Glucose measurement errors in enzymic starch hydrolysates at high enzyme-glucose weight ratios

The 3,5-dinitrosalicylic acid (DNS), o -toluidine, and glucose oxidase methods accurately measured concentrations of standard glucose solutions in the absence of the starch hydrolyzing enzymes Diazyme (amyloglucosidase) and Clarase (α-amylase). In the presence of high enzyme concentrations, particularly at low glucose concentrations, glucose oxidase and o -toluidine somewhat underestimated standard glucose concentrations while DNS overestimated the glucose concentration by 100%. DNS also overestimated glucose in hydrolysates of standard potato starch. Glucose recovery was estimated at almost 200% of that given by glucose oxidase when enzyme starch weight ratios were 9:1 or more. Glucose was underestimated by o -toluidine in starch hydrolysates in the presence of Diazyme at high enzyme-starch weight ratios. DNS similarly overestimated glucose in starch hydrolysates from white spruce ( Picea glauca (Moench.) Voss) and some other species, as enzyme-starch weight ratios increased. The o -toluidine and glucose oxidase reactions were more reliable. Overestimation of the DNS reaction was not improved by treating the glucose-enzyme solutions with anion or cation exchange resins or by removing the enzyme prior to measurement.