DIETARY SUPPLEMENTATION OF PIGMENTS IN COMMERCIAL LAYERS FOR ORANGE /YELLOW YOLK EGG COLOUR

DIETARY SUPPLEMENTATION OF PIGMENTS IN COMMERCIAL LAYERS FOR ORANGE /YELLOW YOLK EGG COLOUR

DR.RAJESH KR. SINGH

The degree of yolk color is an important criterion for table eggs for consumption as well as for manufactures of egg-containing market food products . The egg-yolk color is the result of the deposition and coloring capacity of xanthophylls in the yolk. The content and profile of carotenoid pigments present in the feed primarily determine yolk colour. Corn, marigold and ground clover contain a carotenoid pigment which leads to yellow color (NRC, 1993). Bird’s health condition, the genus and age of hens and other environmental conditions also affect yolk coloring (El Baushly and Raterink, 1989). Hens are not able to synthesize the color pigments, but they have the ability to transport about 20-60% of pigments into yolk from ingested feed (Bartov and Bornstein, 1980). Native breeds of chicken usually produce eggs with pigmented yolk probably due to free range feeding. Various herbal supplements containing carotenoids have been evaluated for their efficacy as egg yolk colour enhancers.

As the saying goes “you eat with your eyes first”, nothing closer to reality: the color of the food is one of the main factors affecting our choice. Within animal production, this organoleptic aspect acquires a great importance in the case of eggs, especially the egg yolk color.

There are great differences between the yolk color preferred in different countries and multiple natural and synthetic colorings have been developed to cover this range of colors.

The color of the egg yolk

As in other foods, the egg color is one of the most important aspects for consumers, especially the color of the yolk. It is an important organoleptic aspect for the acceptance of this product that the consumer relates to its quality. Both the color of the yolk and its homogeneity (within the yolk and between different eggs) are important.

The color of the egg yolk is determined by the type and profile of carotenoids present in the feed and their intestinal absorption. Carotenoids are a fat-soluble group of yellow, red and orange pigments. They can be divided into two large groups: carotenes and xanthophylls.

More than 600 different types of carotenoids have been described. Xanthophylls are more important in egg coloration than carotenes.

It is a common practice to color egg yolks by adding pigments in the diet of layers. In fact, this phenomenon in nature is as old as the very animal kingdom. Carotenoids, and more specifically xanthophylls (carotenoids containing oxygen atoms within their molecules) give the egg yolk its natural color. Carotenoids also lend feathers their red, orange and yellow hues in many bird species, which has been identified as a sign of health and reproductive eligibility. In traditional and self-feed farming systems, xanthophylls, primarily lutein and zeaxanthin, are present in dietary components such as corn, wild flowers, green vegetables, fruit, insects, etc

Modern poultry production has brought about continuous improvements in output levels and feed conversion, as a result of genetic, management and health enhancements. However, this means that for every egg produced, layers take up less carotenoid from raw materials. This makes it necessary to balance out the levels supplied in the diet by additional supplementation. In addition, direct supplementation of carotenoids has enabled unrestricted use of raw materials lacking significant levels of xanthophylls. The use of such external sources also guarantees lower variability of egg yolk pigmentation levels among animals and throughout their productive lives. The use of these xanthophyll supplements had led to renewed interest in the egg as an excellent source of highly bioavailable xanthophylls, which are otherwise not produced endogenously and must be taken up from the diet

 

For marketing of poultry products, appearance and colour have a central role in judging quality. Consumers rate the yolk of an egg as inferior if the dose of oxycarotenoids is insufficient. In regions where maize is traditionally grown, chicks with white skin are rarely marketed and when buying young hens the yellow colour of legs and beak are a quality criterion. In the following, the factors which influence the pigmentation of egg yolk and skin should be considered. Oxycarotenoids are responsible for the pigmentation of egg yolk and skin as well as of legs, beak, comb and feathers and as poultry cannot produce these substances, they must be added via the feed.

