Tree Nut Oils Research Articles

Elemental Analysis of Tree Nuts and Their Pressed Oils by Triple Quadrupole Inductively Coupled Plasma-Mass Spectrometry (ICP-MS/MS)

Trace elements in tree nut oils may be toxic for humans and catalyze the auto-oxidation of the oils, affecting their stability. These elements have not been comprehensively characterized. In this study, we prepared tree nut oils from tree nuts (camellia, acer truncatum, shiny leaf yellow horn, and pecan seeds, as well as walnuts and Brazil nuts) by cold-pressing and determined As, Cd, Cu, Fe, Mn, Pb, Se, and Zn in these seeds and their oils and residues. Moreover, we investigated the elemental migration from seed to oil. The migration of all measured elements from seed to oil was <2%, where Cu exhibited the lowest migration from 0.09 to 0.31%. Moreover, we studied the effect of preheating (25–150 °C) the seeds upon their elemental migration. The Cu, Fe, Mn, and Zn contents increased with the temperature in all tree nut oils. The migration of toxic As, Cd, and Pb did not significantly differ with temperature, suggesting that temperature does not affect the release of these elements from nuts to oil.

Tree Nut Oils: Chemical Profiles, Extraction, Stability, and Quality Concerns

AbstractTree nuts are globally consumed. Their kernels are calorie‐rich, nutrient‐dense foods and contain several bioactive and health‐promoting components. While some nut crops have expanded through the world since ancient times (almond, hazelnut, walnut), more recently, there has been a parallel development of underexploited promising species (Brazil nut, macadamia, pecan). Nut kernels have high lipid content, ranging from 40% to 80% depending on nut species and varieties. In general, nut oils contain significant proportions of nutritionally and medicinally desirable fatty acids and nutraceutical compounds (sterols, tocopherols, and other phenolics). A considerable genetic variability in oil content and composition is present in nut genetic resources worldwide. This suggests the possibility of different breeding lines focused to enhance oil yields, chemical and quality traits. Regarding extraction, screw‐pressing is suitable to achieve high oil recovery and good quality standards, but seed materials should be conditioned appropriately. Seed moisture content and pressing temperature appear as key variables to enhance oil recovery. This article presents an overview on chemical profiles, mechanical extraction, and quality concerns of oils from the most widely produced tree nut crops. The revision is also aimed at identifying areas where knowledge is insufficient and to set priorities for further research.Practical applications: The review updates and increases knowledge about oils from tree nut genetic resources, encompassing genetic variability and environmental effects on oil yield and compositional traits. It also analyzes findings regarding oil extraction and provides useful insights to establish better conditions for achieving sustainable oil yields and good quality standards.

Microwave-assisted digestion for trace elements analysis of tree nut oil: evaluation of residual carbon content

An inductively coupled plasma mass spectrometer method for estimating trace elements in tree nut oils has been developed which employs microwave digestion equipped with high pressure subassembly. Residual carbon content and residual acidity were determined to evaluate the efficiency of digestion. The best digestion efficiency was obtained using Easyprep™ system with 0.5 g of oil, 4 mL concentrated nitric acid, and 2 mL hydrogen peroxide, and a final temperature of 235 °C. Residual carbon content and residual acidity were estimated as 1.7% (corresponding to 852 mg L−1 of carbon in sample solution) and 7.5%, respectively, and recovery values ranged from 90.7% to 107.7%. Whereas, only 0.2 g of oil could be digested through conventional microwave system with 5 mL concentrated nitric acid and 2 mL hydrogen peroxide at 205 °C (residual carbon content = 3.2%). The developed method has been applied to determine nine trace elements (Cr, Mn, Fe, Ni, Cu, As, Zn, Cd, and Pb) in different categories of tree nut oils, and high content of Fe, Mn, and Zn were found in some of those oils. To the best of our knowledge, the present investigation is the first attempt to analyze trace elements in different categories of tree nut oils consumed in China.

