Yield and physicochemical properties of inulin obtained from Iranian chicory roots under vermicompost and humic acid treatments

Chicory (Cichorium intybus L.) is a valuable medicinal plant and belongs to the family Asteraceae. Both chicory and Jerusalem artichoke are used in the production of inulin at industrial levels. Meanwhile, the extraction of inulin from chicory is more commonly considered. In this research, different levels of vermicompost and humic acid were used in order to study the effects on Iranian chicory roots, their growth and the physicochemical properties of their inulin. Treatments were vermicompost (0, 5, 7.5 and 10 tons/ha) and commercial humic acid (0, 0.3, 0.6 and 0.9 kg/ha). In this study, the growth parameters of roots were measured, including their fresh and dry weights, the depth of the root network and root volume. Furthermore, several phytochemical parameters were measured, including total sugars, reducing sugars, percent of inulin and the average degree of polymerization (DPn). Results showed that the combined application of vermicompost 7.5 tons/ha + humic acid 0.9 kg/ha significantly increased the fresh weight of roots (by 50.7%), the dry weight of roots (by 51.47%), depth of the root network and root volume compared to the control. In the same manner, the combination of vermicompost 10 tons/ha + humic acid 0.9 kg/ha significantly increased the fresh weight of roots (by 45%), the dry weight of roots (by 48.5%), depth of the root network and root volume compared to the control. All of the three concentrations of humic acid significantly increased the yield of inulin. The highest level of vermicompost (10 tons/ha) caused the highest amount of inulin (71.87%) which was 8.99% more than the control. The reducing sugars were not influenced by humic acid and vermicompost. However, all concentrations of humic acid as well as the highest level of vermicompost (10 tons/ha), significantly increased the total sugar content compared to the control. The application of 10 tons/ha vermicompost caused the highest value of Dpn (28.67).