Effect of Arabic gum coating enriched with Shirazi thyme essential oil on quality characteristics of fresh pistachio (Pistacia vera L cv. Ahmad-Aghaghi)

Biodegradable edible coatings, their enrichment with essential oils and their use on the surface of fruits are influential approaches that can reduce the problems of post-harvest management, thereby maintaining the quality of the produce. In this study, different concentrations of Arabic gum (0, 6 and 8% w/v) were used in combination with different concentrations of Shirazi thyme essential oil (0, 0.3 and 0.5% w/v), and their effects were measured with respect to various qualitative characteristics of fresh pistachio nuts which were evaluated for a period of 36 days under conditions of storage at a temperature of 3 ± 1°C. The results showed that the growth of mold and yeast and the growth of aerobic bacteria on the samples were significantly less than in other samples when using the 6% Arabic gum concentration enriched with the essential oil of Shirazi thyme at 0.3 and 0.5%. Also, adding the essential oil of Shirazi thyme (at 0.3 and 0.5%) to the formulation of Arabic gum (6%) managed to reduce the occurrence of water loss from the fresh pistacia and significantly reduced the weight loss from the samples. The addition of essential oil to the Arabic gum coating contributed significantly to the preservation of carbohydrates, chlorophylls, phenolic compounds, and antioxidants in the kernels of the fresh pistachios. Therefore, the use of edible coatings of 6% Arabic gum containing Shirazi thyme essential oil (at 0.3 and 0.5%) can maintain the quality and increase the shelf life of fresh pistachio.