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

Abstract

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.