Oxidative stability of algal oils as affected by their minor components

Investigation of the influence of minor components and fatty acid profile of oil on properties of beeswax and stearic acid-based oleogels

Understanding the impact of minor components and the fatty acid profile of oil on oleogel properties is essential for optimizing their characteristics. Considering the scarcity of literature addressing this aspect, this study aimed to explore the correlation between these factors and the properties of beeswax and stearic acid-based oleogels derived from rice bran oil and sesame oil. Minor oil components were modified by stripping the oil, heating the oil with water, and adding β-sitosterol. Oleogels were then prepared using a mixture of beeswax and stearic acid (3:1, w/w) at a concentration of 11.74 % (w/w). The properties of oils and oleogels were evaluated. The findings indicated that minor components and fatty acid composition of the oils substantially influence the oleogel properties. Removing minor components by stripping resulted in smaller and less uniformly distributed crystals and less oil binding capacity compared to the oleogels prepared from untreated oils. A moderate amount of minor components exhibited a significant influence on oleogel properties. The addition of β-sitosterol did not show any influence on oleogel properties except for the oleogel made from untreated oil blend added with β-sitosterol which had more uniform crystals in the microstructure and demonstrated better rheological stability when stored at 5 °C for two months. The oil composition did not show any influence on the thermal and molecular properties of oleogels. Consequently, the oleogel formulation derived from the untreated oil blend enriched with β-sitosterol was identified as the optimal formula for subsequent development. The findings of this study suggest that the physical and mechanical properties as well as the oxidative stability of beeswax and stearic acid-based oleogels are significantly affected by the minor constituents and fatty acid composition of the oil. Moreover, it demonstrates that the properties of oleogels can be tailored by modifying oil composition by blending different oils.

Vitamin E as an essential micronutrient for human health: Common, novel, and unexplored dietary sources

Vitamin E comprises a group of vitamers that includes tocopherols and tocotrienols. They occur in four homologues according to the number and position of methyl groups attached to the chromanol ring. Vitamin E, a liposoluble antioxidant, may participate as an adjuvant in the prevention and treatment of cardiovascular, neurological, and aging-related diseases. Furthermore, vitamin E has applications in the food industry as a natural additive. In this contribution, the most recent information on the dietary sources of vitamin E, including common, novel, and unexplored sources, is presented. Common edible oils, such as those of corn, olive, palm, rice bran, and peanut, represent the most prominent sources of vitamin E. However, specialty and underutilized oils such as those obtained from tree nuts, fruit seeds, and by-products, emerge as novel sources of this important micronutrient. Complementary studies should examine the tocotrienol content of vitamin E dietary sources to better understand the different biological functions of these vitamers.

Quality assessment of large yellow croaker (Larimichthys crocea) roe oil before and after refining

This research aimed to assess the quality of the large yellow croaker (Larimichthys crocea) roe oil before and after refining.

Compositional characteristics and oxidative stability of chia seed oil (Salvia hispanica L)

Abstract

Fatty acid composition and triacylglycerols (TAG) profile of chia seed oil were determined. The main fatty acids present in the tested oil were α-linolenic acid (Ln, 61.1%) > linoleic acid (L, 16.6%) > palmitic acid (P, 6.7%) > oleic acid (O, 6.0%) > stearic acid (S, 3.2%). Five major triacylglycerols in chia oil were LnLnLn, LnLLn, LnLnP, LnOLn, and LLLn and these contributed more than 76% to the total. The oxidative stability under autoxidative and photooxidative conditions before and after the removal of their minor components was also determined. In addition, tocols, chlorophylls and carotenoids were measured in the oil. Oil samples were stripped of their minor components by using a facile silicic acid and charcoal in one pot rather than in a column. Storage under Schaal oven condition and photooxidation were also monitored for both crude oil (non-stripped) and stripped oil using stationary phase material. Total tocopherol contents were in the order of β−/γ- 282.68, δ- 47.44, and α-tocopherols 10.94 mg/kg of oil. Stripping removed all the minor components including tocopherols, chlorophylls and carotenoids. Oxidative stability of the tested seed oil was primarily affected by its composition of fatty acids, triacylglycerols, minor components, and storage conditions.

Graphical abstract

A robust stripping method for the removal of minor components from edible oils

Abstract

Column chromatographic techniques have commonly been used for effective stripping of edible oils from their minor components. However, this method is time consuming, which may lead to oil oxidation. Thus, in the present study, the oils of camelina seed, chia seed, sophia seed, corn, olive, and a docosahexaenoic acid single cell oil (DHASCO) were subjected to a simplified stripping method by using the stationary phase material and examining their minor components such as tocopherols, carotenoids, and chlorophylls as well as their oxidative stability. The results demonstrated that stripped oils prepared by using the simplified stripping method for 2 h were devoid of any tocopherol, chlorophylls and carotenoids and this was as effective as column chromatographic method. Thus, the simplified stripping method provides a facile means of producing stripped oil with better oxidative stability compared to the column chromatographic method.

