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

Palatability critically determines pediatric medication adherence, yet the impact of oral cavity dilution and salivary pH on the sensory performance of formulations remains poorly characterized. This study provides the first systematic, biorelevant evaluation of how dilution and physiologically relevant pH affect the palatability of three commercially available hyoscine butylbromide (HBB) syrup brands (X, Y, and Z), extending prior characterization of undiluted formulations. Samples were evaluated using an Alpha Astree II electronic tongue (ChemFET array). Dilution with water and with 2 mL or 5 mL phosphate-buffered saline (PBS) at pH 6.2, 6.8, and 7.4 replicated residual salivary volumes and physiological pH across pediatric and adult populations. Pure HBB API solutions were tested in parallel. Principal component analysis (>85% cumulative variance) confirmed robust discrimination across all conditions. Water dilution increased bitterness across 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. PBS dilution revealed pH-dependent, brand-specific palatability responses: at pH 6.2, 6.8, and 7.4, the hierarchy was consistently Y > X > Z, confirming the robust superiority of Brand Y's HPMC-based taste-masking system across the full physiological salivary pH range. 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 simulated salivary volume from 2 mL to 5 mL amplified bitterness and attenuated sourness across all brands. 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.