Walnut Kernels Research Articles

Effect of Extracted Walnut Pomace Cake Edible Coating and Packaging Type on Quality Parameters of Walnut (Juglans regia L.) Kernels During Long Storage Periods

Walnuts are highly valued for their rich nutritional content, but their quality degrades during storage due to oxidation and other quality reducing processes. This study investigated the use of bioactive compounds extracted from walnut pomace, a by-product of walnut oil production, to develop an edible coating that extends the shelf life of ‘Milotai 10’ walnut kernels. Walnut kernels were stored for eight months in four different packaging materials (PE, PP, MPP, PLA) and three treatments were used (air or without treatment, nitrogen gas, and walnut pomace extract coating). The effects of these combinations on walnut quality parameters, including polyphenol content, vitamin E, fatty acids, peroxide value, and color, were analyzed. The results show that the combination of metallized polypropylene packaging under nitrogen treatment or with atmospheric air and walnut pomace extract (MPP-A-E+) best preserves walnut quality, making it a promising option for extending shelf-life.

Integrated Transcriptomic and Proteomic Analysis of Nutritional Quality-Related Molecular Mechanisms in "Longjia", "Yangpao", and "Niangqing" Walnuts (Juglans sigillata).

In this study, "Longjia (LJ)" and "Yangpao (YP)"exhibited higher contents of major nutrients compared to "Niangqing (NQ)" walnuts. The combination of transcriptome and proteome by RNA sequencing and isotope labeling for relative and absolute quantification techniques provides new insights into the molecular mechanisms underlying the nutritional quality of the three walnut species. A total of 4146 genes and 139 proteins showed differential expression levels in the three comparison groups. Combined transcriptome and proteome analyses revealed that these genes and proteins were mainly enriched in signaling pathways such as fatty acid biosynthesis, protein processing in endoplasmic reticulum, and amino acid metabolism, revealing their relationship with the nutritional quality of walnut kernels. This study identified key genes and proteins associated with nutrient metabolism and accumulation in walnut kernels, provided transcriptomic and proteomic information on the molecular mechanisms of nutrient differences in walnut kernels, and contributed to the elucidation of the mechanisms of nutrient differences and the selection and breeding of high-quality walnut seedlings.

Automation of the Oil Extraction Process Performed by Means of A Screw Press

Abstract The continuous development of the oil-manufacturing industries causes the necessity of improving extraction technologies. In this case, the specific interest is focused on the control systems of screw presses. Among a great variety of such machines, the small household presses are in significant demand among consumers. Various seeds and kernels require different technological conditions to be provided in order to maximize the qualitative and quantitative characteristics of the extracted oil. Therefore, the main objective of this research is developing and testing the control system allowing for automation of the oil extraction process. Particularly, the temperature parameters of the pressing chamber, extracted oil, and electric motor are to be monitored and limited. In addition, the consumer should be able to predefine the mass of the oil to be extracted. Considering the small household screw press LiangTai LTP200, the general algorithm (block diagram) of the control system operation is proposed and the corresponding experimental prototype is developed. The latter is based on the Arduino Mega microcontroller and is equipped with three temperature sensors, two coolers (fans), one heater, and one mass sensor. The proposed control system allows for continuous monitoring and limiting of the pressing chamber, oil, and electric motor temperatures, as well as the mass of the extracted oil. The experimental data show that the pressing chamber preheating process lasts for about 3 min (170…190 s) and its maximal temperature does not exceed 44°C. The temperature of the extracted oil does not rise over 61°C. The motor temperature changes within the range of 69...71°C. The oil extraction productivity is as follows: 1.2 kg/h (sunflower seeds), 1.06 kg/h (walnut kernels), 0.9 kg/h (almond kernels), and 0.78 kg/h (peanut kernels). The obtained results can used in further investigations focused on analyzing the influence of these parameters on the quantitative and qualitative characteristics of the extracted oil.