 

Feeds for commercial layers are usually supplemented with synthetic pigments to ensure egg yolk has a desired and, even more importantly, consistent color; ranging from golden yellow to deep orange-red depending on local preferences. There is, however, a small but increasingly significant market, in which all-natural ingredients are all that are allowed to be used in layer feeds, and as such, synthetic pigments are excluded. For this market, for which egg yolk color is as important as any other market, two aspects that largely control egg pigmentation must be considered: type and concentration of pigments.

Pigments   that   impart a yellow or orange color to egg yolk belong to an oxycarotenoid group called xanthophylls. The most important xanthophylls for egg yolk coloration are zeaxanthin and lutein. The former is causing egg yolks to be more orange-red in color, while lutein imparts a more yellow hue. The balance between these two major xanthophylls is what determines final color in egg yolks. Equally important to this balance is the total xanthophyll concentration in feed. As a rule of thumb, to achieve a satisfactory saturation of color, the feed must contain at least 15-20 ppm total xanthophylls.

From among commonly available ingredients, maize is considered a good source of xanthophylls (20 ppm), followed by the less frequently encountered but very powerful maize gluten meal (275 ppm), and the infrequently used alfalfa meal (175 ppm). Maize and maize gluten meal are rich in zeaxanthin (4 ppm in whole maize), whereas alfalfa meal is rich in lutein (64 ppm). An unusual source of natural xanthophylls is marigold petal meal, which was added quite frequently in commercial feeds before the advent of synthetic pigments. The concentration of xanthophylls in Marigold petal meal is 7000 ppm. More recently, the use of certain algae as a source of natural pigments has been investigated as it was found they can contain up to 2000 ppm xanthophylls.

Another consideration in the effort to provide layers with feeds rich in natural pigments is that xanthophylls are quite unstable compounds and as such they deteriorate quite easily during storage. As such, the addition of a strong (natural) antioxidant will help maintain the potency of natural pigments for longer. In addition, avoiding excesses of vitamin A will help increase yolk color intensity as this vitamin has been shown to antagonize xanthophylls in their role as pigments. Finally, ensuring pullets enter egg production with highly colored shanks (by providing high levels of xanthophylls in the grower feed) will maintain a deeper egg yolk color for longer as hens draw from their body pigment reserves (shanks and skin) to supplement what they receive from their feed on a daily basis.

 

 

Factors which influence pigmentation-

• Oxycarotenoid source
• Oxycarotenoid content
• Storage period and storage conditions of raw components and feed
• Heat treatment of the feed
• Pigment additives
• Saponification of natural pigment supplements
• Effect of incorrect mixtures regarding pigments
• Feed intake Energy content of the ration Ambient temperature Feed structure (esp. in meal feed) Pellet quality Taste and smell Water intake Light (-programme)
• Additional feeding with wheat
• Fat and fat quality
• Antioxidants
• Vitamin E as antioxidant
• Calcium
• Vitamin A
• Growth promoters
• Feed ingredients with negative effect NSP Mycotoxins
• Helth status
• Housing
• Genetic factors

 

Oxycarotenoid source

In nature, oxycarotenoids are found in many raw materials including various components of poultry feed. Choice of raw materials used in poultry feed is therefore a major influencing factor in pigmentation. Maize, wheat and barley which are major feed components can cause significant variations in egg yolk pigmentation (see Table 1). The visual colour assessment was made using a Hoffmann La Roche yolk fan. The maizecontaining feed led to a fan value of 10, whereas wheat and barley showed extremely pale yolks with a fan value of 4. The reason for these differences, of course, is due to the different oxycarotenoid contents in the raw materials used.

Supplementation of colourants-

So far only raw materials have been mentioned as sources of pigments. However, egg yolk colour demanded by the consumer cannot be achieved with the usual components because this depends on the colouring effect of the oxycarotenoids included in the raw materials. All the raw materials mentioned up to now contain mainly the pure yellow-colouring lutein. Maize additionally contains the orange-colouring zeaxanthin. Even with high inclusion rates in the feed the Roche fan value cannot be raised over 10. For a more intensive yolk colour, therefore, colourants must be added. Similar circumstances apply to skin pigmentation. The high oxycarotenoid level required in the feed necessary to reach a sufficient degree of yellowness in the epidermis cannot be achieved with the usual feed components. Yellow colourants, and in some areas, red colourants must be added.

