Characterization of the Volatile Compounds in Camellia oleifera Seed Oil from Different Geographic Origins

The scent of time: Analyzing the differences in volatile organic compounds of camellia oleifera oil with different oil-tea tree ages using GC-IMS and GC-MS

Camellia oleifera oil (CO) is renowned in China for its exceptional nutritional benefits and distinctive aroma. The aroma of old CO from oil-tea tree ages over 30 years differs markedly from that of young CO aged below 8 years. However, the volatile organic compounds (VOCs) and aroma characteristics of CO from oil-tea tree at different ages remain unclear. This study identified 82 VOCs using GC-IMS and 112 VOCs using GC-MS. PCA, PLS-DA, correlation analysis, and VIP values revealed distinct VOC profiles between CO obtained from young and old oil-tea tree. The principal characteristic VOCs of CO from young oil-tea tree (4 and 8 years) were 3-methyl-3-buten-1-ol (sweet fruit) and 3-methylbutyl propanoate (apple, apricot, and pineapple). Moreover, the predominant characteristic VOCs of CO from old oil-tea tree (30, 40, and 50 years) were 4-methyl-2-pentanol (pungent), butyl acetate (apple and banana), limonene (lemon and orange), and 2-ethyl-6-methylpyrazine (green, nuts, and roasted).

Assembly and analysis of the first complete mitochondrial genome sequencing of main Tea-oil Camellia cultivars Camellia drupifera (Theaceae): revealed a multi-branch mitochondrial conformation for Camellia

BACKGROUND

Tea-oil Camellia within the genus Camellia is renowned for its premium Camellia oil, often described as "Oriental olive oil". So far, only one partial mitochondrial genomes of Tea-oil Camellia have been published (no main Tea-oil Camellia cultivars), and comparative mitochondrial genomic studies of Camellia remain limited.

RESULTS

In this study, we first reconstructed the entire mitochondrial genome of C. drupifera to gain insights into its genetic structure and evolutionary history. Through our analysis, we observed a characteristic multi-branched configuration in the mitochondrial genomes of C. drupifera. A thorough examination of the protein-coding regions (PCGs) across Camellia species identified gene losses that occurred during their evolution. Notably, repeat sequences showed a weak correlation between the abundance of simple sequence repeats (SSRs) and genome size of Camellia. Additionally, despite of the considerable variations in the sizes of Camellia mitochondrial genomes, there was little diversity in GC content and gene composition. The phylogenetic tree derived from mitochondrial data was inconsistent with that generated from chloroplast data.

CONCLUSIONS

In conclusion, our study provides valuable insights into the molecular characteristics and evolutionary mechanisms of multi-branch mitochondrial structures in Camellia. The high-resolution mitogenome of C. drupifera enhances our understanding of multi-branch mitogenomes and lays a solid groundwork for future advancements in genomic improvement and germplasm innovation within Tea-oil Camellia.

Comprehensive analysis of the effects of the traditional stir-fry process on the dynamic changes of volatile metabolites in Hainan camellia oil

The traditional stir-fry process before pressing is crucial to manufacture Hainan camellia oil. To assess the effects of the stir-fry process on Hainan camellia oil, six samples across different stir-fry stages were analyzed. The stir-fry process modified odors, volatile metabolite profiles, and human health-promoting functions of Hainan camellia oil. Totally, 350 volatile metabolites were detected, and heterocyclic compounds were revealed as the main contributors of strong aroma. Potential indicators for monitoring the stir-fry degree were established. Eight key aroma volatile metabolites were identified, including three new ones (1-octen-3-one, 2,3-butanedione, and vanillin). Lipids degradation and the Millard reaction are probably the main pathways for aroma generation. Over-stir-fry treatment diminished the contents of some important volatile metabolites but increased the risk of arising burnt odor. Our work offered insights into the effects of the stir-fry process and over-stir-fry treatment on Hainan camellia oil, which is meaningful for improving the hot-pressing technique.

