The improvement in bioavailability of various bioactives e.g. curcumin, digoxin and resveratrol, after polysorbate 80 (PS80) micellization, has been attributed, in part, to increased digestive stability of the bioactives. This research aimed to evaluate the role of the digestive stability of the PS80 micelles in increasing the in vitro bioaccessibility of bioactive compounds (curcumin, naringenin, Beta-carotene, CoQ10). This was done by comparing pre-micellization (solvent evaporation method) of bioactives in PS80 compared to co-digestion (simulated co-consumption) with PS80 (compared to that of olive oil). Additionally, the effects of relevant digestive compounds, lipase and bile extract, on the particle/micellar surface charge and curcumin bioaccessibility, were investigated. The solubility of the compounds in olive oil or PS80, played a substantial role in the modulation of their bioaccessibility. Co-digestion with PS80 resulted in similar or higher amounts of bioaccessible compounds, but pre-micellization was more efficient in increasing bioaccessibility, indicating some measure of digestive stability of the micelles. The modulating effect of lipase and bile extract on the bioaccessibility of curcumin however, suggests that not all micelles remain intact during the gastrointestinal digestion. While the extent of the digestive stability is still unclear, there is currently no available methods to quantify this.

The improvement in bioavailability of different compounds from PS80 micelles differs widely. This research, for the first time, investigated the effects bioactives, with different physicochemical properties (CoQ10, curcumin, catechin, naringenin, quercetin, β-carotene and retinyl palmitate), have on the micellar characteristics and the in vitro bioaccessibility of the loaded bioactives. There was no link between the physicochemical properties of the bioactives and the loading capacity of the PS80 micelles, which varied between 0.04 and 14.0%, or the average bioaccessibility of the bioactives, which varied between 14 and 86%. Not the ratio of loaded bioactive to PS80, but rather an increased concentration of PS80, increased the bioaccessibility of the loaded bioactive. It is not clear if differences were due to modifications of the PS80 micelles during the digestion process, where e.g. bile salts and/or phospholipids were incorporated into the micelles, or if the micelles totally dissociated and physiological mixed micelles were formed, including the PS80.