Composition and structure of tuber cell walls affect in vitro digestibility of potato (Solanum tuberosum L.)Electronic supplementary information (ESI) available: RDS contents of the potato germplasm collection screened and standard tuber characteristics are displayed in the supporting information allowing an overview of the selection of lines used in this study (Tables S1 and S2). Microscopy images supporting the cell wall interpretations of this study can be obtained from the supporting informa

• Main Authors: Frost, Jovyn K. T, Flanagan, Bernadine M, Brummell, David A, O'Donoghue, Erin M, Mishra, Suman, Gidley, Michael J, Monro, John A
• Format: Journal Article
• Language: English
• Published: 12.10.2016
• ISSN: 2042-6496; 2042-650X
• DOI: 10.1039/c6fo00895j

The digestibility of starchy foods, such as potatoes, can be characterized by the proportion of starch that is rapidly digestible by in vitro hydrolysis (rapidly digestible starch, RDS). This study evaluated the RDS content in a potato germplasm collection consisting of 98 genotypes and identified three advanced lines, Crop39, Crop71 and Crop85, where cooked potato RDS content was significantly lower than that of their respective isolated starches ( P < 0.05). In Crop39, Crop71 and Crop85, the properties of their isolated starch did not differ significantly from that of five control lines with higher RDS contents. Cell wall analyses revealed that, compared with other lines tested, Crop39, Crop71 and Crop85 had at least four times the amount of rhamnogalacturonan-I (RG-I) galactan side-chains that were very firmly attached to the wall and requiring 4 M KOH for extraction. Pectin solubilization during cooking was also remarkably low (2-4%) in these three lines compared with other lines tested (7-19%). The findings suggest that possession of higher amounts of RG-I galactan that interact strongly with cellulose may provide a sturdier wall that better resists solubilization during cooking, and effectively impedes access of digestive enzymes for starch hydrolysis in an in vitro model. Higher amount of 4 M KOH-soluble cell wall pectic galactan is associated with lower in vitro digestibility in three New Zealand potato lines.