Search Results (89)

A simple, rapid, and cost-effective method for the determination of benzo[a]pyrene (BaP) in edible oil was developed and validated. Nickel oxide-deposited silica (SiO₂@NiO) was employed as a solid-phase extraction (SPE) adsorbent for the extraction of BaP from edible oil, followed by high-performance liquid chromatography–diode array detector (HPLC-DAD) analysis of BaP. The edible oil was diluted with n-hexane and directly loaded to SiO₂@NiO for SPE. The n-hexane was also used to clean the fat-soluble interference substance in the edible oil, and BaP was selectively captured using SiO₂@NiO through the electron donor–acceptor interaction. The SPE conditions, including the amount of adsorbent, volume of washing solvent, and type and volume of desorption solvent, were optimized. This SiO₂@NiO-based SPE coupled with the HPLC-DAD method demonstrated good linearity within a BaP concentration range of 6–1875 ng/g in edible oils, with a limit of detection of 1.3 ng/g, spiked recovery of 97.4–105.1%, and relative standard deviation (RSD) of <3.0%. The method was applied to the analysis of BaP in 11 real oil samples (soybean oil, olive oil, corn germ oil, flaxseed oil, walnut oil, sunflower kernel oil, peanut oil, unrefined oil, and high-temperature frying oil), and the results show that the unrefined oil and high-temperature frying oil were at risk of BaP exceeding acceptable level. Full article

This study reports the first successful isolation and characterization of exosome-like nanoparticles from walnut kernels (WELNs). The isolated WELNs exhibited a typical cup-shaped morphology with an average diameter of 139.7 ± 67.5 nm, a concentration of 7.4 × 10¹¹ particles/mL, and a zeta potential of −17.47 ± 4.06 mV. Proteomic and small RNA sequencing analyses confirmed the presence of diverse proteins and microRNAs within WELNs. In vitro assays demonstrated their potent antioxidant capacity, with radical scavenging rates of 67.54% against ABTS⁺ and 48.59% against DPPH⁺ at 102 μg/mL and IC₅₀ values of 89.7 μg/mL and >102 μg/mL for scavenging of ABTS⁺ and DPPH⁺ radicals, respectively. Cytotoxicity assays indicated no adverse effects on RAW264.7 macrophage viability at concentrations up to 60 μg/mL. In LPS-stimulated RAW264.7 macrophages, WELN treatment (20–60 μg/mL) dose-dependently mitigated oxidative stress by reducing intracellular ROS levels (down to 81.22% of the control at 60 μg/mL) and malondialdehyde (MDA) content while restoring the activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Furthermore, WELNs significantly suppressed the production of nitric oxide (NO) and pro-inflammatory cytokines TNF-α, IL-6, and IL-1β (reduced to approximately 30.8%, 22.7%, and 23.6% of LPS-induced levels, respectively, at 60 μg/mL). Mechanistic investigation revealed that the anti-inflammatory effect was mediated through the inhibition of the MAPK signaling pathway, as evidenced by decreased phosphorylation of p38, ERK, and JNK. In conclusion, WELNs exhibit dual anti-inflammatory and antioxidant properties. This study provides the first evidence of bioactivity for walnut-derived exosome-like nanoparticles, advancing the mechanistic understanding of walnuts’ health benefits and highlighting their potential as a natural component for functional food applications. Full article

