Walnut Kernels Research Articles

Walnut green husk extract enhances the effect of chlorine dioxide on kernel quality and antioxidant properties of fresh-eating walnuts during their shelf life.

Fresh-eating walnuts are perishable and become mildewed during shelf life, limiting their sales span. The effects of chlorine dioxide (ClO2) alone and its combination with walnut green husk extract (WGHE) on shelf stored fresh walnuts were investigated to develop a pollution-free preservative for the produce. The initial development of mildew incidence was delayed by both treatments under 25°C, whereas, WGHE+ClO2 acted more effectively than ClO2 under 5°C. The WGHE+ClO2 treatment presented superior effects on improving moisture, soluble sugar and total phenol content, alleviating loss of oil and unsaturated fatty acid and delaying peroxide value increase of walnut kernels at both temperatures. Both treatments inhibited the activities of three lipolytic enzymes and two oxidases at 25°C and 5°C, WGHE+ClO2 acted more effectively at 5°C. The results guide the combined application of WGHE with ClO2 on shelf preservation of fresh walnut.

Screening of the Active Substances for the Assessment of Walnut Kernel in the Treatment of Scopolamine-Induced AD Animals.

Alzheimer's disease (AD) has been a challenge and hotspot in the field of neuroscience research due to the high morbidity. As we all know, walnut kernel (WK) ingestion has been linked to benefits to brain health and has the function of improving memory. This study follows the AD model induced by scopolamine to reveal the active fractions and substances of walnut in the treatment of AD. The histopathological analysis and brain tissue biochemistry assay are revealed the active fractions of WK, and this result determines that walnut kernel organic acids have significant therapeutic effect on AD. The strategy of studying ingredients pointed at lesions is integrated to ascertain the selected brain-targeted effective substances of WK for blood-brain barrier by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry, and a total of eight organic acids are figured out definite absorptivity in rat brains. Finally, the binding interaction between the effective substances and target proteins is analyzed by molecular docking, and the main function related active markers are ascertained as glansreginin A, glansreginic acid, ellagic acid, and ellagic acid 4-O-xyloside. The comprehensive process is helpful to the clinical application of WK as a promising cholinesterase inhibitors for nutritional intervention.

Bioactive oleogel from supercritical carbon dioxide extracted walnut (Juglans regia L.) oil as a butter substitute and utilization of the spent residue in cookie formulations

The scope of the work presented in this paper is based on the principles of circular economy. Functional oleogels were prepared from pre-optimized supercritically extracted walnut oil (350 bar/40 °C/90 min) as a butter alternative that can meet more than 50% of the Required Dietary Allowance of ω-3 fatty acids per serving of 5.75 g. The spent residue of walnut kernel after supercritical extraction was incorporated in cookie formulations to replace wheat flour as a valorization approach. Carnauba and beeswax were used as oleogelator in the oleogels so prepared by optimizing the rheological and textural parameters of the oleogels. Prior to this development, the yield, fatty acid composition, tocopherol content, antioxidant activity as well as total polyphenolic content (TPC) was compared with conventional soxhlet using n-hexane for extraction. Cookies were formulated by replacing 15% w/w refined flour with the protein and fiber-rich spent residue with good overall acceptability (7) when compared to control (8) and textural properties like hardness (4125 g) and fracturability (8 mm). The oleogels could be vulnerable to oxidation during storage and hence their stability as well as the cookies needs further evaluation. Approaches to increase the same are also warranted. The approach so presented can have positive implications for both economy as well as the environment.

Effect of roasting and high-pressure homogenization on texture, rheology, and microstructure of walnut yogurt

The effect of roasting and high-pressure homogenization on the quality of yogurt made from peeled walnut kernels was explored in this study. The G' and G'' values of yogurt made from walnuts roasted at high temperatures were reduced. The water-holding capacity and hardness of walnut yogurt were reduced to 47.73% and 24.22 g, respectively. Increasing the homogenization pressure reduced the particle size of the walnut yogurt to 20.50 μm. Homogenized walnut milk at 150 MPa increased the viscosity, hardness, and consistency of yogurt product from 11.71 to 16.74 Pa.s, from 30.01 to 71.63 g and from 283.17 to 455.24 g·s, respectively. The confocal laser scanning microscope observation demonstrated a reduction in the size of fat and protein micelles in the homogenized yogurt samples, resulting in a compact structure. This study will contribute valuable scientific insights to the advancement of plant-based yogurt quality.

