Physicochemical parameters that influence carotenoids bioaccessibility from a tomato juice

In vitro digestion models have been developed to estimate carotenoid bioavailability but most do not consider that their diffusion from fruit matrix to the lipid phase of the bolus could be a limiting step. Therefore we designed a model in which tomato juice is mixed with oil or oil/water emulsions, and the carotenoids diffusing to oil are measured by spectrometry. Temperature, pH and tomato juice/peanut oil ratio were evaluated for their influence on carotenoid diffusion. When oil/tomato ratio was between 0.11 and 1, extraction of lycopene was limited by the saturation of the oil phase. With a large excess of oil, diffusion was also limited, as only 31 ± 1% of lycopene could be extracted from the juice. Diffusion did not vary significantly with pH but doubled when temperature rose from 10°C to 37°C. When the juice was mixed in an emulsion stabilised with bovine serum albumin or phospholipids the maximum extraction decreased to 14.5 ± 0.2% and 18.5 ± 1.5% respectively, indicating that in addition to the saturation of the oil phase at low oil/tomato ratio and in addition to intrinsic properties of the tomato juice in non-saturating conditions, lycopene diffusion was limited by the structure of the interface in emulsions.