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Xanthophyll depleted, fasted broilers were intubated with various xanthophyll sources in a series of six experiments. The increase in serum xanthophyll per milligram xanthophyll intubated per kilogram body weight was used to estimate exahtnophyll availability. Statistically significant differences among samples within and among generic sources were obtained. As a result, beta-apo-8'-carotenoic acid ethyl ester (apo-EE) was used as a reference standard in Experiments 4 to 6. When the availability of apo-EE was given a relative value of 100, the availability of xanthophyll from corn gluten meal ranged from 47.7 to 89.1% (four samples), from dehydrated alfalfa, 34.6 to 65.4% (eight samples), and from Coastal Bermudagrass, 18.8 to 27.9% (three samples).

The increased consumption of reduced-fat or non-fat products leads to a reduced intake of fat-soluble bioactive substances, such as fat-soluble vitamins. Due to their natural role as transport systems for hydrophobic substances, casein micelles (CM) might depict a viable system. The structure of CM is characterized by a lipophilic core stabilized by an electric double layer-like structure. Modification allows accessibility of the core and, therefore, the inclusion of fat-soluble bioactive substances. Well-known modifications are pH reduction and use of rennet enzyme. A completely new procedure to modify CM structure is offered by pulsed electrical fields (PEF). The principle behind PEF is called electroporation and affects the electric double layer of CM so that it is interrupted. In this way, lipophilic substances can be incorporated into CM. In this work, we evaluated integration of β-carotene into native CM by an industry-compatible process to overcome disadvantages associated with the use of Na-caseinate and avoid great technical effort, e.g., due to treatment with high hydrostatic pressure. Our research has shown that PEF can be used for disintegration of CM and that significant amounts of β-carotene can be incorporated in CM. Furthermore, after disintegration using PEF, a combination of another PEF and thermal treatment was applied to restructure CM and trap significant amounts of β-carotene, permanently, ending up with an encapsulation efficiency of 78%.

A rapid bioassay method for comparing xanthophyll availability from various sources or the pigmenting ability of genetic strains or crosses is proposed. Xanthophyll depleted, fasted birds are intubated with equal amounts of xanthophyll from various sources. Serum xanthophyll is then determined from blood samples obtained 14 to 24 hr following intubation. Results are expressed as the increase in serum xanthophyll (microgram/ml) over the intubated controls per milligram xanthophyll intubated per kilogram body weight. Limitations of the bioassay are discussed.