Unraveling the Metabolomics Mysteries in Camellia Oil: From Cognition to Application

Camellia oil is a high-value edible seed oil, recommended by the Food and Agriculture Organization (FAO). It is essential to develop accurate and rapid analytical methods to authenticate camellia oil due to its susceptibility to adulteration. Recently, hyphenated chromatography-mass spectrometry, especially high-resolution mass spectrometry using chemometrics, has become a promising platform for the identification of camellia oil. Based on the compositional analysis, the fatty acid, sterol, phenol, and tocopherol profiles (or fingerprints) were utilized as predictor variables for assessing authenticity. The review systematically summarizes the workflow of chromatography-mass spectrometry technologies and comprehensively investigates recent metabolomic applications combined with chemometrics for camellia oil authentication. Metabolomics has significantly improved our understanding of camellia oil composition at the molecular level, contributing to its identification and full characterization. Hence, its integration with standard analytical methods is essential to enhance the tools available for public and private laboratories to assess camellia oil authenticity. Integrating metabolomics with artificial intelligence is expected to accelerate drug discovery by identifying new metabolic pathways and biomarkers, promising to revolutionize medicine.

A Comparative Study on the Characteristics of Different Types of Camellia Oils Based on Triacylglycerol Species, Bioactive Components, Volatile Compounds, and Antioxidant Activity

This study aimed to investigate the characteristics of different varieties of camellia oils and their diacylglycerol (DAG)-enriched derivatives in terms of triacylglycerol (TAG) species, bioactive components, volatile compounds, and antioxidant activity. Six types of camellia oils, including C. oleifera (C.O), C. semiserrata (C.S), C. gauchowensis (C.G), along with commercially refined C. oleifera oil (C-C.O) and its DAG-enriched counterparts (at 40% and 80% enrichment), were analyzed and compared. Unique patterns of TAG profiles, fatty acid distributions on different glycerol backbones, tocopherol, squalene, total polyphenols, and volatile compounds were observed, suggesting that these characteristics can be utilized as a criterion to differentiate them. DAG-enriched oils exhibited increased levels of unsaturated fatty acids (UFAs) compared to C-C.O, albeit with decreased contents of tocopherol, squalene, and total polyphenols. Moreover, diverse volatile compounds were identified across all types of camellia oils, among which the DAG-enriched oils had distinct distribution characteristics compared with their crude oils, indicating the influence of the enrichment process on volatile compounds. Furthermore, DAG-enriched oils demonstrated reduced antioxidant activity abilities compared to their counterparts, with the highest activity observed in C.O, followed by C.G. Additionally, strong correlations were observed between antioxidant activity and tocopherol, as well as squalene content.

Genome-wide identification and molecular evolution of Dof gene family in Camellia oleifera

DNA binding with one finger(Dof) gene family is a class of transcription factors which play an important role on plant growth and development. Genome-wide identification results indicated that there were 45 Dof genes(ColDof) in C.oleifera genome. All 45 ColDof proteins were non-transmembrane and non-secretory proteins. Phosphorylation site analysis showed that biological function of ColDof proteins were mainly realized by phosphorylation at serine (Ser) site. The secondary structure of 44 ColDof proteins was dominated by random coil, and only one ColDof protein was dominated by α-helix. ColDof genes' promoter region contained a variety of cis-acting elements, including light responsive regulators, gibberellin responsive regulators, abscisic acid responsive regulators, auxin responsive regulators and drought induction responsive regulators. The SSR sites analysis showed that the proportion of single nucleotide repeats and the frequency of A/T in ColDof genes were the largest. Non-coding RNA analysis showed that 45 ColDof genes contained 232 miRNAs. Transcription factor binding sites of ColDof genes showed that ColDof genes had 5793 ERF binding sites, 4381 Dof binding sites, 2206 MYB binding sites, 3702 BCR-BPC binding sites. ColDof9, ColDof39 and ColDof44 were expected to have the most TFBSs. The collinearity analysis showed that there were 40 colinear locis between ColDof proteins and AtDof proteins. Phylogenetic analysis showed that ColDof gene family was most closely related to that of Camellia sinensis var. sinensis cv.Biyun and Camellia lanceoleosa. Protein-protein interaction analysis showed that ColDof34, ColDof20, ColDof28, ColDof35, ColDof42 and ColDof26 had the most protein interactions. The transcriptome analysis of C. oleifera seeds showed that 21 ColDof genes were involved in the growth and development process of C. oleifera seeds, and were expressed in 221 C. oleifera varieties. The results of qRT-PCR experiments treated with different concentrations NaCl and PEG6000 solutions indicated that ColDof1, ColDof2, ColDof14 and ColDof36 not only had significant molecular mechanisms for salt stress tolerance, but also significant molecular functions for drought stress tolerance in C. oleifera. The results of this study provide a reference for further understanding of the function of ColDof genes in C.oleifera.

