Effect of infrared heating on physical, structural and pasting properties of starch

In this study, potato starch and corn starch were infrared (IR)-heated at 250 W for 45, 65 and 85 min. IR-treated starch and their polymer solutions and physical, structural and pasting properties were analysed. The maximum surface temperature measured by thermal imaging camera for potato starch and corn starch at 85-min IR heating was 92.5 °C and 82.1 °C, respectively. The moisture content of starch decreased with increasing heating period and was recorded as 4.34 and 3.16% at the end of 85-min heating for potato starch and corn starch. The tapped density of native potato starch and corn starch was measured as 789.7 and 517.3 kg/m3. The brightness ‘L’ value was found higher in corn starch (96.65) than in potato starch (92.49) after heating. The average mean diameter of potato starch is 25.22 µm which is higher than that of corn starch size. The pasting properties of native and IR-treated modified starch showed significant differences (P < 0.05). A gradual and continuous increase in viscosity was observed in the samples, and minor reductions in viscosity were observed after peak points. The pasting temperature for potato starch and corn starch was in the range of 64.21–65.81 °C and 75.23–75.63 °C, respectively. Also, FTIR and thermal properties (Tg) of native and modified starch are presented in this paper.