Yanlan Bi

Detection and quantification of adulteration of sesame oils with vegetable oils using gas chromatography and multivariate data analysis

This study was performed to develop a hierarchical approach for detection and quantification of adulteration of sesame oil with vegetable oils using gas chromatography (GC). At first, a model was constructed to discriminate the difference between authentic sesame oils and adulterated sesame oils using support vector machine (SVM) algorithm. Then, another SVM-based model is developed to identify the type of adulterant in the mixed oil. At last, prediction models for sesame oil were built for each kind of oil using partial least square method. To validate this approach, 746 samples were prepared by mixing authentic sesame oils with five types of vegetable oil. The prediction results show that the detection limit for authentication is as low as 5% in mixing ratio and the root-mean-square errors for prediction range from 1.19% to 4.29%, meaning that this approach is a valuable tool to detect and quantify the adulteration of sesame oil.

Solvent-free enzymatic transesterification of ethyl ferulate and monostearin: Optimized by response surface methodology

In this study, enzymatic transesterification of ethyl ferulate (EF) and monostearin for feruloylated lipids production was investigated. Enzyme screening and the effect of feruloyl acceptors on the transesterification were also studied. Effects of reaction variables (reaction temperatures, enzyme load, and reaction time) on the transesterification were optimized using response surface methodology (RSM). The optimum conditions were as follows: reaction temperature 74°C, reaction time 23h, and enzyme load 20% (w/w, relative to the weight of substrates). Under these conditions, EF conversion was 98.3±1.1%, and the transesterification product was consisted of 19.2±2.1% glyceryl ferulate (FG), 32.9±1.9% diferuloylated glycerols (DFG), 36.6±2.2% feruloylated monoacylglycerols (FMAG), 9.1±2.0% feruloylated diacylglycerols (FDAG), and 0.5% ferulic acid (FA). Analysis of variance (ANOVA) showed that the regression equation was adequate for predicting EF conversion. The activation energies for hydrolysis to form FG+DFG and transesterification to form FMAG+FDAG were calculated as 22.45 and 51.05kJ/mol, respectively, based on Arrhenius law.

Simultaneous Analysis of Tertiary Butylhydroquinone and 2-tert-Butyl-1,4-benzoquinone in Edible Oils by Normal-Phase High-Performance Liquid Chromatography

During the process of antioxidation of tertiary butylhydroquinone (TBHQ) in oil and fat systems, 2-tert-butyl-1,4-benzoquinone (TQ) can be formed. The toxicity of TQ was much more than that of TBHQ. In the work, a normal-phase high-performance liquid chromatography (NP-HPLC) method for the accurate and simultaneous detection of TBHQ and TQ in edible oils was investigated. A C18 column was used to separate TBHQ and TQ, and the gradient elution solutions consisted of n-hexane containing 5% ethyl acetate and n-hexane containing 5% isopropanol. The ultraviolet (UV) detector was set at dual wavelength mode (280 nm for TBHQ and 310 nm for TQ). The column temperature was 30 °C. Before the NP-HPLC analysis, TBHQ and TQ were first extracted by methanol, subjected to vortex treatment, and then filtered through a 0.45 μm membrane filter. Results showed that linear ranges of TBHQ and TQ were both within 0.10-500.00 μg/mL (R(2) > 0.9999). The limit of detection (LOD) and limit of quantification (LOQ) of TBHQ and TQ were below 0.30 and 0.91 μg/mL and below 0.10 and 0.30 μg/mL, respectively. The recoveries of TBHQ and TQ were 98.92-102.34 and 96.28-100.58% for soybean oil and 96.11-99.42 and 98.83-99.24% for lard, respectively. These results showed that NP-HPLC can be successfully used to analyze simultaneously TBHQ and TQ in the oils and fats.

Simultaneous analysis of tert-butylhydroquinone, tert-butylquinone, butylated hydroxytoluene, 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, α-tocopherol, γ-tocopherol, and δ-tocopherol in edible oils by normal-phase high performance liquid chromatography

A normal-phase high performance liquid chromatography method for the simultaneous determination of tert-butylhydroquinone, tert-butylquinone, butylated hydroxytoluene, 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, α-tocopherol, γ-tocopherol, and δ-tocopherol in edible oils was investigated. A silica column was used to separate the analytes with the gradient elution. An ultraviolet-visible detector was set at dual wavelengths mode (280 and 310nm). The column temperature was 30°C. The analytes were directly extracted with methanol. Results showed that the normal-phase high performance liquid chromatography method performed well with wide liner ranges (0.10∼500.00μg/mL, R2>0.9998), low limits of detection and quantitation (below 0.40 and 1.21μg/mL, respectively), and good recoveries (81.38∼102.34% in soybean oils and 83.03∼100.79% in lard, respectively). The reduction of tert-butylquinone caused by the reverse-phase high performance liquid chromatography during the injection was avoided with the current normal-phase method. The two isomers of butylated hydroxyanisole can also be separated with good resolution.

Magnetic Mesoporous Palladium Catalyzed Selective Hydrogenation of Sunflower Oil

In this paper, a novel magnetic mesoporous Pd catalyst is used to catalyse selective hydrogenation of sunflower oil at a mild temperature of 50°C. Effects of reaction temperature, stirring speed, time, catalyst loading and hydrogen pressure on the reaction activity, trans fatty acid (TFA) and stearic acid formation were studied. Under the condition of 3.2 mg Pd/100 g oil, 50°C, 1300 rpm stirring speed and 19.0 atm of H2, the lowest amount of TFA generated during the reaction (IV = 80) was 14.9 ± 0.4% while 11.4 ± 0.4% of stearic acid was produced. And this magnetic Pd-catalyst can be reused easily for at least six times without significant catalyst deactivation, the amount of TFA almost remained unchanged. Moreover, this Pd-catalyst shows a good magnetic separation, which provides a potential method for the facile oil modification.

