

India is considered a hub of food diversity in terms of the taste, smell, and colour of foods. The Indian food industry is gaining copious profit by marketing different geographical food styles. Bright attractive colours are the distinctiveness of Indian cuisines which aid the growth of the synthetic food colorant (SFC) industry (CATR 2019). Additionally, the market for natural food colorants is on the rise due to an increase in health awareness among consumers (The Hindu 2022). Besides the potential adverse health effects of SFCs, this hike led to another serious misbranding of natural colorants as synthetic. The misuse of the label ‘natural’ to attract consumers, the adulteration of natural colorants, and the lack of proper legal regulations in the processing of natural colours are serious issues demanding the imperative attention of authorities. There is a pressing need for proper labelling to distinguish the presence of natural colorants as well as to implement systematic standards on the processing and use of natural colorants. We have proposed a label for distinguishing the incorporation of natural colorants in food. Even though India is known for its multi-hued foods and natural resources of colours (Ramamoorthy 2010), hardly a few studies have been published regarding the status of SFCs and natural colorants.

Here we discuss the rapid growth of the Indian food colorant market, the reports on side effects, and the associated regulations in a comprehensive manner. Stringent regulations and government-funded research initiatives are required to tackle together this growing menace.

2 Rapid growth of the Indian food colorant market

Initially, food manufacturing industries utilized SFCs as additives, and nowadays most of them are not used in the U.S. and Europe, but available in India (The Indian Express 2022; Ramamoorthy 2014). The rationale for rather using synthetic colorants rather than natural colorants is more stability, less sensitivity to heat, light, and pH, lesser quantities producing higher intensities, and a cheaper mode of synthesis. Examples of prohibited colorants being sold and still in use in other countries include Patent Blue V, Quinoline Yellow, Ponceau 4R, Amaranth, Rhodamine B, and Azorubin (Sachan 2013). In 2023, the expected worldwide market size of the food colorant industry will be around $ 3.2 bn. and the compound annual growth rate (CAGR) is expected above 7% (Fig. 1). As per reports, developing countries like India, and China is extensively contributing to this surge (MRF 2018).

Fig. 1
figure 1

Expected CAGR food colourant market growth rate globally and in India (GMI 2022; MRF 2018). The coloured countries in world map denotes the major colour producers. (Synthetic colours-North America; Annatto-Brazil, Peru; Carotenoids and Anthocyanins-European countries; Safflower-Kazakhstan; Curcumin-India) (Color figure online)

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Indian foods are well known for their versatile flavours and uniqueness depending on the country’s region. India’s rich culinary heritage could be seen in provincial cuisines which are a blend of herbs and spices. Unfortunately, the increased demand for packaged foods and competition on the food market has largely promoted the use of SFCs in Indian cuisines. The Indian food colorant market will achieve a CAGR of 5.3% by 2027, which is majorly impacted by synthetic colorants (CATR 2019). Further, India’s exports of food colours to the U.S., China, Indonesia, Brazil, Mexico, and Italy are increasing. These export market sizes have increased from $ 203 M to $ 263 M from 2014 to 2019 (CATR 2019). The market for natural food colorants is also growing steeply and is expected to reach $ 92.96 M by 2027, growing at a CAGR of 3.90% (EI 2018). Colorants like tartrazine, sunset yellow, quinoline yellow, indigo carmine, and amaranth are widely used to enhance the visual aesthetic of Indian food. There are hundreds of companies in India manufacturing these chemicals as food colours  (CATR 2019). At the same time, the natural food colorant market is on the rise due to an increase in health awareness among Indian consumers and reports on the harmful side effects of synthetic colorants (Satyanarayana 2022).

3 Indian case studies on toxic effects of SFCs

Previous studies have shown the perilous impact of colorants of health. Feingold (1975) first proposed the parallel link of hyperactivity and increased intake of SFCs in children (Weiss 2012). The stemmed investigations, clinical studies, evidences are ongoing. It has been shown by Arnold et al. (2012) that young children respond to synthetic colorants exceedingly and symptoms included irritability, sleep issues, lack of attention, impulsivity, and hyperactivity [a clinical condition called “Attention-deficit/hyperactivity disorder” (ADHD)]. Using mixtures of Erythrosine, Ponceau 4R, Allura Red, Sunset Yellow, Tartrazine, Amaranth, Brilliant Blue, Azorubine, and Indigotine on female rats and their offspring showed a lessening spatial working memory and sex-specific anti-depressive, anxiolytic behaviors (Doguc et al. 2015). In addition, there are also reports on the synergism between colorants and increased incidence of asthma and allergies (Amchova et al. 2015). Incidences of cancer associated with SFCs Red 40, Yellow 5, and Yellow 6 were also published (Dey and Nagababu 2022). Concerns for genotoxicity after intake of colorants like titanium dioxide, erythrosine, and brilliant black (Silva et al. 2022) should be corroborated in in vivo studies. Numerous organic dyes are also regarded as micro pollutants in aquatic environments owing to their toxic effects on aquatic life forms and their subsequent consumers in the food chain (Tkaczyk et al. 2020).

