Oil/oxidative Stability Index Research Articles

Metabolic engineering of soybean seeds for enhanced vitamin E tocochromanol content and effects on oil antioxidant properties in polyunsaturated fatty acid-rich germplasm

Soybean seeds produce oil enriched in oxidatively unstable polyunsaturated fatty acids (PUFAs) and are also a potential biotechnological platform for synthesis of oils with nutritional omega-3 PUFAs. In this study, we engineered soybeans for seed-specific expression of a barley homogentisate geranylgeranyl transferase (HGGT) transgene alone and with a soybean γ-tocopherol methyltransferase (γ-TMT) transgene. Seeds for HGGT-expressing lines had 8- to 10-fold increases in total vitamin E tocochromanols, principally as tocotrienols, with little effect on seed oil or protein concentrations. Tocochromanols were primarily in δ- and γ-forms, which were shifted largely to α- and β-tocochromanols with γ-TMT co-expression. We tested whether oxidative stability of conventional or PUFA-enhanced soybean oil could be improved by metabolic engineering for increased vitamin E antioxidants. Selected lines were crossed with a stearidonic acid (SDA, 18:4Δ6,9,12,15)-producing line, resulting in progeny with oil enriched in SDA and α- or γ-linoleic acid (ALA, 18:3Δ9,12,15 or GLA, 18:3Δ6,9,12), from transgene segregation. Oil extracted from HGGT-expressing lines had ≥6-fold increase in free radical scavenging activity compared to controls. However, the oxidative stability index of oil from vitamin E-enhanced lines was ~15% lower than that of oil from non-engineered seeds and nearly the same or modestly increased in oil from the GLA, ALA and SDA backgrounds relative to controls. These findings show that soybean is an effective platform for producing high levels of free-radical scavenging vitamin E antioxidants, but this trait may have negative effects on oxidative stability of conventional oil or only modest improvement of the oxidative stability of PUFA-enhanced oil.

Antioxidant activity of Pistacia atlantica var mutica kernel oil and it's unsaponifiable matters.

In this research, antioxidant activity of Pistacia atlantica var mutica (a wild type of pistachio in Iran) kernel oil (PAKO) and unsaponifiable matters of kernel oil (UKO) were compared with those of sesame seed oil (SSO) and rice bran oil (RBO) as well as with their unsaponifiable matters (USO and UBO) and α-tocopherol (natural antioxidant) was selected as control. Also, some chemical properties such as (FRAP, DPPH radical-scavenging, rancimat and oven assays (peroxide value and carbonyl value) were assessed. The amount of unsaponifiable matters of studied oils was between 1.4 and 3.5%. The highest total phenolics was observed in SSO (1024mg/kg), followed by RBO, and PAKO was 174, and 75mg/kg, respectively. In DPPH radical-scavenging assay, the EC50 values of PAKO, SSO, RBO, UKO, USO, UBO, and α-tocopherol were determined as 38.9, 50, 48.4, 14, 12.7, 15.9 and 61.4mg/mL, respectively. In FRAP assay, the highest value was nominated for UKO (434mmol/L); followed by USO, UBO, PAKO, SSO, RBO and α-tocopherol (404, 357, 364, 298, 210 and 58mmol/L; respectively). Also, considering the results of oven test, the incorporation of UKO into pure sunflower oil resulted in the highest oxidative stability; followed by UBO, USO, PAKO, SSO, RBO and α-tocopherol. According to results of the rancimat test, the incorporation of unsaponifiable matters (UKO, USO, and UBO) resulted in the highest oil/oxidative stability index (OSI) in pure sunflower oil, followed by oils studied (PAKO, SSO, and RBO). According to results, UKO had the highest antioxidant activity, followed by USO, UBO, PAKO, SSO, RBO, and α-tocopherol.

Oxidative stability of purified common kilka (clupeonella cultiventris caspia) triacylglycerols as affected by the bene kernel and hull oils and their unsaponifiable matters.

Oxidative stability of purified common kilka (clupeonella cultiventris caspia) triacylglycerols as affected by the bene kernel and hull oils and their unsaponifiable matters.

Investigating Chemical Properties and Oxidative Stability of Kernel Oil from Pistacia khinjuk Growing Wild in Iran

