The Pigmentation of Poultry Products II: The feed stability of red carotenoids

In part one of this series, it was explained that a bright-colored egg yolk always comes from a healthy hen. 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 are by nature susceptible to degradation by light, heat and oxidative agents. Storage, milling, premixing, feed processing and feed storage consequently 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 canthaxanthin in a cornstarch-coated matrix of lignosulfonate. Butylated hydroxytoluene (BHT) is added as an antioxidant. The aim is to have the best-performing and most stable red 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 red 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 canthaxanthin 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 canthaxanthin 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). To define stability, the canthaxanthin content was measured in feed samples after 0, 1 and 3 months.

After the three processes were completed, a calculation of total stability was performed, taking Carophyll® red 10% as the standard. The analysis was performed in duplicate at DSM’s analytical Research Center in Kaiseraugst, Switzerland.

Stability As Is

The initial content and participant products are presented in Table 1.  Nine different samples from seven different makers were analyzed.  Samples from DSM, NHU and ZMC were above the declaration level, while Juyuan was inside the calculated analytical error margin. The rest of the products were below the expected level at the beginning of the trial.  Differences in initial content can be attributed to time after production, packaging, formulation, storage conditions, and coating technology. Several of the products show a satisfactory initial content of canthaxanthin, which is one of the main characteristics that feed companies look for worldwide.  However, an initial low content related to the declaration may be the result of one or several factors that are not in accordance with the customer’s expectations. Graph 1 shows the results of the recovery trial for the product As Is.

Differences between individual products in the degradation rate of canthaxanthin are a direct consequence of different formulation technologies – packaging, storage conditions and timing being equal. After one month of storage at 30 °C with 65% rH, Carophyll® red and the ZMC products were above 90% of the initial value,  while Avixanthin® was at 85%. The product from Leader® was clearly behind the rest at 40%.  However, after 6 months of storage, Carophyll® retained 88% of the initial value, while all the rest were below 66% and the Leader product was at 18%. This is of particular consequence in view of the fact that products are shipped globally and can spend several months in transportation or stored in sub-optimal conditions. The formulation of Carophyll® has been designed to provide the maximum possible protection to the active molecule, especially during transportation and storage.

Stability in vitamin and mineral (VTM) premix

The results of the premix stability trial are shown on Graph 2. There were clear differences among the two different batches of Lucantin® red, with one of them being above 90% recovery at both storage times, while the other was was 15% and 38% lower at 3 and 6 months of storage respectively. Carophyll®, Avixanthin® and ZMC recoveries were at 90%  after 3 months of storage. Notable was the activity reduction of the Leader product even at 3 months. After 6 months, similar stability was presented by most products, except by Leader® and Canthaplus®, which were clearly inferior to the rest. Premixes are particularly aggressive mixtures, given their high content of reactive substances such as minerals and choline. Most of the carotenoids are included in such a small quantities that most professional feed mills prefer to include them in a premix before incorporating them in the final feed. Carotenoid producers have to formulate the product in such a way as to minimize losses and preserve the functionality of the molecule. In this particular study, differences among producers were detected at 3 months of storage in premixes.

Stability in feed

The canthaxanthin recovery data for mash feeds are presented in Graph 3. After 1 month of storage, Carophyll® red, Essention® red and Avixanthin® retain their initial values, while the rest lost between 5% and 25% of their initial activity. 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 may be several weeks. After 3 months of storage, the same trend continued; however, samples from Canthaplus® and Leader® presented significant reduction of their activities with a reduction to 58% and 71% of the original content respectively. The source and formulation of canthaxanthin heavily impact on the pigmenting capacity of the product. 

The effects of pelleting and storage time are presented in Graph 4.  Besides one sample from ZMC, all the other products present good stability after pelleting in these conditions. Thermomechanical stability was not a main differentiator of quality.  The recovery of canthaxanthin after different storage times of pelleted feed  followed the same trend as the mash trial. After 3 months of storage, some samples presented  retention values of 90–100%, with others presenting an intermediate value of around the 70% mark and the Leader® red sample scoring particularly low at 39%. The Carophyll® and one of the Lucantin® samples presented recoveries of more than 80% after 6 months of storage, whereas the rest lost 40% of their initial activity. The sample of Leader® red at 6 months was not available for analysis at this time.

Stability throughout the whole feed processing cycle

In order to have a more comprehensive understanding of the influence of the premixing, pelleting and storage time on the retention of canthaxanthin across different sources of the molecule, the total stability of the feed was calculated in Table 2, considering storage times of conditions of 3 months As Is, 3 months in premix, and 1 month in pelleted feed. The stability was calculated as total (% relative to initial content) or relative, using Carophyll® red as the standard. Considering the whole process, Carophyll® was the top contender in terms of stability, while ZMC came a close second. Some products lost more than 50% of their activity during the process (Lucatin® red 1, NHU’s and Canthaplus), while Leader® presented only 10% of the Carophyll® value. 

The choice of a quality 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 various and harsh conditions of the feed manufacturing process.