Study of the effect of sodium alginate coating containing pomegranate peel extract on chemical, sensory and microbialquality of walnut kernel

Background: Due to the adverse effects of artificial preservatives on food and its harmful effects onhuman health, researchers have been considering replacing these materials with natural substances. Inthis study, the effect of pomegranate peel extract (PPE) on the stability and antifungal activity of thewalnut kernel was studied.Methods: The pomegranate peel was extracted by the solvent and water-solvent method. The extractedsap was evaluated using the antioxidant assay by 2,2-diphenylpicrylhydrazyl (DPPH) assay. The resultsshowed that the extracted sap had 40.11 mg/g dry phenol and 47.27% free radicals scavenging. Fourconcentrations (0%, 2%, 6%, and 10%) of pomegranate liquid extract were prepared and studied for90 days for the walnut kernel coating. Walnut kernels were coated on days 1, 15, 30, 60, and 90, andexamined for moisture, acidity, peroxide, conjugated diene, and anisidine tests. Data were analyzedusing SPSS version 21.Results: By increasing the extract concentration from 2 to 10%, the stability of the walnut kernel duringstorage was increased. Acidity in the samples with 10% PPE coating, decreased from 0.18 to 0.11 on thefirst day until the 15th day, and increased to 0.48 from day 15 to 90. The results showed that the moisturecontent and acidity increased with increasing the extract concentration. By increasing the extractconcentration up to 10%, the sustainability indices, including peroxide, anisidine, and conjugated dienewere significantly decreased. At 90 days, by increasing the concentration of pomegranate extract from2% to 10%, the count of molds and yeasts was reduced from 3.59 to 2.29 CFU/g. The count of molds andyeasts in the uncoated samples was 5.81 CFU/g.Conclusion: According to the results, PPE can increase the stability and antifungal activity of walnut,therefore, the health quality of the product increases.

Keywords:

Antioxidant , Pomegranate peel , Solvent , Free radicals , Phenol