Abstract：
Walnut kernels are prone to oxidation and rancidity due to their rich lipid composition, but the existing evaluation indicators are not sensitive enough to promote their industrial development. This study aims to investigate the potential markers in oxidative rancidity walnut kernels using lipidomics and volatolomics. The results showed that the antioxidant capacity of walnut kernels significantly decreased after oxidation, with the decreasing of total phenolic content from 36276.34 mg GAE/kg to 31281.53 mg GAE/kg, the DPPH and ABTS free radical scavenging activity from 89.25% to 73.54%, and 61.69% to 43.73%, respectively. The activities of lipoxygenase (LOX) and lipase (LPS) increased by 6.08-fold and 0.33-fold, respectively. By combining volatolomics and chemometrics methods, it was found that significant differences existed in the content of hexanal, caproic acid, 1-pentanol, (E)-2-octenal, and 2-heptanenal before and after walnut kernel oxidation (VIP > 1). Based on the results of lipidomics, it can be concluded that the above five compounds can serve as characteristic markers for walnut kernel oxidative rancidity, mainly produced through glycerol phospholipid (GPL), glyceride, linoleic acid (LA), and α-linolenic acid (ALA) metabolism pathways. Possible mechanisms of lipid degradation in oxidized walnut kernels were also proposed, providing technical support for the storage, preservation, and high-value utilization of walnut kernels.
摘要：
核桃仁由于其丰富的脂质成分，容易氧化和酸败，但是现有的评估指标不够敏感，无法促进其产业发展。本研究旨在使用脂质组学和volatolomics研究氧化酸败核桃仁中的潜在标志物。结果表明,核桃仁氧化后的抗氧化能力显著降低,随着总酚含量从36276.34mgGAE/kg下降到31281.53mgGAE/kg,DPPH和ABTS自由基清除活性从89.25%提高到73.54%,和61.69%到43.73%，分别。脂氧合酶（LOX）和脂肪酶（LPS）的活性分别增加了6.08倍和0.33倍，分别。通过结合volatolomics和化学计量学方法，发现己醛的含量存在显着差异，己酸,1-戊醇,(E)-2-octenal,和2-庚烯在核桃仁氧化前后（VIP>1）。根据脂质组学的结果，可以得出结论，上述五种化合物可以作为核桃仁氧化酸败的特征标记，主要通过甘油磷脂（GPL）生产，甘油酯，亚油酸（LA），和α-亚麻酸(ALA)代谢途径。还提出了氧化核桃仁脂质降解的可能机制，为存储提供技术支持，保存,核桃仁的高价值利用。