Arbuscular mycorrhizal fungi and intercropping Vicia villosa mediate plant biomass, soil properties, and rhizosphere metabolite profiles of walnuts

Intercropping is a prevalent soil management strategy within orchards, whereas it is unclear how inoculation with arbuscular mycorrhizal (AM) fungi and intercropping affect tree growth, soil properties, and rhizosphere metabolite profiles. This study investigated the effects of inoculation with Diversispora spurca and intercropping with hairy vetch (Vicia villosa) on biomass production, soil available nutrients, water-stable aggregate (WSA) distribution, phosphatase activity, and secondary metabolite profiles in walnuts (Juglans regia). The intercropping only elevated soil nitrate N levels and WSA distribution at the 0.5–2 mm size, and also triggered 2159 differential metabolites (1378 up-regulated and 781 down-regulated), with armillaramide as the most prominently up-regulated metabolite, followed by the substance diminished upon D. spurca inoculation. Conversely, D. spurca inoculation increased walnut biomass, WSA distribution across the 0.25 − 2 mm size, and acid and neutral phosphatase activities, as well as triggered 2489 differential metabolites (897 up-regulated and 1592 down-regulated), with pteroside D being highest up-regulated differential metabolite, allowing a competitive advantage to AM plants in combating soil pathogens. Despite significantly suppressing root AM fungal colonization and biomass production in AM walnuts, intercropping significantly increased soil ammonium and nitrate N levels in AM walnuts as well as WSAs at the 1–4 mm size, exhibiting a synergistic effect. Flavone and flavonol biosynthesis and pyruvate metabolism were simultaneously involved following AM inoculation or intercropping. Co-application of AM inoculation and intercropping triggered 1006 differential metabolites, with urocanic acid being the most up-regulated metabolite, although it decreased following AM inoculation, suggesting the involvement of mycorrhizal hyphae in soil histidine uptake. Under intercropping, AM inoculation elicited 418 differential metabolites, with the most up-regulated metabolite being implicated in flavonoid pathways. AM inoculation primarily triggered the biosynthesis of unsaturated fatty acids, regardless of intercropping or not, implying a potential increase in unsaturated fatty acid contents of walnut kernels. It concluded that AM inoculation and intercropping interactively affected walnut growth, soil attributes, and soil microenvironment.Graphical

A Model for Fat Content Detection in Walnuts Based on Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIR) is an efficient and accurate method for fat content detection in walnuts. ‘Wen 185’ walnut is grown in large quantities in southern Xinjiang, and its fat content is an important indicator for evaluating the intrinsic quality. The excessive pursuit of yield efficiency, combined with the neglect of quality, agricultural product safety and other factors, has led to the production of poor-quality walnuts. Moreover, research on predicting walnut kernel fat content based on near-infrared spectroscopy technology is rarely reported. Therefore, a technical framework for walnut kernel detection based on near-infrared spectroscopy and the technical standards for ‘Wen 185’ are urgently needed. After first optimizing the initial spectrum data using five preprocessing methods, we established separate prediction models for walnut kernel fat content based on either a back propagation neural network or a support vector regression (SVR) algorithm. The results show that the correction set and validation set coefficients of determination of the walnut kernel fat content prediction model using the back propagation neural network algorithm were 0.86 and 0.89, respectively, with root mean square errors of 1.56 and 1.58, and an RPD value of 2.57; the coefficients of determination for the calibration and validation sets of SVR were 0.90 and 0.83, respectively, with root mean square errors of 1.76 and 1.70, respectively, and an RPD value of 1.70. Thus, near-infrared spectroscopy can be used to establish a foundation for realizing the rapid detection of walnut kernel fat content.