Background/Objectives: The physiological disorder known as “orange spot” in Juglans regia L. cv. Chandler is an emerging kernel quality issue of increasing concern for the Chilean walnut industry. Characterized by a localized orange discoloration of the embryo, its etiology remains unknown. This study aimed to determine whether orange spot is associated with bacterial infection and to elucidate the metabolic alterations underlying its development, testing the hypothesis that it results from oxidative imbalance and lipid disorganization. Methods: Untargeted metabolomic profiling and fatty acid methyl ester (FAME) analysis were applied to compare affected (orange) and unaffected (white) walnut kernels collected from a commercial orchard in Melipilla, Chile, during the 2018 and 2022 seasons. Bacterial DNA was screened by PCR amplification of the 16S rRNA gene (799F/1193R). Results: Orange spot incidence reached 31–34% across seasons. No bacterial-sized amplicons were detected in either kernel type, indicating the absence of detectable bacterial DNA under the analyzed conditions. Metabolomic analyses revealed significant alterations in glyoxylate and dicarboxylate metabolism, glutamate-related pathways, and glycerophospholipid metabolism. Affected kernels exhibited reduced levels of L-glutamic acid and antioxidant-associated metabolites, alongside increased gluconic, citric and quinic acid, consistent with the redox imbalance and membrane oxidative degradation. FAME analysis showed higher total fatty acid content in affected kernels, suggesting intensified lipid turnover associated under oxidative stress. Conclusions: Orange spot is a physiological, non-infectious disorder linked to premature oxidative stress and lipid disorganization, negatively affecting walnut kernel quality. Full article

Walnut (Juglans regia L.) is an important economic and oil-bearing tree species, and the nutritional quality of its kernels is influenced by multiple environmental factors. Elevation is an ecological gradient that integratively reflects variations in environmental conditions such as temperature and light availability and shows a certain degree of correlation with kernel nutritional quality. The aim of this study was to clarify the regulatory effect of elevation on the nutritional quality of walnut kernels in Chongqing and to optimize the layout of high-quality walnut production areas. This study used 181 walnut germplasm resources collected from 16 natural populations (production areas) in Chongqing. Six elevation ranges were defined (I: 200–600 m, II: 600–900 m, III: 900–1200 m, IV: 1200–1400 m, V: 1400–1600 m, VI: 1600–1800 m), and twelve nutritional traits of walnut kernels were systematically analyzed, including total fat, protein, soluble sugar, tannin, saturated fatty acids (stearic acid, palmitic acid, arachidic acid), and unsaturated fatty acids (oleic acid, palmitoleic acid, cis-11-eicosenoic acid, linoleic acid, α-linolenic acid). The results showed that the fat content of walnut kernels was generally higher than 60%, with the highest value in zone VI (62.93%). The protein content was the highest in zone III (17.71%) and the lowest in zone VI (16.06%). Soluble sugar and tannin contents were relatively low, both peaking in zone II (3.10% and 10.85%, respectively). The overall content of saturated fatty acids was low, being slightly higher in zone II, with little variation among components across elevations. Among monounsaturated fatty acids, oleic acid was dominant, showing a decreasing–increasing trend with rising elevation, with the lowest value in zone II (20.98%) and the highest in zone VI (26.93%), while palmitoleic acid and cis-11-eicosenoic acid were maintained at low levels. Polyunsaturated fatty acids were dominated by linoleic acid, ranging from 51.22% to 61.04%, with the highest content in zone II and the lowest in zone VI. Comprehensive evaluation and cluster analysis grouped the six elevation zones into three categories, with zone II showing the best nutritional quality, particularly in terms of soluble sugar, stearic acid, and linoleic acid, while zone I had the lowest score. These findings provide a theoretical basis for the selection of high-quality walnut production areas and the precision cultivation of nutrient-rich walnut fruits, as well as important data support for the scientific planning and high-quality development of the walnut industry in Chongqing. Full article

The separation of walnut kernels from shells is a crucial step in walnut processing. Pneumatic sorting is the mainstream method. However, due to the overlapping suspension speeds of half-shells and eighth-shells, complete separation was not achieved. This paper proposes using a toothed vibrating screen to separate the two. Using EDEM to simulate and analyze the motion forms, collision processes, and stress conditions of walnut shells and kernels on the vibrating screen, the effectiveness of this method was demonstrated, and the mechanisms of shell–kernel retention and loss during the separation process were revealed. Results indicate that 1/8 kernels, being smaller, easily fall into tooth grooves and move upward step by step under the excitation force during reciprocating vibration. The 1/2 shells, being larger, are difficult to fall into the teeth grooves, and their smooth surfaces cause them to slide easily, moving downward continuously under the action of reciprocating vibration and gravity. Using the cleaning rate and loss rate as evaluation indicators, it was found that as the inclination angle of the vibrating screen increased step by step, the cleaning rate consistently increased monotonously. The loss rate initially rose slowly, then surged sharply after reaching 22°, at which point the loss rate was at its lowest, around 10%, and the cleaning rate was at its maximum, at 95%. The shortest retention time of walnut shells on the screen is 2.85 s, and the longest is 10.6 s, with the number of collisions being 458 and 2619, respectively; the collisions between the shells and the kernels account for 51.8%. The failure to thoroughly separate is due to the shell and kernel entangling within the separation area, making it impossible to segregate them. They enter the opposite region, collide, and cause loss and retention phenomena. Full article

