Optimization of the Pistachio Roasting Process with Hot Air Using the Response Surface Methodology

Introduction: Roasting is a thermal process that increases the overall acceptance of edible nuts by physicochemical reactions during heating and reducing the moisture content. Optimizing and controlling the pistachio roasting process requires understanding the process scientifically. This study optimized the roasting process of pistachio nuts with hot air using the response surface methodology. Materials and Methods: The response surface methodology was used to examine the effects of the roasting temperature, time, and hot airflow velocity on the roasted pistachios' physical (moisture content, and color parameteres), chemical (peroxide value, acidic value, and p-anisidine value), and sensory properties (overall acceptance, texture desirability, and crispiness). Twenty treatments with six replications were performed at the central point Based on the central composite design. the best quadratic model with the highest fit was determined using Design Expert 12 software. Results: The temperature was the variable of the highest effect on physicochemical and sensory properties. Airflow velocity has a significant impact only on the parameters of moisture content, lightness (L-value), yellowness (b-value), and the peroxide value. The highest overall acceptance, texture desirability, and the lowest peroxide and p-anisidine value (p.AV) were considered optimal conditions for preparing the desired sample in the roasting process. The optimal sample production conditions included temperature 133.6 oC, airflow velocity of 0.6 m/s, and roasting time of 23.6 minutes. Conclusion: Comparison of predicted response values with laboratory ones showed that the model would be suitable for predicting response values in the pistachio roasting process and determining the optimal conditions.