Fine structural characteristics of pectin are associated with in vitro carotenoid bioaccessibility in juices

This study aims to investigate the impact of high-pressure homogenization (HPH) on the fine structure of pectin, and further investigate the relationships between the fine structure of pectin and carotenoid bioaccessibility in peach, carrot and combined juices. Results showed that HPH affected the yield and structure of water-soluble solids (WSS) pectins. HPH increased the amount of homogalacturonan (HG) extracted, decreased molecular weight, degree of methyl-esterification and degree of acetylation. Furthermore, the distribution of the methyl esters over the HG backbone was modified towards fewer blocks of non-methyl-esterified GalA residues and more segments with a moderate level of methyl esterification. Carotenoid bioaccessibility was found to have negative correlations with certain descriptive parameters of methyl esterification related to methyl ester level and distribution. These descriptive parameters include degree of blockiness (DB), absolute degree of blockiness (DB_abs) and the degree of blockiness of methyl-esterified oligomers by PG (DB_PGme). Our findings showed pectin structure is associated with carotenoid bioaccessibility, and HPH has the potential to enhance carotenoid bioaccessibility.