Carboxylated chitosan improved the stability of phycocyanin under acidified conditions.

Phycocyanin, a natural blue colorant, derived from Spirulina platensis, is now widely used in the food industry. However, its main drawbacks are loss of color and denature of structure in an acidic environment. In this study, carboxylated chitosan (0.1 %-1 % w/v) was chosen as an additive in acid-denatured phycocyanin for preserving phycocyanin's blue color and natural structure. Zeta-potential and particle size revealed that the carboxylated chitosan with high negative charge adsorbed on phycocyanin and provided stronger electrostatic repulsion to overcome the protein aggregation. Ultraviolet-visible absorption spectrum and fluorescence spectroscopy showed that the carboxylated chitosan recovered the microenvironment of tetrapyrrole chromophores and ß-subunits, which led the secondary structure changed and the trimers depolymerized into the monomers changed by the acidic environment. Furthermore, Fourier transform infrared spectroscopy revealed highly negatively charged carboxylated chitosan with the groups (NH2, COOH and OH) could restored the microenvironment of tetrapyrrole chromophores and ß-subunits of phycocyanin, and interact with phycocyanin through hydrogen bonding, NH bonding, ionic bonding and van der Waals, which led to a change in secondary structure and depolymerization of trimers into monomers. Our study demonstrated the carboxylated chitosan played a beneficial role in recovering the structure of acid-denatured phycocyanin and its blue color.

Investigation of the interactions between food plant carbohydrates and titanium dioxide nanoparticles.

Titanium dioxide (TiO2) is commonly used as food whitening in candies, chocolates, and cakes with high carbohydrate contents. The potential interaction between the food carbohydrate and food grade TiO2 nanoparticle was little known. Therefore, we explored the interaction between TiO2 nanoparticles and seven common carbohydrates, including monosaccharides, disaccharides, and polysaccharides. The result showed that all the carbohydrates tested interacted with the surfaces of the TiO2 nanoparticles and formed biocoronas. TEM and SEM images provided information about the morphology formation of biocoronas. The surface potential and size of the TiO2 nanoparticles altered after interacting with the carbohydrates. FTIR spectroscopy and QCM-D findings showed insights into the molecular origin and nature interaction between TiO2 and carbohydrates. The results illustrated that TiO2 nanoparticles can interact with carbohydrates, enter the body as a food additive, and interact with food matrix for a series of reactions. Compared with monosaccharides or disaccharides, food polysaccharides have stronger adsorption on the surface of nanoparticles. This is a preliminary judgment for the subsequent in vitro simulated digestion. Our result could be useful for understanding and controlling the behavior of nanoparticles in food and the human gut.

A Method of Qualitative and Quantitative Analysis on Fluid Catalytic Cracking Full Range Gasoline by Comprehensive Two-Dimensional Gas Chromatography Coupled with Time-of-Flight Mass Spectrometry / 分析化学

A method of qualitative and quantitative analysis on fluid catalytic cracking (FCC) full range gasoline by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOF MS) was established. The results showed that paraffins, olefins, naphthenes and aromatics in FCC gasoline had regional and zonal distribution in two-dimensional contour plots. The distinctions of boiling points and polarity between different compounds were used to achieve the accurate separation and determination in GC×GC-TOF MS analysis, and consequently the co-current flow which was often present in the conventional GC analysis was greatly suppressed. The difference of ionizing efficiency between different compounds was modified by response factors, and moreover, a good quantitative dependency was found between the analysis results of GC and GC×GC-TOF MS on FCC gasoline. Due to the high separation resolution, GC×GC-TOF MS gave more accurate results about the group compositions of FCC gasoline. GC×GC-TOF MS provided an effective way with high precision for the characterization of FCC gasoline.

Characterization of nitrogen compounds in coker gas oil by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and Fourier transform infrared spectroscopy.

In this study, the classes and structures of nitrogen species in coker gas oil (CGO) are characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the m/z of basic and non-basic nitrogen compounds ranges from 180 to 560 and from 200 to 460, respectively. Six basic nitrogen compounds, N1 (a molecule contains one nitrogen atom, similarly hereinafter), N1O1, N1O1S1, N1O2, N1S1, and N2, are identified by their positive-ion mass spectra, and four non-basic nitrogen compounds, N1, N1O1, N1S1, and N2, are characterized by their negative-ion mass spectra. Among these nitrogen compounds, the N1 class species are the most predominant. Combined with the data of ESI FT-ICR MS and FT-IR, the basic N1 class species are likely pyridines, naphthenic pyridines, quinolines, and benzoquinolines. The most non-basic N1 class species are derivatives of benzocarbazole. The N2 class species are likely amphoteric molecules with pyridine and pyrrole core structures.

Advances of two-stage riser catalytic cracking of heavy oil for maximizing propylene yield (TMP) process.

Two-stage riser catalytic cracking of heavy oil for maximizing propylene yield (TMP) process proposed by State Key Laboratory of Heavy oil Processing, China University of Petroleum, can remarkably enhance the propylene yield and minimize the dry gas and coke yields, and obtain high-quality light oils (gasoline and diesel). It has been commercialized since 2006. Up to now, three TMP commercial units have been put into production and other four commercial units are under design and construction. The commercial data showed that taking paraffinic based Daqing (China) atmospheric residue as the feedstock, the propylene yield reached 20.31 wt%, the liquid products yield (the total yield of liquefied petroleum gas, gasoline, and diesel) was 82.66 wt%, and the total yield of dry gas and coke was 14.28 wt%. Moreover, the research octane number of gasoline could be up to 96.