Dried walnuts are rich in unsaturated fatty acids, with linoleic acid and α-linolenic acid accounting for over 70% (China Cereals and Oils Association, *Guidelines for Nut Storage Technology*, 2022 edition). These fatty acids are chemically active and readily undergo auto-oxidation under conditions of oxygen, light, and elevated temperature, producing volatile small molecules such as aldehydes and ketones, leading to a rancid odor. Experimental data shows that in a room temperature environment of 25℃ and 60% relative humidity, unsealed dried walnuts stored for 30 days exhibit a peroxide value (POV) exceeding the national food safety standard limit (0.25 mmol/kg), and the detection rate of "off-odor" reached 100% in sensory evaluation.
Furthermore, although the moisture content of walnut kernels has been reduced to 4%–6%, they will still slowly absorb moisture if the ambient humidity exceeds 70%, providing conditions for the growth of mold (such as Aspergillus flavus). Therefore, inhibiting oxidation and isolating moisture are the core principles of storage, rather than simply pursuing "dryness."
