Glycerol ginger extract addition to edible coating formulation for preventing oxidation and fungal spoilage of stored walnuts

During storage, walnuts can undergo oxidation processes that lead to a decay of product quality and the development of rancidity and off-flavor. The present study investigated how the application of a chitosan coating, containing a glycerol ginger extract (GGE) rich in bioactive compounds, can preserve walnut quality during storage. Glycerol can be considered a green extraction solvent, that allows to obtain extract rich in polyphenols and with high radical scavenging activity. GGE employed in the formulation of a chitosan-based coating determined significantly lower (p < 0.05) lipid oxidation and peroxides values in walnuts stored under stressing temperature conditions (45 °C), in comparison to Control (uncoated sample) and even in comparison to the walnuts coated with sole chitosan. Moreover, when artificially inoculated with Aspergillus flavus spore suspension, walnuts treated with GGE-enriched coating evidenced the lowest disease incidence and the lowest spore concentration. Results obtained encourage the application of coating containing GGE even in other rich lipid matrices that can easily undergo oxidation process or spoilage caused by phytopathogenic fungi.