Process Optimization of GABA Instant White Tea Based on Response Surface Methodology and Analysis of Key Flavor Substances

This study developed an optimized processing strategy for γ-aminobutyric acid (GABA) instant white tea (GABA-IT) using GABA-enriched white tea as raw material, systematically characterizing its chemical composition and volatile profile. In contrast to the conventional instant tea production process, this work integrates response surface methodology with spray-drying parameter optimization. This integrated approach enables the simultaneous enhancement of functional components and sensory quality. A response surface design was employed to refine the extraction and spray-drying variables following preliminary single-factor trials, and the optimal parameter combination was subsequently determined (40% ethanol concentration, material-to-liquid ratio of 1:15, extraction time of 3 days, atomization speed of 300 rpm, and inlet temperature of 120 °C); the resulting GABA-IT exhibited significantly improved quality characteristics. Specifically, the GABA content increased by 209% (reaching 4.42 mg/g), and theanine, catechins, and caffeine were enriched by 200–300%. Regarding volatile profiles, processing led to a reduction in esters but an increase in aldehydes and hydrocarbons. Relative odor activity value (rOAV) analysis revealed that epoxy-β-ionone and linalool were the key contributors to the characteristic aroma of GABA-IT. Collectively, this study demonstrates the technical feasibility of producing GABA-rich instant tea with enhanced functional components and improved sensory quality, providing practical guidance for the large-scale industrial production of functional tea beverages.