The Evolution of the YolkFan™ as the Standard for Measuring Poultry Pigmentation

Humans have been consuming eggs and poultry products for thousands of years. In Jared Diamon’s 1997 classic Guns, Germs, and Steel: The Fates of Human Societies, poultry, and specifically Gallus gallus (the red junglefowl), is cited as one of the most important factors that enabled civilization to flourish in Asia (it is believed that Gallus gallus comes originally from the forests of south-east Asia); and the species was cited in Ancient Greece as early as the 5^th century B.C. (A. Lawler and J. Adler, 2012). However, we can safely assume that egg consumption started earlier in our collective history, when eggs were collected from wild birds to supplement the diet of our forefathers. Eggs in nature are naturally well pigmented, given that female birds will transfer their reserve of carotenoids to the egg in order to increase the hatchability and survival of the chick (McGraw, et al., 2005). When eggs were incorporated in the diet of humans, they were expensive delicacies, and the yolk was expected to be orange as a sign of quality.

After the World War II, the spread of intensive farming methods accelerated, and with it, egg production. Poultry feed was wheat-based in Europe. However, the main problem was the color of the yolks, which were not yellow enough for the taste of the European consumer  The yolk color depends its carotenoid content, in terms of quantity and type; and this is highly influenced by the type of feed, as described by Hughes and Payne as far back as 1937. It was clear, then, that if the yolk color were to be intensified in a natural way, it would be necessary to include carotenoids in the feed of the laying hen. Roche consequently examined the possible use of nature-identical carotenoids, produced by industrial methods, as feed additives (Isler et al., 1956). By 1956, the German egg market was surprised at the appearance of the first yolks pigmented with synthetic carotenoids. The innovation was a success, giving consumers the opportunity to enjoy eggs with a vibrant shade of orange in the winter, just as they were in the summer, when hens have access to plenty of green vegetation (an excellent source of carotenoids).  The addition of beta-carotene, canthaxanthin and, later, apo-ester became a fundamental element in successful egg production and marketing worldwide.  (On a side note, the first ever synthetic canthaxanthin, produced by F. Hoffman-La Roche, was partially responsible for the first ever successful flamingo breeding event in captivity, which occurred at Basel Zoo in 1958.)

However, as with any other productive activity, it was necessary to measure the success pigmentation programs, and the only way to do this was by evaluating yolk color in an objective and consistent way across the value chain. This was quite a task, as described in 1970 by K. Streiff,  an agronomist working for Roche, when he outlined the journey towards the first ever Yolk Color Fan. The ways available for measuring color at that time were either subjective and inconsistent (DIN-Tables, Heiman-Carver Rotor, or the Lovibond tintometer), cumbersome (the NEPA system), or else made use of light absorption of the yolk mass in a photometer. Neither of these methods were user-friendly for poultry producers, nor were they consistent and objective, so Roche’s Art Department of Roche commenced an initiative to collect  eggs from all over the world (imagine coordinating that daunting task in the late 1950s!) and trying to reproduce the color of the various yolks in combinations of round, oval, square and elongated shapes of wood or plastic. The result was the first ever Yolk Color Fan, which was produced  in 1956, with 12 egg-yolk shades, each on a separate blade. The color sheets were spray-dyed press-board lamellae of 3 cm x 16 cm. The paint was blended by hand, and the match was checked by mere visual comparison. This first fan was distributed in a limited fashion, but it played a critical role in establishing the basis of a standardized system for measuring yolk color from the farm to the consumer’s kitchen table (Steinegger and Zanetti, 1957). The situation changed when apo-ester became available for yolk pigmentation, since it was evident that a wider range of orange-yellow hues was  available and therefore the 12-blade version of the fan was no longer enough.

In 2016, in response to requests from customers in Japan and other countries,  a blade number 16 was developed, reflecting the growing requirement of the market for a deeper shade of orange in the yolk (Hayakawa, 2015). Under the guidance of Dr. Umar-Faruk, scientists at DSM’s Animal Nutrition & Health Nutrition Innovation Center in Village-Neuf, France, replicated all the colors of the yolk (Figure 5) from 1 to 16, in order for a team in DSM’s carotenoid laboratory in Kaiseraugst,  Switzerland, led by J. Schierle to measure and objectively calibrate the color of the yolks and translate them into ink formulations that printed with extreme accuracy. This success led to the publication of the current (2016) yolk pigmentation guidelines, together with the new and renamed 16-blade YolkFan™. David Yao in China (2016) reported the successful use of the YolkFan™ in grading the shank pigmentation of chicks and older hens in China.

At the same time that the YolkFan™ was being developed, DSM was entering into a partnership with the Company NIX from Canada to develop the digital YolkFan™, which was launched in 2017 (Miranda, 2017) to provide an objective, consistent and reliable tool to measure egg yolk pigmentation. digital Yolkfan^TM - DSM color fans . This device (Figure 6) works with a smartphone in order to measure, capture and save color data related to yolk in terms of L*a* b* color system and the equivalent YolkFan™ color. Since its launch, the digital YolkFan™ has achieved a high level of acceptance and shown good consistency and reliability.