Several synthetic food colorants banned in developed countries are regularly used as food ingredient in India, e.g. azo dyes (Pratt et al. 2013). Azo dyes possess one or more azo groups (–N=N–) in their chemical structures and are toxic. Tartrazine is one of the widely used azo dyes which is reported to have toxic impacts on the liver, renal function, lipid profiles, and behaviour (Amin and Al-Shehri 2018). Likewise, in vitro studies of sunset yellow in rodents resulted in decreased testicle size and deformed lipid profile (Mathur et al. 2005a; b). And indigo carmine has been shown to have atrioventricular blocking capacity (Takeyama et al. 2014). Regardless, many of these banned dyes are permitted to use in India within certain limits, irrespective of the discrepancies regarding the health impacts of long-term use, the perception of food vendors about the permitted level of use, and the flow of non-permitted food colours on black markets.

Extensive use of non-permitted carcinogenic, neurotoxic colorants is a common practice observed in different parts of India (Nandakumar 2015). Melanil yellow, a potent carcinogenic dye banned by the Government of India was found in turmeric, ladoo, and besan at high levels in unorganized food sectors of West Bengal corroborating the lack of quality control and ignorance of food regulations (Nath et al. 2015). An analytical study performed to investigate synthetic food colorant usage in different states of India revealed that candyfloss, sugar toys, beverages, mouth fresheners, ice candy, and bakery product samples contain exceeded the limit of colourants. Practices of blending colorants with non-permitted colours (e.g. azo dyes sunset yellow, tartrazine) in mass amounts are also highly prevalent (Dixit et al. 2011). Likewise, the exceeding limits of the above SFCs have been detected in samples of coloured crushed ice with 8–20% higher than permitted levels. Non-permitted colorants like rhodamine B, metanil yellow, orange II, malachite green, auramine, quinoline yellow, amaranth, and Sudan dyes was also detected in a variety of foods (Tripathi et al. 2007). An extensive survey conducted in bakeries, supermarkets, street food shops, and fast food joints in urban and rural areas of Hyderabad with different age groups of pre-school (1–5 years) and school kids (6–18 years), adult individuals (19–44 years and > 45 years of age) from high-, middle- and low-income groups showed an intake of tartrazine, erythrosine, and sunset yellow higher than the permitted limits of 100 ppm (Rao and Sudershan 2008).

The literature shows very few case studies and investigations on the SFCs used in India in the last decade. Rapidly changing lifestyles, high inclination toward packaged foods, and rampant modernization with hectic daily schedules are likely leading to an analogous growth of food colorant levels intake and subsequently, a surge of health disorders. All these factors underline the necessity of utilizing safe natural sources of food colorants.

4 Forging food and natural colorants with synthetic colorants

The growth of the natural colorant industry is due to an increased consciousness of serious health effects caused by the colossal use of synthetic dyes. However, the factor restraining the prompt growth of the industry is the high cost of natural colorants when compared to synthetic counterparts. Red is the most demanded food colorant followed by green on the Indian market (EI 2018). Additionally, the COVID-19 pandemic has influenced the Indian organic market reflecting in 40% increased growth (EI 2018). Ironically, consumers who are asserting natural colorants didn’t know what is natural or chemical.

Natural pigments are extracted from both edible as well as non-edible constituents of plants such as flowers, seeds, leaves, fruits, roots, etc. Other major sources apart from plant constituents include marine fungi, insects, and microalgae. Anthocyanins, betalains from grapes, blue berries (Albuquerque et al. 2021), and beta-carotenes from carrots include pigments extracted from edible matter. Pigments like crocin from Crocus sativus, bixin from Bixa orellana (Rodriguez-Amaya 2015), and lutein from the marigold flower (Adeel et al. 2017), carminic acid from cochineal insect (Cooksey 2019) are derived from non-edible matter. Natural pigments are often combined with carriers, emulsifiers, and antioxidants to maintain colour stability since they are highly sensitive to air, light, and temperature. Besides, the impeccable curative properties of natural colorants make them apt candidates for chemo preventive therapy through diets (Saini et al. 2020).