Bioactive composition and medicinal properties of Walnut kernels

The purpose of this review is to evaluate the biological compounds present in walnut kernels and also to assess potential human health benefits. Walnuts are one of the most important tree nuts, belonging to the Juglandaceae family. They are cultivated worldwide, primarily in temperate regions. Throughout history, walnut kernels have been utilized to treat various disorders such as diarrhea, diabetes mellitus, thyroid issues, cancer, anorexia, and infectious diseases, in addition to their dietary benefits. Presently, advanced techniques like UHPLC-MS/MS, HPLC-DAD chromatography, and GC–MS are employed to identify key compounds in walnuts. These include phenolic compounds, phenolic acids, tannins and related compounds, flavonoids, phytosterols, fatty acids, triglycerides, tocopherols, vitamins, and carotenoids. The review also demonstrates that walnut kernels possess numerous medicinal properties, including antioxidants, cardiovascular effects, anti-cancer effects, antidiabetic effects, hepatoprotective effects, and antimicrobial effects. The current review also gives details on plant origin, distribution, classification, cultivation, and consumption as food. The review also described the recent medicinal plant profile, identification, and screening of the active ingredients of walnut's kernels. Researchers around the world are taking an interest in the clinical evaluation of walnut's active ingredients. The current review also gives details of the most recent conducted clinical studies. Mostly the reviews of walnuts are focused on walnut cultivars and/or specific types of compounds, although our current review is mostly focused on the active ingredients of walnut kernels and their specified biological role. In conclusion, different varieties of walnuts are abundant in significant bioactive compounds that possess important medicinal properties.

Enhancing the Shelf Life of Fresh Walnut Kernels Using Plant-Based Nano Pickering Emulsion Coatings Enriched with Peppermint Essential Oil and Green Tea Extract

Enhancing the Shelf Life of Fresh Walnut Kernels Using Plant-Based Nano Pickering Emulsion Coatings Enriched with Peppermint Essential Oil and Green Tea Extract

Design and Optimization of Key Parameters for a Machine Vision-Based Walnut Shell–Kernel Separation Device

The separation of walnut kernels and shells has long been regarded as a bottleneck, limiting processing efficiency, product quality, and industry advancement. In response to the challenges of improving separation accuracy and the inadequacy of existing equipment for meeting industry demands, this paper proposes an innovative walnut shell–kernel separation device based on machine vision technology. An experimental system was constructed, and key parameters were optimized to enhance its performance. The device comprises five main modules: material conveyance, image acquisition, control module, sorting module, and frame. Differential separation technology is used to convert the walnut material group into a stable particle flow, addressing the issue of missed selections due to material blockages. An enhanced YOLOv8n algorithm improves small object detection and interference resistance, enabling accurate identification of walnut kernels. The Box–Behnken Design and Artificial Neural Network prediction model was used to determine the optimal operating parameters for the device. Experimental results showed that effective differential separation was achieved when the dual-stage conveyor system operated at speeds of 0.2 m/s and 1 m/s. The improved I-YOLOv8n algorithm reached an accuracy of 98.8%. Using the neural network model, the optimal operational parameters were determined: an air pressure of 0.72 MPa, a jetting component angle of 10.16°, and a sorting height of 105.12 cm. Under these conditions, the device achieved an actual cleaning rate of 93.56%, demonstrating outstanding separation performance. Compared to traditional separation methods, this device offers significant advantages in terms of efficiency, quality, and ease of operation, providing new technological pathways and support for the automation and intelligent transformation of the walnut processing industry. In the future, the device is expected to undergo further improvements to meet broader market demand and serve as a reference for the separation of other agricultural products.

An innovative walnut cracker: Self-grading and multi-station extrusion mechanism with high efficiency.

