Effects of Dielectric and Steam Heating Treatments on the Pre-Storage and Storage Color Characteristics of Pecan Kernels

Pecan kernels were subjected to steam conditioning and dielectric heating treatments and evaluated initially and during 16 wk of accelerated storage to determine temperature effects on color characteristics. Steam conditioning treatments, which raised kernel temperature to 93°C, caused significantly greater darkening of the kernels initially and during storage than did dielectric heating to 88, 136, and 156°C. Comparison of mean Hunter color values of stored dielectrically heat-treated kernels and kernels that were frozen and maintained as control samples showed a stabilizing influence on kernel darkening by these heat treatments. Lightness (L values) of the kernels was increased by dielectric heating, Hunter a values did not differ significantly from the control, and the hue (θ) of the kernels was increased only by the 156°C dielectric heating treatment.