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Abstract:

Lycopene has been implicated as a health promoting compound which is abundantly present in tomatoes. However, lycopene bioaccessibility is low because it is embedded within subcellular structures in a crystalline form. Processing might assist lycopene release from the matrix and subsequent micellarization by the disruption of these structures. Nonetheless, no clear relationship between the natural structural barriers (cell wall and chromoplast sub-structure), processing and carotenoid bioaccessibility has been established. Therefore, the objective of the present study consisted in investigating the impact of processing (thermal and high pressure homogenization) on these two barriers as responsible structures for lycopene bioaccessibility. Fractions with different levels of lycopene bio-encapsulation were prepared by decomposing the tissue matrix. Thermal treatments were applied to the isolated fractions. In addition, high pressure homogenization was applied to tomato model-systems consisting of a lycopene containing fraction and a soluble/particle phase. Lycopene bioaccessibility was subsequently evaluated through the performance of an in vitro digestion procedure. According to the results, lycopene bioaccessibility decreased upon thermal treatments in the cell clusters and chromoplast fractions. This indicates that process-induced barriers are formed upon thermal processing at the chromoplast level. High pressure homogenization of a cell cluster fraction dispersed in a soluble or particle phase showed a significant increase in lycopene bioaccessibility. Therefore, cell wall disruption through mechanical treatments was proved to effectively promote lycopene release and micellar incorporation. The results highlight the fact that processing may have a two way effect on carotenoid bioaccessibility. On one hand, processing disrupts the natural structural barriers. On the other hand, processing can also induce the formation of new barriers that hinder their release and micellarization. Consequently, adequate processing should be designed to prevent the formation of process-induced barriers that can negatively affect the lycopene bioaccessibility in order to obtain tomato products with higher nutritional qualities.