If the yellow degree of egg yolk or skin needs to be intensified, the synthetic apo-ester or standardised marigold products may alternatively be used. For the intensification of the red colour, two synthetic products – can thaxanthin and citranaxanthin – are available. Standardised paprika products may be a natural alternative. With regard to the pigment content, all colourants should be standardised with a fixed value. Because of the presence of added antioxidants, pigment activity can normally be guaranteed for one year. As the inclusion rate of pigments in feed is low, a homogeneous mixing with all the other feed components is extremely important for good colour efficiency. It is also fundamental, for marigold and paprika products, to choose the correct carrier to ensure stability and optimum mixing in the feed.

 

Feed intake

 

Feed intake and thus oxycarotenoid intake have an important influence on pigmentation. The energy content of the ration plays a significant role, particularly in the laying hen. An increased energy content in the feed normally leads to a decreased feed intake and in such cases all relevant nutrients and active substances (including colourants) must be adjusted. During higher ambient temperatures (e.g. in summer time) a decreased feed intake may also occur. Here corres ponding steps – as mentioned above – can be used to counteract the situation. A precondition for optimum feed intake is a good feed structure. Particularly high amounts of fine particles lead to depression of intake in laying hens. The proportion of particles under 0.5 mm should amount to less than 19 %. If the pigment supplement is among these fine particles, which the hen tends not to eat, this must lead to problems with pigmentation. Attention must be paid to a good pellet quality in fattening poultry so that the animals take in enough feed. As already mentioned in the introduction smell and taste play a minor role in poultry. However, under certain conditions these reactions can also be seen in poultry. e.g. with the use of bitter constituents such as medication or the use of acids. The higher the acidity, the higher is the negative influence on feed and hence water intake. A decreased feed intake can partially be seen at 0.5 to 1.0 % acid use. This particularly applies to fumaric acid and their acetates (decreasing acid-effect: fumaric acid>formic acid>acetic acid>propionic acid). Rancid fats may also lead to reduced feed intake. As is well known, feed and water intake are closely related. A restricted water intake normally leads to a restricted feed intake. In the case of decreased feed intake, the watering system should always be checked (e.g. hydraulic pressure). Furthermore mycotoxins (mainly vomitoxin) as well as amino acids (tryptophan) and amino acid imbalances may influence feed intake.

 

 

Additional wheat feeding

 

In recent years many broiler producers use whole-wheat kernels which they provide together with supplementary broiler feed (a kind of a concentrate) in the later part of the fattening period. A basic precondition for successful “wheat feeding” is homogenous mixing with the concentrate feed. Furthermore, it is important that no separation occurs in the feeding system on the farm. To achieve optimum skin pigmentation, it must be ensured that the pigment quantity taken in with the feed is the same as that from complete feeding. The wheat, therefore, should only be administered together with supplementary feed. Colourants, as well as other nutrients and active sub stances (e.g. coccidiostats), must be added at the correct level based on the quantity of supplemental wheat. But also in case of an optimum composition of the supplementary feed non-uniform results in skin pigmentation – but also in live weight and with regard to fat deposition in the carcass – may occur. The reason: Chickens are able to eat selectively and in particular they prefer wheat grains. If they have the possibility to choose they will eat whole wheat rather than pelleted supplementary feed. This may cause problems, particularly if there is not enough trough area available, because the first birds will increasingly take in wheat leaving the leftovers for the following chicks.