Chemical and nutritive characteristics of tree nut oils available in the U.S. market

Tree nuts have become increasingly popular in the U.S. market due to their healthful fats and beneficial micronutrients and bioactives. The use of specialty tree nut oils has also been growing in popularity. As proper quality control measures are not currently in place, and published information on tree nut oils in the USDA National Nutrient Database for Standard Reference (SR28) is antiquated, an improved understanding of nut oil compositions could be of use to the industry and field. In this study, 20 commercially available brands of specialty tree nut oils, either imported or domestic, were analyzed to determine their contents of fatty acids, tocopherols (Ts), and phytosterols. While recent publications and the USDA Database confirm that γ‐T is the primary homolog endogenous to pecan oil, three of the four pecan oil samples tested were found to be most concentrated in α‐T. The T concentrations were also determined to be highly predictive of nut oil unsaturation (as summarized by calculated iodine values; = 0.913), with the concentration of δ‐T presenting the greatest numeric weight to the model. The compositional information presented in this paper provides more in‐depth information on commercially available specialty tree nut oils.Practical applications: The information reported provides a better understanding of important compositional factors within tree nut oils, which can be of benefit to those that either produce or utilize such oils. These understandings are important to nutritional considerations, and may also inform the optimizations of processing and storage techniques. This study also contributes to our understanding of the relationship between endogenous T concentrations and oil unsaturation, which may improve our knowledge of antioxidative properties of Ts.Consumers are using tree nut oils in food preparations more frequently these days, partially due to the health benefits associated with these specialty oils. Limited research exists in nutritional databases about the lipid constituents – namely the fatty acids, phytosterols, and vitamin E contents – of these oils. This paper reports on the characterization of these constituents in raw and roasted tree nut oils available commercially.

11th Euro Fed Lipid Congress, New Strategies for a High Quality Future (27–30 October 2013, Antalya, Turkey)

11th Euro Fed Lipid Congress, New Strategies for a High Quality Future (27–30 October 2013, Antalya, Turkey)

Oxidative Stability of Tree Nut Oils

The oxidative stability of selected tree nut oils was examined. The oils of almond, Brazil nut, hazelnut, pecan, pine nut, pistachio, and walnut were extracted using two solvent extraction systems, namely, hexane and chloroform/methanol. The chloroform/methanol system afforded a higher oil yield for each tree nut type examined (pine nut had the highest oil content, whereas almond had the lowest). The fatty acid compositions of tree nut oils were analyzed using gas chromatography, showing that oleic acid was the predominant fatty acid in all samples except pine nut and walnut oils, which contained high amounts of linoleic acid. The tocopherol compositions were analyzed using high-performance liquid chromatography, showing that alpha- and gamma-tocopherols were the predominant tocopherol homologues present; however delta- and beta-tocopherols were also detected in some samples. The oxidative stability of nonstripped and stripped tree nut oils was examined under two conditions, namely, accelerated autoxidation and photooxidation. Progression of oxidation was monitored using tests for conjugated dienes, peroxide value, p-anisidine value, and headspace volatiles. Primary products of oxidation persisted in the earlier stages of oxidation, whereas secondary oxidation product levels increased dramatically during the later stages of oxidation. Hexanal was the major headspace aldehyde formed in all oxidized samples except walnut oil, which contained primarily propanal. Results showed that chloroform/methanol-extracted oils were more stable than hexane-extracted oils in both the accelerated autoxidation and photooxidation studies. Oils of pecan and pistachio were the most stable, whereas oils of pine nut and walnut were the least stable.

Antioxidant activity of minor components of tree nut oils

The antioxidative components of tree nut oils were extracted using a solvent stripping process. Tree nut oil extracts contained phospholipids, sphingolipids, sterols and tocopherols. The chloroform/methanol extracted oils had higher amounts of phenolic compounds than their hexane extracted counterparts. The antioxidant activity of tree nut oil minor component extracts were assessed using the 2,2-azino-bis (3-ethylbenzthiazoline sulphonate) (ABTS) radical scavenging activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, β-carotene bleaching test, oxygen radical absorbance capacity (ORAC) and photochemiluminescence inhibition assays. Results of these studies demonstrated that extracts of chloroform/methanol extracted oils possessed higher antioxidant activities than extracts of their hexane extracted counterparts. Meanwhile the extract of chloroform/methanol extracted pecan oil possessed the highest antioxidant activity.