Potential anti-Alzheimer’s disease effect of defatted walnut powder through remodeling gut microbiota and modulating amino acid metabolite levels

Alzheimer’s disease (AD) is a major health challenge due to its high morbidity. This study aimed to investigate the potential effects of defatted walnut powder (DWP), which is the residue obtained after extracting oil from walnut kernels, on memory improvement. HPLC was used to establish the fingerprints of 14 batches of DWP extract (DWPE) obtained from various origins. Behavioral experiments and functional indicators were conducted to evaluate the efficacy of DWPE on AD. The results indicated that DWPE regulated the cholinergic system disorder in brain tissue. Additionally, DWPE reduced oxidative stress levels, neuroinflammation, and the damage of pyramidal cells in both the cortex and the hippocampal CA3 region. Subsequently, targeted amino acid metabolomics, gut microbiota sequencing and fecal microbiota transplantation confirmed that DWPE played a regulatory role in amino acid metabolism regulated by gut microbiota, effectively decreasing the levels of fat-soluble neurotoxic factor ammonia.

Genome-wide identification and molecular expression profile analysis of FHY3/FAR1 gene family in walnut (Juglans sigillata L.) development

BackgroundJuglans sigillata L. (walnut) has a high economic value for nuts and wood and has been widely grown and eaten around the world. Light plays an important role in regulating the development of the walnut embryo and promoting nucleolus enlargement, which is one of the factors affecting the yield and quality of walnut. However, little is known about the effect of light on the growth and quality of walnuts. Studies have shown that far red prolonged hypocotyl 3 (FHY3) and far red damaged response (FAR1) play important roles in plant growth, light response, and resistance. Therefore, FHY3/FAR1 genes were identified in walnuts on a genome-wide basis during their growth and development to reveal the potential regulation mechanisms involved in walnut kernel growth and development.ResultsIn the present study, a total of 61 FHY3/FAR1 gene family members in walnuts have been identified, ranging in length from 117 aa to 895 aa. These gene family members have FHY3 or FAR1 conserved domains, which are unevenly distributed on the 15 chromosomes (Chr) of the walnut (except for the Chr16). All 61 FHY3/FAR1 genes were divided into five subclasses (I, II, III, IV, and V) by phylogenetic tree analysis. The results indicated that FHY3/FAR1 genes in the same subclasses with similar structures might be involved in regulating the growth and development of walnut. The gene expression profiles were analyzed in different walnut kernel varieties (Q, T, and F). The result showed that some FHY3/FAR1 genes might be involved in the regulation of walnut kernel ripening and seed coat color formation. Seven genes (OF07056-RA, OF09665-RA, OF24282-RA, OF26012-RA, OF28029-RA, OF28030-RA, and OF08124-RA) were predicted to be associated with flavonoid biosynthetic gene regulation cis-acting elements in promoter sequences. RT-PCR was used to verify the expression levels of candidate genes during the development and color change of walnut kernels. In addition, light responsiveness and MeJA responsiveness are important promoter regulatory elements in the FHY3/FAR1 gene family, which are potentially involved in the light response, growth, and development of walnut plants.ConclusionThe results of this study provide a valuable reference for supplementing the genomic sequencing results of walnut, and pave the way for further research on the FHY3/FAR1 gene function of walnut.

Sustainable utilization of unsaleable walnut kernel in substitution for corn grain in the diet of fattening lambs improves growth performance and meat quality.

