A New Centrifugation-Free Procedure Based on Smartphone Imaging for a Miniaturized Determination of Reducing Sugars

Reducing sugars play a key role in the nutritional, technological, and sensory properties of food and beverages. Their quantification is, therefore, essential in various processes of quality control and process monitoring. Traditional methods such as the Lane–Eynon titration or spectrophotometric procedures provide reliable results but are usually time-consuming, create a large amount of waste products, and require specific instrumentation. In this study, two miniaturized and cost-effective analytical procedures for the colorimetric determination of reducing sugars based on digital image analysis (DIA) are presented. Classical Benedict and 3,5-dinitrosalicylic acid (DNS) reactions were adapted for microplate analysis, eliminating the centrifugation step that is usually carried out, and acquiring the images using a smartphone. Key experimental parameters – reagent-to-sample ratio, temperature, heating time, and RGB channel selection – were optimized to ensure a robust analytical performance. Both methods exhibited good linearity in their respective working ranges (1.0–7.0 g/L for Benedict; 1.0–10.0 g/L for DNS), and low detection limits were obtained (0.81 g/L and 0.92 g/L, respectively). Intra- and inter-day precision values were below 10% for both procedures. Application to real samples (syrups, soft drinks, and beer) showed good agreement with the AOAC reference titration method, with relative errors below 12.4%. Considering the miniaturization, low energy consumption and semi-automation of the methods, the analytical greenness was evaluated using the AGREE metric, yielding a score significantly higher than the classical titration method, and that way confirming the environmental benefits of the presented methods. Overall, the proposed DIA-based Benedict and DNS assays provide fast (less than 30 minutes of reaction time), inexpensive, high-throughput, and sustainable alternatives for routine reducing sugar determination in beverage analysis. • Novel centrifugation-free smartphone imaging for reducing sugars was developed. • Benedict and DNS assays were adapted to rapid microplate and smartphone-based use. • Results in beverages show strong agreement with the official AOAC reference method. • AGREE metrics confirm superior sustainability over classical titration methods.