Graphical abstract

Lipase-catalysed synthesis of palm oil-omega-3 structured lipids

In this work, Candida antarctica lipase A was applied to selectively remove saturated fatty acids from palm oil to prepare palm oil acylglycerol concentrate (POAC), where palmitic acid decreased from 40.0 to 28.7% and oleic acid increased from 40.0 to 50.5% after 3 h of hydrolysis. Lipozyme RMIM from Rhizomucor miehei was then used to incorporate either alpha linolenic acid (ALA) or eicosapentaenoic acid (EPA) into the resulting POAC. Optimum omega-3 incorporation was achieved when POAC to omega-3 ratio was 6 : 3, reaction temperature was 40 °C and reaction time was 18 h. Under these conditions, the ALA content in the separated ALA incorporated structured lipid (POAC-ALA) was 27.1%, and the EPA content in the EPA incorporated structured lipids (POAC-EPA) was 30.9%. The formed structured lipids had lower levels of saturated fatty acids, and significantly lower melting points, in both cases below 8 °C. The enzymatic process developed produces new structured lipids, with lower saturated fat and higher omega-3, with potential as a healthy palm oil derived lipid ingredient.

Chemical Characteristics of Cold-Pressed Blackberry, Black Raspberry, and Blueberry Seed Oils and the Role of the Minor Components in Their Oxidative Stability

The chemical characteristics of cold-pressed blackberry, black raspberry, and blueberry seed oils were evaluated for their fatty acid composition, positional distribution of fatty acids, triacylglycerol (TAG) profile, and minor component profile. The role of minor components, including tocols and pigments, on the oxidative stability was also investigated using high-temperature- and fluorescent-lighting-induced oxidation before and after tested berry seed oils were stripped of their minor components. The results indicated that all tested berry seed oils contained significant levels of palmitic (C16:0), stearic (C18:0), oleic (18:1), linoleic (C18:2ω-6), and α-linolenic (C18:3ω-3) acids, along with a favorable ratio of ω-6/ω-3 fatty acids (1.49-3.86); palmitic, stearic, oleic, and α-linolenic acids were predominantly distributed on the terminal positions. Six TAGs, namely, LnLnLn, LnLLn, LLLn, LLL, OLL, and OLLn, were the major species detected in the tested berry seed oils. Total tocol contents were 286.3-1302.9 mg/kg, which include α-, γ-, and δ-tocopherols as well as δ-tocotrienol. Oxidative stability of the three berry seed oils was compromised after the removal of tocols under high-temperature-induced oxidation, while the loss of pigments (chlorophylls) led to weak oxidative stability when exposed to fluorescent lights.

Biosynthetic production of universally (13)C-labelled polyunsaturated fatty acids as reference materials for natural health product research

Long-chain polyunsaturated fatty acids (LCPUFA) including eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have become important natural health products with numerous proven benefits related to brain function and cardiovascular health. Not only are omega-3 fatty acids available in a plethora of dietary supplements, but they are also increasingly being incorporated as triglycerides into conventional foods, including bread, milk, yoghurt and confectionaries. Recently, transgenic oil seed crops and livestock have been developed that enhance omega-3 fatty acid content. This diverse array of matrices presents a difficult analytical challenge and is compounded further by samples generated through clinical research. Stable isotope (13)C-labelled LCPUFA standards offer many advantages as research tools because they may be distinguished from their naturally abundant counterparts by mass spectrometry and directly incorporated as internal standards into analytical procedures. Further, (13)C-labelled LCPUFAs are safe to use as metabolic tracers to study uptake and metabolism in humans. Currently, (13)C-labelled LCPUFAs are expensive, available in limited supply and not in triglyceride form. To resolve these issues, marine heterotrophic microorganisms are being isolated and screened for LCPUFA production with a view to the efficient biosynthetic production of U-(13)C-labelled fatty acids using U-(13)C glucose as a carbon source. Of 37 isolates obtained, most were thraustochytrids, and either DHA or omega-6 docosapentaenoic acid (22:5n-6) were produced as the major LCPUFA. The marine protist Hyalochlorella marina was identified as a novel source of EPA and omega-3 docosapentaenoic acid (22:5n-3). As proof of principle, gram-level production of (13)C-labelled DHA has been achieved with high chemical purity ( >99%) and high (13)C incorporation levels (>90%), as confirmed by NMR and MS analyses. Finally, U-(13)C-DHA was enzymatically re-esterified to glycerol to yield a (13)C-labelled tridocosahexaenoin.