Characterization and supercritical carbon dioxide extraction of walnut oil

An overview on lipids in nuts and oily fruits: oil content, lipid composition, health effects, lipidomic fingerprinting and new biotechnological applications of their by-products

Tree nuts and oily fruits are used as a diet complement and are highly consumed worldwide. The production and consumption of these foods have been increasing, and an enormous global market value is forecasted for 2023. Besides their high nutritional value and lipid content, they provide health benefits to fat metabolism, heart, skin, and brain. The industrial by-products of these oily foods represent promising raw materials for many industries. However, the lipidomic analysis of nuts and oily fruits is still in its early stages. State-of-the-art analytical approaches for the lipid profiling and fingerprinting of nuts and oily fruits have been developed using high-performance liquid chromatography and high-resolution mass spectrometry for the accurate identification and structural characterization at the molecular species level. It is expected to bring a new understanding of these everyday foods' nutritional and functional value. This review comprises the oil content and lipid composition of various nuts and oily fruits, particularly those mostly consumed worldwide and having recognized beneficial health effects, biological activities associated with the lipids from different oily foodstuffs, analytical methodologies to analyze lipids in nuts and oily fruits, and the potential biotechnological applications of their industrial by-products for a lipid-based commercial valorization.

Research progress on Walnut oil: Bioactive compounds, health benefits, extraction methods, and medicinal uses

Walnut oil is extracted from walnut kernels (Juglans regia Linne) or iron walnut kernels (Juhlans sigillata Dode). The percentage of oil in walnuts is 52%-70%. The main constituents in oil are fatty acids, phenols, sterols, squalene, melatonin, vitamins, and minerals. Many extraction methods such as supercritical carbon dioxide extraction, maceration, modified "bligh and dyer extraction," aqueous enzymatic extraction, ultrasonic extraction, soxhlet extraction, and cold-press extraction methods are reported in the literature. Walnut oil showed anti-inflammatory, antitumor, antioxidant, immunomodulatory, neuroprotective, cardioprotective, antidiabetic, and antihyperlipidemic activities. The reported data in the literature suggest that walnut oil has many health benefits. This review summarizes the extraction methods, bioactive constituents, health benefits, and pharmacological actions of walnut oil. PRACTICAL APPLICATIONS: Walnut oil is a natural vegetable oil of significant importance due to their nutritional, and intelligence-boosting benefits. Several factors, including the processing parameters and the phytochemical profile, affect walnut oil products' flavor and color. In addition, storage environment of walnut oil can also affect walnut oil quality. Apart from the predominant ingredient fatty acids, the chemical composition of walnut oil comprises phenols, sterols, squalene, melatonin, vitamins, and minerals. These bioactive compounds are of potential value owing to their health-promoting benefits, including antioxidant, antitumor, and cholesterol-lowering effects. Many chemical constituents were isolated from walnut oil; however, all the compounds are not explored for their possible medicinal value. Thus, clinical studies, exploration of the therapeutic potential and the molecular mechanisms of all the compounds, and development of convenient dosage forms either for therapeutic or functional food purposes are warranted.

Influence of the Extraction Method on the Quality and Chemical Composition of Walnut (Juglans regia L.) Oil