Comparative Study of Soybean Oil and the Mixed Fatty Acids as Acyl Donors for Enzymatic Preparation of Feruloylated Acylglycerols in Ionic Liquids

Feruloylated acylglycerols (FAGs) are the lipophilic derivatives of ferulic acid. In this work, soybean oil (SBO) and the mixed fatty acids (MFA) were selected as fatty acyl donors, and reacted with glyceryl monoferulate (GMF) to prepare FAGs in ionic liquids (ILs). Effect of various reaction parameters (time, temperature, enzyme concentration, and substrate ratio) and ILs on the GMF conversion and the reaction selectivity for FAGs formation were investigated. Response surface methodology (RSM) based on a 3-level-4-factor Box-Behnken experimental design was employed to evaluate the inactive effect of reaction parameters. For the esterification of GMF with MFA, the maximum GMF conversion (98.9 ± 0.9%) and FAG yield (88.9 ± 0.6%) were achieved in [C10mim]PF6. However, for the transesterification of GMF with SBO, the maximum GMF conversion (94.3 ± 0.7%) and FAG yield (83.8 ± 1.0%) were obtained in [C12mim]PF6. High FAG selectivities (∼0.90) were also obtained using SBO or MFA as acyl donors.

Enzymatic epoxidation of biodiesel optimized by response surface methodology

During the enzymatic epoxidation of biodiesel, stearic acid was selected as oxygen carrier. Enzyme screening and the load of stearic acid were investigated. The effects of four main reaction conditions including reaction time, temperature, enzyme load, and mole ratio of H2O2/C=C-bonds on the epoxy oxygen group content (EOC) of epoxidized biodiesel were analyzed. Response surface methodology (RSM) was employed to study and optimize the reaction variables in the enzymatic epoxidation of biodiesel. A second-order model satisfactorily fitted the data (R 2 = 0.9893), with non-significant lack of fit. A higher EOC (6.40 ± 0.20%) of epoxidized biodiesel was obtained at the optimum conditions of 55.4°C, 3.91% enzyme load (relative to the weight of biodiesel), 2.93:1 mole ratio of H2O2/C=C-bonds, and 7.3 h. The relationship between initial reaction rate and temperature was also established, and the activation energy (Ea) of the enzymatic epoxidation is 16.03 KJ/mol.

Antioxidative properties and interconversion of tert-butylhydroquinone and tert-butylquinone in soybean oils

During the process of antioxidation of tert-butylhydroquinone (TBHQ) in oil and fat systems, tert-butylquinone (TQ) can be formed, which has higher toxicity than TBHQ. The changes of TBHQ and TQ in edible oils at room temperature (RT) or under thermal treatment were investigated. Under thermal treatment, volatilization was the main pathway of TBHQ loss in edible oils. TQ was the main oxidation product of TBHQ under thermal treatment as well as at RT. The amount of TQ in thermally treated oils was much less than that in oils stored at RT due to the decreased amount of oxygen dissolved in oils and easy volatilization of TQ at high temperature. In addition, TQ can be reduced to TBHQ by reduction components in edible oils, but the conversion amount was very small. Thus, TQ, theoretically having no antioxidative property, presented a very weak antioxidative activity equivalent to that of BHA due to the presence of insignificant amount of TBHQ formed from TQ in edible oils. The narrow potential difference of 0.059 between oxidation and reduction peaks of TBHQ and TQ resulted in easy interconversion of TBHQ and TQ under the action of common oxidation and reduction substances which have a higher oxidation potential or a lower reduction potential than they have.

Thermal Losses of Tertiary Butylhydroquinone (TBHQ) and Its Effect on the Qualities of Palm Oil

The rules and patterns of thermal losses of tertiary butylhydroquinone (TBHQ) in palm oil (PO) and its effect on the qualities of PO were investigated by oven heating method. Volatilization and transformation products of TBHQ in PO were also studied in detail under heating treatment. Results showed that at low temperature (< 135°C), TBHQ had better antioxidative properties, while its antioxidative potency to PO was significantly weakened at high temperature (≥ 135°C). In addition, as heating temperatures increased and heating time prolonged, losses of TBHQ significantly increased in PO. Volatilization was the major pathway for losses of TBHQ in PO under heating treatment. Meanwhile, a small portion of TBHQ was transformed and the major transformation product was 2-tertbutyl-1,4- benzoquinone (TQ). Moreover, TQ and several decomposition products of PO were also observed in the volatilization products of TBHQ.

Using Consensus Strategy and Interval Partial Least Square Algorithm in Wavelet Domain for Analysis of Near-infrared Spectroscopy

To improve the stability and precision performance of partial least square regression (PLS) model in near-infrared analysis application, the consensus strategy was applied in the wavelet domain. Taking the advantage of multiscale property of wavelet packet analysis, a new modelling method was developed based on the idea of the interval PLS algorithm and named as WpCo-iPLS algorithm. In WpCo-iPLS model, wavelet packet transform (WPT) algorithm was firstly adopted to split the raw spectra into a series of frequency components in wavelet domain. Then, coupled with the consensus strategy, multiple members of PLS models were established on the interval frequency components. To reduce the dependence on single model, an optimization of the weight parameters of member models was conducted. At last, a consensus model was achieved by effectively combining all the member models. To validate the WpCo-iPLS algorithm, it was applied to measure the six kinds of contents concentration of diesel samples using NIR spectra. The experimental results showed that the prediction ability and robustness of WpCo-iPLS model was stronger than that of conventional consensus algorithms, indicating that it is a promising consensus strategy for modelling using NIR spectra.