As a cost-effective typical co-product of walnut processing; this study aimed to investigate the effects of feeding poor quality, unsaleable walnut kernel, also known as wasted walnut (WW) kernel, on growth performance, carcass characteristics, meat quality and fatty acid (FA) composition of fattening lambs. The experiment was conducted using 24 fattening lambs (27 ±1.07 kg initial BW) assigned to two total mixed concentrate-based diets, over a 80-day experimental period on a completely randomized design. Dietary treatments were: 1) WW (10% WW), and 2) CON (without WW). Average daily and total gain, and final weight increased with WW inclusion (P < 0.05). Also, a significant enhancement in feed conversion ratio (P < 0.05) and carcass cooler shrink loss (P = 0.03) were observed by feeding WW. Dry matter intake (DMI) was not influenced by feeding WW as did carcass prime cuts, meat, bone and fat-tail; however, the backfat thickness was increased (P = 0.01). WW inclusion reduced cholesterol and increased protein load in muscle tissue (P ≤ 0.05). Moreover, this inclusion led to higher concentration of vaccenic acid (VA), conjugated linoleic acid (CLA) and C20 polyunsaturated FAs (PUFA), total n3 and n6 PUFA in muscle and fat-tail (P ≤ 0.05). Due to enhanced animal performance, also chemical and FA composition of muscle and adipose tissue, WW can be included in fattening lamb diets as a rich source of protein and PUFA.

Impact of steaming and roasting heat‐treatment on physico‐chemical and functional properties of walnut kernel

AbstractIn this study, the effect of steaming and roasting treatment on the physicochemical and functional properties of walnut kernel at 95°C for different time (15, 20, and 30 min) was investigated. Steaming and roasting treatments significantly increased the enthalpy change for protein denaturation, in‐vitro digestibility, viscosity, storage modulus (G′) and loss modulus (G″) (p &lt; 0.05), the order from high to low was steaming (7.11–8.69 J g−1; the gastric and intestinal digestion: 1.21%–17.83% and 1.51%–27.31%, respectively; 134.04–450.49 Pa s; 214.28–1047.14 and 61.72–196.09 Pa) &gt; roasting (6.24–7.07 J g−1; the gastric and intestinal digestion: 1.26–15.42% and 1.21–22.37% a, respectively; 16.92–86.07 Pa s; 6.58–209.85 and 3.08–67.14) &gt; untreated (4.53 J g−1; the gastric and intestinal digestion: 0.24%–4.18% and 1.00–7.58%, respectively; 17.06 Pa s; 5.78 and 1.79 Pa). All samples contained the essential amino acids, the amino acid score of samples by steaming was the highest. In addition, the protein of walnut kernel after heating treatment contained more α‐helix and random coil structures compared to the untreated sample, while β‐sheet and β‐turns structures decreased. Moreover, the thermal treatment could cause the changes of the water/oil holding capacity, foaming and emulsifying properties of walnut kernel flour. When there were differences between the results of steaming and roasting samples, it was concluded that the water played an important role in steaming. These results suggested that the thermal treatment as an effective approach could improve the physico‐chemical, structural and functional properties of walnut kernel and be potentially applied in the food processing.

Quality Preservation of Walnut Kernels: Effect of Storage Temperature and Vacuum Packaging

Quality Preservation of Walnut Kernels: Effect of Storage Temperature and Vacuum Packaging

The Antioxidant Activities In Vitro and In Vivo and Extraction Conditions Optimization of Defatted Walnut Kernel Extract.

The objective of this study was to determine the antioxidant activities of defatted walnut kernel extract (DWE) and whole walnut kernel extract (WE) in vitro and in vivo. Three spectrophotometric methods, DPPH, ABTS, and FRAP, were used in in vitro experiments, and mice were used in in vivo experiments. In addition, response surface methodology (RSM) was used to optimize reflux-assisted ethanol extraction of DWE for maximum antioxidant activity and total phenolic content. The results of in vitro experiments showed that both extracts showed antioxidant activity; however, the antioxidant activity of DWE was higher than that of WE. Both extracts improved the mice's oxidative damage status in in vivo studies. An ethanol concentration of 58%, an extraction temperature of 48 °C, and an extraction time of 77 min were the ideal parameters for reflux-assisted ethanol extraction of DWE. The results may provide useful information for further applications of defatted walnut kernels and the development of functional foods.