The present study investigated and compared the quality and chemical composition of Moroccan walnut (Juglans regia L.) oil. This study used three extraction techniques: cold pressing (CP), soxhlet extraction (SE), and ultrasonic extraction (UE). The findings showed that soxhlet extraction gave a significantly higher oil yield compared to the other techniques used in this work (65.10% with p < 0.05), while cold pressing and ultrasonic extraction gave similar yields: 54.51% and 56.66%, respectively (p > 0.05). Chemical composition analysis was carried out by GC−MS and allowed 11 compounds to be identified, of which the major compound was linoleic acid (C18:2), with a similar percentage (between 57.08% and 57.84%) for the three extractions (p > 0.05). Regarding the carotenoid pigment, the extraction technique significantly affected its content (p < 0.05) with values between 10.11 mg/kg and 14.83 mg/kg. The chlorophyll pigment presented a similar content in both oils extracted by SE and UE (p > 0.05), 0.20 mg/kg and 0.16 mg/kg, respectively, while the lowest content was recorded in the cold-pressed oil with 0.13 mg/kg. Moreover, the analysis of phytosterols in walnut oil revealed significantly different contents (p < 0.05) for the three extraction techniques (between 1168.55 mg/kg and 1306.03 mg/kg). In addition, the analyses of tocopherol composition revealed that γ-tocopherol represented the main tocopherol isomer in all studied oils and the CP technique provided the highest content of total tocopherol with 857.65 mg/kg, followed by SE and UE with contents of 454.97 mg/kg and 146.31 mg/kg, respectively, which were significantly different (p < 0.05). This study presents essential information for producers of nutritional oils and, in particular, walnut oil; this information helps to select the appropriate method to produce walnut oil with the targeted quality properties and chemical compositions for the desired purpose. It also helps to form a scientific basis for further research on this plant in order to provide a vision for the possibility of exploiting these oils in the pharmaceutical, cosmetic, and food fields.

Health-Promoting Properties of Borage Seed Oil Fractionated by Supercritical Carbon Dioxide Extraction

Borage (Borago officinalis L.) seed oil is an important source of γ–linolenic acid, which is normally used as a treatment against different pathologies. Since the fractionation of this interesting seed oil has many environmental, economic and biological benefits, two borage fractionation techniques after extraction with CO₂ under supercritical conditions have been studied: precipitation in two cyclone separators and countercurrent extraction column. Both techniques have successfully collected free fatty acids in one fraction: (i) two separators set up in series obtained the highest concentration of free fatty acids in separator 2 at 90 bar/40 °C; (ii) when countercurrent extraction column was used, the acidity index of the raffinate stream was independent from the operating conditions (2.6 ± 0.5%). Furthermore, the composition of the fatty acids, as well as their antioxidant and cytotoxic activities, were determined. The profile of the fatty acids obtained by either of these two methods remained unaltered, so that the crude oil exhibited improved antioxidant and cytotoxic properties. All the extracts obtained in the two cyclone separators at the same pressure/temperature conditions displayed high tumouricidal activity against HL 60 promyelocytic leukaemia cells, even if the extracts at 50% concentration from separator 2 presented a lower inhibitory activity (IC₅₀). The extracts from separator 2 at 90 bar/40 °C exhibited the highest anti-proliferative activity at low doses (IC₅₀ of 0.3 μL/mL for the trypan blue exclusion test). To reach the lethal dose—IC₅₀—with the product obtained through countercurrent column fractionation, a concentration of 2 μL/mL of crude borage oil raffinate was required.

Comparative Assessment of Physical and Chemical Characteristics of Prickly Pear Seed Oil from Opuntia ficus-indica and Opuntia megacantha Varieties

The prickly pear (Opuntia spp.) is an important plant in the economies of arid and semiarid areas, considering its low agronomic requirements and high water use efficiency. Characterizing the chemical composition of this plant will open new avenues for food, pharmaceutical, and cosmetic applications. In this context, this study examined the physical and chemical parameters of fruit seed oils of two prickly pear species from Rhamna area located in the center of Morocco: Opuntia ficus-indica (OFI), represented by the varieties “Safra” and “Aakria,” and Opuntia megacantha (OM), represented by the variety “Derbana.” The evaluated parameters included oil content, free acidity, specific extinction coefficients (K232 and K270), pigment content, fatty acid, and triglyceride composition. The seed oil contents of the three varieties “Safra,” “Aakria,” and “Derbana” were 8.09%, 8.74%, and 8.04%, respectively. OM (“Derbana”) seed oil was the most stable. The three studied varieties had higher contents of α-pheophytin and carotenoids than that of chlorophyll. Oil from the “Aakria” variety was distinguished by having the highest contents of α-pheophytin and chlorophyll. Significant differences in some fatty acid and triglyceride contents were noted. The major fatty acids of the three varieties were linoleic acid (60.55%–63.46%), followed by oleic acid (18.88%–21.81%) and palmitic acid (13.03%–13.75%). Furthermore, the chromatographic profiles of the triglycerides have shown the dominance of trilinolein (LLL, 24.33%–26.49%) and oleoyl-dilinoleoyl-glycerol (OLL, 20.92%–21.92%). Some triglycerides could be considered species markers, especially OLL, dipalmitoyl-linoleoyl-glycerol (PPL), oleoyl-linoleoyl-linolenoyl-glycerol and palmitoyl-oleoyl-dilinoleoyl-glycerol fraction (OLLn + PoLL), and stearoyl-dioleoyl-glycerol (SOO). This study provides a basis for qualitatively evaluating the therapeutic and cosmetic potential of prickly pear derivatives and for establishing quality standards of seed oil derived from the two species studied.