Walnut bacterial blight (WBB), caused by Xanthomonas arboricola pv. juglandis, is one of the most damaging diseases in walnut production, capable of reducing yields by up to 50%. Despite its economic importance, tissue-specific defense mechanisms in walnut fruit remain poorly understood. In this study, we performed an integrative approach with metabolomic and biochemical analyses of walnut fruit responses to WBB, examining primary and secondary metabolites, antioxidant activities, and enzyme dynamics across affected and non-affected tissues of the husk, stalk, as well as kernel pellicle and flesh. Using LC-MS, GC-MS, and spectrophotometric assays, we identified distinct compartmentalized defense strategies. The husk showed strong phenolic-mediated responses, with naphthoquinone levels increasing by 125%. However, oxidative processes in necrotic areas may have reduced the stability of these compounds by 50%. In contrast, affected kernel tissues exhibited lower phenolic activity, suggesting that carotenoids and fatty acids could be involved as a protection mechanism, undergoing early oxidation to help preserve lipid integrity. Antioxidant enzymes were upregulated in husk and kernel pellicle, while volatile terpenes and sugars accumulated in infected tissues, indicating metabolic shifts toward localized defense. Overall, our findings reveal a tissue-specific, multi-layered defense network in walnut fruit that could constitute specific markers associated with disease progression. Full article

High-throughput phenotyping has become essential for plant breeding programs, replacing traditional methods that rely on subjective scales influenced by human judgment. Machine learning (ML) computer vision systems have successfully used convolutional neural networks (CNNs) for image segmentation, providing greater flexibility than thresholding methods that may require carefully staged images. This study compares two quantitative image analysis methods, rule-based thresholding using the magick package in R and an instance-segmentation pipeline based on the widely used Mask-R-CNN architecture, and then compares the output of each to two different sets of human evaluations. Walnuts were collected over three years from over 3000 individual trees maintained by the UC Davis walnut breeding program. The resulting 90,961 kernels were placed into 100-cell trays and imaged using a 20-megapixel Basler camera with a Sony IMX183 sensor. Quantitative data from both image analysis methods were highly correlated for both lightness (L*; r² = 0.997) and size (r² = 0.984). The thresholding method required many manual adjustments to account for minor discrepancies in staging, while the CNN method was robust after a rapid initial training on only 13 images. The two human scoring methods were not highly correlated with the image analysis methods or with each other. Pixel classification provides data similar to human color assessments but offers greater consistency across different years. The thresholding approach offers flexibility and has been applied to other color-based phenotyping tasks, while the CNN approach can be adapted to images that are not perfectly staged and be retrained to quantify more subtle kernel characteristics such as spotting and shrivel. Full article

