| Author | Napasiri Laosanguanek |
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Science in
Food Engineering and Bioprocess Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | The drying of turmeric (Curcuma longa) slices by different drying methods, namely, hot air, vacuum, infrared, infrared-convection, infrared-vacuum drying at temperature of 40, 60 and 80oC and fluidized bed drying in the temperature range of 120-160oC were investigated to understand of drying characteristics and effect on qualities of turmeric. The results revealed that the temperature had significant effect on drying rate and various qualities of dried turmeric. In all drying methods, increase of drying temperature caused shorter drying time. Combined infrared-convection drying gave shorter drying compared to hot air drying at the same temperature. Infrared gave the shortest time to achieve final moisture content compared to infrared-vacuum drying and vacuum alone. Five mathematical drying models (Lewis, Page, Henderson and Pabis, Modified Page and Two-term) for describing time dependence of the moisture ratio change were fitted to experimental data and model parameters by multiple regression analysis. Modified Page model gave good fit model for predicting the change of moisture content with time and to be the most suitable model for explaining and understanding the drying behavior for all drying methods comparing the coefficient with the highest coefficient of determination (R2), the lowest of root mean square error (RMSE), and the lowest of reduced chi-square (χ2). The values of the effective diffusivity at each temperature were obtained using Fick’s second law of diffusion. The effective diffusivity increased with increase of temperature for all drying methods. The temperature dependence of the effective diffusivity coefficient was described by Arrhenius-type relationship. Activation energy for the moisture diffusion was determined range of 20.34-41.28 kJ/mol.
For comparison of drying methods on qualities, the yellowness of dried turmeric from vacuum and infrared-vacuum drying gave nearly values with the fresh turmeric. Infrared-vacuum gave the highest range of total curcuminoids content. The extraction yield using soxtec extraction of infrared-vacuum at 40oC gave the highest values and fluidized bed at 160oC gave the lowest of extraction yield. For antioxidant qualities, the DPPH radical-scavenging activity of vacuum at 40oC was the highest, but it was not significantly different from infrared-vacuum drying. The total phenolics content of infrared-vacuum at 40oC gave the highest values. Most of drying methods gave higher values of extraction yield, DPPH radical-scavenging activity and total phenolics content than commercial capsule. Therefore, combined of infrared and vacuum drying is one of recommended drying methods to receive better qualities. |
| Year | 2009 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Athapol Noomhorm; |
| Examination Committee(s) | Rakshit, Sudip K. ;Anal, Anil K. ; |
| Scholarship Donor(s) | RTG Fellowship; |