Background: Inulin is widely used in functional foods throughout the world for its health-promoting and technological properties. Burdock tuber can be a valuable source of inulin. It is cultivated widely in the northern & western parts of Iran. But scarce studies about its extraction exist. It has been increasingly used in functional foods due to its texture improvement, sugar and fat replacer characteristics and beneficial nutritional attributes, as prebiotic ingredient.

Objective: Optimize conventional extraction of inulin, by using central composite design (CCD) and response surface methodology (RSM).

Methods: In this Research, a series of statistically designed studies such as central composite design and response surface methodology were performed to investigate the effect of each of the independent variables, solvent: solid ratio (5 - 15 v/w), temperature (40 - 90°C) and time (5 - 40 min) on yield of inulin extraction from burdock tubers. Response surface methodology was employed to optimize multiple variables to predict the best performance conditions with a minimum number of experiments. According to determination of inulin content of extraction liquid, firstly total carbohydrate was determined by the phenolsulphuric acid method, then reducing sugar was determined by the dinitrosalicylic acid method and finally the inulin content was measured with the difference between total carbohydrate and reducing sugars. Inulin extraction yield (%) was calculated using the following relationship = (inulin content × volume of extraction liquid/mass of Burdock tuber powder) ×100.

Results: Based on canonical analysis, the optimal conditions for maximizing inulin extraction yield (12%) were at 66.14°C for 37.6 min and solvent: solid ratios of 14: 98 (v/w).