D Pencheva, N Petkova, P Denev
A simple, rapid and sensitive spectrophotometric method for the qualitative determination of inulin in dough products (salty sticks with inulin) was successfully developed. The method includes sample preparation steps-pretreatment with petroleum ether, ultrasonic extraction of inulin with hot water and its determination by resorcinol assay. The proposed spectrophotometric method has been based on the formation of colored compound by interaction of inulin with resorcinol and thiourea in the
more » ... hiourea in the hydrochloric acid medium, as described by the familiar Seliwanoff test for ketoses. The presence of aldose did not show any interference during the inulin analysis. Satisfactory linearity (R 2 =0,997) was obtained in the concentration range of fructose 0,5-20 μg/ml. The results showed good method precision with average RSDs of 5 % for repeatability and 7 % for reproducibility. The developed spectrophotometric method was compared with test analysis of the salty sticks by HPLC with refractive index detection. The results demonstrated that the spectrophotometric method is accurate, reproducible, cheap and less time consuming.