Olga (Olya) Vvedenskaya
Sci. Communications Officer
Dr. Dr. Olya Vvedenskaya studied medicine, and further obtained her PhD in the field of molecular oncology. She loves to deliver scientific messages in a clear and accessible manner.
• Cold-pressed seed oils are often adulterated
• Camelina, flax, and hemp seed oils have distinct lipid profiles
• These profiles could be used to identify oil composition alterations
Olga (Olya) Vvedenskaya
Sci. Communications Officer
Dr. Dr. Olya Vvedenskaya studied medicine, and further obtained her PhD in the field of molecular oncology. She loves to deliver scientific messages in a clear and accessible manner.
Lipids are an essential part of our diet, as they are a source of energy, essential fatty acids, and fat-soluble vitamins (A, D, E, K). Lipids are found in many foods we consume daily, and the total amount of lipids is typically listed on the food package. Some foods are high in lipid content, while others have lower fat content. Lipids themselves vary greatly, and while some serve mainly as energy sources, others, like vitamins and certain fatty acids, are essential for other aspects of our metabolism and are main components (or main building block) of our cells (or cell membranes) and our body.
As interest in vegetable oils grows globally, so does the risk of adulteration. That means that oil producers adjust oil lipid compositions and partially substitute high-quality oils with low-quality oils, and also mix cold-pressed oils with refined oils. Detecting adulteration typically involves measuring the amounts and ratios of certain components like triglycerides (TAGs) and fatty acids (FAs). However, accurately profiling TAGs in oils is difficult because they have very similar properties and come in many varieties, with numerous different fatty acids.
DAG and TAG lipid species in cold-pressed seed oils were categorized based on their molecular composition, indicated as the sum of carbon atoms in the hydrocarbon moiety and the sum of double bonds in the hydrocarbon moiety (for example, TAG 52:4, DAG 36:3). However, the detailed composition by the identification of the FA esterified in TAG is essential for identity and nutritional quality, yet remains a major challenge. Moreover, for DAGs, both individual molecules (for instance, DAG 18:1/18:2) and molecular groups (for instance, DAG 36:3) were available.
Number of TAG and DAG lipid species detected in the plant oil samples. The bottom line shows the number of DAGs with exact acyl moieties detected, identified, and quantified in camelina, flax, and hemp oils.
Nikolaichuk et al., Molecules 2022, 27(6), 1848; 10.3390/molecules27061848
In comparison to flax and hemp seed oils, camelina oil had lower amounts of MUFAs and PUFAs in DAGs. In terms of the double bond content, hemp seed oil had the highest amount of DAGs with four double bonds, and flax seed oil had the highest amount of DAGs with six double bonds.
PUFA content in TAGs of all the analyzed in this study oils was much higher than MUFA content. The highest concentration of TAGs with two, three, and five double bonds was detected in camelina seed oil. Camelina seed oil also had the lowest content of DAGs with 34 and 36 carbons and the highest content of DAGs containing 38 carbons. Interestingly, only flax seed oil contained DAGs with 32 carbons. Finally, TAGs with 54 carbons were the most abundant in all three analyzed oils.
Number of carbons in DAGs (left) and in TAGs (right) in camelina, flax, and hemp seed oils. Nikolaichuk et al., Molecules 2022, 27(6), 1848; 10.3390/molecules27061848
To evaluate the discriminatory potential of DAG and TAG profiles and determine the level of characterization needed for successful classification, principal component analysis (PCA) models were constructed.
The PCA models showed that clear separation among camelina, flax, and hemp seed oil samples is possible based on both datasets. This indicates the high potential of lipidomic profiles for classification and discrimination purposes.
PCA plots of the oil lipidomes. A based on TAG and DAG lipid species (the sum of carbon atoms in the hydrocarbon moiety and the sum of double bonds in the hydrocarbon moiety), B based on TAG (the sum of carbon atoms in the hydrocarbon moiety and the sum of double bonds in the hydrocarbon moiety) and DAG (with the information about exact fatty acid composition) lipid species.
Nikolaichuk et al., Molecules 2022, 27(6), 1848; 10.3390/molecules27061848
These findings indicate that rapid and straightforward mass spectrometry shotgun lipidomics analysis, coupled with data processing, can effectively distinguish camelina, flax, and hemp seed oils based on their unique lipid composition. Samples of the same oil type consistently clustered together in various parts of the PCA space, regardless of the level of detail in TAG and DAG characterization.
Camelina seed oil displayed distinct patterns in its DAGs (36:X) and TAGs (56:X, 58:X, and 60:X), which serve as markers for identifying camelina seed oil. Hemp seed oil had high levels of DAG 34:2, DAG 36:4, and DAG 36:5, while flax seed oil showed high levels of DAG 36:3 and DAG 36:6. Moreover, specific markers unique to each oil type were identified, such as DAG 32:3 for flax seed oil, DAG 38:4 for camelina seed oil. These markers contribute to the precise identification of each oil type.
Potential differentiation markers in camelina, hemp, and flax oils. A Potential DAG markers, B Potential DAG differentiation markers.
Nikolaichuk et al., Molecules 2022, 27(6), 1848; 10.3390/molecules27061848
The study showed that identifying each seed oil based on the DAG or TAG lipid profiles is achievable. In each instance, multivariate data analyses resulted in clear classification and differentiation of the oils.
Distinctive lipid markers were pinpointed, which could be utilized in developing specific methods for oil testing. However, using particular lipid markers should be addressed with caution. For example, DAG composition of plant oils heavily depends on processing and could be artifactual in some cases. Nonetheless, using shotgun lipidomic analysis for oil quality control proves to be a potent analytical tool applicable to oil authentication, and managing the complexity of data processing can be easily addressed by establishing lists of targets.
Lipotype Lipidomics technology provides support to food researchers by offering advanced lipid analysis tools, enabling comprehensive exploration of food composition and its impact on human health.
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