Quality Preservation of Walnut Kernels: Effect of Storage Temperature and Vacuum Packaging

• Published in: Erwerbsobstbau Vol. 65; no. 6; pp. 2407 - 2418
• Main Authors: Shojaee, Azam, Rastegar, Somayeh, Tajeddin, Behjat, Sayyad-Amin, Pegah
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-12-2023; Springer Nature B.V
• Subjects: Agriculture; Air temperature; Biomedical and Life Sciences; Cultivars; Genotypes; Kernels; Life Sciences; Low temperature; Original Article; Originalbeitrag; Packaging; Phenols; Plant Sciences; Polyphenol oxidase; Rancidity; Shelf life; Storage conditions; Storage temperature; Vacuum packaging; Walnuts; Postharvest; Browning; Oxidative; Nut; Rancidity; Color
• ISSN: 0014-0309; 1439-0302
• DOI: 10.1007/s10341-023-00944-2

Walnut kernels are susceptible to oxidative rancidity and rapid deterioration due to their high oil content. Despite its global importance, little is known about this nut’s optimal storage conditions and shelf life. This research was conducted to evaluate the effect of different temperature (4 °C and 25 °C) and packaging (5% vacuum and air-containing package) on walnut kernels quality during 6 months’ storage. The cultivars ‘Common’ and ‘Claw tip’, both of which are important to the market, were examined. According to the results, the lowest level of peroxide value was observed in stored samples at the temperature of 4 °C under 5% vacuum packaging, while control samples stored at 25 °C with air packaging showed a four-fold increase over the same period in both genotypes. The antioxidant capacity and total phenol of the samples stored in a 5% vacuum at 4 ℃ were significantly higher in both cultivars than in other treatments. In both cultivars, polyphenol oxidase activity was effectively reduced by 5% vacuum packaging and low temperature. The highest L* index was observed in ‘Claw tip’ cultivar in 5% and air-containing package at 4 ℃, while in the ‘common’ cultivar, the highest level of L* was observed in 5% vacuum at 4 ℃. These results showed that low temperature and 5% vacuum significantly improved kernel quality of walnut cultivars ‘Common’ and ‘Claw tip’ during storage.