Abstract:

The liquefied corn starch produced by simultaneous extrusion and enzymatic hydrolysis was further saccharified
by the same procedure except using glucoamylase instead of α-amylase. The optimization of saccharification conditions for
improved dextrose equivalent (DE) was investigated by the combined use of single factor experiments and response surface
methodology. The results showed that when the saccharification was carried out by adding 140 U of glucoamylase per g of
dry matter, adjusting the concentration of the liquefied corn starch to 70% and performing extrusion at 85 ℃, the maximum
DE value of 42.12% was obtained. The contents of glucose, maltose and maltotriose of the saccharified product with a DE
value of 38% were 26.17%, 25.29% and 14.86%, respectively, compared to 29.57%, 33.40%, and 17.23% for that with a
DE value of 42%, respectively, as determined by high performance liquid chromatogram (HPLC). In the infrared spectrum
of the extruded saccharified starch the characteristic peaks of oligosaccharides such as glucose were observed. The scanning
electron microscope images showed that the product formed a porous structure. The X-ray diffraction results showed
that new crystalline forms were generated. The curves from rapid viscosity analysis indicated that the product had a low
viscosity, which contained a large amount of small-molecule soluble sugar.

Key words: simultaneous extrusion and enzymatic hydrolysis, corn starch, saccharification