Laurie Kronenberg and Brad Beissner
FIGURE 1. Two Points in the Three-Dimensional Color Plane.
Consumer demand for safer products sparks push to eliminate artificial colorantsThe $28 billion nutraceutical market in the United States might face stricter regulation in the near future, some experts say.1 Artificial and genetically modified ingredients, generally shunned by consumers and oral dosage form manufacturers, could become limited in use, and producers of these coating products will likely improve their offerings to remain competitive.
To answer the call for more health-conscious coating choices, companies like Ashland Specialty are creating natural offerings that not only offer a wide variety of colors and palettes but also address the need for safer and more stable products.
Synthetic food colors are rapidly falling out of favor in the European Union, a phenomenon largely spurred by the release of a 2007 British study that identified a list of six particular colorants that showed a link to hyperactivity and attention disorders in children.2 These additives have become known as the “Southampton Six.” The colors in the study are Alurra Red (also called Red 40, E129); Ponceau 4R (E124); Tartrazine (Yellow 5, E102); Sunset Yellow FCF/Orange Yellow S (Yellow 6, E110); Quinoline Yellow (E104); and Carmoisine (E122). These six must now carry a warning label in the EU that states that the colorant “may have an adverse effect on activity and attention in children,” and there is legislation pending in the EU to ban these colors.3 With such an advisory in place, consumers are understandably interested in natural alternatives.
The call for natural colorants is also growing in many other parts of the world. A recent Nielsen poll of 5,000 respondents, commissioned by Chr. Hansen, revealed that 92% were concerned about artificial colors, and many are willing to pay a premium for products made with natural colors.4 Many suppliers of coloring agents to the food, nutraceutical, and pharmaceutical industries are working on more reliable and varied natural color formulations in response to this increased demand. Ashland Specialty Ingredients is working with these suppliers to develop compliant, color-stable coating systems.
The fully formulated Aquarius coating systems natural colors palette contains 72 hues of reds, pinks, oranges, yellows, greens, blues, purples, and browns compliant with current U.S. and EU regulations. Notable differences between the two sets of regulations include iron oxide, which is permitted as a food colorant in the EU but restricted to pharmaceutical use in the U.S., and carmine, which has a strict usage limit in Europe but no restrictions in the U.S. There are numerous other differences in the regulations between the U.S., the EU, and other parts of the world, and these regulations change frequently.
Regulatory ConcernsThe development process for the Aquarius coating systems natural color palette began when Gernot Warnke, Ashland Specialty Ingredients’ Technical Manager for Pharmaceuticals, Europe, scoured the lists of regulations in the U.S. and EU to locate coloring agents that were acceptable under both sets of rules. The list was disappointingly small. As a result, the current natural color offerings include three separate groups of colors: one that complies with regulations in the EU and the U.S., one that meets EU regulatory requirements, and one that meets U.S. regulations. Some shades are EU and U.S. compliant.
Many of the tablet coating formulations are aluminum free. The use of aluminum lakes in food colorants may be banned or at least strictly controlled in the future. Particular colors have been banned previously in some European countries. The aluminum-free colors in the Aquarius coating systems natural colors palette anticipate the possibility of a ban on aluminum lakes.
Color StabilityThe scientists working on this new line of natural colors knew that in addition to the regulatory constraints, good color stability—over time and with exposure to light—would be an important requirement. Natural colors are notoriously unstable under prolonged light exposure. To ensure good quality colors, the natural colors palette began with decisions about what would not be included. Annatto- and chlorophyll-based colorants were not even considered for the new line. The Aquarius natural colors coatings are based on more stable colorants such as carmine, riboflavin, caramel, and anthocyanins.
Each of the natural colors formulations underwent exhaustive light stability testing, using International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use standard protocols for photostability. Samples were exposed to simulated daylight for 1.2 million lux hours under the most stringent conditions, direct light exposure.
A spectrophotometer was used to measure the ΔE of two L*a*b* readings for each sample, a protocol developed by the Color Measurement Committee (CMC) of the Society of Dyers and Colorists (see Figure 1). L* is a reading in the white to black plane, a* is in the red to green plane, and b* is in the yellow to blue plane. The ΔE CMC is simply a Pythagorean distance calculation between the two measured points. A ΔE of 3.0 or less is the amount of color shift for which the average observer will be unable to perceive a color difference. The hues chosen for the current natural colors coatings palette have color stability that ranges from good (ΔE 5.0 to 7.0) to good (ΔE 3.0 to 5.0) to excellent (ΔE < 3.0). Because these testing conditions are extreme, Ashland Specialty Ingredients’ scientists are confident that all the natural colors offerings are color stable under normal lighting conditions.
For color storage stability testing, we again chose to follow ICH guidelines. We used an accelerated stability test that is run at 40 degrees C and 75% relative humidity. Coated tablets were placed in high-density polyethylene bottles for up to three months and measurements were taken with a Hunter LabScan spectrophotometer at one-, two-, and three-month intervals. Again, ΔE values of less than 3.0 were considered stable, and those colors were included as part of the natural colors palette.
Additional QualitiesAs with the entire line of Aquarius coating systems colors, natural colors are sprayable at 20% solids, making them an efficient and economical choice, with shorter tablet coating times. This has the added benefit of allowing effective coating of friable or moisture- and temperature-sensitive cores. The formulations in the natural colors palette are color stable, label friendly, and easy to use. In addition, they can be combined with Aquarius barrier coating technology for protection against moisture and odor.
All of the Aquarius coating systems natural colors palette offerings have been formulated from Ashland Specialty Ingredients’ line of cellulose polymers. Ashland is the only film coating supplier that is back integrated in the manufacturing of hydroxy propyl methylcellulose, the cellulose polymer raw ingredient in many film coatings. This polymer know-how gives Ashland the ability to make specific polymer grades for coating applications and leads to a strong technical advantage in delivering film coating products. Ashland Specialty Ingredients’ technical experts work on customized coatings, color matching, and troubleshooting, and can even provide tablet development at state-of-the-art technical centers across the globe.
- Nutrition Business Journal. NBJ supplement business report. NewHope360 website. Sept. 1, 2011. Available at: http://newhope360.com/2010-supplement-business-report-0. Accessed March 19, 2012.
- Food Standards Agency. FSA advice to parents on food colours and hyperactivity. FSA website. Available at: www.food.gov.uk/safereating/chemsafe/additivesbranch/colours/hyper. Accessed Sept. 28, 2011.
- Fusaro D. When it comes to synthetic food colors: beware the “Southampton Six.” Food Processing.com. July 6, 2010. Available at: www.foodprocessing.com/articles/2010/colorants.html. Accessed March 19, 2012.
- Byrne J. Nielsen poll indicates global preference for natural food colors. FoodNavigator.com. Oct. 6, 2011. Available at: www.foodnavigator.com/Financial-Industry/Nielsen-poll-indicates-global-preference-for-natural-food-colours. Accessed March 19, 2012.
- May RK, Evans MJ, Zhong S, et al. Terahertz in-line sensor for direct coating thickness measurement of individual tablets during film coating in real-time. J Pharm Sci. 2011;100(4):1535-1544.
- Maurer L, Leuenberger H. Terahertz pulsed imaging and near infrared imaging to monitor the coating process of pharmaceutical tablets. Int J Pharm. 2009;370(1-2):8-16.
- Ho L, Müller R, Gordon KC, et al. Terahertz pulsed imaging as an analytical tool for sustained-release tablet film coating. Eur J Pharm Biopharm. 2009;71(1):117-123.