Determination via hydrolysis with α-amylase of curdlan in the presence of proteins

A novel method of determining curdlan in the presence of water-insoluble but alkaline solution-soluble proteins via hydrolysis with α-amylase was developed. The hydrolyzed products were mainly composed of the reducing sugars (1→3)-β-d-glucan oligosaccharides, which were determined using the 3,5-dimethylsalicylic acid method. The observed absorbance at 540 nm was linear with respect to the curdlan concentration (regression coefficient: 0.9897). The new method is specific for the determination of curdlan and exhibits high accuracy, particularly in the sample containing water-insoluble but alkaline solution-soluble proteins. The method can be used to assay the curdlan content up to 3.2 mg/mL and can overcome the shortcomings of the gravimetric method.