Search

Summary: Hazelnut oils obtained from three varieties of Chinese hybrid hazelnuts (cv. 'Liaozhen 3 (LZ)', 'Pingou 21' (PG) and 'Yuzhui' (YZ)) were used to compare the lipid oxidation characteristics (peroxide value, p‐anisidine value and conjugated diene value), fatty acid profiles and major active components (squalene, carotenoids and tocopherols) under oxidation condition at 60 °C for 40 days, in addition, the molecular structure changes in the three hazelnut oils were monitored by Raman spectroscopy. The lipid oxidation of the three hazelnut oils had similar tendencies, and the oxidation rate was slower in the early stage and faster in the later stage. Polyunsaturated fatty acids (PUFAs) tended to decrease mainly due to the decrease in linoleic acid. LZ had higher contents of tocopherol, carotenoids and PUFAs than the other varieties, while YZ owned the highest content of squalene. Tocopherol and carotenoids of the three hazelnut oils showed easy loss, while squalene was relatively stable. Raman spectroscopy can effectively indicate the degree of oxidation and carotenoid levels of hazelnut oil. This study can provide a scientific basis for variety selection in planting and utilisation of active ingredients for the hazelnut industry. [ABSTRACT FROM AUTHOR]

Cold pressed hazelnut oil was accelerated oxidized at 60℃. The color of oil was changed with the deepening of oxidation. The free radical intensity was a good indicator of lipid oxidation level, which matched with lipid color change. The UPLC--EQ/MS method was used to track and monitor the oxidative metabolites of hazelnut oil, while the oxidative metabolic pathway of hazelnut oil was analyzed by bioinformatics method. Application of metabonomics to elucidate the material basis of oxidative metabolism of hazelnut oil. [Display omitted] • Deep oxidation results in complete discoloration of hazelnut oil. • Free radical intensity is a good indicator of the oxidation degree of hazelnut oil. • Total of 1010 metabolites in 12 super classes were detected in fresh hazelnut oil. • Linoleic acid metabolism and sphingolipid metabolism are the most important metabolic pathways in hazelnut oil oxidation process. • Application of metabonomics to elucidate the material basis of oxidative metabolism of hazelnut oil. The oxidation metabolites of hazelnut oil are complex and vary with different degrees of oxidation. At present, few studies have investigated the change law of metabolites during the oxidation process of hazelnut oil. In this study, ultrahigh-performance liquid chromatography tandem Q-Exactive high-resolution mass spectrometry (UPLC-QE/MS) was used to analyze the differential metabolites resulting from the oxidation of cold-pressed hazelnut oil during storage for 40 days with accelerated oxidation. The oxidation level of cold-pressed hazelnut oil was evaluated by monitoring the free radical relative strength during accelerated oxidation. A total of 1010 metabolites in 12 super classes were detected in fresh hazelnut oil. Based on multivariate statistical analysis of all metabolites and the change law of free radicals in hazelnut oil, it was found that hazelnut oil enters the deep oxidation stage after accelerated oxidation for 30 days. A statistical analysis of differential metabolites and metabolic pathways was also carried out. The metabolite map obtained in this study can further distinguish hazelnut oil with different degrees of oxidation. Bioinformatics analysis indicated that linoleic acid metabolism and sphingolipid (SP) metabolism are the most important metabolic pathways in the entire oxidation process. These results provide a basis for better understanding the composition of hazelnut oil metabolites with different oxidation levels, identifying markers for oxidation level evaluation and analyzing the oxidative metabolism mechanism of hazelnut oil. This study provides new resources and new ideas for studying methods to prolong the shelf life of edible oils. [ABSTRACT FROM AUTHOR]

This study used partial least squares regression (PLSR) to explore the evolution of the oxidative characteristics (peroxide value, p -anisidine value, conjugated diene value), antioxidant capacity (DPPH and ABTS assays), fatty acids, bioactive compounds (tocopherols, squalene, carotenoids and phytosterols) and free radicals in hazelnut oil during accelerated oxidation for 40 days. After 25 days of oxidation, hazelnut oil entered a highly oxidative state; as radicals began to be heavily generated, the antioxidant capacity decreased significantly. The contents of tocopherols, squalene, carotenoids, linoleic and linolenic acid were significantly reduced, which was significantly negatively correlated with the oxidative degree of hazelnut oil. In addition, electron spin resonance (ESR), which is an effective nondestructive method of measuring radicals, could be used online to detect the oxidative degree of hazelnut oil. Carotenoids and tocopherols play important roles and may be provide effective selection of the natural antioxidants to prevent hazelnut oil oxidation. • Comprehensive understanding quality of hazelnut oil during the oxidation process. • ESR technique can as a nondestructive method of measuring oxidation in hazelnut oil. • Fatty acid composition of hazelnut oil was identified precisely by GC × GC-TOF/MS. • PLS models was useful application for understanding the oxidation evolution. [ABSTRACT FROM AUTHOR]