Neuroprotective mechanisms of defatted walnut powder against scopolamine-induced Alzheimer's disease in mice revealed through metabolomics and proteomics analyses

Ethnopharmacological relevanceDefatted walnut powder (DWP), the byproduct remaining after extracting oil from the walnut kernel, has the actions of nourishing liver and the kidney, replenishing blood, and calming the nerves, which is believed to be a brain-nourishing in Chinese medicine. DWP is rich in phenolic substances with demonstrated anti-inflammatory, antioxidant, lipid-lowering and neuroprotective effects. Despite these promising properties of DWP, its effectiveness in treating Alzheimer's disease (AD) remains unclear, and further research is needed to understand the mechanism of action. Aim of the studyThis study aimed to investigate the potential mechanism of DWP on AD by constructing the overall metabolic profile of mice with an anti-scopolamine AD model and verification of the highly correlated pathway. Materials and methodsThe neuroprotective efficacy of DWP in a mouse model of AD established by scopolamine injection was examined. Spatial memory performance in the Morris water maze (MWM), markers of cholinergic function in hippocampus and cortex, and neuropathological changes were compared among control, model, and DWP-consuming model group mice. In addition, combined metabolomic and proteomic analyses were conducted to investigate changes in metabolite and protein expression profiles in AD model mice induced by DWP consumption. Differentially expressed proteins and metabolites were then analyzed for KEGG pathway enrichment and results confirmed through targeted amino acid metabolomics. ResultsThe results showed that consumption of DWP improved spatial learning and memory in the MWM, enhanced cholinergic function, and reduced histopathological damage in the cortex and hippocampus of AD model mice. Based on differentially abundant metabolites and proteins, 43 metabolic pathways modulated by DWP were identified, mainly involving in amino acid metabolic pathways strongly associated with cellular energetics and antioxidant capacity, and targeted amino acid metabolomics confirmed that DWPE significantly elevated the levels of Arginine (Arg), Histidine (His), Proline (Pro), Serine (Ser), and Tyrosine (Tyr), while reducing the levels of Glutamate (Glu). This ultimately resulted in an improvement in the progression of AD. ConclusionThis study identified numerous metabolic networks modulated by DWP that can mitigate scopolamine-induced AD neuropathology and cognitive dysfunction. DWP is a promising resource to identify AD-related pathogenic pathways and therapeutic strategies.

Walnut Kernel Oil and Defatted Extracts Enhance Mesenchymal Stem Cell Stemness and Delay Senescence.

Decreased stemness and increased cellular senescence impair the ability of mesenchymal stem cells (MSCs) to renew themselves, change into different cell types, and contribute to regenerative medicine. There is an urgent need to discover new compounds that can boost MSCs' stemness and delay senescence. Therefore, this study aimed to investigate the impact of walnut kernel oil (WKO) and defatted (WKD) extracts on bone marrow (BM)-MSC stemness and senescence. Premature senescence and inflammation were induced in BM-MSCs using H2O2 and LPS, respectively. Phytochemical constituents of WKO and WKD extracts were detected by HPLC. The stemness (proliferation and migration), senescence-related markers (p53, p21, SIRT1, and AMPK), oxidative stress/antioxidant markers, inflammatory cytokines, and cell cycle of BM-MSCs were measured by MTT assay, qPCR, ELISA, and flow cytometry. WKO and WKD extracts improved rat BM-MSC stemness, as evidenced by (1) increased cell viability, (2) decreased apoptosis (low levels of Bax and caspase3 and high levels of Bcl2), (3) upregulated MMP9 and downregulated TIMP1 expression, and (4) cell cycle arrest in the G0/G1 phase and declined cell number in the S and G2/M phases. Additionally, WKO and WKD extracts reduced rat BM-MSC senescence, as indicated by (1) decreased p53 and p21 expression, (2) upregulated expression and levels of SIRT1 and AMPK, (3) reduced levels of ROS and improved antioxidant activity (higher activity of CAT, SOD, and GPx and upregulated expression of NrF2 and HO-1), and (4) declined levels of TNFα, IL1β, and NF-κB. When compared to the WKO extract, the WKD extract had a greater impact on the induction of stemness and reduction of senescence of BM-MSCs due to its stronger antioxidant activity, which could be attributed to its higher levels of flavonoids and phenolic compounds, as detected by HPLC analysis. WKO and WKD extracts enhance rat BM-MSC stemness and protect them from senescence, suggesting their potential use as enhancers to increase MSCs' therapeutic efficacy.

