OBJECTIVE:Effects of heat-denaturation time duration and temperature on the surface reactive amino group content of spray-dried bovine serum albumin microspheres were investigated.METHOD:Bovine serum albumin (BSA) microspheres were prepared by a spray-drying method under optimized experimental conditions and heat denatured at different temperatures for different time.Suface reactive amino group content was determined by a reported method with slight modification,using trinitrobenzene-sulfonic acid (TNBS).TNBS and BSA microspheres were incubated in alkaline buffer to ensure complete reaction between TNBS and surface the reactive amino groups.Excess of TNBS was colored by reaction with L-valine and determined spectrophotometrically at a wavelength of 410nm.Surface reactive amino group content was calculated through the difference between initial TNBS added and TNBS remained.RESULTS:Heat-denaturation time duration seemed to have little effect on surface reactive amino group content.Higher heat denaturation temperature may reduce surface reactive amino group content.CONCLUSION:Heat-denaturalion temperature is the main factor affecting the surface reactive amino group content of spray-dried bovine serum albumin microspheres.