How Does Exposure Durations (0h, 12h, 24h, 36h, 48h, 60h) to Uv Light affect the Caffeine Concentration of Caffeine of Matcha Tea, Measured by Uv- Spectrophotometric Analysis?

This study aimed to quantitatively investigate the effects of ultraviolet (UV) light exposure duration (0, 12, 24, 36, 48, and 60 hours) on the caffeine concentration in matcha powder (Camellia sinensis), as measured by UV-Vis spectrophotometric analysis, and to elucidate the associated photodegradation kinetics.A controlled experimental design was implemented. Uniform samples of matcha powder (0.05 g ± 0.002 g) were spread in quartz dishes and subjected to precise periods of UV light exposure. Caffeine was subsequently extracted using a standardized volume of dichloromethane (DCM, 50 mL). The concentration of caffeine in each extract was determined by measuring absorbance at 275 nm using a UV-Vis spectrophotometer and interpolating from a pre-established five-point calibration curve (1-5 ppm) of pure caffeine in DCM. All extractions and measurements were performed in triplicate to ensure statistical reliability. Key variables, including solvent volume, sample mass, ambient temperature (25 ± 1 °C), and filtration methodology, were rigorously controlled.The caffeine concentration exhibited a clear exponential decrease with increasing UV exposure time, described by the function y = 3.3099e^(-0.026x) (R² = 0.9865). The mean initial caffeine concentration (0-hour exposure) was 3.48 ppm, which declined to 0.79 ppm after 60 hours of irradiation. Qualitatively, a visible colour transition of the matcha powder from vibrant green to a brownish-yellow hue was observed, indicative of concurrent chlorophyll photodegradation. The calculated degradation rate constant (k = 0.026) was significantly higher than values reported for uncatalyzed caffeine photodegradation (k = 0.00036), suggesting a catalytic role of reactive oxygen species (ROS) generated from photo-sensitizers like chlorophyll within the matcha matrix.Prolonged UV light exposure induces significant exponential degradation of caffeine in matcha. While matcha contains inherent antioxidants (e.g., vitamin C), their concentration is insufficient to mitigate this degradation process effectively. These findings underscore the critical importance of light-protective packaging for preserving the bioactive compound content and functional properties of matcha and similar light-sensitive food products. The results further suggest that chlorophyll acts as a potent photosensitizer, catalyzing the photodegradation of caffeine.