Simple and cost-effective approaches for quantification of reducing sugar exploiting digital image analysis

Simple, low-cost, and fast analytical procedures for reducing sugar quantification in beverages are proposed by digital image analysis. The procedures are based on the colorimetric spot test reaction of the analyte with 3,5-dinitrosalicylic acid (DNS method) and its oxidation by the cupric ion (Cu2}) (Benedict method). Digital im-ages were acquired using a flatbed scanner and converted to RGB values. Values of channel G and R were taken as analytical responses for DNS and Benedict method, respectively, because of the complementarity with the color of the reaction product. Linear responses were observed in the glucose concentration range between 0.10 and 0.30 g L-1, with a detection limit of 2.9 x 10(-2) g L-1 for the DNS method and from 1.0 to 5.0 g L-1, with a detection limit of 0.5 g L-1 for the Benedict method. Recovery values between 97% and 103% were obtained in the addition and recovery experiments for both procedures. These analytical procedures were applied to different beverage samples (juice, coconut water, and sugar cane spirits) and the results were in close agreement with those obtained using a reference method, with a confidence level of 95%.