Journal of the American Oil Chemists Society最新文献

Accurate shelf-life prediction for fats and oils is essential, yet traditional lipid oxidation models are often time-consuming and unreliable. Since antioxidants deplete as oxidation progresses, tracking their loss alongside oxidation products could improve lag phase predictions. This study investigates a rapid, cost-effective spectrophotometric test to quantify antioxidant depletion in soybean and corn oils for potential use in mathematical modeling. Results showed that α-tocopherol was fully degraded by the end of the oxidation lag phase, while (γ + β)- and δ-tocopherols concentrations remained at > 70% (soybean oil) and 65% (corn oil). DPPH scavenging activity initially declined with tocopherol loss but later increased (up to 79%), likely due to lipid radical interference. Further analysis confirmed DPPH reacts with free radicals, compromising its specificity to only detecting antioxidants. To address this, the ABTS assay was tested, requiring prior antioxidant extraction from oil due to its water-soluble nature. Unlike DPPH, ABTS inhibition dropped to zero once all tocopherols were depleted, confirming its higher specificity. However, this depletion did not align with the oxidation lag phase, as (γ + β)- and δ-tocopherols were not completely depleted at the end of the lag phase. These findings highlight three key insights: (i) (γ + β)- and δ-tocopherols are less effective than α-tocopherol in inhibiting lipid oxidation in commercial oils, persisting even after oxidation begins; (ii) the direct application of DPPH in lipid-containing matrices can yield misleading results, as it reacts with lipid radicals during oxidation; (iii) while ABTS specifically tracks antioxidant depletion, it might be unsuitable for kinetic modeling due to minimal change during the lag phase.

This study evaluated the contents of tocopherols and plastochromanol-8, as well as the acid values, in oils extracted from yellow-seeded Brassica napus L. lines stored under adverse post-harvest conditions. Seeds were stored at temperatures of 25°C and 30°C, with adjusted seed moisture contents of 10.5%, 12.5%, and 15.5%, corresponding to relative humidity levels of 81%, 85%, and 91%, respectively. A statistically significant reduction in total tocopherol content—up to 22% (p < 0.05)—was observed in seeds with the highest moisture content (15.5%) stored at 30°C. In contrast, seeds with 12.5% moisture stored at 25°C exhibited a smaller but still significant decrease of 11%–14% (p < 0.05). The lowest tocopherol degradation (2%–5%) occurred in seeds with 10.5% moisture stored at 25°C. Additionally, degradation rates differed between tocopherol homologues: α-tocopherol decreased more rapidly than γ-tocopherol, as evidenced by a significant decline in the α-T/γ-T ratio under high-moisture and high-temperature conditions. The most pronounced reduction in this ratio was recorded in seeds stored with 15.5% moisture at 30°C. Plastochromanol-8 was also highly sensitive to storage parameters, exhibiting an even more pronounced reduction than tocopherols under high-moisture conditions (p < 0.05). A significant increase in acid value was also observed under high temperature and moisture conditions, exceeding the acceptable threshold of 3.0 mg KOH/g in some cases, indicating advanced lipid hydrolysis during storage.

Lipase selectivity is a key factor in determining the efficiency, specificity, and applicability of lipases in various industrial processes. It is also a significant aspect in the theoretical understanding of enzymatic reactions and the design of improved biocatalysts through protein engineering. This paper presents a comprehensive review of strategies employed in conformational engineering and the selection of reaction media to modulate the selectivities of lipases. It examines various factors that influence conformational engineering, such as organic solvents, pH levels, ionic liquids, reaction temperatures, additives, and immobilization techniques. Additionally, the review analyzes the impact of reaction media, including the use of organic solvents, supercritical fluids, and ionic liquids and the means of energy transfer (microwave irradiation) on selectivity. Special emphasis is placed on the modulation of product selectivity in glycerolysis reactions by using ionic liquids as the reaction media. This review aims to provide insights for the design of enzymatic selective catalysis mediated by lipases and to lay the groundwork for understanding the mechanisms of selective catalysis at the molecular structural level. By exploring these strategies and their effects on lipase selectivity, the paper contributes to the advancement of more efficient and targeted enzymatic processes in various industrial applications.

Novel structured lipids (SLs) were successfully produced from virgin coconut oil (VCO) and docosahexaenoic acid (DHA) and/or eicosapentaenoic acid (EPA). Stereospecific analysis results indicated that both DHA and EPA were predominantly esterified at the sn-1 and sn-3 positions. For DHA-enriched VCO, caprylic acid (CyA, C8:0) was mainly esterified at the sn-2 position, while capric acid (CaA, C10:0) and lauric acid (LaA, C12:0) were primarily located at the sn-3 position. In EPA and DHA + EPA-enriched VCO, C8:0 and C10:0 were almost randomly distributed across all three positions, except for C12:0, which was mostly found at the sn-2 position. The oxidative stability results of the SLs showed higher levels of conjugated dienes (CD) and 2-thiobarbituric acid reactive substances (TBARS) after 12 days of storage. Furthermore, the primary volatile compounds identified in the SLs using headspace gas chromatography–mass spectrometry (HS GC–MS) included acetaldehyde, propanal, and 2-propenal (acrolein), which were absent in the unmodified oils. These results indicate that the modified oils exhibited a higher susceptibility to oxidation compared to their unmodified counterparts. Oils high in polyunsaturated fatty acids (PUFAs) require protection from oxidation to mitigate the detrimental effects of oxidation products and preserve their nutritional and health benefits.

