Biorelevant Electronic Tongue Assessment of Dilution- and pH-Dependent Palatability of Commercially Available Hyoscine Butylbromide Syrups

Palatability has an impact on pediatric medication adherence, yet the influence of water dilution, PBS volume fraction, and salivary pH on the sensory performance of formulations is poorly characterized. This study provides the first systematic, biorelevant evaluation of how water dilution factor, PBS volume fraction, associated ionic strength change, and physiologically relevant pH affect the palatability of three commercially available hyoscine butylbromide (HBB) syrup brands (X, Y, and Z), extending earlier characterization of undiluted formulations. Samples were evaluated using an Alpha Astree II electronic tongue (ChemFET array. Water dilution (Batch B) and PBS volume fractions of 2 mL or 5 mL at pH 6.2, 6.8, and 7.4 within a fixed total measurement volume of 25 mL simulated salivary pH and ionic composition across the physiological range relevant to pediatric and adult populations. Pure HBB API solutions were tested in parallel. Principal component analysis (>85% cumulative variance) confirmed robust discrimination across all conditions. The water dilution factor increased bitterness for all brands by disrupting excipient matrix integrity, with cellulosic polymer-containing Brands X (HEC) and Y (HPMC) retaining superior taste masking over polymer-free Brand Z. The PBS volume fraction revealed pH-dependent, brand-specific palatability responses, at pH 6.2, 6.8, and 7.4, and the hierarchy was consistently Y > X > Z, confirming the superiority of the Brand Y formulation, combining HPMC with sodium cyclamate and saccharin sodium, across the full physiological salivary pH range, noting that this superiority reflects the broader excipient composition of Brand Y, rather than polymer choice alone. Notably, Brand X exhibited substantially higher ANS sweetness scores than Brand Y at 2 mL pH 7.4 PBS, reflecting differential sweetener system sensitivity to near-neutral PBS ionic conditions. Increasing the PBS volume fraction from 2 mL to 5 mL within a fixed total measurement volume of 25 mL, increased the ionic strength and pH contribution of the simulated salivary component, amplified bitterness and attenuated sourness across all brands, reflecting changes in the ionic environment at the ChemFET sensor membrane, rather than any increase in the intrinsic bitterness of HBB itself. Taste-masking strategies that rely solely on sweeteners, without viscosity-building polymers, are inadequate under biorelevant oral conditions. pH-stratified assessment is essential for comprehensive characterization of palatability in pediatric oral liquid formulations.