Thermal Kinetics of Colour Degradation and Storage Characteristics of Onion Paste

The kinetics of colour degradation at selected temperatures and effects of packaging materials and storage temperatures on colour of onion paste were determined. Colour change during thermal processing of onion paste followed first-order reaction kinetics. The tristimulus colour value combination La/b adequately described the colour degradation. Dependence of the rate constant during thermal processing of onion paste obeyed the Arrhenius relationship. The activation energy for onion paste was estimated to be 16.2 kJ/mol. The total colour of onion paste was significantly affected (P<0.05) by packaging materials, temperature and duration of storage. The paste was more stable at low temperature (5 °C) than at higher temperatures (25 °C) with respect to colour, and colour degradation was minimum when the paste was packed in a high-density polyethylene pouch.