Characterizing the antioxidant and antifungal properties of nano‐encapsulated pistachio hull extract in fenugreek seed gum to maintain the quality and safety of fresh pistachio

Abstract

The quality of pistachio, one of the export products of Iran, will be decreased during storage as a result of mold spoilage, toxins production, and oil oxidation. This study aimed to investigate the capability of pistachio hull extract (PHE) loaded in fenugreek seed gum (FSG):whey protein isolate (WPI) nanoemulsion to control oil oxidation, and fungi growth in fresh pistachio nut during storage at 4°C. The total anthocyanin and total phenolic content of the PHE were 125.44 μg/g and 675.18 mg/g, respectively. The DPPH radical scavenging activity of PHE at 100 ppm was higher than that of tert-butylhydroquinon (TBHQ). In comparison with other concentrations, 50 ppm showed the strongest antifungal activity against <i>Aspergillus flavus</i>, <i>Aspergillus parasiticus</i>, and <i>Aspergillus nomius</i>. All nanoemulsions have a mean size lower than 265 nm. The polydispersity index (PDI) of different nanoemulsions was lower than 0.3, and a negative zeta potential was observed. The encapsulation efficiency was higher than 67.0% and all nanoemulsions had spherical morphology. The pistachio nuts were coated with different coating solutions containing 0 and 100 ppm of PHE and stored at 4°C for 8 weeks. The results showed that the pistachio sample coated with a composite coating of WPI and FSG containing 100 ppm of PHE has a higher moisture content and lower changes in <i>L</i>*, <i>a</i>*, and <i>b</i>* indexes, oil oxidation, fungi development, and total mold and yeast count. This treatment exhibited higher overall acceptance than other samples at the end of storage time. The results of this study suggest the use of biodegradable coatings enriched with natural extracts that have high antioxidant and antifungal activities.