To effectively address the issues of poor ventilation, light deficiency, increased pest and disease pressure, and declining fruit quality in closed-canopy walnut orchards, this study was conducted in a standard, densely planted ‘Xinwen 185’ walnut orchard. Three treatments were established: an unthinned control (CK), a 1-year thinning treatment (T1), and a 2-year thinning treatment (T2). All parameters were uniformly investigated during the 2023 growing season to analyze the effects of thinning on orchard population structure, microenvironment, leaf physiological characteristics, fruit quality, and yield. The results demonstrated that tree thinning significantly optimized the population structure: crown width expanded by 6.22–6.76 m, light transmittance increased to 27.74–33.64%, and orchard coverage decreased from 100% to 75.94–80.51%. The microenvironment was improved: inter-row temperature increased by 2.34–4.08 °C, light intensity increased by 5.38–25.29%, and relative humidity decreased by 2.15–3.30%. Furthermore, leaf physiological functions were activated: in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively; the leaf carbon-to-nitrogen ratio increased by 18.67%; the net photosynthetic rate (Pn) during fruit expansion increased by 34.21–46.10%; and the intercellular CO₂ concentration (Ci) decreased by 10.18–10.31%. Fruit quality and yield were synergistically enhanced: single fruit weight increased by 23.39~37.94%, and kernel weight increased by 26.79–41.13%. The total sugar content in inner-canopy fruits increased by 16.50–16.67%, while the protein and fat content in outer-canopy fruits increased by 0.69–12.50% and 0.60–2.18%, respectively. Yield exhibited a “short-term adjustment and long-term gain” pattern: the T2 treatment (after 2 years of thinning) achieved a yield of 5.26 t·ha⁻¹, which was 20.38% higher than the CK. The rates of diseased fruit and empty shells decreased by 65.71% and 93.22%, respectively, and the premium fruit rate reached 90.60%. This study confirms that tree thinning is an effective measure for improving the growing environment and enhancing overall productivity in closed-canopy walnut orchards, providing a scientific basis for sustainable orchard management and increased orchard profitability. Full article

Walnuts (Juglans regia L.) are recognized for their rich nutritional profile and health-promoting properties. This study investigates the impact of biostimulation, via wood distillate application, on the chemical composition and therapeutic potential of walnut kernels, focusing on their wound healing activity. Biostimulated walnuts showed enhanced levels of phenolic compounds including antioxidants, sugars, and amino acids compared to untreated or agrochemically treated controls. Phytocomplexes extracted from walnut kernels using green methodologies were tested on human keratinocytes (HaCaT), revealing pro-migratory effect, boosted by biostimulation. Molecular analyses demonstrated the activation of epithelial–mesenchymal transition (EMT) pathways, marked by downregulation of epithelial markers and upregulation of mesenchymal genes such as MMP3, MMP9, vimentin, and SMAD3. Furthermore, a synergistic effect was observed between extracts derived from biostimulated kernels and manuka honey in promoting wound closure. These findings suggest that kernels from biostimulated walnuts may serve as functional foods, paving the way for their use in regenerative medicine. Full article

This study used Xinxin 2 (Juglans regia L. ‘Xinxin2’), a major cultivated walnut variety in Xinjiang, China, to clarify the response and adaptation mechanisms of the anatomical structures of walnut related to source–sink–flow under altered source–sink relationships. We anatomically observed the leaves, fruit stalks, and fruit of bearing branches by artificially adjusting the leaf-to-fruit ratio (LFR). The LFR substantially affected the leaf structure and thickness of the fruit-bearing branches obtained via girdled (p < 0.05). The results of the analysis of the leaf anatomy revealed that a low LFR impeded leaf growth and internal structural development while accelerating senescence, whereas a high LFR promoted leaf growth and delayed senescence. The same trend was observed for the phloem area (PA) of the fruit stalk with the increase in fruit load when the number of leaves on the fruit branch was the same. The maximum PA was reached when the number of fruits was high (except for 4L:3F). This indicates that the micro-anatomical structure of the fruit stalk is more developed under the treatment of a higher number of pinnate compound leaves and fruit level of LFRs. The cells of the 1L:3F and 2L:3F were considerably smaller in the green peel and kernel of the fruit on the branches obtained via girdled than those of 5L:1F plants (p < 0.05). No significant difference was found in the number of cells per unit area or the cross-sectional area of cells in the pericarp and kernel of the fruit under LFRs (p > 0.05); however, a large difference was noted in the microanatomical structure of the pericarp and kernel of fruit. Changes in the structural adaptation characteristics of walnut leaves (source), fruit stalk (flow), and fruit (sink) are related to source–sink regulation. A change in the LFR affects the carbohydrate synthesis in the leaves (source), transport in fruit stalks (flow), and the carbohydrate reception in fruits (sink). Full article