Nervonic acid (NA), a very long-chain monounsaturated fatty acid with critical roles in neurological health and brain development, has garnered increasing interest for microbial production via metabolic engineering. Previously, the laboratory constructed a recombinant strain using Rhodosporidium toruloides as the chassis, which is capable of synthesizing NA. However, the lack of systematic medium optimization remains a major bottleneck for enhancing NA titers in the engineered strains. This study aimed to develop an economical and efficient fermentation medium for NA biosynthesis using the engineered strain in shake-flask cultures. Through one-factor-at-a-time optimization, glucose and corn steep liquor (CSL) were identified as the optimal carbon and organic nitrogen sources, respectively. Further analysis revealed that precise concentrations of glucose (120 g/L), CSL (10 g/L), and ammonium sulfate (1.1 g/L) were critical for balancing cell growth and lipogenesis. Notably, inorganic salts (CaCl₂, MgSO₄·7H₂O, KH₂PO₄) were dispensable in the presence of CSL, which inherently supplied essential trace elements. Maintaining the initial pH at its natural value (4.3) proved optimal, as artificial pH adjustments severely impaired lipid accumulation. Under the optimized conditions, the NA titer reached 7.5 g/L, representing a 29.3% increase over the initial medium (5.8 g/L) and establishing the highest reported shake-flask titer for microbial NA production. This work not only provides a cost-effective medium formulation by eliminating inorganic salts and utilizing low-cost CSL but also offers strategic insights for scaling up NA biosynthesis in bioreactors. The findings underscore the importance of tailored nutrient optimization in aligning metabolic engineering advancements with bioprocess practicality.

The main challenge to the use of vegetable oils as green lubricants is their oxidative stability. In this work, biolubricants with efficient antioxidant properties have been specifically designed and synthesized with the aim of maximizing the oxidative stability of vegetable oils by combining biophenols (p-coumaric, ferulic, and sinapic acids) with epoxidized ring-opened soybean oil in a single molecule. The synthetic products were named OIS-ESO-PCA (epoxidized ring-opened soybean oil grafted with p-coumaric acid), OIS-ESO-FA (epoxidized ring-opened soybean oil grafted with ferulic acid), and OIS-ESO-SA (epoxidized ring-opened soybean oil grafted with sinapic acid), respectively. Biophenols improve biolubricant antioxidant properties, addressing energy, and environmental challenges. The modified samples were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). The free radical scavenging activity of the oil samples was evaluated using the DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) method and was found to be much higher than that of the soybean oil (SBO). The oxidation resistance and thermo-oxidative stability of the oil samples were evaluated based on pressure differential scanning calorimetry (PDSC), rotary bomb oxidation test (RBOT), and thermogravimetry (TGA). Compared with SBO, the oxidative induction time of OIS-ESO-PCA, OIS-ESO-FA, and OIS-ESO-SA increased by 118%, 296%, and 384%. The modified oils showed excellent antioxidant properties compared to the SBO. Therefore, biophenolic acid can be effectively used to improve the antioxidant properties of vegetable oils.

Petroleum-based lubricants commonly used in machinery pose environmental risks due to their non-biodegradable and non-renewable nature. Switching to sustainable alternatives based on non-edible oils instead of conventional lubricants is a viable approach to mitigate environmental conflicts. The present study aims to assess the suitability of Madhuca indica seed oil (Mahua oil) as a feedstock for environmentally friendly lubricants. Chemical modifications, specifically transesterification and epoxidation, were conducted on Mahua oil, and its lubricant properties were compared with that of a commercial lubricant. The study covers various aspects such as physicochemical, thermal, oxidative, rheological, and tribological properties. SiO₂ nanoparticles are also incorporated into the oil samples to study the resulting changes in tribological properties. Results show significant improvements in chemical stability and performance: acid and peroxide values decreased considerably post-modification, and epoxidized Mahua oil (EMO) demonstrated superior thermal stability and tribological performance. With nanoparticle addition, the coefficient of friction (COF) and wear scar diameter (WSD) were reduced by 39.1% and 8.87%, respectively, indicating enhanced lubrication compared to unmodified Mahua oil. Both modified oils exhibited higher viscosity indices than the commercial fluid. These findings highlight that Epoxidation is more advantageous for chemically modifying vegetable oils, while transesterification proves particularly effective with oils high in free fatty acids. The resulting chemically modified Mahua oils show promising potential as alternatives to their petroleum-based counterparts.

The present work is devoted to studying the regularities of synthesis and decomposition of hydroperoxides of methyl esters of fatty acids. Fatty acid methyl esters of sunflower oil were used as raw material. In the case of non-catalytic oxidation at 70°C, the maximum concentration of hydroperoxides is observed (~45 wt.%), but 14 h of synthesis are required to achieve it. The use of N-hydroxyphthalimide as a catalyst makes it possible to reduce the reaction time to 8 h without affecting the yield of hydroperoxides. In turn, the results of studying the decomposition of hydroperoxides in the temperature range of 90°C–170°C demonstrate the presence of an unusual temperature dependence of the process activation energy. Upon passing to elevated temperatures, from approximately 120°C, a decrease in the activation energy of the process is observed from 83.6 to 35.8 kJ/mol, which means the transition of the process to the region of entropy control, in which the decomposition of hydroperoxides is preceded by the formation of hydrogen bonds of hydroperoxide molecules with each other and/or with other components of the reaction mixture.