Walnut oil oxidizes and becomes rancid during storage, that could be significantly affecting flavor and quality. This study aimed to monitor the volatile compounds present in walnut oil during storage, identify the characteristic markers of walnut oil at different oxidation levels, and establish a correlation network analysis based on the relationship between the olfactory analyzer and the characteristic markers to understand their correlation. The results indicated that the oxidation level of walnut oil had a positive correlation with the response of the olfactory analyzer. 219 volatile compounds were identified in walnut oil, with 89 identified as key volatile compounds (VIP >1). Among these, compounds such as (E, E)-2,4-decadienal (6.10%-23.04%)，(E, E)-2,4-heptadienal (2.23%-13.61%)，(E)-2-octenal (0.95%-11.71%)， hexanoic acid (1.63%-4.30%)，1-octen-3-ol (2.53%-19.01%)，(Z)-2-heptenal (5.95%-25.01%)，2,3-dihydro-furan (1.08%-3.20%)，2-pentyl-furan (0.13%-0.54%), pyrazine (0.33%-1.32%), hexanal (24.52%-1.33%)，3-hethylbutylacetate (12.44%-1.29%)， 2-methyl butyl acetate (7.74%-1.56%) and ethenyl hexanoate (4.39%-0.41%) were found to be characteristic volatile compounds in the oxidation process of walnut oil. Furthermore, the correlation network analysis revealed a strong correlation between the olfactory analyzer sensors and the characteristic volatile compounds. The findings of this study can provide valuable data for the development of rapid determination of the oxidation level of walnut oil.

Odor is an important characteristic of walnut oil; walnut oil aromas from different varieties smell differently. In order to compare the differences of volatile flavor characteristics in different varieties of walnut oil, the volatile organic compounds (VOCs) of walnut oil from five different walnut varieties in Northwest China were detected and analyzed using headspace gas chromatography–ion mobility spectrometry (HS–GC–IMS). The results showed that 41 VOCs in total were identified in walnut oil from five different varieties, including 14 aldehydes, 8 alcohols, 4 ketones, and 2 esters. Walnut oil (WO) extracted from the “Zha343” variety was most abundant in VOCs. The relative odor activity value (ROAV) analysis showed that aldehydes were the main aroma substances of walnut oil; specifically, hexanal, pentanal, and heptanal were the most abundant. Fingerprints and heat map analysis indicated that WO extracted from the “Xin2”, “185”, “Xin’guang”, and “Zha343” varieties, but not from the “Xinfeng” variety, had characteristic markers. The relative content differences of eight key VOCs in WO from five varieties can be directly compared by Kruskal–Wallis tests, among which the distribution four substances, hexanal (M), hexanal (D), pentanal (M), (E)-2-hexanal (M), presented extremely significant differences (P<0.01). According to the results of the principal component analysis (PCA), WO extracted from the “Zha343” variety was distinct from the other four varieties; in addition, WO extracted from the “Xin2” variety exhibited similarity to WO extracted from the “185” variety, and WO extracted from the “Xinfeng” variety showed similarity to WO extracted from the “Xin’guang” variety. These results reveal that there are certain differences in the VOCs extracted from five different WO varieties, making it feasible to distinguish different varieties of walnut oil or to rapidly detect walnut oil quality based on its volatile substances profile.

Previously, research adopted an ultrasound-assisted extraction method to isolate crude polysaccharide from blackened jujube, followed by preliminary structural identification of the purified polysaccharide (BJP). This manuscript analyzed the accurate structure and immunomodulatory activity of BJP. Further structural identification indicated that BJP was mainly composed of →3)-α-L-Araf-(1→, →3,5)-α-L-Araf-(1→, →3)-β-D-GalpA-(1→, →2,4)-β-D-Galp-(1→, →4)-β-D-GalpA-(1→, →3)-α-L-Rhap-(1→ and →3,4)-α-L-Rhap-(1→. The immunomodulatory effects of BJP were examined using a mouse model with immunosuppression induced by cyclophosphamide. The findings suggested that BJP could relieve the condition of immunosuppressed mice. BJP could inhibit decreases in the body weight and organ index of mice, and HE staining showed that BJP could alleviate the harm to spleen and thymus tissues. BJP enhanced the secretion of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-2 (IL-2), interleukin-6 (IL-6), immunoglobulin A (IgA), and immunoglobulin G (IgG) in serum. It also reduced liver oxidative stress by increasing superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activities, while lowering malondialdehyde (MDA) levels. Moreover, BJP contributed to the maintenance of gut homeostasis by stimulating the generation of short-chain fatty acids in the cecal contents. The study aims to establish a solid basis for the comprehensive development of blackened jujube and furnish a theoretical framework for its polysaccharides’ role in immune modulation.