Optimization and Validation of Rancimat Operational Parameters to Determine Walnut Oil Oxidative Stability

This study was performed to optimize and validate Rancimat (Metrohm Ltd., Herisau, Switzerland) operational parameters including temperature, air-flow, and sample weight to minimize Induction-Time (IT) and IT-Coefficient-of-Variation (CV), using Response Surface Methodology (RSM). According to a Box–Behnken experimental design, walnut oil equivalent to 3-, 6-, or 9-g was added to each reaction vessel and heated to 100, 110, or 120 °C, while an air-flow equal to 10-, 15-, or 20-L·h−1 was forced through the reaction vessels. A stationary point was found per response variable (IT and CV), and optimal parameters were defined considering the determined stationary points for both response variables at 100 °C, 25 L·h−1, and 3.9 g. Optimal parameters provided an IT of 5.42 ± 0.02 h with a CV of 1.25 ± 0.83%. RSM proved to be a useful methodology to find Rancimat operational parameters that translate to accurate and efficient values of walnut oil IT.

Enzymolysis of walnut (Juglans regia L.) meal protein: Ultrasonication-assisted alkaline pretreatment impact on kinetics and thermodynamics

To improve the utility of walnut meal protein, influences of ultrasonication on the kinetic and thermodynamic constraints of enzyme (trypsin) hydrolysis were assessed using a multi-frequency counter current S-type ultrasound machine. Results revealed that both the ultrasonication treatment and control hydrolysis obeyed the first-order kinetics within the study constraints. After 90 min hydrolysis time, the uppermost percentage conversion rate (57.5%) of substrate to product and the percentage increase (25.42%) in hydrolyzed protein concentration were obtained at 323 K and 10% substrate concentration, respectively. The Michaelis constant (K_M ) in ultrasonic enzymolysis declined by 58.66% over the control. The reaction rate coefficient (k) for the proteolysis improved by 84.75%, 52.43%, 48.25%, and 37.79% at 219, 303, 313, and 323 K, correspondingly. Generally, the bond energy (E_a ), enthalpy change (ΔH), entropy change (ΔS), and Gibbs free energy (ΔG) were reduced by the ultrasound pretreatment with 36.61%, 28.05%, 18.22%, and 5.24%, respectively. PRACTICAL APPLICATIONS: Walnut meal protein has a well-balanced amino acid profile and its economic utilization could be increased practicably as a food ingredient via production of hydrolysates/peptides for the production of improved food ingredients instead of being cast off as animal feed. This study demonstrated a positive bearing of ultrasonication-assisted alkaline pretreatment on proteolytic reaction characteristics and its energy efficiency for walnut meal protein, which makes this technique applicable to the enhancement of plant proteins for inclusion in food products, especially tree nut and oil seed waste products from the oil industry.

