Two purple tea beverage variants were prepared using aqueous extracts of purple tea leaves (Camellia sinensis var. TRFK 306) as the primary functional ingredient. The variants differed in the concentration of purple tea extract and the balance of complementary natural ingredients, allowing comparison of functional performance, sensory quality, and storage stability while protecting proprietary formulation details. All variants were processed under identical manufacturing conditions to ensure that observed differences were primarily associated with formulation composition rather than processing variations. 

Physicochemical analysis was performed to establish the baseline quality of each purple tea variant and monitor changes that could influence product stability during storage. Parameters including pH (AOAC 981.12), total soluble solids (AOAC 932.12), colour (CIE Lab*), and titratable acidity (AOAC 942.15) were measured to evaluate beverage consistency, colour retention, acid balance, and processing suitability. 

Purple tea is naturally rich in polyphenols, anthocyanins, catechins, and other antioxidant compounds that contribute to its functional value. Therefore, total polyphenols (ISO 14502-1) and antioxidant activity (DPPH assay) were analysed to compare the functional characteristics of the variants and establish reference values for bioactive retention during storage. 

Sensory evaluation was conducted to understand how the phenolic-rich composition of purple tea influenced the beverage’s sensory characteristics and consumer perception. Using ISO 13299 descriptive analysis and a 9-point Hedonic Scale, attributes including colour, aroma, flavour, bitterness, astringency, mouthfeel, and overall acceptability were assessed to identify the variant offering the best balance between functional properties and sensory appeal. 

Storage stability studies were performed under accelerated and real-time conditions to evaluate how each variant performed during storage and whether it could maintain its functional quality throughout the intended shelf life. Periodic monitoring included physicochemical characteristics, bioactive compound retention, antioxidant activity, colour stability, microbiological quality, and sensory attributes. The collected data were used to determine the effect of storage on product quality, verify shelf-life performance, and assess overall product stability.