The HPLC Analysis of the Concentration and Enantiomeric Purity of Selected Amino Acids in Two Highly Fermented Foods

A HPLC system linked to a variable wavelengths UV detector was used to sequentially determine the total concentration and enantiomeric composition of two selected free amino acids (leucine, phenylalanine) in two highly fermented foods, bean curd and paste soy bean (i.e., miso), after their derivatization with N‐benzoyl chloride. As was expected, fermented bean curds tended to have a higher percentage of D‐enantiomers and greater total amount of amino acids than paste soy beans or fermented soy beans as reported previously. In one case, the relative amounts of D‐phenylalanine and D‐leucine exceeded 40% of the individual amino acids. Interestingly, paste soy bean made in Japan is found to be better than that made in Taiwan in terms of a higher total level of amino acids and a lower percentage of D‐enantiomers. In most samples, leucine was found to have a lower average percentage of D‐enantiomer but higher total concentration than phenylalanine. This finding is consistent with what was observed for fermented soy beans. Only a trace of amino acids (leucine, phenylalanine) was found in raw soybeans and bean curd, which was thought to be a result of a lack of microbial activities (e.g., fermentation, aging, etc.).     

A Calorimetric Study on the Interaction of Zinc and Cadmium Ions with Jack Bean Urease

A thermodynamic study on the interaction of Jack bean urease, JBU, with Zn²⁺ and Cd²⁺ ions was studied by isothermal titration calorimetry (ITC) at 290, 300 and 310 K in 30 mmol/L Tris buffer solution, pH 7.0. The heats of JBU+Zn²⁺ and JBU+ ²⁺ interactions are reported and analyzed in terms of the extended solvation theory. It was indicated that there is a set of 12 identical and non‐interacting binding sites for Zn²⁺ and Cd²⁺ ions. The interactions of Zn²⁺ and Cd²⁺ ions with JBU are exothermic and both enthalpy and entropy driven. The association equilibrium constants for JBU+Zn²⁺ complexes are 4118.20, 3354.70 and 2790.62 L·mol^?1 at 290, 300 and 310 K respectively. The association equilibrium constants for JBU+Cd²⁺ interactions are 2831.6 and 2386.28 L· ^?1 at 300 and 310 K, respectively.     

Molybdenum Speciation in Raw Phloem Sap of Castor Bean

Abstract

Separation and quantification of molybdenum (Mo) in raw phloem sap from castor bean (Ricinus communis L.) was performed by size exclusion chromatography (SEC) and further purification was performed using quantitative preparative native continuous polyacrylamide gel electrophoresis (QPNC-PAGE). For elemental detection, an inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) was applied. Two different SEC columns were utilized: column A, Sephadex G-50 SF (700 mm × 24 mm), and column B, Sephadex G-25 M (28 mm × 9 mm). The protein content of the fractions was determined by the Bradford method. Using column A, two peaks of Mo were detected consisting of a main peak (Mo_A2) in the low molecular weight area (< 1.35 kDa), and a minor peak (Mo_A1, ≥ 30 kDa) at the void volume of the column. Both Mo species were detected at the ultraviolet (UV) active absorption area of raw phloem sap. Two peaks of Mo were also detected using column B, the first peak (Mo_B1) being at the same elution volume as the protein of raw phloem sap, and the second one (Mo_B2) was eluted in the area of 1.5 to 2.4 mL of elution volume. Raw phloem sap digested by proteinase K-enzyme indicates a significant reduction of Mo_B1 peak, which suggests that the peak may contain Mo bound to protein or polypeptides. The raw phloem sap and SEC fraction containing highest Mo concentration (Mo_A2) were furthermore separated by QPNC-PAGE. The result reveals that the Mo-containing fraction from the raw phloem sap was eluted at the same retention volume as the purified sample. This implies that the Mo species were also successfully separated and purified using QPNC-PAGE.     

Ultrasound assisted hydration of navy beans (Phaseolus vulgaris)

The use of ultrasound to enhance the transport phenomena in food processes has been well recognised in recent times. The objective of this study was to evaluate the effect of sonication on hydration rate and pasting profile of navy beans. The hydration kinetics for control and ultrasound assisted soaking was mathematically described using mechanistic (Fickian diffusion) and empirical (Peleg’s equation, Weibull model and First Order equation) models. Ultrasound enhanced the rate of hydration which was evident from the plot of kinetic data and model parameters. The effective diffusivities for water transport without and with ultrasound application were estimated to be 1.36 × 10⁻¹⁰ m²/s and 2.19 × 10⁻¹⁰ m²/s respectively, considering Fickian diffusion. The Weibull model was concluded to best predict the hydration kinetics of navy beans in an ultrasonic field. Significant increase in peak viscosity of sonicated bean powder was observed compared to control.     

Application of a simple calorimetric data analysis on the binding study of cyanide ions by Jack bean urease

<正>Cyanide ion was studied as an effector of Jack bean urease(JBU) at 300 K in 30 mmol/LTris buffer,pH 7 by isothermal titration calorimetry(ITC).The simple novel model was used for CN~- + JBU interaction over the whole range of CN~- concentrations.The binding parameters recovered from the simple novel model were attributed to the cyanide ion interaction.It was found that cyanide ion acted as a noncooperative inhibitor of JBU,and there is a set of 12 identical and independent binding sites for CN~- ions.The dissociation equilibrium constant is 750μmol/L.The molar enthalpy of binding is△H= -13.6 kJ mol~(-1).The technique used provided an accurate and quick assessment of the effectiveness of the compounds to inhibit Jack bean urease.     

