Uncharacteristic of most whole foods, the major component of tree nuts is lipid; surprisingly, information on the lipid constituents in tree nuts has been sporadic and, for the most part, not well reported. Most published papers focus on only one nut type, or those that report a cultivar lack a quality control program, thus making data comparisons difficult. The present study was designed to quantify the healthful lipid constituents of 10 different types of commercially important tree nuts (i.e., almonds, black walnuts, Brazil nuts, cashews, English walnuts, hazelnuts, macadamias, pecans, pine nuts, and pistachios) according to standardized, validated methods. The total lipid content of each nut type ranged from 44.4 ± 1.9% for cashews to 77.1 ± 1.7% for macadamias. As expected, the major fatty acids present in the tree nuts were unsaturated: oleic (18:1 ω9) and linoleic (18:2 ω6) acids. A majority of the lipid extracts contained <10% saturated fatty acids with the exceptions of Brazil nuts (24.5%), cashews (20.9%), macadamias (17.1%), and pistachios (13.3%). The total tocopherol (T) content ranged from 1.60 ± 1.27 mg/100 g nutmeat in macadamias to 32.99 ± 0.78 in black walnuts. The predominant T isomers in the nut types were α- and γ-T. Tocotrienols were also detected, but only in 6 of the 10 nut types (i.e., Brazil nut, cashews, English walnuts, macadamias, pine nuts, and pistachios). In most cases, total phytosterol contents were greater in the present study than reported in peer-reviewed journal papers and the USDA National Nutrient Database for Standard Reference, which is attributed to total lipid extraction and the inclusion of steryl glucosides in the analysis; the levels were highest for pistachios (301.8 ± 15.4 mg/100 g nutmeat) and pine nuts (271.7 ± 9.1 mg/100 g nutmeat). Minor sterols were also quantified and identified using GC-FID and GC-MS techniques.

The phenolic acids and proanthocyanidins (PACs) of pecans possess bioactive properties, which might be useful in retarding the onset of and ameliorating the status of certain chronic disease states. There is a general lack of information in the literature regarding such compounds, especially the PACs. Crude phenolic extracts pooled from eight commercially significant cultivars were selected based on their relatively high antioxidant capacities. The pooled extracts were separated via Sephadex LH-20 column chromatography into five ethanolic low-molecular-weight (LMW) fractions and one acetonic high-molecular-weight (HMW) fraction. The preparations were then characterized using RP-HPLC-ESI-MS/MS and diol-phase HPLC-ESI-MS/MS in order to determine the key constituents present in the LMW and HMW fractions, respectively. As previously observed in pecan nutmeat, ellagic acid and (+)-catechin were found to be the major phenolics in the LMW fractions. The last eluting LMW fraction did not contain phenolic acids; rather it possessed PAC monomers and dimers. The HMW fraction comprised a majority of its PACs as dimers; yet, monomers, trimers, tetramers, pentamers, and hexamers were also separated and characterized.

Sulfites are widely used food preservatives that can cause severe reactions in sensitive individuals. As a result, the U.S. FDA requires that sulfites be listed on the label of any food product containing >10 mg/kg (ppm) sulfite (measured as sulfur dioxide). Currently, the optimized Monier-Williams (MW) method (AOAC Official Method 990.28) is the most common approach for determining sulfite concentrations in food samples. However, this method is time-consuming and lacks specificity in certain matrices. An improved rapid, sensitive, and selective method has been developed using electrospray ionization (ESI) high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of sulfite in various food matrices. A total of 12 different types of foods were evaluated. These included dried fruits and vegetables, frozen seafood, sweeteners, and juices. The matrix is extracted with a buffered formaldehyde solution, converting free and reversibly bound sulfite to the stable formaldehyde adduct, hydroxymethylsulfonate (HMS). Extracts are prepared for injection using a C18 SPE cartridge to remove any lipophilic compounds. HMS is then separated from other matrix components using hydrophilic interaction chromatography (HILIC) and detected using multiple reaction monitoring (MRM). The method was validated at 5 concentrations in 12 food matrices. Accuracy data showed spiked recoveries ranging from 84 to 115% in representative foods. Six commercially available sulfited products were analyzed using the LC-MS/MS method, as well as the MW method, to determine if differences exist.

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