Abstract: In this study,the alkaline hydrolysis and acid hydrolysis conditions for extracting bound polyphenols were optimized with response surface method,after free polyphenols removed from the freeze-dried powder of Psidium guajava.Based on single factor experimental data,influences factors such as solution concentration,hydrolysis temperature and hydrolysis time on the extraction yield of bound polyphenols was optimized with response surface analysis.The optimized alkaline hydrolysis conditions for bound polyphenols were NaOH of 7.24 mol/L,hydrolysis temperature of 98.22 ℃,hydrolysis time of 24.88 h,with the finally yield of bound polyphenols of 1.238%.The result showed that the optimized acid hydrolysis conditions were:HCl of 4.05 mol/L,hydrolysis temperature of 94.87 ℃,hydrolysis time of 29.95 h,with the finally yield of bound polyphenol of 2.002%.

Key words: Psidium guajava Linn., bound polyphenols, alkaline hydrolysis, acid hydrolysis, response surface methodology