Slowly digestible property of highly branched alpha-limit dextrins produced by 4,6-alpha-glucanotransferase from Streptococcus thermophilus evaluated in vitro and in vivo

Abstract

Starch molecules are first degraded to slowly digestible alpha-limit dextrins (alpha-LDx) and rapidly hydrolyzable linear malto-oligosaccharides (LMOs) by salivary and pancreatic alpha-amylases. In this study, we designed a slowly digestible highly branched alpha-LDx with maximized alpha-1,6 linkages using 4,6-alpha-glucanotransferase (4,6-alpha GT), which creates a short length of alpha-1,4 side chains with increasing branching points. The results showed that a short length of external chains mainly composed of 1-8 glucosyl units was newly synthesized in different amylose contents of corn starches, and the alpha-1,6 linkage ratio of branched alpha-LDx after the chromatographical purification was significantly increased from 4.6% to 22.1%. Both in vitro and in vivo studies confirmed that enzymatically modified alpha-LDx had improved slowly digestible properties and extended glycemic responses. Therefore, 4,6-alpha GT treatment enhanced the slowly digestible properties of highly branched alpha-LDx and promises usefulness as a functional ingredient to attenuate postprandial glucose homeostasis.