Biochemical, antioxidant and thermal properties of cryogenic and ambient ground turmeric powder.

Abstract

In present study, effect of grinding conditions, namely ambient and cryogenic, on the quality traits such as colour parameters, volatile oil, curcumin content, oleoresin content, total phenols and antioxidant activity in DPPH assay, specific heat, thermal conductivity, thermal diffusivity, glass transition temperature of turmeric powder were investigated at a moisture content of 11.5% (d.b.). Volatile oil, oleoresin, curcumin, total phenols content, antioxidant activity and b colour value varied significantly with the grinding conditions. Cryo-ground turmeric powder retained 15%-25% more volatile oil, oleoresin, curcumin, phenol content and antioxidant activity as compared to ambient grinding. Specific heat increased from 10.36 to 15.57 kJ kg-1 °C-1 with increasing temperature (-100ºC to +100ºC) at both grinding conditions. Thermal conductivity and thermal diffusivity increased from 0.049 to 0.061 W m-1 °C-1 and 9.509 × 10-8 to 11.4 × 10-8 m2/s, respectively in a temperature range of -40°C to 55°C. A higher value of glass transition temperature was found at ambient grinding conditions. Specific heat and thermal diffusivity displayed second order polynomial relationships whereas thermal conductivity was found to be varied linearly with temperature. Such biochemical and thermal property evolution data are useful in academia as well as applicable in designing and fabrications of ambient and cryogenic grinding system for turmeric and other similar commodities.