LIPID CLASS COMPOSITIONS, TOCOPHEROLS AND STEROLS OF TREE NUT OILS EXTRACTED WITH DIFFERENT SOLVENTS

ABSTRACT The chemical compositions of tree nut oils were examined. The oils of almonds, Brazil nuts, hazelnuts, pecans, pine nuts, pistachios and walnuts were extracted using hexane and chloroform/methanol. The chloroform/methanol system afforded a higher oil yield for each tree nut type examined (pine nuts had the highest oil content while almonds had the lowest). The lipid class compositions of the tree nut oils were analyzed using the thin‐layer chromatography‐flame ionization detector and showed that triacylglycerols were the predominant lipid class present. Smaller amounts of sterols, sterol esters, phospholipids and sphingolipids were also present. The fatty acid compositions of the tree nut oils were analyzed using gas chromatography, showing that oleic acid was the predominant fatty acid in all samples except pine nut and walnut oils, which contained high amounts of linoleic acid. The sterol and stanol content and compositions were analyzed using gas chromatography; β‐sitosterol was the predominant sterol present in all samples, with lower amounts of campesterol, stigmasterol, Δ5‐avenasterol, 22‐nordehydrocholesterol, 24‐methylenecholesterol, cholesterol, cholestanol and β‐sitostanol also present. The tocopherol compositions were analyzed using high‐performance liquid chromatography, showing that α‐ and γ‐tocopherols were the predominant tocopherol homologs present; however, δ‐ and β‐tocopherols were also detected in some samples. PRACTICAL APPLICATIONSTree nut oils contain health‐promoting unsaturated fatty acids and minor components that may render beneficial effects. The lipid class compositions of the oils are reported as these affect the stability of the tested oils. Results may have significance in terms of practical applications for food and use in nutraceutical and/or cosmoceuticals products.

Three major tree nut oils of southern central Africa: Their uses and future as commercial base oils

Summary There is a pressing need for sustainability of the ecology and environment of Africa. Deforestation is taking place at an alarming rate, and this situation will continue to escalate unless local communities can be given a sufficiently attractive and viable reason to look after their forests and animals. The development of international markets for the tree seed oils is a major step towards solving this growing dilemma. In Zambia the development of sustainable harvest systems and market outlets for the highly valued indigenous tree seed oils, along with the establishment of sustainable wild harvest for ‘non-timber forest products’ to accredited international certification criteria has enable sustainable livelihoods for large numbers of disadvantaged rural communities from indigenous plant products at the same time as helping to maintain the natural environment.

Allergenicity of gourmet nut oils processed by different methods

Background: No information is available on allergenicity of tree nut oils, and information on peanut oils has been conflicting. Many of the nut oils now on the market undergo minimal processing and may contain residual antigen. Objective: This study was carried out to determine whether several of the new “gourmet” tree nut oils, as well as peanut oils, contain residual proteins that could bind IgE from sera of patients with allergy. Methods: Several brands of walnut, almond, hazelnut, pistachio, and macadamia nut oils were examined. Peanut oils, both unrefined oils (which have been shown to contain allergenic proteins) and refined oils (without previously demonstrable allergens), were also examined to confirm reproducibility of immunoreactivity as reported by other investigators. Oils were extracted with 0.2 mol/L ammonium bicarbonate, and protein concentrations in the aqueous extracts were measured. IgE binding was assayed by slot-blot and Western immunoblotting. Pooled sera from patients with a history of systemic reactions to various tree nuts or peanuts were used as appropriate. Results: The oil extracts known to be from oils that had undergone less processing at lower temperatures tended to demonstrate qualitatively greater IgE binding and higher protein concentrations. Conclusion: Tree nut and peanut oils may pose a threat to patients with allergy, depending on the method of manufacture and processing. (J Allergy Clin Immunol 1997;99:502-6.)

Technical note: Fatty acid composition of tree nut oils

Technical note: Fatty acid composition of tree nut oils