Enhancing the Quality of Fresh Pistachio Fruit Using Sodium Alginate Enriched with Thyme Essential Oil

The combined coating-effects of Sodium Alginate (SA) and Thyme Essential Oil (TEO) was investigated at three levels of, respectively, (0.0, 1.0, and 1.5 %) and (0.0, 0.3, and 0.5%) on fresh pistachio during 6 weeks of cold (3±1°C) storage. Physiochemical parameters (hull and hard-shell color, hull hardness, soluble sugar, chlorophyll, and soluble solids content) and microbial load (plate count agar) were measured every 2 weeks of storage. Similarly, the sensory attributes of pistachio were evaluated by trained panelists and Quantitative Descriptive Analysis (QDA) method from minimum (1) to maximum level (15) score. While weight loss of each pistachio sample increased during storage time, those treated with alginate had considerably less weight losses than other treatments. The pistachio treated with combination of SA (1%) and TEO(0.3 or 0.5%) showed significantly higher hull hardness, L* values, soluble sugar, chlorophyll, and lower growth of microorganisms (mainly yeast and mold) than other treated and non-treated (control) samples. The highest sensory scores of 12.3 and 10.6 for hull color of pistachio were related to samples coated again with combinations of SA (1%) and TEO (0.3 or 0.5%), respectively, and were significantly higher than the score of control sample (6.4). Since the pistachio treated with the above-mentioned concentrations of SA and TEO had significantly higher physiochemical, microbiological, and sensory attributes than the other samples, their quality indicators were superior to other treatments (including control samples) and, most probably, they had longer shelf lives and potential to preserve their natural characteristics of fresh pistachio during storage.