Modeling and Effects of Various Drying Methods on Sweet Potato Starch Properties

• Main Authors: Ho Minh THAO, Athapol NOOMHORM
• Format: Article
• Language: English
• Published: Walailak University 2011-11-01
• Series: Walailak Journal of Science and Technology
• Subjects: Sweet potato starch; drying method; effective diffusivity; activation energy
• Online Access: http://wjst.wu.ac.th/index.php/wjst/article/view/26
• ISSN: 1686-3933; 2228-835X

Eleven mathematical models (Lewis, Page, Henderson and Pabis, modified Henderson and Pabis, Wang and Singh, logarithmic, two term, two term exponential, Midilli, approximation of diffusion and Verma et al, model) were used for describing the drying behavior of sweet potato starches under tray, infrared and fluidized bed drying at 45, 55 and 65 °C. The results indicated that to reach a final moisture content of 10 % at 45, 55 and 65 °C, the drying time for tray drying was 15, 8.5 and 5.5 h for infrared drying was 12, 6.5 and 4.5 h and for fluidized bed drying was 0.42, 0.28 and 0.2 h respectively. The high R2 (> 0.93), and low RMSE (0.002739 to 0.085240) and χ2 (0.000003 to 0.007160) were found for all models, in which the Midilli model was found to be the best for explaining the starch drying behavior for all drying conditions. The generalized Midilli model also was developed for each drying method. The effective diffusivity (Deff) for fluidized bed drying at 45 to 65 °C was 4.92´10-7 - 7.26´10-7 (m2/s), significant higher than those in tray and infrared drying, ranging from 2.049´10-9 to 5.674´10-9 (m2/s). The activation energies (Ea) in tray and infrared drying were 35.88 and 33.21 (kJ/mol) respectively, and nearly double that in fluidized bed drying (17.33 kJ/mol). The drying conditions only slightly affect the color, gel texture, swelling power, solubility and pasting properties of starches. Graphical abstract Research highlights ► The 11 mathematical models were used to well describe drying behaviour of sweet potato starches under tray, infrared and fluidized bed drying at from 45 to 65oC. ► The generalized Midilli model, the effective diffusivity (Deff) and the activation energy (Ea) were determined and proposed for each drying method. ► These drying conditions almost did not affect starch properties in terms of color, gel texture, swelling power, solubility and pasting. ► We concluded that as drying starch under gelatinization temperature, the starch properties were almost unchanged regardless to drying methods.