Natural pigments like carotenoids are often water-insoluble, and organic solvents are employed for the extraction of pigments, leading to the selective separation of the pigment alone, without the minerals or carbohydrates and proteins of the overall natural pigment source. Although the extraction process does not contribute to any structural or chemical change in the pigment, how suitable the highly purified pigment remains for direct intake is a subject of investigation. Antioxidants such as ascorbyl palmitate are added to prevent oxidative degradation of pigments. Water insoluble pigments are altered to water-soluble substances by means of polysorbates, fatty acid sucrose esters, and additional encapsulation through polysaccharides and plant extracts. In India, safety of these additives should be regulated more stringently.

These extraction procedures and the lacunae of abundant raw materials trigger forging. For instance, the anthocyanin level in grapes is 30–750 mg per 100 g. Henceforth, synthetic counterparts of pigments are now accessible. These colorants have a higher market value compared to natural colorants. For consumed carotenoids this means that 76% are synthetic (Leepica and Siva 2021). The high cost of naturally derived pigments, the seasonal production (anthocyanins can only be produced during the fruiting season), and the acceptable coloration provided in fewer amounts by SFCs (Beate et al. 2020) also subsidize adulteration.

One of the challenges in largely populated developing nations such as India is vigilant and comprehensive monitoring of every small food selling outlet like street food vendors, where detection of illegal and prohibited ingredients, colorants, and several other additives becomes arduous to keep track of and eliminate. Each Indian state having separate procedures for registration and licensing prevents the coordination and regulation of food laws between the states. This leads to a whole heap of ambiguities in the food safety system, and quality regulation fuelled by a disagreeable practice of adulterating natural colorants and marketing synthetic colorants labelled as “natural”.

4.1 All natural?

An adulteration is the addition of non-permitted food colour additives to a food product. The accumulation of permitted food colours in exceeding levels is also an adulteration that results in severe health hazards (Gizaw 2019). Adulterated milk with chalk or diluted water, coffee seeds spiked with tamarind or mustard seeds), ice cream with pepperoni or washing powder etc. are examples of food fraud in order to make more profit (India today 2018). Synthetic colorants emerged in order to deceive consumers regarding food freshness, and to increase the visual attractiveness of food, e.g. malachite is green in vegetables, Metanil yellow in dal, Sudan red in red chili powder (India today 2018). Nevertheless, recent strategies are trying to promote the ‘naturalistic fallacy’: Around 490 food samples and 62 samples of natural, herbal colours were collected by the Society of Pollution and Environmental Conservation Scientists (SPECS) from places like Dehradun, Vikas Nagar, Sahaspur, Doiwala, Rishikesh, Haridwar, Rajpur, Mussoorie were adulterated with toxic chemical synthetic dyes (The Tribune 2016). One of the world’s most demanded spice and food colorant saffron was found to be adulterated with Sudan dyes (Petrakis et al. 2017), and the food colours anthocyanin and betalain with the textile dye ‘Reactive 95’ (Müller-Maatsch et al. 2016). Turmeric labelled as natural and organic was highly adulterated with lead chromate (Erasmus et al. 2021). Many “organic” labelled foodstuffs like tea powder, jaggery, and edible oils were also reported to contain non-permitted colorants (Pradeshi 2019).

Some of the used analytical techniques in the quality assessments of food colorants include spectrometry, thin layer chromatography, ion chromatography, coupled plasma mass spectrometry, gravimetric analysis, and the more sensitive and robust reverse-phase high-performance liquid chromatography (HPLC), quadrupole time of flight mass spectrometry (Martins et al. 2016). Although a broad range of food colorants used in foods are keenly inspected and certified by food regulatory boards for health safety, still the presence of prohibited colorants and additives cannot be excluded. Therefore, stricter regulations are obligatory to endorse natural colorants and natural food products without their synthetic counterparts.

4.2 Safety of natural colorants

The use of natural colorants in India is good within the permitted limits and in permitted foods (Table 2). Unfortunately, cases of adding natural food colorants unrestrained manner have been reported in India, e.g. the addition of annatto to cow milk for a yellowish appearance to resemble buffalo milk (Singh and Gandhi 2015). Above and beyond, the label “natural” may not mean that the used pigment for the food colorant has undergone numerous clinical trials without any reports of allergies and carcinogenic effects. Reports of urticaria, angioedema, hypotension, anaphylaxis in hypersensitive individuals on the use of plant pigment pressures for broad systematic clinic-level research on natural pigments (Singh and Gandhi 2015). Extensive studies are still necessitated to regulate the admissible levels of pigments although it is natural.