The internal quality detection is extremely important. To solve the challenges of walnut quality detection, we presented the first comprehensive investigation of walnut quality detection method using X-ray imaging and deep learning model. An X-ray machine vision system was designed, and a walnut kernel detection (called WKD) dataset was constructed. Then, an effective walnut kernel detection network (called WKNet) was developed by employing Transformer, GhostNet, and criss-cross attention (called CCA) module to the YOLO v5s model, aiming to solve the time consuming and parameter redundancy issues. The WKNet achieved an mAP_0.5 of 0.9869, precision of 0.9779, and recall of 0.9875 for walnut kernel detection. The inference time per image is only 11.9 ms. Extensive comparison experiments with the state-of-the-art (SOTA) deep learning models demonstrated the advanced nature of WKNet. The online test of walnut internal quality detection also shows satisfactory performance. The innovative combination of X-ray imaging and WKNet provide significant implications for walnut quality control. Full article

Walnut (Juglans regia L.) fruit rot significantly impacts yield and quality, yet the pathogens responsible for it remain insufficiently characterized. In this study, we identified several fungi associated with the disease and characterized their morphology and physiology. Pathogenicity tests at two developmental stages of the walnut fruit were performed for the newly described pathogen. Among the Botrytis, Alternaria, and Penicillium species, Botrytis cinerea sensu lato stands out as a newly identified pathogen of the cultivated walnut. Growth assessments revealed variability in B. cinerea strains, with consistent patterns found across different temperatures. Pathogenicity of the isolated B. cinerea strains differed: one strain caused husk necrosis, three strains caused kernel necrosis in younger fruits, while two strains induced kernel necrosis in the later developmental stages. Additionally, we evaluated the biocontrol potential of Trichoderma strains against B. cinerea and demonstrated their efficiency in suppressing each isolated B. cinerea strain (76–100% inhibition), highlighting their potential in sustainable disease management in walnut production. Full article

Walnut (Juglans regia L.) exhibits a high sensitivity to water deficit, making it crucial to comprehend this characteristic in order to optimize irrigation strategies to improve its productivity. Deficit irrigation is widely used under drought conditions to achieve water savings goals. This study examines the impact of sustained deficit irrigation (SDI) strategies—applying 33%, 50%, or 75% of the crop water demand—on yield and quality parameters of two walnut cultivars (Chandler and Cisco) over a three-year monitoring period. These treatments were compared against control trees receiving full irrigation at 100% of crop water requirements (C₁₀₀). The nut yield was significantly and proportionally reduced under the SDI treatments. In the experiment, the average yield for cv. Chandler amounted to 6.7, 6.4, and 12.2 kg tree⁻¹ under SDI₃₃, SDI₅₀, and SDI_75, respectively, which were less than 13.9 kg tree⁻¹ in the C₁₀₀ plot. Similarly, cv. Cisco yielded 8.0, 11.6, 11, and 15.6 kg tree⁻¹ under SDI₃₃, SDI₅₀, SDI₇₅, and C₁₀₀, respectively. These findings indicate that the cultivar Cisco exhibits greater tolerance to moderate and intermediate levels of water deficit. Furthermore, the SDI treatments notably influenced several morphological and physicochemical kernel parameters. The key affected attributes include the weight, size, color, profiles of specific sugars, and mineral content (notably potassium, iron, and zinc), as well as the composition of unsaturated fatty acids (palmitoleic and cis-vaccenic) and polyunsaturated fatty acids (linoleic and α-linolenic), with pronounced effects observed particularly under the SDI₇₅ treatment. Thus, deficit irrigation did not drastically affect the kernel quality parameters, and it is also possible to augment them by selecting the appropriate water stress level. Therefore, for both walnut cultivars, approximately 25% of the irrigation water (SDI₇₅), equivalent to an average of 1681 m³ ha⁻¹, can be conserved relative to the total crop water requirement without negatively impacting walnut tree performance in the short to medium term. Here, we show the key role of adjusting irrigation practices by stressing the benefits of SDI that can save water, foster water productivity, and boost walnut health-promoting phytochemicals. Full article

