Multi-glycomic characterization of fiber from AOAC methods defines the carbohydrate structures

Authors: BACALZO, NIKITA - University Of California, Davis; COUTURE, GARRET - University Of California, Davis; YE, CHEN - University Of California, Davis; Luthria, Devanand - Dave; PHILLIPS, KATHERINE - Virginia Tech; Fukagawa, Naomi; LEBRILLA, CARLITO - University Of California, Davis; TAREQ, FAKIR - University Of Maryland; Harnly, James - Jim; Pehrsson, Pamela; McKillop, Kyle

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2022
Publication Date: 11/3/2022
Citation: Bacalzo,.P., Couture, G., Ye, C., Luthria, D.L., Phillips, K.M., Fukagawa, N.K., Lebrilla, C.B., Tareq, F.S., Harnly, J.M., Pehrsson, P.R., McKillop, K.A. 2022. Multi-glycomic characterization of fiber from AOAC methods defines the carbohydrate structures. Journal of Agricultural and Food Chemistry. 70(45):14559-14570. https://doi.org/10.1021/acs.jafc.2c06191.
DOI: https://doi.org/10.1021/acs.jafc.2c06191

Interpretive Summary: Dietary fiber has long been known to be an essential component of a healthy diet and recent investigations into the gut microbiome-health paradigm have identified fiber as a prime determinant in this interaction. Further, fiber is now known to impact the gut microbiome in a structure-specific manner, conferring differential bioactivities to these specific structures. However, current analytical methods for food carbohydrate analysis do not capture this important structural information. To address this need, we utilized rapid-throughput LC-MS methods to develop a novel analytical pipeline to determine the structural composition of soluble and insoluble fiber fractions from two AOAC methods (991.43 and 2017.16) at the total monosaccharide, glycosidic linkage, and free saccharide level. Two foods were chosen for this proof-of-concept study: oats and potato starch. For oats, both AOAC methods gave similar results. For raw potato starch, each AOAC method gave markedly different results in the soluble fiber fractions. These observed differences are attributable to the resistant starch content of potato starch and the different starch digestion conditions used in each method. Together these tools are a means to obtain the complex structures present within dietary fiber while retaining “classical” determinations such as soluble and insoluble fiber. These efforts will provide an analytical framework to connect gravimetric fiber determinations with their constituent structures to better inform gut microbiome and clinical nutrition studies.

Technical Abstract: Dietary fiber has long been known to be an essential component of a healthy diet and recent investigations into the gut microbiome-health paradigm have identified fiber as a prime determinant in this interaction. Further, fiber is now known to impact the gut microbiome in a structure-specific manner, conferring differential bioactivities to these specific structures. However, current analytical methods for food carbohydrate analysis do not capture this important structural information. To address this need, we utilized rapid-throughput LC-MS methods to develop a novel analytical pipeline to determine the structural composition of soluble and insoluble fiber fractions from two AOAC methods (991.43 and 2017.16) at the total monosaccharide, glycosidic linkage, and free saccharide level. Two foods were chosen for this proof-of-concept study: oats and potato starch. For oats, both AOAC methods gave similar results. Insoluble fiber was found to be comprised of linkages corresponding to ß-glucan, arabinoxylan, xyloglucan, and mannan while soluble fiber was found to be mostly ß-glucan with small amounts of arabinogalactan. For raw potato starch, each AOAC method gave markedly different results in the soluble fiber fractions. These observed differences are attributable to the resistant starch content of potato starch and the different starch digestion conditions used in each method. Together these tools are a means to obtain the complex structures present within dietary fiber while retaining “classical” determinations such as soluble and insoluble fiber. These efforts will provide an analytical framework to connect gravimetric fiber determinations with their constituent structures to better inform gut microbiome and clinical nutrition studies.