 

 Fat and fat quality

The resorption of fat-soluble oxycarotenoids is influenced by the fat included in the feed. Soybean oil and lard increase the oxycarotenoid deposition in the egg linearly up to a dose of 5 %. Using for example 6 % soybean oil in the feed, the citranaxanthin dosage can be decreased from 6 ppm to 4 ppm compared with the control without oil supplementation, without any change in the egg yolk pigmentation. The use of long chain, polyunsaturated fatty acids has a positive effect on the oxycarotenoid deposition, however, the use of long chain saturated fatty acids should be avoided. The contradictory results found in the literature with the use of long-chain polyunsaturated fatty acids have to do with the fact that these fatty acids have a considerably higher tendency to oxidation. In the intestinal tract oxidised fatty acids react with the oxycarotenoids and destroy them resulting in less colourants being accumulated in the yolk and skin.     The relation between fat quality and deposition of colourants was demonstrated by Oertel and Hartfiel (1981; Figure 4). The peroxide value in the feed increased over a 77-day storage period especially with soybean oil and lard, but less so with tallow. The canthaxanthin content of the egg yolk took a contrary course – shown here as a change in comparison to the initial value. In the fist two weeks soybean oil causes a rapid and considerable colourant increase in the egg yolk. Afterwards the pigment content in the egg yolk decreases continuously – particularly with use of soybean oil. Thus the fat quality in poultry feed should be regarded as especially important. Oxidised fats may considerably reduce the deposition of colourants and as both fat oxidation and temperature have a negative effect it is sensible to exercise caution during the summer months.

 

 Antioxidants

 

Because of fat oxidation, antioxidants must be taken into consideration. Oxidation processes can be retarded or stopped using antioxidants and hence fat quality maintained for a longer time. Figure 5 shows the results of a stability test with the aforementioned alfalfa concentrate. A non-treated control was investigated with two further treatments, ethoxyquin and Loxidan (an antioxidant mixture) supplemented directly during the production. In contrast to the negative control, with a pigment loss of 30 % within 4 months of storage, the decrease with the ethoxiquin stabilisation was 14 %, and in case of Loxidan treatment only 10 %. A trial by Harms, who administered ethoxyquin to laying hens via the drinking water, shows that ethoxyquin develops its protective effect mainly in the intestinal tract (Table 4). Feed intake was unchanged by treatments and yolk colour spectrum – judged by the wave length – was identical. Ethoxyquin given via the drinking water led to a significantly more intense yolk colour compared to untreated water. Synthetically produced antioxidants react with the decomposition products of the fat oxidation in the intestine and thus also protect other feed additives which are endangered by fat oxidation. Besides oxycarotenoids antioxidants can also protect vitamin E against oxidation. Because of the acetate form vitamin E feed supplements are protected against oxidation during feed storage. However, in the intestinal tract vitamin E is split into free tocopherol and acetate. If oxidised fats are present in the intestinal tract any free tocopherol can act as an antioxidant and can be used up. As a result, less tocopherol is absorbed through the intestinal wall and its important function, as a biological antioxidant in the organism, is reduced. In extreme cases vitamin E deficiency symptoms may occur. In addition the negative effects regarding stability of poultry and poultry products during storage must be considered.

 

Vitamin E as a natural antioxidant

As already mentioned with regard to fat quality, tocopherols also act as antioxidants and their supplementation in the feed therefore has a positive effect on pigmentation. Tocopherols may protect the oxycarotenoids in the intestinal tract against oxidation but with the result that less tocopherols are absorbed as a biological antioxidant.

 

Calcium

The calcium content in feed is repeatedly mentioned in the literature in connection with egg yolk pigmentation. High calcium levels negatively influence yolk colour. If the calcium content is raised from 2.5 % to 3.5 % in layer feed it is necessary to include 1.7 ppm citraxanthin instead of 1.0 ppm to achieve the same yolk pigmentation. In a further trial an increase of the calcium content from 3 % to 4 % led to a decreased yolk colour of one on the Roche fan scale. There are also references in the literature to a reduction of feed intake with an increased calcium content in the ration which will result in a reduced oxycarotenoid intake. Thus the calcium content in the feed should not be adjusted higher than is necessary.