The walnut cracking process is the most critical and delicate step for achieving high-quality kernels. The traditional method for cracking (manually) is labor-intensive, time-consuming, and tedious. The existing cracking approaches are low production efficiency and serious walnut kernel breakage. Increasing cracking efficiency with minimum kernel breakage has been a challenging issue in the preliminary processing of walnuts. Therefore, this study develops an innovative walnut cracker with self-grading and multi-station extrusion, combined with theoretical investigation and experiment verification. First, a statistical analysis of walnut physical properties was conducted, including dimensions, shell thickness as well as shape characteristics. The mechanical properties of walnut cracking were examined by a series of experiments. Based on mechanical theory, a grading mechanism was designed for preliminary processing before walnut cracking. Then a shaftless screw conveying mechanism and an extrusion cracking mechanism were developed. To evaluate the cracker's performance, a comprehensive examination was carried out. The experiments yielded impressive results, with a grading rate of 87.3%, a shell-breaking rate of 91.50%, and a kernel-exposed rate of 84.72%. These outcomes signify a substantial improvement in production efficiency while minimizing kernel breakage. The developed walnut cracker plays a crucial role in walnut processing and kernel extraction, thereby elevating economic value. PRACTICAL APPLICATION: A self-grading multi-station extrusion walnut cracker is developed, which includes a grading mechanism with a shaftless screw conveyor and a grid-type trommel screen for conveying and classifying walnuts. This cracker can adapt to different walnut varieties by changing the gap-adjusting guide to control the breaking gap. Compared to similar extrusion-type walnut crackers, the developed cracker not only incorporates preliminary classification but also exhibits superior performance. HIGHLIGHTS: A novel multi-station extrusion mechanism for walnuts cracking is developed. The cracker can accommodate various walnut sizes for self-grading and screening. The design with semi-arc plates converts extrusion force into alternating stress. The shell-breaking rate and kernel-exposed rate achieves 91.50% and 84.72%.

Walnut kernel against liver damage induced by salt processed Psoraleae Fructus through regulating bile acid metabolism in ovariectomized rats

Walnut kernel (WK) is a globally popular health food known for its potent antioxidant properties. WK shows a promising prospect in protecting against liver damage induced by salt processed psoraleae fructus (SPF). This study explored the impact of WK in mitigating liver damage induced by SPF in an ovariectomized (OVX) rat model. Serum metabolomics was employed to explore potential detoxification mechanisms. The levels of Farnesoid X receptor (FXR), Bile salt export pump (BSEP), and Cholesterol 7α-hydroxylase (CYP7A1) proteins were determined through western blot analysis. The results demonstrated that WK exhibits a noteworthy protective effect against liver damage induced by SPF. The WK normalized the metabolic disorder and reversed sixteen liver injury biomarkers and five metabolic pathways induced by SPF. These results demonstrated that WK exhibits a protective effect against SPF-induced liver damage in OVX rats by regulating bile acid metabolism.

Phytochemical analysis and biological activity of some local and imported walnut

To study the bioactive substances of the walnut kernel of six cultivars which were newly selected from Kurdistan-Iraq and one type import from America, analyzed for their phytochemical contents and antioxidant activities. HPLC (High-performance liquid chromatography) was used for phenolic compound estimation, GC (Gas chromatography) for fatty acid analysis, and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging. In terms of fatty acids, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid of all seven types we analyzed, all of them had a significant result. As for antioxidants, the same as before, the antioxidants were significant for all the chosen samples. In terms of phenolic compounds, quinic acid, gallic acid, 1,2,3,6 trigalloyl glucose, vanillic acid, syringic acid, and rutin, all types were significant as well. Finally, our results show that most of them were of high significance. Some regions in the Kurdistan region of Iraq showed high results for important secondary products, while the American counterpart is lower but still better than some of the Kurdistan region walnuts

Study of physical and mechanical properties of plant fruits on the example of walnut

Perennial plantations that are zoned in Ukraine allow to obtain high-quality fruits (nuts), which are widely used in the perfumery, pharmaceutical, oil, confectionery and other industries, as well as in the production of feed and feed additives. The known technologies of mass processing of walnut kernels mostly work well with crops that have a spherical or close to spherical external shape. The simplest, but least productive, are primitive manual devices for peeling walnut shells. Despite the simplicity of their design, these devices are inefficient and unsuitable for adjusting their operation to different varieties and physical and mechanical properties of biological fruits. The analysis of the known designs of walnut shell destruction machines and mechanisms showed the need to study the physical and mechanical properties of biological fruits (walnuts), to develop technical recommendations for the design of impact mechanisms to improve the quality of shell destruction and the possibility of their application in mass production technologies. A research methodology was developed, a laboratory setup was manufactured, and experiments were conducted. To determine the strength characteristics, the author designed and manufactured a device. It consists of a lever mechanism and a deforming device. The dimensions and load measurements were carried out according to well-known methods of physical mechanics. The statistical analysis of the results showed the need for in-depth scientific research of the geometric parameters of the design of the working bodies of machines for destroying the walnut shell in the mechanisms of fruit peeling machines, taking into account the quality indicators performance of works with certain conditions of their implementation. We conclude that according to the results of the experiments, there is a fairly high dependence between the geometric dimensions of the walnut fruit at the level of 0.72, 0.57 and 0.49, respectively. The weight of the fruit also depends on its dimensional characteristics, which is logical at the level of 0.6–0.75. The force of critical static fracture has a weak correlation with the dimensional characteristics at the level of 0.3. And it depends little on the plane of its application.

