Determination of Peeling Efficiency, Free Fatty Acid, Peroxide Value and Sensory Evaluation of Peeled Pistachio Kernel using Hot Water

Abstract

Pistachio green kernel, is obtained by removing the red testa of around the whole kernel. In this study, the suitable peeling conditions for removing the testa of the kernel were determined using hot water in five termperature levels of 75, 80, 85, 90, and 95°C and diffetent hot water immersion times of 2, 4, 6, 8, and 10 minutes in riped and unripe samples. Quality factors including the number of pistachio green kernels with remained red testa, free fatty acids, and peroxide value were measured at 3 and 6 months after peeling. Sensory evaluations (including appearance, color, taste, and texture) of the best treatments from the previous stage, were measured by 10 trained panelists. Peeling performance were not good using temperatures of 75 and 80°C in both riped and unripe samples. Peeling performance of 100%, was obtained at 85 and 90°C (6, 8 and 10 min) and 95°C (2, 4, 6, 8 and 10 min) kernel immersion in hot water in riped and unripe cultivars. The qualitative factors, free fatty acids and peroxide value, has have increased in both riped and unripe samples during storage. After 6 months of storage, the lowest peroxide value was observed at 90°C (10 min immersion in hot water) and 95°C (2, 4, 6, 8 and 10 min immersion in hot water). The minimum free fatty acid, was observed in riped ripe samples at 90° C (10 min immersion) and in the unripe samples at 95°C (2 and 4 min immersion). According to the comments of trained panelists, the significant differences between treatments were not observed in terms of the sensory characteristics such as taste, texture, color, and appearance at 5% level. In general, with respect to the performance of peeling, free fatty acids, peroxide value, and sensory evaluation, temperature of 95°C (2 min kernel immersion in hot water) can be used for peeling of riped and unripe samples.