Enhancement of Composition and Oxidative Stability of Chia (Salvia hispanica L.) Seed Oil by Blending with Specialty Oils

Chia seed (Salvia hispanica L.) oil is mainly composed of ω-3 fatty acids (61% to 70%). Despite being nutritionally favorable, higher amounts of polyunsaturated fatty acids result in poorer oxidative stability. Thus, the aim of this work was to produce edible vegetable oil blends rich in ω-3 fatty acids and with greater oxidative stability than pure chia oil. Blending of chia with other specialty oils (walnut, almond, virgin, and roasted sesame oils) was assessed in the following respective proportions: 20:80, 30:70, and 40:60 (v/v). An accelerated storage test was conducted (40 ± 1 °C, 12 days). Primary and secondary oxidation products, free fatty acid content, antioxidant compounds, fatty acid composition, and induction time were determined. The blends presented higher oxidative stability indices than chia oil. Sensory analysis showed that, given a pure oil, judges did not identify statistically significant differences among the blends. The results suggest that blending of chia oil is an adequate alternative to obtain ω-3-enriched oils with higher oxidative stability indices. PRACTICAL APPLICATION: Vegetable oil blending is a widely used practice in the edible oil industry to produce blended oils with enhanced stability and nutritional and sensory properties at affordable prices. The blends developed in this study from chia, sesame, walnut, and almond oils take advantage of the properties of each parent oil to yield products with improved oxidative stability, essential fatty acid presence, and sensory characteristics. To achieve a daily intake of 2.22 g/day of ω-3 fatty acids as recommended by the Intl. Society for the Study of Fatty Acids and Lipids (ISSFAL), it is necessary to consume approximately one spoonful of the formulated mixtures.

Effects of Cold-Press and Soxhlet Extraction Systems on Antioxidant Activity, Total Phenol Contents, Fatty Acids, and Tocopherol Contents of Walnut Kernel Oils

In this study, physico-chemical properties, fatty acid composition, and tocopherol contents of several walnut kernel oils obtained through cold-press and Soxhlet extractions were investigated. The acidity, peroxide, and unsaponifiable matter of oil samples extracted in the Soxhlet system were found higher. Total phenol contents of the oils obtained in cold press and Soxhlet extraction systems were 121.9 mg GAE/100g (Kaman-2) and 154.6 mg GAE/ 100g (Büyükoba), and between 135.9 mg GAE/100g (Kaman-2) and 163.8 mg GAE/100g (Büyükoba), respectively (p < 0.05). In addition, antioxidant activity valuesof walnut oils obtained in cold press and Soxhlet extractions varied between 17.3% (Kaman-2) and 19.7% (Kaman-5), and between 18.4% (Kaman-2) and 23.8% (Büyükoba), respectively (p < 0.05). Linoleic acid contents of the oil samples extracted in cold-press varied between 55.19% (Kaman-5) and 56.71% (Kaman-2), while that extracted from Soxhlet extraction system varied between 54.47% (Kaman-2) and 55.93% (Büyükoba). ɣ-Tocopherol contents of walnut oils extracted in cold press and Soxhlet extraction ranged between 9.41 mg/100g (Büyükoba) and 10.83 mg/100g (Kaman-2), and 8.76 mg/100g (Kaman-5) and 9.33 mg/100g (Kaman-2), respectively, and were statistically significant (p < 0.05).

Supercritical fluid extraction effectively removes phthalate plasticizers in spores of Ganoderma lucidum

Phthalate plasticizers residue in food is a serious threat to public health. Spores of Ganoderma lucidum are easy to be contaminated with phthalates during collection and processing. In this study, supercritical fluid extraction (SFE) was performed to remove phthalates in spores of G. lucidum, and the effects on acid and peroxide values of spores' oil were also evaluated. The results showed SFE removed 100% of the residual di-iso-butyl phthalate, di-n-butyl phthalate and di-2-ethylhexyl phthalate in the spores of G. lucidum. No significant differences in polysaccharides content and fatty acid composition were observed between SFE and control spores. However, the triterpenoid extracts of SFE spores had a 7.45% increase, significantly higher than that in control spores. Accelerated oxidation tests further implied that SFE could improve the stability of spores' oil. Our results suggested SFE is a potential approach to remove phthalate from food related products.

Application of supercritical fluids in cholesterol extraction from foodstuffs: a review

Various innovations have so far been devised to extract cholesterol from foods. Achieving a supercritical fluid is perhaps one of the greatest human successes in the field of extraction from foodstuffs in last 2 decades. Supercritical fluid extraction (SFE) offers a rapid, environment-friendly and selective method for extracting cholesterol from foods. This review aims at investigating the application of supercritical fluids in extraction of cholesterol. Various factors affecting the SFE, collection systems, examples of cholesterol extraction and SFE benefits are some of the issues discussed in this study.

