Studies on the Determination of Gelatin in Yogurt by Electrophoresis on Cellulose Acetate Strips

Abstract

General methods of detection or determination of gelatin in yogurt are the qualitative test of the AOAC and the determinative test of hydroxyproline. However, these methods are only qualitative or time consuming. The electrophoretic determination of gelatin in yogurt on cellulose acetate strips was studied as an easier method for direct detection and determination, and the following results were obtained. It was possible to determine the gelatin content accurately by the following procedure. After removal of casein from yogurt by isoelectric precipitation with sodium acetate solution, the filtrate was spotted on a cellulose acetate strip. Electrophoresis was conducted in 0.05M Na2B4 O7-NaOH buffer (pH 10) and stained by Coomassie Brilliant Blue R-250. After destaining and drying, the gelatin content was determined by densitometry at 550nm. It was able to distiguish between alkali processed gelatin and acid processed gelatin from their electrophoretic mobilities by this method. The recoveryies of gelatin added to yogurts were 80-110%. The calibration curve gave linearity in the range of 0.1-1.0% of gelatin in yogurt.