Effects of deacetylated konjac glucomannan on the quality, retrogradation and digestion properties of instant black highland barley rice.

Abstract

This study investigated the influence of deacetylated konjac glucomannan (DKGM) on the quality, retrogradation and digestion properties of instant black highland barley rice (IBHBR). Compared with KGM, DKGM shortened the cooking time of IBHBR by 21.78 %, reduced cooking loss by 47.63 %, and decreased hardness by 44.70 %. In addition, DKGM enhanced water absorption capacity and viscoelasticity, thereby improving cooking properties and textural characteristics of IBHBR. Following 7 days of storage at 4 °C, IBHBR exhibited increased retrogradation enthalpy, relative crystallinity, and short-range molecular ordering. However, the inclusion of DKGM suppressed these retrogradation parameters. A more continuous gel network structure was observed in the DKGM-added samples, with the porosity increasing from 29.54 to 48.59 %, suggesting that DKGM retarded starch retrogradation. Importantly, DKGM with a degree of deacetylation of 63.57 % increased the resistant starch while reducing the rapidly digestible starch, yielding an estimated glycemic index of 68.34 and classifying it as a medium-glycemic index food. This effect may be attributed to the enhanced interaction between DKGM and starch molecules and inhibit digestive enzymes activity. These findings offer meaningful insights for the formulation of instant rice products with improved nutritional benefits, including enhanced resistance to both retrogradation and enzymatic digestion, by incorporating DKGM with a moderate degree of deacetylation.