Chemical composition, molecular weight distribution, secondary structure and effect of NaCl on functional properties of walnut (Juglans regia L) protein isolates and concentrates

Chemical composition, molecular weight distribution, secondary structure and effect of sodium chloride concentration on functional properties of walnut protein isolates, concentrates and defatted walnut flour were study. Compared with walnut protein concentrates (75.6%) and defatted walnut flour (52.5%), walnut protein isolates contain a relatively high amount of protein (90.5%). The yield of walnut protein isolates and concentrates was 43.2% and 76.6%, respectively. In molecular weight distribution study, Walnut protein isolates showed one peak with molecular weight of 106.33 KDa (100%) and walnut protein concentrates showed four peaks with molecular weight of 16,725 KDa (0.8%),104.943 KDa(63.9%), 7.3 KDa (11.4%), 2.6 KDa (23.9%). The secondary structure of walnut protein isolates was similar to that of walnut protein concentrates, but was differ from that of defatted walnut flour. The addition of sodium chloride (0 ~ 1 M) could improve the functionality of walnut protein concentrates, isolates and defatted walnut flour. The maximum solubility, water absorption capacity, emulsifying properties and foaming properties of walnut protein isolates, concentrates and defatted walnut flour were at sodium chloride solutions of 1.0 M, 0.6 M, 0.4 M, 0.6 M, respectively. The solubility of walnut protein concentrates (32.5%) in distilled water with 0 M sodium chloride was lower than that of walnut protein isolates (35.2%). The maximum solubility of walnut protein isolates, concentrates and defatted walnut flour in solution were 36.8%, 33.7% and 9.6% at 1.0 M sodium chloride solutions, respectively. As compared with other vegetable proteins, walnut protein isolates and concentrates exhibited better emulsifying properties and foam stability.

Application of response surface methodology to optimise supercritical carbon dioxide extraction of volatile compounds from Crocus sativus

BACKGROUND

Crocus sativus has been used as a traditional Chinese medicine for a long time. The volatile compounds of C. sativus appear biologically active and may act as antioxidants as well as anticonvulsants, antidepressants and antitumour agents. In order to obtain the highest possible yield of essential oils from C. sativus, response surface methodology was employed to optimise the conditions of supercritical fluid carbon dioxide extraction of the volatile compounds from C. sativus. Four factorswere investigated: temperature, pressure, extraction time and carbon dioxide flow rate. Furthermore, the chemical compositions of the volatile compounds extracted by supercritical fluid extraction were compared with those obtained by hydro-distillation and Soxhlet extraction.

RESULTS

The optimum extraction conditions were found to be: optimised temperature 44.9°C, pressure 34.9 MPa, extraction time 150.2 min and CO₂ flow rate 10.1 L h⁻¹. Under these conditions, the mean extraction yield was 10.94 g kg⁻¹. The volatile compounds extracted by supercritical fluid extraction and Soxhlet extraction contained a large amount of unsaturated fatty acids.

CONCLUSION

Response surface methodology was successfully applied for supercritical fluid CO₂ extraction optimisation of the volatile compounds from C. sativus. The study showed that pressure and CO₂ flow rate had significant effect on volatile compounds yield produced by supercritical fluid extraction. This study is beneficial for the further research operating on a large scale.

Quality of Cosmetic Argan Oil Extracted by Supercritical Fluid Extraction fromArgania spinosaL

Argan oil has been extracted using supercritical CO2. The influence of the variables pressure (100, 200, 300, and 400 bar) and temperature (35, 45, 55°C) was investigated. The best extraction yields were achieved at a temperature of 45°C and a pressure of 400 bar. The argan oil extracts were characterized in terms of acid, peroxide and iodine values, total tocopherol, carotene, and fatty acids content. Significant compositional differences were not observed between the oil samples obtained using different pressures and temperatures. The antioxidant capacity of the argan oil samples was high in comparison to those of walnut, almond, hazelnut, and peanut oils and comparable to that of pistachio oil. The physicochemical parameters of the extracted oils obtained by SFE, Soxhlet, and traditional methods are comparable. The technique used for oil processing does not therefore markedly alter the quality of argan oil.

