The Pigmentation of Poultry Products III: The feed stability of synthetic yellow carotenoids

In part one of this series, it was explained that a bright-colored egg or a well-pigmented chicken always comes from a healthy bird. It was also explained that the pigmentation depends on several factors but that a key one is the source and feed stability of the carotenoids used for the process. Carotenoids by nature are susceptible to degradation by light, heat, humidity and oxidative agents. Storage, milling, premixing, feed processing and feed storage present multiple opportunities to reduce the number of active particles per gram of final product. Technology has therefore been developed to protect them  throughout the entire feed manufacturing process.

DSM uses a beadlet technology containing apo-ester in a corn-starch-coated matrix of lignosulfonate. Butylated hydroxytoluene (BHT) is added as an antioxidant. The aim is to have the best-performing and most stable yellow carotenoid in the animal nutrition market. In order to verify the process, DSM’s Nutrition Innovation Center in Kaiseraugst, Switzerland, carried out an experiment involving the most important brands of yellow carotenoids. Samples were received from different markets, analyzed for initial content verification, and stored at 4 °C until they were ready to be tested. They were then subjected to three different processes in order to evaluate their stability across the whole feed production cycle.

1.     Stability As-Is:

Samples were stored at 30 °C with 65% relative humidity (rH) in polyethylene (PE) pouches, and the apo-ester content was measured after  0, 1, 3 and 6 months.

2.     Stability in premix:

Samples were incorporated in a vitamin/mineral premix containing 3.8% of choline chloride and 2.5% of trace minerals. After incorporation, the samples were stored at 25°C with 60% rH, and the apo-ester content was evaluated after 1, 3 and 6 months of storage.

3.     Stability in feed:

Feed containing 64% wheat and 28% soybean meal was prepared at the feed mill of the Nutrition Research Center in Village-Neuf, France. After mixing, it was processed at 90°C and stored in polyethylene (PE) bags at an ambient temperature (20–25°C, with 30–60% rH).  The apo-ester content was measured in feed samples after 0, 1 and 3 months. Feed was analyzed either in mash or pelleted form.

After the three processes were completed a calculation of total stability was performed,  considering Carophyll® yellow 10% as the standard. Analysis was performed in duplicate at DSM’s Analytical Research Center in Kaiseraugst, Switzerland.

Stability As-Is

Initial content and participant products are presented in Table 1.  A total of four different samples were analyzed from three different producers of apo-ester. All samples were above the declared levels.  Differences in initial content can be attributed to time after production, packaging, formulation, storage conditions and coating technology. All products are showing a satisfactory apo-ester content, which is one of the main characteristics that is reviewed by feed companies across the world.  Graph 1 shows the results of the recovery trial for the product As Is.

Differences in the degradation rate of the carotenoid across different products are a direct consequence of different formulation technologies – packaging, storage conditions and timing all being equal. In this particular data set, the initial content differed across the four different samples. However, similar content was found after 1, 3 and 6 months of storage. Under these conditions, all the sources of apo-ester lost more than 30% of their initial content, highlighting the need to keep all the products at the recommended room temperatures and as far as possible in the original package so as to avoid carotenoid degradation. In the case of  Carophyll® Yellow, it is recommended to keep this product below 15°C, and in the unopened original container. Once opened, the contents should be used quickly.

Stability in vitamin and mineral (VTM) premix

The results of the premix stability trial are shown in Graph 2. Vitamin-mineral premixes are very aggressive on carotenoids and therefore the time, temperature and premix composition are crucial for the total stability of apo-ester. Under the experimental conditions, the four tested products experienced a content reduction of 13%–30% in the first month and up to 50% after 6 months of storage. Moreover, after 3 months of storage it was possible to observe important differences of 7%–17% lower than  Carophyll®. After 6 months, ApoEplus® 10S and Lucantin® Yellow  retained only between 50%–60% of their initial value. Premixes are particularly aggressive mixtures,  given their high content of reactive substances such as minerals and choline. Most carotenoids are applied at such low concentrations that most professional feed mills prefer to include them in a premix before incorporating them into the final feed. Carotenoid producers have to formulate the product in such a way as to minimize losses and preserve the functionality of the active ingredient.

Stability in feed

The apo-ester recovery data for mash feeds are presented in Graph 3. Differences of up to 15% were detected after the first month, showing the need to use mash feed as soon as possible and also the need to use stable sources of carotenoids such as Carophyll®. These differences can significantly impact the functionality of the carotenoid source, since feeding storage is highly variable in terms of conditions and time. This is especially important for commercial feed companies, where the time between feed production and final consumption can be several weeks. After 3 months of storage, the same trend continued, with one batch of the Lucantin® Yellow product showing a reduction of up to 35% of the original content. The source and formulation of apo-ester  heavily influence the pigmenting capacity of the product.   The effect of pelleting and storage time are presented in Graph 4.  The initial retention after pelleting at 90°C shows a good response for all the different apo-ester sources, with Lucantin® Yellow and ApoEplus® 10S showing retentions in excess of 100% . However, the way the source is modified during the pelleting process affects the stability during storage, with significant differences showing after 1 month and yet more evident after 3 months, where the differences in retention can be of up to 8%. The product from BASF (Lucantin® Yellow) presented significant differences between the two analyzed batches.  This resulted in differences of up to 20% in retention rate between one batch and the next. Thermomechanical stability was not a main differentiator of quality.  

Stability throughout the whole feed processing cycle

To achieve a more holistic understanding of the influence of the premixing, pelleting and storage time on the retention of apo-ester across different commercial sources, the total stability of the feed was calculated, considering storage times of conditions of 3 months As Is,  3 months in premix, and 1 month in pelleted feed (Table 2). The stability was calculated as total (% relative to initial content) or relative to Carophyll® yellow as the standard. Considering the whole process, Carophyll® Yellow was the top contender in terms of stability, while the other three products  came around 1% behind. In some of the steps, they were closer to  Carophyll® yellow, but considering the whole process, it is clear that we can observe differences of 10%–15%.  Table 3 shows a similar trend for pelleted feeds, with  Carophyll® Yellow being  20% higher than the other products studied.  

The choice of a quality-sourced carotenoid is important for the success of any poultry pigmentation program. Stability is one of the main qualities, since the molecule itself is the same across different sources. The formulation to protect the pigment is of crucial importance for preserving the molecule’s integrity across the different and harsh conditions of the feed manufacturing process.