Vitamin D₃ bioaccessibility: Influence of fatty acid chain length, salt concentration and l-α-phosphatidylcholine concentration on mixed micelle formation and delivery of vitamin D₃

Vitamin D (VD) is a fat-soluble vitamin with high deficiency levels evident globally. Bioaccessibility of VD is influenced by formation of mixed micelles (MM) during digestion. This study assessed the impact of fatty acid (FA) type, phospholipid concentration on MM formation and stability of MM to salts. MM formation occurred at NaCl and KCl concentrations ranging from 20 to 100 mM, when octanoic acid (C8) or stearic acid (C18) were used. MM hydrodynamic size increased with increasing l-α-phosphatidylcholine concentration (1.5–7.5 mM) for both C8 and C18, above which concentration MM did not form. FA chain length impacted MM with hydrodynamic size increasing from 3.8 nm for decanoic acid (C10) to 4.4 nm for C18. VD₃ incorporation in MM was not influenced by the FA used (C10 or C18). Understanding stability and formation of MM and VD₃ loading is an essential first step towards manipulating food structures for improving delivery of VD.