Spray drying of inulin component extracted from Jerusalem artichoke tuber powder using conventional and ohmic-ultrasonic heating for extraction process

In this study, various ohmic heating conditions and conventional heating were applied in the inulin extraction process from Jerusalem artichoke tuber (JAT) powder. The inulin extracts were evaporated to be around 30 °Brix and then spray-dried to be inulin powder. The main objectives were (1) to compare the quality of inulin extracts obtained from different extraction conditions and (2) to evaluate the yield of inulin powder production from JAT powder and the inulin powder quality. The results showed that the electrical conductivities of JAT powder solutions ranged between 0.0677 and 0.2057 S/m. The application of ohmic heating method at electrical frequency of 20 kHz and electrical field strengths of 15 and 20 V/cm could not raise the inulin extraction yield when comparing with the conventional heating. The addition of ultrasonic treatment step into the ohmic heating process could not escalate the extraction yield. The sugar and inulin contents in the extracts obtained from various ohmic heating treatments and conventional heating were not much different. The inulin contents of all extract samples were roughly in range between 75 and 80 g/100 gdry mass. The production yields of inulin powder from JAT powder were 14.53-17.29% which was rather low due to the loss of solids occurring in the extraction and spray drying processes. The scanning electron micrographs illustrated that the particle sizes of inulin powders produced in this study were much smaller than those of commercial inulin powders.