AbstractIn this study in order to introduce a new vegetable oil, oxidative stability and chemical characteristics of Pistacia khinjuk kernel oil (PKKO) as compared with P. atlantica kernel oil (PAKO) and extra virgin olive oil (EVOO) were investigated. Oxidative stability of studied oils was considered based on the conjugated diene value (CDV), carbonyl value (CV) and oil/oxidative stability index (OSI) through an 8‐h thermal process at 170 °C. Also, chemical characteristics [fatty acid composition, unsaponifiable matter (USM), total tocopherols (TT), total phenolics (TP) and total sterols (TS), iodine value, saponification number and waxes] of these oils were analyzed. The ratio of polyunsaturated fatty acids to saturated fatty acids and the oxidizability (Cox) value of PKKO (1.14 and 2.78; respectively) were between those of PAKO (2.37 and 4.23; respectively) and EVOO (1.14 and 2.78; respectively). USM content of the three studied oils was between 1.1 and 1.51 %. TT and TP contents of PKKO (619.4 and 26.6 ppm) were lower than those of PAKO (845.33 and 75.22 ppm) and higher than those of EVOO (365.23 and 19.78 ppm). TS contents of PKKO, PAKO and EVOO were 2,500, 2,150 and 3,800 ppm, respectively. Oxidative stability data indicated that PKKO is the most resilient oil against lipid oxidation, followed by PAKO and EVOO. CDV significantly increased by the lowest speed for PKKO, followed by PAKO and EVOO. Increase of CV and reduction of OSI for PKKO, PAKO and EVOO were 29.2, 128 and 338.7 and 32.8, 67.9 and 79.3 %; respectively.

Antioxidant activity of the fractions separated from the unsaponifiable matter of bene hull oil

The unsaponifiable matter (USM) of bene hull oil were separated into hydrocarbons (7.3%), carotenes (7.1%), tocols (48.4%), linear and triterpenic alcohols (1.7%), methyl sterols (11.2%), sterols (6.2%), and triterpenic dialcohols (18.0%). Regardless hydrocarbons fraction, the whole USM and all fractions had the EC50 (mg/ml) value significantly lower than (USM, 0.99; tocols, 1.05; carotenes, 3.93; triterpenoids, 1.74–9.89) that of α-tocopherol (36.7). α-Tocopherol, the whole USM, and all fractions were able to increase significantly the stability of sunflower oil at 50°C, so that the highest stabilizing effect belonged to the USM fractions with no significant differences amongst them, followed by the whole USM and α-tocopherol. The sunflower oil had an OSI (oil/oxidative stability index) of 3.54h, which was considerably promoted by some of components (tocols, 4.35; hydrocarbons, 4.43h; USM, 4.5h; triterpenic alcohols, 5.1h; carotenes, 5.49h). The FRAP and DPPH tests showed nearly similar results.

Simultaneous monitoring of the conventional qualitative indicators during frying of sunflower oil

Deterioration of sunflower oil during a 32 h frying was studied by monitoring the levels of polar compounds (total content, TPC; triglyceride polymers, TGP; triglyceride dimmers, TGD; oxidised triglyceride monomers, oxTGM; diglycerides, DG; and free fatty acids, FFA), carbonyl value ( CV), oil/oxidative stability index ( OSI), and conjugated diene value ( CDV). The frying process increased the level of TPC in the oil from 2.8% to 28.9%. The TGP, TGD, oxTGM, DG, and FFA increased 186.5, 29.1, 6.1, 5.1, and 5.4 times, respectively. The CV, OSI, and CDV changed from 7.9 μmol/g, 2.7 h, and 10.6 mmol/l to 70.9 μmol/g, 1.2 h, and 61.6 mmol/l, respectively. The TPC or TGDP ( TGD + TGP) contents were significantly correlated with the CV, OSI, or CDV. Finally, it was recommended that the sunflower oil should be discarded at 10% TGDP, 20% TPC, or 44 mmol/l CDV.

The effect of commercial refining steps on the rancidity measures of soybean and canola oils

The effect of commercial refining steps on the peroxide value (PV), acid value (AV), carbonyl value (CV), total polar compounds (TPC) content, polar compounds distribution, and oil/oxidative stability index (OSI) of soybean and canola oils was studied. The PVs were changed during the different refining steps. The AVs significantly decreased after the neutralisation step. The CVs continuously increased during the refining steps. The marked decrease observed in the TPC contents after the neutralisation step was mainly due to the decrease in the content of free fatty acids (FFA) and oxidised triglyceride monomers (oxTGM) than in the content of the other polar compounds. On the contrary, the study showed more significant changes in diglycerides (DG) and triglyceride dimers (TGD) contents than in the FFA and oxTGM contents during the deodorisation step. The OSIs significantly decreased after the neutralisation step and indicated no considerable changes during the further refining steps.

Frying Stability of Canola Oil Blended with Palm Olein, Olive, and Corn Oils

AbstractThe fatty acid composition, peroxide value (PV), acid value (AV), iodine value (IV), total tocopherols (TT) content, and total phenolics (TP) content of canola oil (CAO), palm olein oil (POO), olive oil (OLO), corn oil (COO), and the binary and ternary blends of the CAO with the POO, OLO, and COO were determined. The blends were prepared in the volume ratios of 75:25 (CAO/POO, CAO/OLO, CAO/COO) and 75:15:10 (CAO/POO/OLO, CAO/POO/COO). The CAO and its blends were used to fry potato pieces (7.0 × 0.5 × 0.3 cm) at 180 °C. During the frying process, the total polar compounds (TPC) content, AV, oil/oxidative stability index (OSI), and color index (CI) of the CAO/blends were measured. In general, frying stability of the CAO was significantly (P < 0.05) improved by the blending, and the frying performance of the ternary blends was found to be better than that of the binary blends.