Thermal degradation kinetics of aqueous anthocyanins and visual color of purple corn (Zea mays L.) cob

Purple corn cob was the byproduct during the corn processing. Thermal degradation kinetics and Hunter color parameters (a*, b*, C*, h degrees and Delta E) of aqueous anthocyanins from purple corn cob were studied at selected temperatures (70 degrees C, 80 degrees C and 90 degrees C) at pH 4.0. The results indicated that the thermal degradation of anthocyanin and Hunter color C*, a* and Delta E parameters followed the first-order reaction kinetics, while Hunter color h degrees and b* parameters followed zero-order reaction kinetics. The calculated values of activation energies (Ea) were 18.3, 35.9, 37.1, 31.6, 34.9 and 30.0 kJ/mol for anthocyanins, C*, a*, Delta E, h degrees and b* parameters, respectively. The higher Ea indicated that greater temperature sensitivity of visual color as compared to anthocyanins content. The degradation of anthocyanins showed positive correlation with C* (R-2>0.909), a* (R-2>0.860) and Delta E (R-2>0.940), while the degradation of anthocyanins showed negative correlation with h degrees (R-2>0.828) and b* (R-2>0.735) during heating. (C) 2007 Elsevier Ltd. All rights reserved.