Yiming Ha

Determination of thermally induced trans-fatty acids in soybean oil by attenuated total reflectance fourier transform infrared spectroscopy and gas chromatography analysis.

The intake of edible oil containing trans-fatty acids has deleterious effects mainly on the cardiovascular system. Thermal processes such as refining and frying cause the formation of trans-fatty acids in edible oil. This study was conducted to investigate the possible formation of trans-fatty acids because of the heat treatment of soybean oil. The types of trans-fatty acids in heated soybean oil are determined by attenuated total reflectance Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry methods. The effects of the heating temperature on the trans-fatty acids in soybean oil were evaluated using gas chromatography flame ionization detection analysis. Results show that heat treatment at 240 °C causes the formation of trans-fatty acids in soybean oil and the amount of trans-fatty acids increases with heating time. The only peak observed at 966 cm(-1) of the samples indicates the formation of nonconjugated trans isomers in the heated soybean oil. The major types of trans-fatty acids formed were trans-polyunsaturated fatty acids. Significant increases (P < 0.05) in the amounts of two trans-linoleic acids (C18:2-9c,12t and C18:2-9t,12c) and four trans-linolenic acids (C18:3-9c,12c,15t, C18:3-9t,12c,15c, and C18:3-9t,12t,15c/C18:3-9t,12c,15t) in soybean oil heated to temperatures exceeding 200 °C were compared with those of the control sample. The heating temperature and duration should be considered to reduce the formation of trans-fatty acids during thermal treatment.

Thermally induced isomerization of linoleic acid in soybean oil.

The molecular mechanisms of the thermally induced cis/trans isomerization of the non-conjugated linoleic acids (C18:2) were investigated in a combined experimental and computational study of C18:2 isomers. C18:2 isomers in soybean oil heated at two temperatures (180 and 220 ° C) were analyzed by GC method. C18:2-9c, 12t and C18:2-9t,12c were both the main trans isomers in heated soybean oil. Two alternative isomerization schemes via the proton transfer paths were developed. The geometries in ground states, transition states, and intermediates were optimised using the density functional theory (DFT) at B3LYP/6-31G* level. The formation of C18:2-9t, 12t had two barriers; the first of which was the formation of C18:2-9c, 12t or C18:2-9t, 12c. Zero-point energy corrections of each isomer was calculated at B3LYP/6-311++G** level. The intrinsic reaction coordinates (IRCs) were obtained to examine the transition states and intermediates. The activation energy differences between the cis and trans isomers of C18:2 possibly contributed to the distribution of the final ratio of the isomers. The DFT calculations indicated that the obtained experiment data was well explained by the isomerization mechanism developed.

A novel biosensor regulated by the rotator of F0F1–ATPase to detect deoxynivalenol rapidly

A novel biosensor (immuno-rotary biosensor) was developed by conjugating deoxynivalenol (DON) monoclonal antibodies with the rotator ε-subunit of F(0)F(1)-ATPase within chromatophores with an ε-subunit monoclonal antibody-biotin-avidin-biotin linker to capture DON residues. The conjugation conditions were then optimized. The capture of DON was based on the antibody-antigen reaction and it is indicated by the change in ATP synthetic activity of F(0)F(1)-ATPase, which is measured via chemiluminescence using the luciferin-luciferase system with a computerized microplate luminometer analyzer. 10(-7)mg/ml of DON can be detected. The whole detection process requires only about 20min. This method has promising applications in the detection of small molecular compounds because of its rapidity, simplicity, and sensitivity.

Development of a Competitive Indirect Enzyme-Linked Immunosorbent Assay Based on Monoclonal Antibodies for the Detection of 2-Dodecylcyclobutanone in Irradiated Beef

A highly sensitive and specific competitive indirect enzyme-linked immunosorbent assay (ciELISA) based on monoclonal antibodies was developed for the detection of 2-dodecylcyclobutanone (2-DCB), a chemical marker for irradiated lipid-containing foods. 2-Oxocyclobutane undecanoic acid was used as an alternative to 2-DCB and conjugated to BSA and OVA via a conventional carbodiimide condensation reaction to prepare the immunogen and the coating antigen for 2-DCB. The monoclonal antibody against 2-DCB was obtained using the hybridoma technique, with a high specificity and low cross-reactivity for 2-tetradecylcyclobutanone (2-TCB; <8%) and other structurally related compounds (<0.1%). The ciELISA method was applicable at optimal experimental conditions of 0.001-100 μg/mL 2-DCB in a buffer solution, with an IC50 value of 0.25 μg/mL and a limit of detection (defined as the IC20) of approximately 0.004 μg/mL. The recovery efficiency of 2-DCB from ground beef patties ranged from 84.4 to 109.8%. The intra-assay and interassay coefficients of variation were <10.0 and <12.0%, respectively. The proposed method was validated by gas chromatography-mass spectrometry with high correlation. The same method was used to detect 2-DCB in ground beef patties irradiated at 0.5, 1.0, 3.0, 5.0, and 7.0 kGy; the 2-DCB concentration linearly increased with the radiation dose.

