The Effect of Tragacanth Edible Coating Containing α-Tocopherol on the Chemical and Sensory Properties of Roasted Pistachio Nuts During Storage

Pistachio nuts are considered a functional foodstuff containing various antioxidants consumed mostly in a roasted form. Mild to severe roasting conditions can cause oil oxidation. Therefore, different methods, such as coating, are used to increase the shelf life of nuts.

Tragacanth-based edible coatings were prepared using propylene glycol as a plasticizer both individually and in combination with free α tocopherol (FT), or its Nanocapsules (NC) and Nanoesphers (NS). Chemical and sensory properties of coated pistachio nuts were measured during 6-month storage at 40, 50, and 60ᵒC.

At storage temperatures of 40, 50, and 60°C, PV and Pa.V were evaluated 3.92, 3.85, 7.1 and 6.89, 13.3, 21.1 meq/kg, respectively. Unlike acidic value, coating with tragacanth caused a significant reduction in PV and Pa.V indices as they did not exceed 4 and 6, respectively. Sensory evaluation showed the overall acceptance of uncoated roasted pistachios to be lower than average after 120 and 60 days of storage at 50 and 60°C, respectively. Thus, the anisidine value was measured in the range of 2.9-5.6. No significant difference was observed in oxidation indices and sensory properties of coated samples with different forms of α-tocopherol.

Using nanoparticle forms of α-tocopherol in coating reduced the oxidation rate and improved overall acceptance during storage. There was a correlation between the chemical markers of oxidation and sensory properties of roasted pistachio nuts, and p-anisidine value was appropriate to monitor pistachio nuts' oxidative during shelf-life.