Impact of low oxygen storage on post-storage quality of pasteurized walnut (Juglans regia L.) kernels

Walnut (Juglans regia) kernels were obtained from two facilities, each using a different method for pasteurization to achieve a log 4 and log 5 reduction in the bacterial load on the kernel surface. Continuous pasteurization utilized high temperature steam applied for a short period, and batch pasteurization utilized lower temperature steam applied in a pressurized chamber for a longer period. Log 4 and 5 walnut kernels from both treatment methods were stored at 20 °C in air or sealed in bags with a low oxygen transmission rate, and an oxygen absorbing sachet was inserted to reduce internal oxygen concentrations to < 0.5 %. After pasteurization and packaging, walnuts were stored and evaluated periodically for peroxide value, hexanal, free-fatty acids, and total tocopherols. These objective quality measures were compared to descriptive sensory analyses of walnut taste, texture, and aroma conducted by a trained sensory panel. Continuous pasteurization of walnuts increased the rate of oil oxidation and loss of total tocopherols, but storage of walnuts in low oxygen atmospheres mitigated some of the negative quality impacts. Continuous pasteurization resulted in an immediate decreased in total tocopherols prior to storage under low oxygen atmospheres; however, low oxygen storage reduced subsequent losses in tocopherols. Batch pasteurization did not enhance quality degradation as compared to unpasteurized controls, but storage under low oxygen reduced oil oxidation and slowed the degradation of total tocopherols, as typically observed during walnut storage.

Lipidomics characterized TAG biosynthesis of developing kernels in three walnut cultivars in Xinjiang region.

Walnut oil with very high proportion of polyunsaturated fatty acids exhibits many health beneficial effects. We hypothesized that the oil composition is led by a special pattern/mechanism for triacylglycerol (TAG) biosynthesis as well as accumulation in walnut kernel during embryo development. To test this hypothesis, shotgun lipidomics was performed for class-targeted lipid analysis (including TAG, phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid, phosphatidylglycerol, phosphatidylinositol, and lysophosphatidylcholine species) in walnut kernels from three cultivar collected at three critical stages of embryo development. The results indicated that TAG synthesis in the kernel happened before 84 days after flowering (DAF) and was significantly enhanced between 84 and 98 DAF. Moreover, TAG profile was changing along with DAFs due to the increased composition of 18:1 FA in TAG pool. Moreover, lipidomics also demonstrated that the enhanced acyl editing was responsible for the flux of FA through phosphatidylcholine for eventual TAG synthesis. Therefore, TAG biosynthesis in walnut kernel was characterized directly from lipid metabolism.

Non-destructive method to classify walnut kernel freshness from volatile organic compound (VOC) emissions using gas chromatography-differential mobility spectrometry (GC-DMS) and machine learning analysis

Analysis of volatile organic compounds (VOCs) can be an effective strategy to inspect the quality of horticultural commodities and following their degradation. In this work, we report that VOCs emitted by walnuts can be studied using gas chromatography-differential mobility spectrometry (GC-DMS), and those GC-DMS data can be analyzed to predict the rancidity of walnuts, i.e., classify walnuts into grades of freshness. Walnut kernels were assigned a class n depending on their level of freshness as determined by a peroxide assay. VOC samples were analyzed using GC-DMS. From these VOC data, a partial least square regression (PLSR) model provided a freshness prediction value m, which corresponded to the rancid class n when m=n±0.5. The PLSR model had an accuracy of 80% to predict walnut grade and demonstrated a minimal root mean squared error of 0.42 for the m response variables (representative of walnut grade) with the GC-DMS data. We also conducted gas chromatography-mass spectrometry (GC–MS) experiments to identify volatiles that emerged or were enhanced with more rancid walnuts. The findings of the GC–MS study of walnut VOCs align excellently with the GC-DMS study. Based on our results, we conclude that a GC-DMS device deployed with a pre-trained machine learning model can be a very effective device for classifying walnut grades in the industry.

