The changes in color, taste, aroma, and quality of pine pollen vinegar during fermentation were evaluated in terms of bioactive ingredients, antioxidant capacity, color difference, electronic tongue analysis, free amino acids, organic acids, volatile compounds, and sensory scores. Principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), and odor activity values (OAV) were then employed for differential analysis. The results indicated that the contents of total phenols, total flavonoids, vitamin C, free amino acids, and organic acids in pine pollen juice significantly increased during the fermentation process. The electronic tongue analysis showed that the bitterness of pine pollen juice decreased while its umami taste increased. By gas chromatography-mass spectrometry (GC-MS), a total of 110 volatile compounds were detected during the fermentation process, among which, aldehydes, acids, and esters were identified as the major aroma substances of pine pollen vinegar, and ethanol, 2-ethylhexanol, phenylethanol, isobutyric acid, ethyl acetate, nonanal, anisole, and acetic acid as the key differential substances during the fermentation process, conferring a pleasant aroma on pine pollen vinegar. Furthermore, sensory evaluation showed that pine pollen vinegar was superior to pine pollen juice in terms of color, flavor, aroma, and overall acceptability. These findings lay a theoretical foundation for the production of high-quality pine pollen vinegar a, hence promoting the deep processing and utilization of pine pollen.

Fresh hazelnuts were treated by ⁶⁰Co-γ irradiation (0, 0.25, 0.50, 0.75 and 1.00 kGy) and stored at (4.0 ± 0.5) ℃ for up to three months. Changes in physiological indexes and lipid nutrition were monitored during the storage period. The results showed that irradiation at a dose of 0.25–1.00 kGy delayed the decline in superoxide dismutase (SOD) and catalase (CAT) activity, and reduced the activity of polyphenol oxidase (PPO) in fresh hazelnuts. The irradiation dose of 0.50 kGy was the most effective, and at the end of storage, the respiratory intensity, malondialdehyde (MDA) content and lipoxygenase activity of the irradiated sample decreased by 25.81%, 18.50% and 4.18% compared with those of the non-irradiated one, respectively. However, irradiation had no significant effect on fatty acid composition and content, peroxide value (POV) or acid value (AV). Principal component analysis (PCA) performed on fresh hazelnuts stored for 90 d also showed that 0.50 kGy ⁶⁰Co-γ irradiation imparted the best storage quality to fresh hazelnuts. These results suggest that ⁶⁰Co-γ irradiation can delay the senescence and effectively extend the shelf life by affecting the postharvest physiology of fresh hazelnuts.

Although hazelnut oil is rich in nutrients, its quality is greatly affected by how it is processed. However, no studies to date have comprehensively analyzed the lipid composition of hazelnut oil using different processing methods. Here, we conducted a lipidomics analysis using UPLC-QTOF-MS to characterize the lipid composition of cold-pressed hazelnut oil (CPO), ultrasonic-assisted hexane hazelnut oil (UHO) and enzyme-assisted aqueous hazelnut oil (EAO). A total of 10 subclasses of 98 lipids were identified, including 35 glycerolipids (GLs), 56 glycerophospholipids (GPs) and 7 sphingolipids (SPs). The total lipid and GL content were the highest in CPO, GP content was the highest in UHO and the ceramide content in SPs was most abundant in EAO. Multivariate statistical analysis showed that the lipid profiles of hazelnut oil prepared with different processing methods varied. Twelve significantly different lipids (TAG 54:3, TAG 52:2, TAG 54:4, TAG 54:2, TAG 52:3, TAG 54:5, DAG 36:2, DAG 36:4, DAG 36:3, PC 36:2, PA 36:2 and PE 36:3) were identified, and these lipids could potentially be used as biomarkers to distinguish between hazelnut oil subjected to different processing methods. Our results provide useful information for hazelnut oil applications and new insight into the effects of edible oil processing.