Functional and relaxing properties of coffee leaf tea: An integrative food cognition approach

• Optimized brewing achieved 35.61 mg GAE/g phenolic in oolong coffee leaf tea (OCLT). • OCLT contains 0.40 mg/g GABA, diphenyl sulfone and phenyl-methylene heptanoate. • OCLT reduced cortisol and improved emotional responses. • High sweetness, low bitterness, and strong preference for OCLT. • OCLT validated as a functional and relaxing beverage. Coffee leaf tea, rich in bioactive compounds such as phenolic and gamma-aminobutyric acid (GABA), demonstrates potential as a relaxing and functional beverage. This study optimized total phenolic content (TPC) using Response Surface Methodology (RSM), varying brewing temperature (74–81°C) and duration (4–12 minutes). Relaxation properties were assessed through chemical analysis of GABA and volatile aromatic compounds using UPLC and GC-MS, respectively. Sensory evaluation incorporated Emotional Time Intensity (ETI) and self-stress assessments, coupled with Facial Emotion Recognition (FER) and Facial Landmark Distances (FLD) using Convolutional Neural Networks. Physiological validation was performed through salivary and blood cortisol as well as heart rate and blood pressure. Results revealed that oolong coffee leaf tea (OCLT) contained the highest TPC (35.61 ± 0.13 mg GAE/g), GABA (0.40 ± 0.01 mg/g), diphenyl sulfone and phenyl-methylene heptanoate, contributing to its superior relaxation potential. OCLT also elicited positive emotional expressions, as observed via FER and FLD, while significantly reducing salivary cortisol levels (p < 0.05). Sensory evaluation highlighted its high sweetness and low bitterness, enhancing overall preference compared to green and black variants. This study establishes oolong coffee leaf tea as a promising relaxing beverage, supported by its chemical composition, sensory appeal, and physiological effects. Thus, the findings underscore the relevance of coffee leaf tea in the beverage industry as a promising alternative to conventional relaxation drinks, offering a natural solution to combat stress and promote well-being. Further research is recommended to explore its long-term health benefits and scalability for commercial production, thereby contributing to the growing demand for functional beverages in the market.