The Effect of Antioxidant Compounds and Polymer Coatings on the Quality and Shelf Life of Fresh Ahmad Aaghaei Pistachio

Due to its taste and nutritional properties, pistachio (Pistacia vera) is one of the most popular nuts in the world. One of the problems regarding the storage of fresh pistachios is hull browning. The phenomenon is the result of the formation of complex compounds and colored polymers caused by enzyme reactions, which damage the texture, aroma, taste and even the appearance of the fruit.

A study was conducted to investigate the effects of citric acid (0, 1, 1.5 and 2%) and ascorbic acid (0 ,15, 25 and 35 ppm), as well as two types of polyethylene (LDPE) and polystyrene coatings on the shelf life (day zero, 25 and 45) of Ahmad Aghaei pistachio cultivar. The samples were prepared from a pistachio orchard located in gardens in the area of Hozdagh in Kerman province. This experiment was performed with three factors in a factorial design based on a completely random design. Each value is the average of four replications (200-gr in each replicate). Sources of variation were treatment (Ascorbic and Citric acid), polymer coatings (polyethylene and polystyrene) and storage period (0, 25 and 45).

The results indicated significant effects of the treatments, polymer coatings and storage periods on some quantitative and qualitative characteristics of the pistachios. Slight weight loss during storage was observed in samples which were higher in polyethylene (0.45%) coatings compared to polystyrene (0.22%). Treatments did not have a significant effect on the pistachio firmness as compared with the effect of shelf life and coating. The hull firmness decreased (30.5%) during storage, but it first decreased and then increased in the kernel. In addition, the samples in the polystyrene coatings had more rigidity (3.5%) than the pistachios in the polyethylene package. In terms of browning, the appearance of the pistachios in the packaging of polystyrene coatings was more desirable than that of polyethylene coatings

In general, weight loss, firmness, apparent quality, and color indices were better in polystyrene coatings than polyethylene ones.