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U.S. pecans and Chinese hickory nuts possess a wide array of phenolic constituents with potential health benefits including phenolic acids and proanthocyanidins. Only limited information is available, however, on their compositions. The present study optimized the separation performance and characterized the low-molecular-weight phenolic fractions of these nuts with C18 and pentafluorophenyl (PFP) fused-core LC columns by employing a kinetic approach. Although both types of reversed-phase columns demonstrated similar performance in general, the PFP column furnished greater plate numbers and superior peak shapes for the low-molecular-weight fractions as well as overall separations of ellagic acid derivatives. The high-molecular-weight fraction of pecans, analyzed by a 3-μm HILIC column, possessed more proanthocyanidins than the Chinese hickory nuts with dimers and trimers (31.4 and 18.34 mg/g crude extract, respectively) being present at the greatest levels. Chinese hickory nuts had lower proanthocyanidin content but possessed tetramers and pentamers at 4.46 and 4.01 mg/g crude extract, respectively.

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; Radj.2 = 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.

Volatile compounds are responsible for the characteristic aroma of raw and roasted pecans. Yet, much is unknown about the specific effects of roasting on pecan volatiles. In this study, the volatiles of raw “Desirable” pecans from Georgia and 3 roasted pecan samples (175 °C for 5, 10, and 15 min) were determined by HS‐SPME coupled to GC‐MS using stable deuterium‐labeled volatiles as internal standards for quantitation. As expected, roasting markedly impacted the volatile profile of pecans: a total of 63 flavor‐active compounds were identified in roasted samples, including 9 compounds not detected in raw “Desirable” pecans. Pyrazines, notable indicators of the Maillard reaction, were found only in roasted samples and demonstrated continual increases throughout observed roasting times. Furthermore, it was noted that hydrocarbon derivatives showed substantial increases with roasting, likely a result of the degradation of nonvolatile lipids. The observed changes correspond well to prior sensory investigations concerning the impact of roasting on pecan flavor, and explain increases in intensity for roasted, nutty, buttery, and sweet sensory traits. Practical Application The results of this study document the volatile constituents generated during the roasting of pecans, and this may help formulators, who are trying to develop natural and artificial pecan flavors in new food products.

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