Walnut kernel (Juglans regia L.) Rancidity and Browning as affected by Nitrogen and Carbon Dioxide Environmental Storage Conditions

CRISOSTO, C. H.; POLARI J.; WANG S.; LAMPINEN B.; ORTIZ C.M.; FIELDS R.; LABAVITCH J.M.; VICENTE A.R.

Santiago de Chile

Congreso; IX Congreso Iberoamericano de Tecnología Postcosecha y Agroexportaciones; 2017

Facultad de Ciencias Agronómicas Universidad de Chile

Low oxygen atmosphere created by using the inert gas nitrogen (N2) is commercially utilized to extend postharvest life of European walnuts. In this ongoing study, we compared the benefits on using 100% N2 and 100% CO2 on kernel shelf life. ?Chandler? and ?Howard? kernels were stored at 35˚C (forced evaluation test) for 0, 4 and 6 weeks and evaluated for visual (DFA scores) and colorimeter (L*, Hue) color measurements, ethanol soluble phenolics, free fatty acids (FFA), and peroxide value (PV). We also determined volatile aldehyde production by gas chromatography coupled to mass spectrometry (CG-MS) and ?rancidity? perception by a trained panel. In both cultivars, the low oxygen storage under 100% N2 and 100% CO2 was equally and highly effective in delaying kernel browning and phenolic compound degradation. These modified atmospheres delayed lipid hydrolysis, oxidation, cleavage, and sensory perception of rancidity, and formation of undesired volatiles (aldehydes) as compared to air-stored kernels. In our forced high temperature storage test, free fatty acids increased faster in kernels held in air than kernels stored under high CO2 or high N2. Additionally, high CO2 or N2 storage conditions delayed the increase of peroxidase values and lipid peroxidation. However, lipid peroxidation inhibition was higher in CO2 stored kernels than other storage conditions. Thus, our preliminary results support the need of a full range of temperatures and water activities combined with anaerobic conditions (N2 or CO2) to maximize kernel walnut storage life studies. Therefore, further studies using commercial storage range conditions are needed to establish a reliable low O2 technology for protecting kernels from darkening and rancidity development.