5 The need for more stringent regulations

5.1 Authorities

The global organizations that govern international food standards include Codex Alimentarius Commission (CAC), an inter-governmental body established by FAO and WHO that devises the global food standards of which developing countries like India. Starting with the industrial revolution, the use of synthetic colorants became widespread. The United States first published the list of approved food colours in 1906 to curb the use of toxic chemical dyes. In 1957, the UK published legally approved colorants. In the early 1950s, a joint committee under the leadership of FAO and WHO was established to assess the safety of food additives including colorants (Lehto et al. 2017). In India, the Food Safety and Standards Act (2006) prescribes food regulations that are implemented by the Food Safety and Standards Authority of India (FSSAI), which is authorized and functions under the Ministry of Health and Family Welfare of India. As per FSSAI regulations, the final concentration of synthetic food colorants should not exceed 100 ppm in foods and beverages (FSSAI 2009).

FSSAI has published the list of natural and synthetic colorants with permitted limits in 2 regulations (2009, 2011). Table 1 provides details of FSSAI-approved synthetic colorants. The non-permitted colours are Fast red, Rhodamine B, Metanil yellow, Bromo-cresol purple, Green S, Sudan 1, Sudan 2, Sudan 3, and Sudan 4, as well as the overuse of permitted colours (Deva 2007). Table 2 shows FSSAI approved natural colorants in India. However, the regulations do not provide a proper definition to define artificial colouring substances. There is no distinction between natural colours and the synthetically produced natural colours. As per FSSAI, food products are sold under the label ‘contains permitted natural colours/permitted synthetic colours/contains permitted natural and synthetic colours’ without any depiction of the used colorant (FSSAI 2011). There are also no rules regarding the labelling of the colorant amount added to the food. Only the synthetic food colorant package should indicate the total dye content (FSSAI 2009).

Table 1 FSSAI approved synthetic colorants, their chemical name, structure along with colour index (FSSAI 2009; 2011)
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Table 2 FSSAI approved natural colours and their specifications
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The international identification number of colours needs to be listed on the label. The presence of annatto colour in oils is labelled as ‘annatto colour in oil’. But there is no specification about other colorants. The readability of these terms for consumers is also questionable. The manufacturing and sale of synthetic colours should be under license and their packaging labelled as ‘food colours’. There are certain specifications regarding the diluents, filler materials for the preparation of synthetic colours. Around 29 diluents including sugar, salt, ethanol, lactose can be used for the preparation of colorants (FSSAI 2009). There are permitted levels of synthetic food colorants as well as natural food colorants. But, is there any limit for a maximum daily uptake of permitted food colours in India? Are there any reports on the cumulative effects of these pigments accumulating in our bodies?

Regulatory standards with a proper HACCP system implemented by the industry are the most appropriate means to ensure the industrial production of natural food colorants. In the context of natural colorants production, proper quality checking throughout the supply chain is mandatory, starting from the collection of raw materials to sales, to ensure adulterant-free natural colours. The minimum amounts of toxic metals, pesticides, contaminants, solvent residues, and adulterants should be the benchmark for the quality and approval of natural colorants. Chemicals will stabilize the natural colorants that underwent multiple processing to enhance their colouring. A crystal image of regulations limiting the additional chemicals added to natural colorants should also lessen the adulteration in colorants.

5.2 Traders

The unrestrained use of colorants in Indian street food markets urgently needs to be appraised. Analysis studies on street food vendors in Chennai underpin that 94% are unaware of even the hygiene practices, and 74% believe that applying for a license is an arduous task (Abraham and Krishnan 2017). The conditions are even worse in other metropolitan and rural areas of India, where tourists are largely attracted by street foods (Gupta et al. 2020). There should be initiatives from the regional level itself to curtail the sources of banned pigments and to conduct awareness programs for street vendors about the hazards. With the collective effort strengthened by officials at the regional and national level, street food vendors will undoubtedly alter the fortune of Indian cuisines and magnetize more foreigners.

Most of all, the food monitoring frequency should also be renewed on par with the bourgeoning number of small-scale as well as large-scale outlets. Regular updates of legal regulations, and redefining the rationale for permitted food colorants considering the increased dependency on fast food is also desirable. The negligible scientific reports on the use of natural, and synthetic food colorants purpose the requisite of large-scale funded research to understand the current scenario of Indian food colorants, as well to frame solutions considering primarily the health of consumers.

