Fluorescence-based viscosity determination of corn starch using Auramine O

Viscosity is a critical rheological property in food hydrocolloids such as starch, influencing texture, stability, and digestibility. Conventional viscometry is labor-intensive, requires large sample volumes, and is unsuitable for real-time monitoring. In this study, a fluorescence-based method employing Auramine O, a molecular rotor probe, was applied for rapid, non-invasive microviscosity determination in corn starch systems. A strong linear correlation was observed between fluorescence intensity and bulk viscosity across starch concentrations from 0.1 % to 2.5 % (w/v), following the Förster-Hoffmann relation (R² = 0.9929). Auramine O was found to be stable across pH 5-9 and during 240 min of monitoring, with minimal ionic interference. Fluorescence intensity increased approximately tenfold in 2.5 % corn starch compared to water. This sensitive, low-sample-volume, real-time technique is presented as a versatile platform for characterizing starch and other hydrocolloids, supporting food quality control, clarifying starch-viscosity relationships, and enabling rapid, scalable, high-throughput process monitoring and control.