In order to determine the appropriate harvesting period of Carya illinoinensis planted in Nanjing city of China, this study analyzed the phenotypic characteristics and inclusions, including single fruit quality, fruit transverse and vertical diameter, kernel rate, water content, color, respiratory strength, crude fat, soluble sugar, soluble protein, and total phenols, of two cultivars ‘Pawnee’ and ‘Wichita’ during September and October, respectively. Results showed that the respiration intensity and I_AD values of pecan fruits decreased as the harvest date was delayed. ‘Pawnee’ fruits exhibited the highest seed kernel fullness, ∆E value, fruit transverse diameter, shape index, kernel yield, crude fat, and total phenolic content in late September and early October, while the quality of ‘Wichita’ fruits reached its peak in late October. The appropriate harvest period is conducive to the material accumulation of Carya illinoinensis, which is of great practical significance for improving the commodity value of pecans. The optimal harvesting period for ‘Pawnee’ in Nanjing is from the end of September to the beginning of October, and the optimal harvesting period for ‘Wichita’ is from mid- to late-October to the end of October.

This study aimed to evaluate the impact of conventional (pressing extraction [PSE], solvent extraction [STE]), and non-conventional (microwave-assisted solvent extraction [MSE], subcritical fluid extraction [SBFE], supercritical fluid extraction [SPFE]) techniques on the quality of pecan oil using foodomics. The results indicated that MSE, STE, and SBFE yielded higher oil quantities. SPFE selectively extracted free fatty acids, leading to a higher acid value. MSE-derived oil exhibited the highest oxidative stability index. A total of 844 lipid molecules were identified, with glycerolipids and glycerophospholipids as the predominant classes. MSE and SBFE showed superior efficiency over conventional methods for the extraction of glycerophospholipids and saccharolipids. Additionally, 48 volatile compounds were identified, predominantly aldehydes and esters, with seven recognized as key aroma contributors. Dimethyl trisulfide had the most significant impact on the overall aroma. These findings offer a theoretical foundation for the efficient and sustainable production of pecan oil.

Traditional analytical methods for assessing oil oxidation frequently depend on expensive and intricate equipment or elaborate procedures, thereby hindering their practical use in everyday situations. Sensory evaluation and GC-MS analysis indicated that during storage, the peroxide value (PV) and aldehyde content of pecan oil increased, consistent with progressive oxidation, while the acid value (AV) remained stable. The shelf-life prediction model further underscores its reliability as an oxidation marker. The coefficient of determination (R²) for the first-order kinetic model at temperatures of 20, 40, 50, and 60 °C ranged from 0.9183 to 0.9841. The correlation coefficients between the measured and predicted shelf-life values were 0.9993 for cold-pressed pecan oil (CPO) and 0.9866 for hot-pressed pecan oil (HPO). A filter-paper-based colorimetric aldehyde sensor was developed for the visual assessment of pecan oil shelf-life, which leverages the chemical reaction between hydroxylamine sulfate and aldehydes to generate a distinct naked-eye color shift from red to purple-blue—this enables the qualitative identification of whether cold-pressed (CPO) and hot-pressed (HPO) pecan oil complies with the national peroxide value (PV) limit of 0.25 g/100 g or exceeds it. Specifically, CPO is deemed to be expired when a* ≤ 11 and HPO when a* ≤ 15; consistent red-to-purple-blue color changes for the sensor yielded 100% sensitivity and 100% specificity for both oils at the national PV limit, thereby validating its application as a highly accurate qualitative (pass/fail) indicator for oil oxidation. By contrast, sensory evaluation can also reliably distinguish when pecan oil exceeds the national PV limit qualitatively, yet it lacks quantitative accuracy due to inherent subjective biases.