Walnut (Juglans regia L.) kernel oil bodies recovered by aqueous extraction for utilization as ingredient in food emulsions: Exploration of their microstructure, composition and the effects of homogenization, pH, and salt ions on their physical stability

Natural oil-in-water emulsions containing plant oil bodies (OBs), also called oleosomes, rich in health-promoting omega-3 polyunsaturated fatty acids (ω3 PUFA) are of increasing interest for food applications. In this study, we focused on walnut kernel OBs (WK-OBs) and explored their microstructure, composition and physical stability in ionic environments as well as the impact of homogenization. A green process involving aqueous extraction by grinding of WK allowed the co-extraction of OBs and proteins, and centrifugation was used to recover the WK-OBs. Confocal laser scanning microscopy images showed the spherical shape of WK-OBs with an oil core envelopped by a layer of phospholipids (0.16 % of lipids) and embedded proteins. Their mean diameter was 5.1 ± 0.3 µm. The WK-OBs contained 70.1 % PUFA with 57.8 % ω6 linoleic acid and 12.3 % ω3 α-linolenic acid representing 68 % and 11.6 % of the total fatty acids in the sn-2 position of the triacylglycerols (TAG), respectively. Trilinolein was the main TAG (23.1 %). The WK-OBs also contained sterols (1223 ± 33 mg/kg lipids; 86 % β-sitosterol), carotenoids (0.62 ± 0.01 mg/kg lipids; 49.2 % β-carotene), and tocopherols (322.7 ± 7.7 mg/kg lipids; 89 % γ-tocopherol), confirming their interest as health-promoting ingredients. The decrease in the size of WK-OBs under high-pressure homogenization avoided phase separation upon storage. The anionic WK-OB surface at neutral pH was affected by stressful ionic environments (pH, NaCl, CaCl2), that induced aggregation of WK-OBs and decreased the physical stability of the emulsions. Emulsions containing WK-OBs are promising to diversify the market of the ω3-rich plant-based food products and beverages.

Walnut Protein: A Rising Source of High-Quality Protein and Its Updated Comprehensive Review.

Recently, plant protein as a necessary nutrient source for human beings, a common ingredient of traditional processed food, and an important element of new functional food has gained prominence due to the increasing demand for healthy food. Walnut protein (WP) is obtained from walnut kernels and walnut oil-pressing waste and has better nutritional, functional, and essential amino acids in comparison with other vegetable and grain proteins. WP can be conveniently obtained by various extraction techniques, including alkali-soluble acid precipitation, salting-out, and ultrasonic-assisted extraction, among others. The functional properties of WP can be modified for desired purposes by using some novel methods, including free radical oxidation, enzymatic modification, high hydrostatic pressure, etc. Moreover, walnut peptides play an important biological role both in vitro and in vivo. The main activities of the walnut peptides are antihypertensive, antioxidant, learning improvement, and anticancer, among others. Furthermore, WP could be applied in the development of functional foods or dietary supplements, such as delivery systems and food additives, among others. This review summarizes recent knowledge on the nutritional, functional, and bioactive peptide aspects of WP and possible future products, providing a theoretical reference for the utilization and development of oil crop waste.

Effect of γ-irradiation on the physicochemical and sensory properties of fresh walnut kernels (Juglans regia) during storage

The current study examined the total phenol content, antioxidant activity, sensory quality and fatty acid composition of fresh walnut kernels as a function of irradiation dose to determine dose levels that resulted in the least amount of undesirable changes to fresh walnut kernels at regular intervals of time. Fresh walnut kernels were exposed to 60Co radiation at doses of 0.5, 1.5, 3, 6, 8, and 10 kGy and stored at ± 4 °C for 28 days. Irradiation doses of 0.5 and 0.1 KGry have no significant effect on total phenol content (1.56±0.04–1.30±0.02mgGAE/g), antioxidant activity (95±0.02–85±0.01%), peroxide value (0.49±0.04–0.72±0.03%) and free fatty acid values (0.14±0.01–0.29±0.03%) respectively. However, irradiation doses of 1.0, 2.0, 3.0 and 4.0 resulted in increased peroxide values (0.89±0.02%, 0.98±0.01%, 1.05±0.01%, 1.17±0.03%), increased free fatty acid values(0.05±0.01%, 0.58±0.03%, 0.63±0.02±0.01%, 0.67±0.04%) and also the organoleptic quality were decreased (2.0 ± 0.01, 1.7 ± 0.03, 1.4 ± 0.02%, 1.2 ± 0.03%) during 28 days of storage. The use of gamma irradiation appears to be a promising technology for improving the chemical quality of fresh walnut kernels, but food safety concerns must be addressed before it can be recommended as a useful conservation alternative.