2-Dodecylcyclobutanone as an irradiation dose indicator to identify and estimate original dose in irradiated ground beef

Abstract2-Dodecylcyclobutanone (2-DCB), as a chemical marker of irradiated lipid-containing foods, was used to detect whether ground beef patties were irradiated and to estimate the original absorbed dose. The ground beef patties (70/30) were irradiated at five targeted absorbed doses of 0.5, 1.0, 3.0, 5.0, and 7.0xa0kGy and stored for 0, 7, 14, 21, and 28xa0days, respectively at 4xa0°C. A rapid analytical method based on direct solvent extraction (DSE)/gas chromatography–mass spectrometry (GC–MS) was developed to analyze 2-DCB in γ-ray irradiated ground beef patties. The samples were extracted with acetonitrile via DSE using a tissue-mashing instrument, and then purified with a 1-g silica cartridge and analyzed via GC–MS. The results indicate a linear relationship between irradiation dose and the amount of 2-DCB produced in the irradiated samples (yxa0=xa00.0608x–0.0004, R²xa0=xa00.9899). In addition, a linear relationship was observed between the loss (%) of 2-DCB and storage time (Lxa0=xa01.958d–1.6596, R²xa0=xa00.9597). Thus, a method for estimating the initial dose of irradiated food was developed based on these two line equations; this method explored the establishment of a determination model of the original irradiation dose of lipid-containing foods. The method was used to successfully estimate 2–7xa0kGy irradiated beef samples within 28xa0days with minimal deviation within ±15xa0%.

Development of a novel biosensor based on F0F1-ATPase for the detection of 2-dodecylcyclobutanone in irradiated beef

A novel biosensor regulated by the rotator of F0F1-ATPase was developed to analyze 2-dodecylcyclobutanone (2-DCB) to detect γ-ray irradiated beef rapidly. The biosensor was assembled by conjugating 2-DCB monoclonal antibodies with the rotator ε-subunit of F0F1-ATPase within chromatophores through an ε-subunit monoclonal antibody-biotin-avidin-biotin linker. The limit of detection (LOD) of 2-DCB was approximately 10(-8) μg/mL. The recovery ratio of 2-DCB from ground beef patties ranged from 75.1% to 116.4%. The intra-assay and inter-assay coefficients of variation were both <15.0%. The proposed method was validated by gas chromatography-mass spectrometry with high correlation. The biosensor was used to detect 2-DCB in ground beef patties with different fat contents (10%, 20%, and 30%) irradiated at 0.5, 1.0, 3.0, 5.0, and 7.0 kGy. The 2-DCB concentration linearly increased with the radiation dose in all the beef samples. 2-DCB concentration increased with fat levels in the three samples.

Optimisation design of cylindrical containers for improving the detection efficiency of a high-purity germanium detector using the LabSOCS

The LabSOCS software was used to optimise the geometric dimensions of cylindrical containers and improve the detection efficiency of a high-purity germanium detector for the measurement of environmental radioactivity samples. The optimum ratio of diameter and height for different sample volumes were determined. In addition, the degrees of influence of the sample volume and density when the amount of sample was fixed were compared. Results show that the effect of sample volume on detection efficiency was significantly greater than that of sample density for a given sample amount.

Effect of the chemical composition of the standard calibration source for measuring radionuclides in biological samples by gamma spectrometry

Sample composition is a very important but easily ignored factor affecting the measurement of radionuclides in biological samples. In this paper, we study the effect of the chemical composition of the standard calibration source on determining radionuclides using Laboratory Sourceless Object Calibration Software. Results show that the accuracy of determining radionuclides emitting low-energy photons (<100xa0keV) strongly depends on the differences between the average atomic numbers of the test samples and selected standard reference material (SRM). We also find that high moisture content reduces detection efficiency, especially for low-energy gamma rays.