5.3 Consumers

Consumers are impelling factors in the progress of SFC safety and the natural colorant market. A consumer perception investigation performed in Switzerland revealed that consumers prefer natural colour additives based on the risk and regulation factors (Bearth et al. 2014). In Germany, people prefer natural colorants derived from plants and not animal sources (Müller-Maatsch et al. 2018). A survey conducted in Ethiopia showed that 64.15% of people are not aware of the possible adverse consequences of food additives, and 70.96% would continue to consume them even after discerning the effects Moreover, a large part of consumers was not interested in checking the labels to determine food safety and quality (Getasew et al. 2016). This accentuates the need of presenting labelling with good readability and logos to specify the use of natural colorants for consumers to differentiate synthetic from natural colorants (Fig. 2). Moreover, awareness programs at regional and national levels will generate the active, knowledgeable, discriminative consumers.

Fig. 2
figure 2

Proposed logo for denoting natural permitted food colorants in food packages. Pigments extracted from plants are used to colour candies. The candy package is labelled with a proposed logo

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6 Future perspectives

Meeting the rising demands of natural colorants is challenging owing to the tedious extraction procedures, low raw material availability, and high cost. Fruitful strategies such as gene editing technologies like CRISPR/cas 9, optimization of tissue culture techniques, utilization of stress factors like sonication, ultrasound, and magnetic field, and recognition of molecular markers for breeding should be employed for augmenting colorant production. For instance, lipases and carotenogenic genes were expressed in Saccharomyces cerevisiae to induce production of β-carotene (Fathi et al. 2021). Production of another natural colourant annatto have been enhanced through application of abiotic elicitors like methyl jasmonate, salicylic acid, paclobutrazol (Parimalan et al. 2011). However, research is still going on for the replacement of natural with synthetic substitutes, with studies on natural pigments being at substandard levels and their original function uncertain. Instead, more focus should be given to elucidating promising natural sources for pigments. For instance, beta-carotenes from microalgae such as Chlorella vulgaris and Dunaliella salina (Damergi et al. 2017; Xu et al. 2018) Additionally, research in exploring the likelihood to produce pigments from endophytic microbial sources (Sujithra and Ramamoorthy 2022; Sujithra et al. 2021) and large-scale production in bioreactors are providing possibilities for safer food colorant production.

More profound knowledge of natural pigments could help the progress and expansion of healthier, safety-specific functional food products. Besides, the intake of natural colourants in food also provides several health benefits including cardioprotective activity (Varghese et al. 2022). There needs to be a focus on scientific innovations and upgradation in the processing and storing conditions of the food such that it would reduce or eliminate the inclusion of food additives and also assist in the contribution of risk-free, secure food products to consumers without compromising on their catch factors and demands. Due to this demand and change in consumer expectations, food industries have been collaborating with top food research institutions to apply scientific knowledge to produce high valued nutrient-enriched food products (Garnweidner-Holme et al. 2021). The collaboration also aids the industries to stay updated on the latest progress in food science research to make possible the commercialization of safe, natural, healthy, and functional ingredients and foods in industrial food products. Currently, microparticles are used to enhance the solubility of pigments by a 100-fold, encapsulation inside emulsion system and polymers is used for stability of pigments over longer storage periods. Gamma irradiations have also remained a reliable technique to extend shelf life and stability (Martins et al. 2016).

Considering the regulatory and societal aspects of food colorants in India, a regularly updated list of permitted and non-permitted food colorants is needed. There should be an unbiased, unambiguous standard founded on the toxicity levels for permitting the colorants and their use. A delegated apprehensible description of the norms in production and sources of natural colorants is obligatory. Most of all, proper labelling defining the colorant should be provided esteeming the rights of consumers to know the ingredients of the food they intake.

7 Conclusion

According to Hippocrates, ‘leave your drugs in the chemist’s pot if you can heal the patient with food’. Paradoxically, we are in the state of consuming medicines because of the food we intake. The extensive use of synthetic colorants without any constraints is the causative factor of many health disorders. Some consumers are making informed choices and opting for natural and organic food products and also have become very specific towards their inclination for natural food colorants and flavorings, mainly because of the reports on health and environmental threats that synthetic colorants potentially have. However, the misbranding of “natural” and adulteration of natural colorants are also issues to combat. Collective efforts of authorities, traders, and consumers are required to promote the use of natural colorants without any adulteration.