Lipidomics and metabolomics reveal the molecular mechanisms underlying the effect of thermal treatment on composition and oxidative stability of walnut oil

Roasting walnut kernel significantly improves the oxidative stability and sensory properties of its oil. However, the effect of roasting temperatures on the molecular change of main components and micronutrients in walnut oil is still unclear. Herein, lipidomics and metabolomics were integrated to comprehensively profile the walnut oil obtained at different roasting temperatures (30 °C, 120 °C, 140 °C, 160 °C, and 180 °C). Lipidomics showed that the content of glycerolipids, sphingolipids, and glycerophospholipids decreased with roasting temperatures, while the oxidized fatty acids and triglycerides increased. Ratios of linoleic acid and linolenic acid varied with roasting temperatures and were most close to 4–6:1 at 140 °C, 160 °C, and 180 °C. Major classes of micronutrients showed a tendency to increase at the roasting temperature of 120 °C and 140 °C, then decrease at 160 °C and 180 °C. Liposoluble amino acids identified for the first time in walnut oil varied with roasting temperatures. Correlation analysis demonstrated that the higher contents of liposoluble amino acids and phenolics are positively associated with enhanced oxidative stability of walnut oil obtained at 140 °C. Furthermore, glutamine and 5-oxo-D-proline were expected to be potential biomarkers to differentiate the fresh and roasted walnut oil. The study is expected to provide new insight into the change mechanism of both major lipids and micronutrients in walnut oil during the roasting process.

Utilization of low-grade walnut kernels for oil extraction using eco-friendly methods: a comparative analysis of oil composition, antioxidant and antimicrobial activity

Walnut oil was extracted using three different eco-friendly extraction methods, solvent extraction (using ethyl acetate [EA] and ethanol [ET]), aqueous enzymatic extraction (AEE), and ultrasound-assisted enzymatic extraction (UAEE), and their lipid yield, lipid composition, physicochemical analysis, mineral composition, total phenols, antioxidant capacity, and antimicrobial activity were analyzed and compared. The AEE technique offered a greater yield (50.6%) than the other extraction methods and gave comparatively higher linoleic acid (66.12%) content. Palmitic, oleic, linoleic, linolenic, and stearic acids were the principal components that GC/MS detected in all the oil samples. UAEE produced the most polyphenols (0.49 mgGAE/g), followed by AEE (0.46 mgGAE/g), EA (0.45 mgGAE/g), and ET (0.35 mgGAE/g). The DPPH assay results were in the order of UAEE (191 μmolTE/kg) > AEE (186 μmolTE/kg) > EA (153 μmolTE/kg) > ET (130 μmolTE/kg). The FRAP assay findings showed a similar pattern: UAEE (112 molTE/kg) > AEE (102 molTE/kg) > EA (96 molTE/kg) > ET (82 molTE/kg). Results suggested that for a higher extraction yield, AEE is the better technique and UAEE is the recommended method for enhancing walnut oil antioxidant capacity. Additionally, it was found that polyphenols considerably increased the antioxidant capacity of walnut oil and are thought to be health-promoting. The results demonstrated the antibacterial effectiveness of the extracted oil against Bacillus subtilis, Bacillus licheniformis, and Staphylococcus aureus. This study provides information about low-cost and ecofriendly technologies of walnut oil extraction for food, cosmetic, and medical uses.

