Text Box: 9:30 AM Text Box: CHEMISTRY & NUTRITION Text Box: Bioaccessibility of Water-Soluble Annatto Pigments Text Box: Karina Polar-Cabrera, Dr. Failla, and Dr. Schwartz Text Box: Natural pigments have recently gained attention as potential antioxidants present in the human diet. However, delivery to target tissues is essential for efficacy. Annatto is widely used in the food industry as a natural pigment providing yellow to red hues in some dairy and starch products. The purpose of this study was to assess the in vitro bioaccesibility of norbixin (NBX), a water-soluble carotenoid present in Annatto. A commercial preparation of aqueous Annatto containing 15% NBX (w/v) was added to skim, low fat (2%), and whole milk (88.8µg/ml). Samples were subjected to simulated gastric and intestinal phases of digestion in the absence or presence of bile salts. Recovery of extracted NBX from the original food was 78.6+1.1%. Stability of NBX after digestion was >99.6%, although approximately 10% of the predominant 9’-cis-NBX was isomerized into other cis and trans isomers. Transfer of NBX from food sample to the filtered aqueous (bioaccessible fraction) was 29.4+2.0%, 11.1+0.6 %, 7.2+0.2%, for skim, low-fat, and whole milk, respectively, when bile was not present during small intestinal digestion. Transfer efficiencies of NBX to the filtered aqueous fraction were: 57.8+1.9%, 62.7+5.4%, 62.0+2.2%, for skim, low-fat, and whole milk, respectively, during small intestinal digestion with added bile extract. These data suggest that physiologic concentrations of bile salts enhance the bioaccessibility of NBX and that bile salts offset any effects of milk fat on the bioaccessibility of this pigment. Moreover, NBX appears to partition both inside and outside micelles within the aqueous fraction. Finally, NBX bioaccessibility is generally greater than that of the C40 carotenoids in fruit and vegetables as assessed by in vitro digestion. Due to the unique structure of this carotenoid and its reported biological activities, examination of its uptake and absorption using the Caco-2 human intestinal cell model is warranted.