The Pigmentation of Poultry Products IV: The feed stability of extracted 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.. On the other hand, the poultry producer has the alternative of using chemical extracts of Tagetes (marigolds) as a source of the pigmenting carotenoids lutein and zeaxanthin. These compounds are largely unformulated and in concentrations of 2%–4%. One particular exception is the product Colortek® (EW Nutrition), which has concentrations of up to 10%. In order to verify the process, DSM’s Nutrition Innovation Center in Kaiseraugst, Switzerland, carried out an experiment involving several different brands of Tagetes from around the globe. Samples were received from different markets, analyzed for initial content verification, and stored at 4°C until they were ready to be tested. The samples were subjected to three different processes in order to evaluate their stability across the whole feed production cycle.

1.     Stability As-Is (Test 1):

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

2.     Stability in premix (Test 2):

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 apo-ester or lutein + zeaxanthin content was evaluated after 1, 3 and 6 months of storage.

3.     Stability in feed (Test 3):

Feed containing 64% wheat and 28% soybean meal was prepared at the feed mill of DSM’s 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).  Apo-ester or lutein + zeaxanthin content was measured in feed samples after 0, 1 and 3 months. Feed was analyzed either in mash or in pelleted form.

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

Test 1. Stability As-Is.

Initial content and participant products are presented in Table 1.  A total of 11 different samples were analyzed from 7 different producers of Tagetes, and were compared to a standard sample of Carophyll® Yellow.  All samples were below the declared levels.  Differences in initial content can be attributed to time after production, packaging, formulation, storage conditions and formulation. There is huge variability in initial content, ranging from 48%–88% of declared level, depending of the supplier. It is very important to ask to perform laboratory analysis in order to check the initial content of the products that is being acquired. Most of the Tagetes products are not formulated and are therefore significantly exposed to high environmental temperature, light and oxygen.

 Differences in the degradation rate of the carotenoid across different products are a direct consequence of different formulation technologies – packaging, storage conditions and timing being equal. In this particular data set, the initial content was different among the different samples. Big differences were found among the different suppliers, with Carophyll being clearly superior after 1 and 3 months of storage. Some other products presented less than 40% of the declared content after 3 months of storage. After 6 months, there were some products with no activity whatsoever, while Pixafill and Avizant retained more than 60% of their declared value. Under these conditions, all the sources 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, in order 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 content should be used quickly. Tagetes sources showed highly varying levels of degradation. For this reason, it is very important to understand the product, the source and the vendor. Not all sources of Tagetes performed equally.

Test 2. Stability in vitamin and mineral (VTM) premix

The results of the premix stability trial are shown in Figure 1. For this test, 3 samples of the product Colortek were evaluated together with Carophyll® Yellow. 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 and marigold extracts. Under the experimental conditions, the tested products experienced a content reduction of up to 53% in the first month and up to 86% after 3 months of storage. From the Colortek samples, a wide variation was observed, dependent on the kind of antioxidant used. When EMQ was the main antioxidant, the stability was reasonably good and closer to Carophyll® Yellow. However, on the two samples using BHT as an antioxidant, there was an important reduction in lutein/zeaxanthin content after 3 months of storage. 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. The formulation differences between Carophyll® and Colortek are shown in Figure 2. The formulation technology applied in the Colortek® product does not show good protection, and this results in poor premix stability.  

Test 3. Stability in feed

The recovery data for yellow carotenoids for mash feeds are presented in Figure 3. After 1 month of storage, the retention is as expected for all of them, at around 90% when compared with the initial values. After 3 months of storage, differences can be found, with Carophyll® holding a retention value above 80%, while the three samples of Colortek showed retention values of  54%–72%. It should be noted that the two samples of Colortek using BHT (current form) are the ones showing the lowest stability values. In practical terms, differences at 3 months can come in to play when one considers commercial feed and/or the effects of feed being stored in holding bins, especially in the summertime. Figure 4 shows the retention values in pelleted feed. The initial pellet stability is quite good for all sources of carotenoids, and these values hold after 1 or 3 months storage.

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 feed manufacturing process, it is evident that the formulation of the Carophyll® product is effective in preserving the content of the carotenoid in the final product, premix and feed when compared with a concentrated source of lutein/zeaxanthin such as the product Colortek®.

The choice of a quality-sourced carotenoid is important for the success of any poultry pigmentation program. Carotenoids are quite sensitive to light and temperature, and the right formulation has to be achieved across the feed manufacturing process. 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.