In vitro fecal microbiota modulation properties of pectin and xyloglucan from hazelnut (Corylus avellana L.) skin, an industrial byproduct, and their incorporation into biscuit formula

Abstract

The aim of this study was to extract water-soluble dietary fibers (WSDFskin), pectin (PECskin), and xyloglucan (XGskin) from hazelnut skin and to determine their impacts on colonic microbiota and metabolic function. WSDFskin, PECskin, and XGskin were extracted by water, acid, and alkali treatments, respectively. Monosaccharide analysis revealed WSDFskin and PECskin were dominated by uronic acids, while the XGskin was found to contain xyloglucan- and pectin-associated sugars. In vitro fecal fermentation analysis showed that WSDFskin, PECskin, and XGskin are fermented to different microbial short-chain fatty acid profiles by identical microbiota. 16S rRNA sequencing demonstrated that PECskin promoted Faecalibacterium prausnitzii and Lachnospiraceae related operational taxonomic units (OTUs), which are recognized as beneficial members of the human gut, whereas WSDFskin and XGskin stimulated Bacteroides OTUs. Interestingly, increased abundances of F. prausnitzii and Lachnospiraceae OTUs in PECskin were higher than those in commercially available pectin. Finally, PECskin and XGskin were tested in a biscuit model and the results showed that either PECskin or XGskin can be incorporated into biscuit formulations without impacting physical, textural, and sensory properties of the final product. Overall, our results demonstrated that hazelnut skin, an industrial byproduct, can be utilized for the production of functional dietary fibers, especially pectin, to improve colonic health.