Flavor release from walnut kernels in an in-vitro mastication model with decoupled oral parameters

Consumer preferences for walnut products are largely determined by the flavors released during mastication. In this study, a peeled walnut kernel (PWK) model was established with oral parameters decoupled using a Hutchings 3D model. The model explored in vitro variations using head-space solid-phase microextraction-gas chromatography-mass spectrometry and intelligent sensory techniques. The fracture strength, hardness, particle size, adhesiveness, springiness, gumminess, and chewiness were significantly reduced during mastication. We identified 61 volatile compounds and found that 2,5-dimethyl-3-ethylpyrazine is a key component, releasing predominantly baking and milky notes. Glutamic acid, alanine, arginine, and sucrose were identified as the key compounds in taste perception. The method can help establish a mastication model for nuts and facilitate breakthroughs in the development of walnut products and processing methods.

Short Cold Storage as a Sustainable Postharvest Handling Method for Natural Enrichment in Antioxidants of Fresh and Dried Walnut Kernels—Cultivar Effect

Fresh (raw, non-dried) walnuts (kernel moisture > 17%) have unique sensory and nutritional attributes but a narrow time availability due to their rapid deterioration during storage. In the present study, the storage (1 °C, 90% RH) potential of fresh walnuts for 20 and 40 days was assessed in relation to cultivar (Chandler, Hartley, Ioli) and the form of exposure to storage (shelled or in-shell). The effect of low-temperature exposure (at 1 °C for 0, 10 and 20 days) before nut drying was also examined. Fresh walnuts from different cultivars showed diverse quality (size, color) and physiological (respiration, weight loss) traits. Using a very low storage temperature (1 °C) was feasible to store fresh walnuts marginally up to 40 days without losing the ‘fresh’ character. The form of in-shell storage compared with shelled ones helped to determine the retention of kernel moisture and had a mild protective role in the prevention of kernel browning. The storage of fresh walnuts at 1 °C resulted in increased total phenolics (TP, by 26% in average) and antioxidant capacity (by 46%, in average) of the kernels, supporting the improvement of nutritional value due to low temperatures. The dried kernels after this short cold storage showed increased TP levels by 35–40% in comparison with conventional dried ones. Therefore, the 10 d cold exposure could be proposed as a sustainable step for incorporation in the regular postharvest handling chain for the natural enrichment of fresh and dried kernels in antioxidants.

Разработка хлебобулочных изделий нутриентно-адаптированных для питания спортсменов-легкоатлетов

Proper nutrition of an athlete is an important component of the effectiveness of sports results. An athlete’s daily diet should cover his increased nutrient needs due to heavy physical activity. The purpose of the research was to develop bakery products that were nutrient-adapted to the nutritional requirements of athletes using the example of track and field athletes. The recipe for the new product included wheat flour, oat flour, micellar casein, flaxseed oil, date syrup, and crushed walnut kernels. A study of the influence of new ingredients on the quality of semi-finished products and finished products showed that the addition of oat flour and casein slightly increased the moisture and acidity of the finished products, but the indicators remained within the limits defined by the regulatory documentation for bakery products made from wheat flour. With an increase in the dosage of oatmeal and casein, the products acquired a slight taste of oatmeal; casein had no effect on taste. A new type of bakery product is characterized by good organoleptic and physicochemical quality indicators and has increased nutritional value. Consumption of 100 g of the developed “Fitbulka” bakery product allows you to satisfy the daily need for biologically complete protein by 8.9%, carbohydrates by 5.3%, fat by 7.2%, including polyunsaturated fatty acids of the omega-3 family by 39.6% and omega-6 by 5.4%. The degree of satisfaction of the daily requirement for minerals increases in comparison with the control sample and amounts to 16.0% for calcium, 13.5% for phosphorus, 17.4% for magnesium, 7.4% for potassium, and 7.5% for iron. Analysis of amino acid score calculations showed that the biological value of the protein fraction of the test sample was 17.6% higher compared to the control. The developed “Fitbulka” bakery product can be recommended for inclusion in the diet of athletes as an additional source of polyunsaturated fatty acids, dietary fiber, protein, calcium and magnesium in the diet.