Quantification of Corn Adulteration in Wet and Dry-Processed Peaberry Ground Roasted Coffees by UV–Vis Spectroscopy and Chemometrics

In this present research, a spectroscopic method based on UV–Vis spectroscopy is utilized to quantify the level of corn adulteration in peaberry ground roasted coffee by chemometrics. Peaberry coffee with two types of bean processing of wet and dry-processed methods was used and intentionally adulterated by corn with a 10–50% level of adulteration. UV–Vis spectral data are obtained for aqueous samples in the range between 250 and 400 nm with a 1 nm interval. Three multivariate regression methods, including partial least squares regression (PLSR), multiple linear regression (MLR), and principal component regression (PCR), are used to predict the level of corn adulteration. The result shows that all individual regression models using individual wet and dry samples are better than that of global regression models using combined wet and dry samples. The best calibration model for individual wet and dry and combined samples is obtained for the PLSR model with a coefficient of determination in the range of 0.83–0.93 and RMSE below 6% (w/w) for calibration and validation. However, the error prediction in terms of RMSEP and bias were highly increased when the individual regression model was used to predict the level of corn adulteration with differences in the bean processing method. The obtained results demonstrate that the use of the global PLSR model is better in predicting the level of corn adulteration. The error prediction for this global model is acceptable with low RMSEP and bias for both individual and combined prediction samples. The obtained RPD_p and RER_p in prediction for the global PLSR model are more than two and five for individual and combined samples, respectively. The proposed method using UV–Vis spectroscopy with a global PLSR model can be applied to quantify the level of corn adulteration in peaberry ground roasted coffee with different bean processing methods.     

Dynamic mechanical behavior of the dioctyl phthalate plasticized polyvinyl chloride-epoxidized soya bean oil

The mixing of polyvinyl chloride (PVC) with dioctyl phthalate (DOP) shows two stages of gelation and fusion, but the homogeneity of each stage is influenced by the thermal stability of PVC and its rheological behavior. A torque rheometer has been used to gather almost all critical data related to the plasticized PVC in the epoxidized soya bean oil (ESBO). This study shows that, rheological data reflects the effects of DOP and epoxidization levels of SBO, in a DOP plasticized PVC-ESBO. The DOP plasticizer forms a thermodynamically miscible solution with ESBO; that reduces the rate of fusion and torque at balance of PVC. The storage modulus and tanδ of the plasticized PVC-ESBO have been used to show the extent of the homogeneity; but the dynamic mechanical behavior of PVC-ESBO is strongly influenced by DOP and the epoxidization level of SBO. The glass transition temperatures and dynamic properties of DOP plasticized PVC-ESBO are also reported and discussed in terms of the thermal stability and homogeneity of PVC.     

月见草油中溶剂残留测定方法的改进

An improved method for the analysis of residual solvent in EPO by gas chromatographic headspaceanalysis is presented.A better accuracy and a lower detectable limit of this method in comparing with thoseof GB 5009.37-85 were obtained.     

Applicability of winged bean extracts as organic corrosion inhibitors for reinforced steel in 0.5 ​M HCl electrolyte

Corrosion inhibition properties of winged bean (WB) extracts on reinforced steel in 0.5 ?M HCl solution was studied through experimental and theoretical calculation methods. The electrochemical studies suggested that inhibition efficiency increased with increasing concentration of WB extracts up to 95%. Nyquist diagrams revealed an increase in the charge transfer resistance values and a decrease in the constant phase element as the concentration of WB extracts were increased. The potentiodynamic polarization results revealed that WB extracts behave as mixed-type inhibitors, which physically adsorbed onto the reinforced steel surface. Effect of temperature study demonstrated that the corrosion resistance behaviour of WB extracts decreased with an increase in temperature, yielding a corrosion rate of 3.39 mmpy and 4.02 mmpy at 333 ?K with the incorporation of 1000 ?ppm WBW and WBE extracts, respectively. The thermodynamic study implied that the adsorption process follows the Langmuir isotherm with free energy adsorption of ΔG_ads WBW ?= ?-17.29 ?kJ ?mol^-1 and ΔG_ads WBE ?= ?-16.81 ?kJ ?mol^-1. Corresponding to the molecular modelling study, the semi-empirical method and molecular dynamics (MD) simulation investigated the correlation between the inhibitor compounds and the metal surface. One of the phenolic molecule constituents (gallic acid) was chosen to establish the structural and electronic parameters responsible for the high inhibition efficiency. A greater E_binding of 0.181 (a.u.) indicates that gallic acid in WB extracts can easily bind with the Fe surface, thus projecting a higher inhibitory performance. Surface morphology study affirmed the effective adsorption of WB extracts onto the surface of reinforced steel.     

分光光度法测定豆类中铁的含量(Ⅱ)

豆类无污染,无农药残毒,营养丰富,具有特殊风味,并且很多豆类还有医疗保健作用.用分光光度法直接测定了豆类中铁的含量,方法简便快速准确,对指导人们合理食用豆类补铁及进一步开发豆类提供了可靠的理论依据.