Optimization of Processing Variables for Pistachio Paste Production

Background: Pistachios is one of the popular tree nuts in Iran and other countries. The effect of pistachio kernel roasting and milling parameters on the quality of pistachio paste was investigated in this study. Material and Methods: Roasting variables were roasting temperature (90-190°C) and roasting time (5-65 min). Four grinding gap sizes (20, 40, 60, and 80 μm) were used to prepare pistachio pastes. Results: Increasing roasting time and temperature had inverse associations with colour attributes of both kernels and pistachio powders, except for 'a' value of pistachio powder. The hardness (N) and colour parameters (yellowness index, L value and b value) of pistachio kernels and the 'a' value of pistachio powder can be used to control the roasting quality of pistachio kernels. The colloidal stability (CS) of pistachio pastes was found to be affected by particle size. Conclusion: The recommended roasting condition ranges of the kernels for the pistachio paste production were 130-140°C (30-40 min). The most stable pistachio paste was obtained when the gap size of the mill was 20 μm.