Polyphenol removal with ultrasound-assisted ethanol extraction from defatted walnut powder: optimization of conditions and effect on functional properties of protein isolates.

Walnut kernels are high in polyphenols (PPs), which cause low protein solubility, limiting the use of walnut protein in the food industry. To obtain the best technical parameters of the dephenolization treatment, the defatted walnut powder was dephenolized using ultrasound-assisted ethanol extraction (UAE), and the response surface optimization was performed on the basis of single factor. On this basis, the effects of dephenolization on the solubility, emulsifying properties and foaming properties of walnut protein isolates (WPIs) were compared to those of defatted walnut powder without dephenolization. The results showed that PP extraction in the UAE could significantly increase PP yield. The optimal process parameters were as follows: 51% (v/v) ethanol concentration, 140 W ultrasound power, 10 min extraction time, 30 °C ultrasound temperature, and a material-liquid ratio of 1:30 (w/v). The results revealed that the UAE dephenolization treatment significantly improved the functionality of WPI and that the functionality of the dephenolized WPI by UAE was superior to that of the protein without dephenolization, and that the functionality of both walnut proteins was the worst at pH 5, with solubility of 5.31% and 4.86%, emulsifying activity index (EAI) of 24.95 and 19.91 m2 /g, and foaming capacity (FC) of 3.66% and 2.94%, respectively; and the best at pH 11, with solubility of 82.35% and 73.55%, EAI of 46.35 and 37.28 m2 /g, and FC of 35.85% and 18.87%, respectively. The study found that dephenolization by UAE can significantly improve the functionality of WPI, and this method should be promoted and used in walnut and walnut protein processing industries. © 2023 Society of Chemical Industry.

Total lipid and fatty acids components of some Persian walnut (Juglans regia) cultivars

The world's walnuts (Juglans regia L.) production showed rapid growth from less than one million tons to more than three million tons during 1990–2020. The walnut kernel contains a high amount of fats, proteins, and carbohydrates. In this study, the total lipids, proteins, and carbohydrates contents of four commercial walnut cultivars: Alvand, Chaldoran, Caspian, and Persia, together with two promising genotypes: C-25 and 35t, were compared to cv. Chandler in 2019 and 2020. Based on the results, the average percentage of protein in cultivars in two years varied from 15.00% to 19.27%, the percentage of carbohydrates from 17.40% to 29.10%, and the percentage of total lipids from 50.60% to 70.00%. The fatty acids contents showed that the predominant was linoleic acid ranging from 44.60%-63.09%, followed by oleic acid (12.40%-35.02%), linolenic acid (6.64%-14.97%), palmitic acid (7.04%-8.97%) and stearic acid (2.28%-3.63%). Meanwhile, the nut protein (14.90%-19.86%) and carbohydrate (17.40%-29.10%) showed high variability too. The results showed that among the cultivars/genotypes, the highest amount of protein belonged to promising genotype 35t, and the highest amount of total lipid percentage was observed in cv. Persia, and the highest amount of carbohydrates was related to cv. Caspian. The cv. Chandler had the highest linoleic acid content (60.53%), while the cv. Persia had the lowest amount (46.90%). Analysis of regression between fatty acids components showed a close relationship r2 (0.876) between linoleic acid and oleic acid. The analysis of results in two years regarding the total lipids showed that the effect of the year was more than the genotype. Factor analysis using five fatty acids components showed that the first and second factors demonstrated more than 70% of the total variance. The first factor influenced the oleic acid (-0.978) and linoleic acid (0.941) highly. The loading plot of the first and second factors indicated that the change in oleic acid was opposite to linoleic acid, linolenic acid, and stearic acid. In conclusion, walnut cultivars' fatty acids contents showed significant variability, so Chandler, Chaldoran, and 35t were rich in linoleic and linolenic acids. In contrast, others like Persia and C-25 were rich in oleic acid.