Walnuts, which are rich in unsaturated fatty acids (UFAs), are highly susceptible to oxidation during storage, leading to quality degradation. Consequently, antioxidant technologies for the oxidative stability of walnuts have garnered significant attention. The addition of antioxidants remains the most cost-effective and efficient method currently available, with synergistic effects enhancing the efficacy of mixed antioxidant combinations compared to single antioxidants. In this study, four lipophilic antioxidants—tert-butylhydroquinone (TBHQ), butylated hydroxytoluene (BHT), dilauryl thiodipropionate (DLTP), and propyl gallate (PG)—were paired with four hydrophilic antioxidants—rosemary extract (RE), phytic acid (PA), tea polyphenols (TPs), and sodium ascorbate (SA)—resulting in 16 experimental groups to investigate synergistic effects. The effects of water-soluble and fat-soluble antioxidant combinations on walnut oxidation were systematically evaluated through peroxide value, acid value, thiobarbituric acid reactive substances, and DPPH radical scavenging capacities. Additionally, fatty acid composition analysis was employed to assess the preservation of beneficial UFAs. Mechanistic insights were obtained via thermogravimetric analysis and electron paramagnetic resonance spectroscopy. Notably, two combinations, 0.03% TBHQ + 0.03% TPs (w/w) and 0.03% DLTP + 0.03% SA (w/w), exhibited good oxidative stability of walnut kernels. These formulations demonstrated superior antioxidant performance and effectively inhibited oxidative pathways while maintaining UFA integrity, demonstrating their potential as advanced preservation strategies for lipid-rich foods. Full article

This study systematically analyzed the fruit traits of four sources and 117 families of Juglans mandshurica Maxim. in Jilin Province. By measuring key traits such as fruit phenotype and nut phenotype, the relationship between fruit characteristics and environmental adaptability was explored, leading to the selection of superior materials with high oil content potential. The study used fruit from J. mandshurica of 117 families (random sampling) across four provenances as experimental materials and measured 13 fruit phenotypic traits, including fruit length and fruit width. Finally, principal component analysis and genetic variation parameters were conducted. The results of the variance analysis (ANOVA) indicated that except for the nut roundness index, all other traits exhibited highly significant differences among provenances and families (p < 0.01). The range of genetic and phenotypic variation coefficients for the various traits was 7.47–23.23% and 8.76–29.59%. The family heritability ranged from 0.968 to 0.988. Correlation analysis among fruit traits revealed a non-significant correlation between fruit width and seed yield, fruit type index and nut weight, kernel weight and kernel yield, as well as nut longitudinal diameter and kernel yield. However, significant correlations were observed among all other traits. The Pearson correlation analysis between fruit traits and environmental factors revealed a significant negative correlation between longitude and seed yield. Cluster analysis results, based on the Euclidean distance method, showed that materials from four provenances were categorized into three groups at a genetic distance of 5. Principal Component Analysis (PCA) revealed that the cumulative contribution rate of four principal components reached 87.00%. PCI demonstrated the highest contribution rate and included traits such as fruit length, nut longitudinal diameter, nut transverse diameter, nut side diameter, three-diameter mean, and nut weight. One elite provenance and five elite families were preliminarily selected. The realized gain for the selected provenance fruit traits was higher for fruit weight and kernel weight, with values of 2.41% and 3.67%, respectively. For the selected families, the genetic gain was highest for kernel yield and kernel weight, with values of 16.51% and 26.66%, respectively. The findings will provide insights into breeding strategies to enhance walnut oil yield. The identified traits may be used to guide breeding programs for developing high-oil-content varieties; However, further validation studies are required to confirm these traits and their applicability in large-scale breeding efforts. Full article