Physicochemical Properties of Deacetylated Konjac Glucomannan and Its Effects on the Quality and in Vitro Digestion Characteristics of Cold Noodles

Abstract

In this work, the structures of deacetylated konjac glucomannan (DKGM) with different degrees of deacetylation were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and their viscosity, water-holding capacity (WHC) and thermal stability were evaluated and compared. The effects of DKGM with high degree of deacetylation (72.70%) on the texture and in vitro digestion characteristics of cold noodles were analyzed. The results showed that the characteristic absorption peak of acetyl group at 1 735 cm?1 in DKGM decreased, the surface became rough, the crystallinity and the thermal stability increased, and the viscosity and WHC decreased with the increase in the degree of deacetylation when compared with konjac glucomannan (KGM) (P < 0.05). After adding DKGM with high degree of deacetylation, the hardness, chewiness and cohesiveness of cold noodles showed a downward trend, and its in vitro digestibility decreased. In conclusion, addition of DKGM with high degree of deacetylation can improve the mouthfeel and digestion resistance of cold noodles, which may provide a theoretical basis for the application of DKGM and starch blends in low glycemic index foods.

Keywords

• konjac glucomannan; deacetylated; cold noodles; in vitro digestion