Determination of Total Catechins in Green Tea Bread

 An assay method was established for thedetermination of total catechins, the major functional component of tea, inbread made with ultrafine green tea powder as an ingredient. The method was optimizedwith a 3-factor (i.e., solid-liquid ratio, extraction temperature, and extractiontime) and 3-level orthogonal experiment for the 95% ethanol extraction prior toa colorimetric measurement after the sulfuric acid-vanillin reaction. The optimizedethanol extraction was conducted under a solid-liquid ratio of 1:20 (g·mL^-1) in a 70℃water bath for 45m. Subsequently, 0.5 mL of the extract were added with 2.5mL each of 1% vanillin and 30% sulfuric acid ethanol solutions to stand at 20℃ for 10～30 min. Spectrophotometricabsorbance at 500 nm of the reaction solution was obtained. The readings werefound correlated linearly with the standard catechins concentrations in therange of 0.025～0.3 mg·mL^-1 with a R² of 0.9996. The RSD of 6 replicates measured by thenew method was 1.31%. And, the catechins recovery at high-to-low concentrationsranged from 98.75% to 103.25%. The method appeared appropriate for the totalcatechins determination in bread containing green tea.