 

 Vitamin A

We return to the vitamins. In high doses, vitamin A disturbs the absorption of oxycarotenoids because both compete for the same transport mechanism. Several years ago the feed industry used this fact to include high amounts of vitamin A (up to 100,000 IU/kg) in broiler feed. A white carcass could be produced even though high amounts of maize were used – at that time maize was very cheap. Legislation was introduced to limit vitamin A during the fattening because of the possible risk of excessive vitamin A contents in foodstuffs of animal origin (e.g. liver, liver products). Incorrect mixtures with high vitamin A contents – or also massive doses of vitamins administered via the drinking water – can be a reason for insufficient pigmentation of skin and yolk. A 3-fold overdose – 36,000 IU instead of 12,000 IU vitamin A/kg feed – leads to a decreased colourant concentration in the tissue of toes and blood plasma of almost 50 %. The content of colourant in the liver decreases by about 30 %, accompanied by a significant increase of the vitamin A concentration.

 

Growth promoters

 

There are different findings concerning the influence of growth promoters on pigmentation. Positive effects can be seen in some trials, whereas other trials show no difference. Some authors assume, that performance promoters may improve the absorption of pigments by exerting a positive effect on intestinal health especially in situations of subclinical diseases of the intestine.

 

Feed ingredients with an unfavourable effect on pigmentation

 

It is known that barley, as a component in poultry feed, has a negative effect on pigmentation. This is explained by the fact that barley contains non-starch-polysaccharides (beta-glucan), which cause a higher viscosity of the intestinal content and therefore unfavourably influence the digestion and resporption of pigments. Similarly, wheat with a high pentosan content may lead to similar effects. Supplementation with enzymes (beta-glucanase, xylanase etc.) leads to a positive effect on yolk pigmentation (Figure 6). In a trial with 68 % barley, carried out in Spain, an improvement of 0.2 according to the Roche scale was registered with very high initial fan values . With a significantly lower initial fan value (6 – 9), the effect of enzyme supplementation was much more evident in the Australian trial and which also applied in the wheat ration. Australian wheat is characterised by its high amounts of soluble pentosans.

 

Mycotoxins can also unfavourably influence the pigmentation of yolk and carcass. Ochratoxin in particular, as well as aflatoxin and fusarium-toxin must be mentioned in this connection. The oxycarotenoid metabolism can be changed by the presence of mycotoxins as follows:

• Dilution of oxycarotenoids in the intestine
• Reduced resorption via the intestinal wall
• Reduced transport in the serum
• Changed storage in the liver
• Changed deposition in the tissues. As the aforementioned mycotoxins hamper fat transport in general, an indirect influence on the fat soluble oxycarotenoids can be expected. Ochratoxin and aflatoxin may be a cause for increased meat and blood spots in eggs as well as bleeding in the carcass. Aflatoxin, and also T2-toxin (source is maize), may cause intestinal resorption irritations. Fat metabolism is especially affected by a decreased lipase and bile production. Fat is excreted via the faeces. Another feed ingredient with a negative effect on yolk pigmentation is gossypol from cottonseed. Gossypol forms complexes with iron, which lead to undesirable greenish to dark spots in the yolk.

 

Health

 

Some poultry diseases have a specially negative effect on pigmentation of yolk and carcass. Coccidiosis out breaks occur more frequently in alternative housing systems affecting broilers but also laying hens. Even a light coccidiosis without obvious symptoms may cause reduced skin pigmentation. The coccidia type, as well as the gravity of the disease and the respective intestinal area affected, are decisive factors effecting colour. Coccidia, which settle in the anterior intestine have a stronger effect on pigmentation than, for example, caecal coccidia. The effect of an infection of the small intestine with Eimeria acervulina is demonstrated in the following Table (6). Already, 3 days after the infection, the contents of lutein and canthaxanthin in the serum and in the liver have dropped dramatically. Five days after the infection canthaxanthin is hardly detectable in serum and liver and in the toe web only 30 % of the initial values were found. These figures illustrate clearly the effect of coccidiosis on pigmentation.

 

There are several other diseases that show a direct influence on pigmentation. Diseases of the intestine, Contagious Avian Coryza, Newcastle Disease as well as helminthosis belong to this category. Similarly, Fatty Liver Syndrome in laying hens may lead to alterations in pigmentation. Thus, it can be said that a consistent colouring of carcass and egg yolk may be regarded as an indicator of good health and good practical hygienic conditions.

