On-line FT-Raman spectroscopic monitoring of starch gelatinisation and enzyme catalysed starch hydrolysis

The hydrolysis of starch by a-amylase and amyloglucosidase and the kinetics of these technically important. reactions were investigated by FT-Raman spectroscopy. During the technical starch hydrolysis process, three reactions proceed one after the other but partly in parallel: the gelatinisation, the hydrolysis of starch to dextrin (liquefaction) by a-amylase, and the hydrolysis of dextrin to glucose (saccharification) by glucoamylase. These three reactions were studied separately. Potato starch or dextrin in concentrations of 50 g/l were suspended or dissolved in water, the reaction chamber was placed in a heated water bath, and defined, varied amounts of enzymes in solution were added, The reactions were monitored on-line in a bypass loop. The greatest spectral changes were observed due to the swelling and gelatinisation of starch. The liquefaction of starch to dextrin was started with the addition of cu-amylase at a temperature of 80 degrees C and the spectral changes were monitored. In a similar way, a solution/suspension of dextrin was used to investigate the reaction of glucoamylase at 50 degrees C. Both enzymatic reactions were performed at four different enzyme activities. All reactions showed distinctive spectral changes, which can, in principle, be evaluated for the determination of the degree of starch hydrolysis, As a Nd:YAG laser at 1064 nm was used, fluorescence excitation was not observed despite the use of crude, technical-grade enzymes. The findings demonstrate the potential use of Raman spectroscopy in monitoring and control of technical enzyme reactions. (C) 2000 Elsevier Science B.V. All rights reserved.