Acta Scientiarum Polonorum Technologia Alimentaria

Background. Guava (Psidium guajava L.) leaves are rich in polyphenols and flavonoids with established an­tioxidant and antidiabetic properties. However, the quality and functionality of guava leaf tea are influenced by processing parameters, including leaf maturity, drying temperature, grinding size, and brewing conditions. This study aimed to determine the optimal processing conditions for enhancing the bioactive compound con­tent and functional properties of guava leaf tea bags.
Materials and methods. Leaves at three maturity stages (young, mature, and old) were dried under different temperatures (40–70°C and cooling drying at 45°C), ground into four particle size ranges, and packed into tea bags. The teas were brewed at water temperatures between 70°C and 100°C. Total polyphenol content (TPC) and total flavonoid content (TFC) were quantified spectrophotometrically. Antioxidant capacity was assessed by DPPH radical scavenging, while α-glucosidase inhibitory activity was measured to evaluate antidiabetic potential. Sensory attributes were evaluated by a trained panel.
Results. Drying at 50°C retained the highest TPC (176.19 mg GAE/g dw) and TFC (9.72 mg QE/g dw), while grinding to 0.5–1 mm enhanced compound extraction without compromising sensory quality. Brewing at 100°C yielded the greatest concentrations of bioactive compounds; however, infusions prepared at 90°C received the highest flavor and aroma scores. The optimized tea infusion also exhibited strong antioxidant activity (35.92% DPPH inhibition) and potent α-glucosidase inhibitory activity (IC₅₀ = 6.97 μg/mL), approxi­mately 17 times more effective than acarbose.
Conclusion. These findings indicate that guava leaf tea, when processed under optimal conditions, has the potential to serve as a functional beverage with significant health-promoting properties, particularly through its antioxidant activity and blood sugar–regulating effects.