Comparison of the main analytical methods used in quality control of tomato paste

Methods commonly used in quality control analysis of tomato paste were compared as a means of selecting improved means of specification for trade. Methods studied included reducing sugars using Fehling's reagent, HPLC, and enzymatic analysis; total acidity by volumetric titration (with indicator and combined electrode); volatile acidity with two different steam distillation apparatus and separation columns; and citric acid using HPLC and enzymatic methods. The use of nonspecific methods of analysis, such as Fehling's method and volumetric titration using phenolphtalein for total acidity determination, causes significant errors; moreover, the results strictly depend on the concentration of the samples.