On-line monitoring of starch enzymatic hydrolysis by near-infrared spectroscopy

The enzymatic hydrolysis of starch is an industrial process involving two consecutive steps (viz., liquefaction and saccharification with the enzymes α-amylase and glucoamylase, respectively, which cleave α-1,4-glycosidic bonds and yield soluble dextrin chains in the first step and a mixture of glucose, maltose and residual higher polysaccharides in the second). This paper reports a near-infrared spectroscopic (NIRS) method for monitoring the process. Partial least-squares (PLS) regression is used to construct calibration models based on synthetic mixtures of sugars (glucose, maltose, dextrin and soluble starch) with a view to determining the glucose and polysaccharide concentrations, and the dextrose equivalent (DE). The models thus developed were used to monitor the degradation of starch from corn and dextrins; the results thus obtained were consistent with the DE provided by the Luff-Schoorl method. The proposed NIR method is thus an effective alternative to traditional methods for the same purpose.