Evaluation of Anti-Fungal and Anti-Oxidant Properties of Chitosan and its Effect on the Moisture Absorption and Organoleptic Characteristics of Pistachio Nuts

Iran is one of the largest pistachio producer and exporter in the world. Unfavorable environmental storage conditions causes aflatoxin production، moisture absorption، tissue destruction، fat oxidation and undesirable flavor that leads to a drop in the quality of the final product. The aim of this study is to evaluate the anti-fungal and antioxidant properties of chitosan and its impact on the organoleptic characteristics of pistachio nuts. Pistachio nuts were prepared and coated with 1% (V/V) acetic acid and chitosan at 0. 5، 1 and 1. 5% (V/W) concentrations. Acetic acid coated pistachio was used to understand the antimicrobial effect of acetic acid. Pistachio kernels were coated and kept at room temperature (25-27 °C) for six months. During storage samples were examined every two weeks for mould and yeast growth and development of Aspergillus، peroxide value، TBA value، moisture and weight changes and sensory characteristics. Experiments were performed in factorial form in a completely randomized design. The results showed that chitosan and acetic acid significantly (p <0. 05) inhibited the growth of the Aspergillus. Chitosan reduced the rate of oxidation reactions and by increasing chitosan concentration the anti-fungal and anti-oxidant activities were increased. Chitosan also prevented moisture absorption and weight changes in pistachio nuts. Chitosan at 1. 5%concentration had a significant effect (p <0. 05) on the flavor of pistachio، but at other concentrations did not affect the flavor. Chitosan did not affect the color، texture and general acceptance significantly (p >0. 05). Chitosan was found to be a proper material for coating of pistachio nuts. Chitosan solution at 1% concentration was selected as the best treatment