Rapid and Low-Cost Quantification of Adulteration Content in Camellia Oil Utilizing UV-Vis-NIR Spectroscopy Combined with Feature Selection Methods

This study aims to explore the potential use of low-cost ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy to quantify adulteration content of soybean, rapeseed, corn and peanut oils in Camellia oil. To attain this aim, test oil samples were firstly prepared with different adulterant ratios ranging from 1% to 90% at varying intervals, and their spectra were collected by an in-house built experimental platform. Next, the spectra were preprocessed using Savitzky-Golay (SG)-Continuous Wavelet Transform (CWT) and the feature wavelengths were extracted using four different algorithms. Finally, Support Vector Regression (SVR) and Random Forest (RF) models were developed to rapidly predict adulteration content. The results indicated that SG-CWT with decomposition scale of 25 and the Iterative Variable Subset Optimization (IVSO) algorithm can effectively improve the accuracy of the models. Furthermore, the SVR model performed best for predicting adulteration of camellia oil with soybean oil, while the RF models were optimal for camellia oil adulterated with rapeseed, corn, or peanut oil. Additionally, we verified the models' robustness by examining the correlation between the absorbance and adulteration content at certain feature wavelengths screened by IVSO. This study demonstrates the feasibility of using low-cost UV-Vis-NIR spectroscopy for the authentication of Camellia oil.

Metabolomic profiles and health-promoting functions of Camellia drupifera mature-seeds were revealed relate to their geographical origins using comparative metabolomic analysis and network pharmacology approach

To insight into the chemical components and their health-promoting function of Camellia drupifera mature-seeds (CMS) in Hainan and Liangguang, UPLC-MS/MS- and HS-SPME/GC-MS-based metabolomic analyses and network pharmacology approaches were combined preformed to Camellia drupifera mature-seeds samples (CMSSs). Totally, 1057 metabolites were identified, of which 76 and 99 metabolites were annotated as key active ingredients in Traditional Chinese Medicines and the active pharmaceutical ingredients for seven human disease-resistance, respectively. Comparative analysis revealed different metabolomic profiles of CMSSs from Hainan and Liangguang. KEGG annotation and enrichment analysis showed secondary metabolic pathways, especially "flavone and flavonol biosynthesis", were played important roles. Finally, 22 metabolites that only detected in CMSSs from Hainan or Liangguang were explored as potential indicators to separate CMS from Hainan out of Liangguang. Our findings enhanced the understanding of chemical compositions of CMS and provided valuable information for the healthy development of oil-tea Camellia industry in Hainan.

