Biological Availability of Docosahexaenoic Acid from Fish Oil Encapsulated in Zein-Coated Porous Starch Granules in Rats

The investigation was designed to study whether DHA in fish oil encapsulated in porous starch granules coated with water-insoluble corn protein, zein, can be utilized during passage through the gastrointestinal tract in rats. The in vitro digestion trial showed that zein used for coating starch granules was decomposed by proteolytic enzymes. After feeding porous starch granules containing fish oil, coconut oil, or corn oil for 3 weeks, serum triglycerides and phospholipids were significantly lower in the rats on fish oil than in the other rats. The proportion of DHA in total fatty acid of the fish oil group was significantly higher in both liver and brain lipids than in the other two groups. These results clearly show that fish oil encapsulated in porous starch granules coated with zein could be digested and absorbed. Moreover, it was confirmed that the granules had been changed morphologically by scanning electron microscopic analysis of the contents of the alimentary sections, showing that the film of zein had been digested in stomach and small intestine. The digestibility of fish oil in the capsules was shown to be 96.8%.