In this investigation,beverages were prepared in two pH conditions(pH 4.9 and pH 6.7)and stored in three temperature conditions(4,20 and 37 ℃),and the mechanism of color formation was preliminarily discussed,by determination of browning index,pH value,free amino acids,total sugar and reducing sugar content,in the step of sterilization and during storage.The results showed the browning index in pH 6.7 groups was higher than that of pH 4.9 groups not only during the sterilization but during the storage,in which temperature promoted the browning action as a whole.Composition analysis showed that both groups of beverage were similar in change of compositions,but the pH 6.7 group was more violent than that of pH 4.9 group.The kinds of amino acids and their concentrations became fluctuant during storage,in which,some amino acids such as aspartic acid increased remarkably,while some amino acids such as threonine,serine,cystein,tyrosine and arginine decreased evidently.On the other hand,the concentrations of total sugar and reducing sugar were decreased obviously during storage.These results imply amino acids such as threonine,serine,cystein,tyrosine,arginine,and reducing sugar involved the browning reaction whose distribution to be a Maillard reaction,and consequently causing the beverage color down during processing and storage,where both pH value and storage temperature were the major influencing conditions.