Typical Characterization of Commercial Camellia Oil Products Using Different Processing Techniques: Triacylglycerol Profile, Bioactive Compounds, Oxidative Stability, Antioxidant Activity and Volatile Compounds

The processing technique is one of the key factors affecting the quality of camellia oil. In this study, camellia oils were obtained using four different processing techniques (cold-pressed, roast-pressed, fresh-pressed, and refined), and their triacylglycerols (TAGs) profile, bioactive compound (tocopherols, sterols, squalene, and polyphenols) level, oxidative stability, and volatile compounds were analyzed and compared. To further identify characteristic components in four camellia oil products, the TAG profile was analyzed using UPLC-QTOF-MSE. Five characteristic markers were identified, including OOO (m/z 902.8151), POL (m/z 874.7850), SOO (m/z 904.8296), PPL (m/z 848.7693), PPS (m/z 852.7987). Regarding the bioactive compound level and antioxidant capacity, the fresh-pressed technique provided higher α-tocopherols (143.15 mg/kg), β-sitosterol (93.20 mg/kg), squalene (102.08 mg/kg), and polyphenols (35.38 mg/kg) and showed stronger overall oxidation stability and antioxidant capacity. Moreover, a total of 65 volatile compounds were detected and identified in four camellia oil products, namely esters (23), aldehydes (19), acids (8), hydrocarbons (3), ketones (3), and others (9), among which pressed oil was dominated by aldehydes, acid, and esters, while refined oil had few aroma components. This study provided a comprehensive comparative perspective for revealing the significant influence of the processing technique on the camellia oil quality and its significance for producing camellia oil of high quality and with high nutritional value.

Extraction of Oils and Phytochemicals from Camellia oleifera Seeds: Trends, Challenges, and Innovations

Camellia seed oil, extracted from the seeds of Camellia oleifera Abel., is popular in South China because of its high nutritive value and unique flavor. Nowadays, the traditional extraction methods of hot pressing extraction (HPE) and solvent extraction (SE) are contentious due to low product quality and high environmental impact. Innovative methods such as supercritical fluid extraction (SCFE) and aqueous extraction (AE) are proposed to overcome the pitfalls of the traditional methods. However, they are often limited to the laboratory or pilot scale due to economic or technical bottlenecks. Optimization of extraction processes indicates the challenges in finding the optimal balance between the yield and quality of oils and phytochemicals, as well as the environmental and economic impacts. This article aims to explore recent advances and innovations related to the extraction of oils and phytochemicals from camellia seeds, and it focuses on the pretreatment and extraction processes, as well as their complex effects on nutritional and sensory qualities. We hope this review will help readers to better understand the trends, challenges, and innovations associated with the camellia industry.

The specific DNA barcodes based on chloroplast genes for species identification of Theaceae plants

More than 600 species in over 40 genera have been identified in family Theaceae worldwide. The accurate identification of Theaceae plants can ensure the market economic order, and it plays a vital role in achieving the sustainable utilization of germplasm resources. DNA barcoding, one of the most potential species identification technologies at present, has advanced in the rapid, accurate and repetitive discrimination of species. In this study, matK + ndhF + ycf1 was observed as the optimal combined candidate gene sequence of DNA barcodes by analyzing genetic information of four single chloroplast DNA sequences, including matK, rbcL, ndhF and ycf1, as well as six combined gene sequences. Subsequently, the experiments were performed on phylogenetic analysis based on genetic distance to study the phylogenetic relationship of Theaceae plants and evaluate the species identification accuracy of matK + ndhF + ycf1. Lastly, the species-specific DNA barcodes were designed by searching the variable sites (one type of single nucleotide polymorphism sites) for the accurate identification of Camellia amplexicaulis, Franklinia alatamaha, Gordonia brandegeei and Stewartia micrantha. The previous methods of screening and testing candidate gene sequences were optimized, and innovation was made in the above methods. The process of making visual DNA barcodes was standardized. Besides, DNA barcoding technology increased the accuracy of species identification and DNA barcoding was analyzed in accordance with the theories of population genetics (e.g., neutral theory of molecular evolution). The results of the study will lay a basis for the identification and protection of Theaceae species and germplasm resources.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-022-01175-7.