Coccidiostats and helminthica

It is known that the use of nicarbazin or piperacin causes spots in egg yolks.

Influence of the housing system

A number of studies on the influence of daylight on pigmentation have been undertaken. Thus daylight causes a more intense pigmentation of yolk and skin with the skin mainly showing a shift from yellow to orange. The increased feed intake due to daylight is not the reason for this. Possible reasons may either be a pigment change in the feed influenced by light (isomerization of betacarotene to zeaxanthin) or a change in the pigment metabolism of the animal (transformation of zeaxanthin to astaxanthin). Remember the cock with its red comb, the colour of which is caused by astaxanthin and which would not be found in animals that were housed without daylight. With regard to the increased interest in alternative housing systems and the claims of the animal welfare this subject is becoming more important.

 

Genetic

Factors Today mostly hybrid layers and broilers are used and genetic effects on pigmentation are not seen. It is known that the epidermis of certain breeds of fattening poultry cannot be coloured but now only hybrids are used in economical poultry breeding and these are able to be pigmented due to crossing with Asian breeds. Thus genetic factors have no influence on changes in pigmentation.

 

 

 

• What does the color of the yolk depend on?

The color of the egg yolk depends on numerous factors that can be divided into primary factors, those that depend on the type and concentration of carotenoids, and secondary factors, those that depend on the animal.

 

Primary factors include digestibility, metabolism, transference to the egg and deposition percentage of carotenoids administered with the diet. Food disbalances, such as vitamin deficiencies, can also affect the color of the yolk. Some of these carotenoids are precursors of vitamin A, metabolizing to this vitamin when there are deficiencies and reducing the quantity that is deposited in the yolk.

The composition of the diet affects the absorption of these pigments, for example, diets rich in fats favor their absorption. The percentage of deposition also shows great variations between the different carotenoids, from 14% fir astaxanthin to 40% for canthaxanthin.

Secondary factors include age, lineage, health status, as well as animal management. Studies show that all those factors that affect digestive health such as mycotoxins, aflatoxins or ochratoxins have a noticeable impact on the absorption of pigments and diseases, such as coccidiosis or the Newcastle disease.

Maintaining the intestinal health of the animals, for example, by using intestinal conditioner pronutrients, is key for an adequate and maintained pigment absorption throughout the laying phase.

Intestinal conditioner pronutrients are active molecules of botanical origin that act at a metagenetic level on intestinal cells. They stimulate the synthesis of functional proteins and increase the renewal of enterocytes, thus favoring the intestinal physiological status and nutrient absorption, including pigments present in feed.

• How to get the desired coloration by the consumer

A key point that egg producers should keep in mind is that there is no coloring capable of meeting the needs of all markets. There is a wide variation in the colors demanded by different countries and regions, ranging from pale yellow, for example, in Switzerland or Canada, to an intense reddish yellow, as demanded, for example, in the Japanese market.

Such preferences are usually determined by geographical and cultural differences. A factor that also influences consumer preferences for one or another color is the availability of raw materials to feed of hens. For example, in Tanzania, sorghum is used in feed and, since it contains a lower proportion of carotenoids than maize, yolks of a lighter color are preferred.

In order to evaluate the color of the egg yolk, a wide variety of scales have developed in recent decades. However, the scale of La Roche, created by the La Roche Vitamins laboratory, is the most accepted one. This scale relates a given color of yolk to a numerical value on a scale of 1-15, from lowest to highest color intensity.

 

The preferences between the different European countries can be classified following this scale. In Germany, the Netherlands, Spain and Belgium, consumers prefer more orange colors, with values between 13-14 on the scale of La Roche, while countries such as Ireland, Sweden or the north of England prefer paler colors, with values between 8-9. There are also countries looking for intermediate colors such as northern France, the South of England and Finland, who demand colors with values between 11-12 in the La Roche scale.

 

Certain raw materials present in poultry diets contain natural pigments, such as maize or lucerne, although they are not in a quantity enough to obtain the color demanded by most countries. This is why concentrated extracts from certain plants such as marigold and paprika are used. The use of pronutrients also contributes to the absorption of the pigments in these raw materials.