Composition, structure and functional properties of protein concentrates and isolates produced from walnut (Juglans regia L.)

In this study, composition, structure and the functional properties of protein concentrate (WPC) and protein isolate (WPI) produced from defatted walnut flour (DFWF) were investigated. The results showed that the composition and structure of walnut protein concentrate (WPC) and walnut protein isolate (WPI) were significantly different. The molecular weight distribution of WPI was uniform and the protein composition of DFWF and WPC was complex with the protein aggregation. H(0) of WPC was significantly higher (p < 0.05) than those of DFWF and WPI, whilst WPI had a higher H(0) compared to DFWF. The secondary structure of WPI was similar to WPC. WPI showed big flaky plate like structures; whereas WPC appeared as a small flaky and more compact structure. The most functional properties of WPI were better than WPC. In comparing most functional properties of WPI and WPC with soybean protein concentrate and isolate, WPI and WPC showed higher fat absorption capacity (FAC). Emulsifying properties and foam properties of WPC and WPI in alkaline pH were comparable with that of soybean protein concentrate and isolate. Walnut protein concentrates and isolates can be considered as potential functional food ingredients.

Tree nut phytochemicals: composition, antioxidant capacity, bioactivity, impact factors. A systematic review of almonds, Brazils, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts

Tree nuts contain an array of phytochemicals including carotenoids, phenolic acids, phytosterols and polyphenolic compounds such as flavonoids, proanthocyanidins (PAC) and stilbenes, all of which are included in nutrient databases, as well as phytates, sphingolipids, alkylphenols and lignans, which are not. The phytochemical content of tree nuts can vary considerably by nut type, genotype, pre- and post-harvest conditions, as well as storage conditions. Genotype affects phenolic acids, flavonoids, stilbenes and phytosterols, but data are lacking for many other phytochemical classes. During the roasting process, tree nut isoflavones, flavanols and flavonols were found to be more resistant to heat than the anthocyanins, PAC and trans-resveratrol. The choice of solvents used for extracting polyphenols and phytosterols significantly affects their quantification, and studies validating these methods for tree nut phytochemicals are lacking. The phytochemicals found in tree nuts have been associated with antioxidant, anti-inflammatory, anti-proliferative, antiviral, chemopreventive and hypocholesterolaemic actions, all of which are known to affect the initiation and progression of several pathogenic processes. While tree nut phytochemicals are bioaccessible and bioavailable in humans, the number of intervention trials conducted to date is limited. The objectives of the present review are to summarise tree nut: (1) phytochemicals; (2) phytochemical content included in nutrient databases and current publications; (3) phytochemicals affected by pre- and post-harvest conditions and analytical methodology; and (4) bioactivity and health benefits in humans.

Walnut (Juglans regia L.): genetic resources, chemistry, by-products

Walnut (Juglans regia L.) is the most widespread tree nut in the world. There is a great diversity of genotypes differing in forestry, productivity, physical and chemical nut traits. Some of them have been evaluated as promising and may serve as germplasm sources for breeding. The nutritional importance of the nut is related to the seed (kernel). It is a nutrient-dense food mainly owing to its oil content (up to 740 g kg(-1) in some commercial varieties), which can be extracted easily by screw pressing and consumed without refining. Walnut oil composition is dominated largely by unsaturated fatty acids (mainly linoleic together with lesser amounts of oleic and linolenic acids). Minor components of walnut oil include tocopherols, phospholipids, sphingolipids, sterols, hydrocarbons and volatile compounds. Phenolic compounds, present at high levels in the seed coat but poorly extracted with the oil, have been extensively characterised and found to possess strong antioxidant properties. The oil extraction residue is rich in proteins (unusually high in arginine, glutamic and aspartic acids) and has been employed in the formulation of various functional food products. This review describes current scientific knowledge concerning walnut genetic resources and composition as well as by-product obtainment and characteristics.