Transcriptomic Analyses Reveal the Effects of Walnut Kernel Cake on Adipose Deposition in Pigs.

With the rising cost of animal feed protein, finding affordable and effective substitutes is crucial. Walnut kernel cake, a polyphenol-, fiber-, protein- and fat-rich byproduct of walnut oil extraction, has been underexplored as a potential protein replacement in pig feed. In this study, we found that feeding large Diqing Tibetan pigs walnut kernel cake promoted adipose deposition and improved pork quality during pig growth. Transcriptome analysis revealed the upregulation of genes ANGPTL8, CCNP, ETV4, and TRIB3, associated with adipose deposition. Pathway analysis highlighted enrichment in adipose deposition-related pathways, including PPAR, insulin, PI3K-Akt, Wnt, and MAPK signaling. Further analysis identified DEGs (differentially expressed genes) positively correlated with adipose-related traits, such as PER2 and PTGES. Single-cell transcriptome data pointed to the specific expression of CD248 and PTGES in adipocyte progenitor/stem cells (APSCs), pivotal for adipocyte differentiation and adipose deposition regulation. This study demonstrates walnut kernel cake's potential to substitute soybean cake in pig feed, providing high-quality protein and promoting adipose deposition. It offers insights into feed protein replacement, human functional food, fat metabolism, and related diseases, with marker genes and pathways supporting pig breeding and pork quality improvement.

Rapid detection of endogenous impurities in walnuts using near-infrared hyperspectral imaging technology

Impurities in walnut-based products pose a significant risk to human health, necessitating the development of rapid and efficient methods for detecting endogenous impurities in walnut shell-breaking materials. To address this issue, this study aims to investigate the feasibility of near-infrared hyperspectral imaging (NIR-HSI) in conjunction with conventional chemometric methods and deep learning models. First, biochemical experiments demonstrated differences in the total phenolic and flavonoid contents of different walnut kernels. An improved support vector machine model based on the butterfly optimization algorithm was constructed for classification using an NIR dataset of endogenous impurities in walnuts, achieving an accuracy of 96.12 %. In addition, this study proposed the WT-NIRSNet model, a deep neural network with an additional attention mechanism, and compared it to a traditional chemometric approach. The study demonstrated an accuracy of 99.03 % on the test set using WT-NIRSNet to solve the fast classification problem of endogenous impurities in walnuts. It can achieve desirable classification results using only raw spectral data without complex preprocessing operations and is superior to traditional chemometric models. Therefore, the NIR-HSI technique combined with deep neural networks has a significant potential for detecting endogenous impurities in walnuts.

Comparative investigation on the phenolic compounds and antioxidant capacity of walnut kernel from different drying methods

Drying techniques are being used more and more to extend the shelf life of industrial products. Drying could influnce the content of phenolics in food and their antioxidant activity. This study estimated the effects of different drying methods (freeze drying (FD), gradient hot air drying (GHD), and constant hot air drying (CHD)) on phenolic profiles and antioxidant activities in walnut kernels. With a maximum content of 3.61 mg g−1, GHD was found to be the most effective in preserving total phenols, while CHD and FD had maximum contents of 2.66 mg g−1 and 1.96 mg g−1, respectively. The concentration of most monomeric phenols detected in the kernels increased with temperature, particularly in the free and bound forms. Gallic acid (free form) levels in GHD2 (194.54 µg g−1) were 55.77 and 60.08 times higher, respectively, than in FD and CHD. GHD dried walnuts had higher antioxidant activity than FD and CHD dried walnuts. Furthermore, bioinformatics analysis revealed three key metabolic pathways associated with the mechanisms underlying drying changes. The GHD technique, according to these findings, is a better choice for drying walnut in order to preserve its phenolics and antioxidant activity.Graphical