To get the desired yolk color in each country, it is necessary to add pigments to the diet of birds. As each country, and region has different preferences in terms of yolk color, the dose of pigments should be adjusted for each individual case.

• Types of pigments

These pigments can have a natural origin, such as concentrated extracts from certain plants such as marigold or paprika, or a synthetic one. The current trend is to standardize the doses of natural pigment needed for different yolk colors.

There are 6 main types of carotenoids, three that provide yellow color: zeaxanthin, lutein and apo-ester, and other three that provide red color: canthaxanthin, astaxanthin and capsanthin. Different combinations of these pigments allow to obtain different yolk colors, for example, the combination of 2- 4 mg/kg canthaxanthin and 10-20 mg/kg of zeaxanthin allows to obtain eggs with a yolk color between 12 and 15. We must keep in mind that, for values greater than 10 on the La Roche scale, it is necessary to add a red pigment.

 

The importance of color in food

The food color has played a fundamental role in our diet since prehistory, allowing us to discern between those healthy and nutritious foods and those that are toxic or in poor conditions.

This importance of the food color has been etched in our genes so that, to this day, the food color remains one of the organoleptic factors with a greater importance to the consumer. We relate the presence or absence of a certain color with quality and freshness and associate each product with a specific color.

 

A practical example of the importance of color in food can be found in the cola soft drink. In 1993, the multinational Pepsi launched a new transparent cola in order to differentiate itself from other cola soft drinks on the market. However, this product was a complete failure because it was a transparent product and people associated the cola with a dark color, so the previously established relationship between the color and taste of the product was not fulfilled.

Color is one of the main factors with effect on the choice of a food product by the consumer and, as the saying goes, “you eat with your eyes first”. Therefore, since ancient times different food additives have been used to meet the demands of the consumers.

The importance of color also affects products of animal origin, having a special relevance in poultry, where both the color of the egg yolk and the color of the skin and the legs of the chicken are of great importance from a commercial point of view.

• Food colorings

The use of food colorings is not a recent practice, in fact, Egyptians used natural colorings for candies (1500 b. C.). There are references to saffron as a food additive in Homer’s Iliad and it is known that, in the Middle Ages, dyes were used in products such as wine.

 

These additives were generally used to improve the appearance of foods by masking their natural color. However, in the absence of any legislation, any type of compound, such as chalk as a dye for bread, could be used to enhance its whitish color. This led to the emergence of the first legislations on the use of such products, and King Edward I (1272 to 1307) was the first person who regulated the use of food colorings in bread in England.

During industrialization the first synthetic additives were developed, and along with them, the first official laws emerged. Perkin’s mauveine or Perkin´s purple was the first synthetic coloring developed by the chemist William Henry Perkin in 1856.

Currently, the laws determine in detail those compounds that can be used as food colorings, both in animal and human food. In the case of the European Union (EU), this information is in the European (EU) Regulation No 1333/2008, which describes the food colorings as those additives that provide color to a food or return its original color. In the case of the United States, the FDA is the agency that determines the compounds that are eligible in the CFR (Code of Federal Regulations) 21 70.3.

• Pigments in animal feed

In order to offer to the consumers products of animal origin with a certain color that suits their preferences, pigments are commonly added to feed.

These pigments are absorbed by the animal and deposited in the different organic tissues to acquire the desired color. The percentage of deposition will depend on the species and the type of pigment. For example, in the case of birds, xanthophylls are more absorbed than carotenes.

The pigments used in animal feed can be natural or synthetic compounds. They are mainly used in poultry to obtain a certain yolk color and to enhance the color of the skin and legs of these animals. They are also used in salmonid aquaculture to enhance the orange color of muscle tissue.

Conclusion

The color of the egg yolk, as in other foods, plays a fundamental role in the consumer’s choice of the product. Therefore, it is essential to know the demands of each country and to add the necessary pigments to obtain such color.

It is also essential that animals maintain a good intestinal health, to ensure the proper absorption of such pigments, avoiding diseases such as coccidiosis or Newcastle disease, which directly affect the pigment absorption.

Reference-On Request