Studying the Interaction of Xanthan Gum and Pectin with Some Functional Carbohydrates on the Rheological Attributes of a Low-Fat Spread

Effects of xanthan gum (XG) (0.1 wt%) and pectin (PE) (0.5 wt%) alone and in combination with different concentrations (0.2 and 0.4 wt%) of locust bean gum (LBG), modified starch (MS), and Na-alginate (ALG) on some of the rheological characteristics of low-fat spreads, including flow behavior curves, rheological modeling, apparent viscosity, rheological modules (storage modulus (G′) and loss modulus (G″)), and delta degree (G″/G′) were studied. Results showed the power-law model was better than the Herschel–Bulkley model to describe the flow curve of dispersions. The k-value in the power-law model increased with increase in biopolymers concentration in solution. All samples exhibited shear-thinning flow behavior with a low yield stress. Dynamic oscillatory shear test showed that the spreads had a viscoelastic solid behavior with a gel-like structure. The G′ value was increased by increasing frequency from 0.03 to 15 Hz, while the G″ and G″/G′ values decreased. Also, MS in combination with XG and PE led to increase the G′ values of spreads in comparison with ALG and LBG. Moreover, microstructural and stability observations revealed that the spreads prepared with 0.1% XG-0.2% LBG significantly had the highest oiling out.     

天然高分子材料——杜仲胶的研究进展

概述了国内外有关杜仲胶的研究概况.首先介绍了杜仲胶的提取方法、分子结构及生物合成机理.接着介绍了杜仲胶结晶特性,如晶型的确定、制备方法及晶型之间的相互转化,结晶熔点及结晶焓,结晶速度及影响结晶速度的条件.然后重点介绍了本小组近年来有关杜仲胶应用方面的研究,如杜仲胶硫化三阶段,弹性临界转变规律,杜仲胶受温度控制的两个活跃...     

Graft Copolymerization of Artemisia Seed Gum with Acrylic Acid under Microwave and its Water Absorbency

A super‐absorbent polymer was prepared by grafting copolymerization of acrylic acid onto Artemisia seed gum, using microwave irradiation and ammonium persulfate as an initiator. The effect of various preparation conditions on its water absorbency, such as the ratio of acrylic acid to Artemisia seed gum, degree of acrylic acid neutralization, amount of initiator and microwave irradiation time, was investigated by orthogonal tests. The optimal reaction conditions were 3 min (irradiation time), 70% neutralization degree of acrylic acid and 2% initiator on the basis of the mass of acrylic acid used. When the mass ratio of acrylic acid to Artemisia seed gum is 5:0.5, the product has a water absorbency close to 400 times at room temperature in distilled water, this indicated that is has a high water absorbency. The structure of the graft copolymer was confirmed by Fourier transform infrared spectrometer (FT‐IR) and thermogravimetric analysis (TGA). Further more, this microwave irradiation processing method to prepare water absorbent materials has no industrial cast off produced, that is to say, this method is environmentally friendly.     

Preparation,Characterization and Anticoagulant Activity of Guar Gum Sulphate

Guar gum was chemically modified by sulphonation using chlorosulphonic acid (ClSO₃H) as a reagent. Effects of molar ratio of ClSO₃H to glucopyranosic unit (ClSO₃H/GU), reaction time and reaction temperature on the degree of sulphonation (DS) and molecular weight (Mw) of products were studied. The structures of guar gum sulphate were investigated by GPC, FT‐IR and UV‐Visible spectroscopy. Activated partial thromboplastin time (APTT) assay showed that the guar gum sulphate could inhibit the intrinsic coagulant pathway. The anticoagulant activity strongly depended on the DS and Mw of polysaccharides. DS>0.56 was essential for anticoagulant activity. The guar gum sulphate with the DS of 0.85 and the Mw of 3.40×10⁴ had the best blood anticoagulant activity.     

Acylhydrazone-modified guar gum material for the highly effective removal of oily sewage

Oily sewage poses a serious environmental risk normally; thus, herein, the modified guar gum (GG-SH) was prepared through rapid condensation reaction between polysaccharide and stearic hydrazide. GG-SH exhibited high removal efficiency of crude oil, the maximum adsorption capacity was calculated to be 2157.3 mg?g-1. The kinetics and isotherm statistical theories showed that the sorption of crude oil onto GG-SH was governed by pseudo-second-order, and Langmuir models, respectively. The removal rate was still high after six cycles of regeneration, indicating an outstanding technique to prepare polysaccharide-based material for the oily sewage treatment with high efficiency and recyclability.     

Double Emulsions Stabilized by Xanthan in the Absence of Hydrophilic Surfactant

The preparation of double water-in-oil-in-water (W/O/W) emulsions containing xanthan gum (XG) in the absence of hydrophilic surfactant was investigated. The emulsions were prepared by the two-step emulsification process. The stability of these systems was evaluated through the evaluation of physicochemical and rheological properties. Microscopic observations in combination with particle size analysis were also performed. The obtained results show that it is possible to prepare stable double emulsions with a single polysaccharide by using the indirect process. The stability depends on the viscosity of the continuous phase and hence the concentration of XG. The apparent viscosity of the emulsions increased with the increase of XG concentration. Particle size analysis shows that the droplet sizes are directly related to XG concentration.     

Pore-Scale Studies on the Stability of Microfoam and the Effect of Parameters on Its Bubble Size

This paper presents a new method to prepare microfoam with excellent stability and high by using a sandpack foam generator. The micromorphology of microfoam were analyzed, and average bubble diameter and uniformity of microfoam were studied by microscope. The stability of xanthan gum-stabilized microfoam and common microfoam at the pore scale was also compared. The results showed that a highly uniform microfoam ranging in size from 10 to 100 µm in diameter with a variable coefficient less than 10% was successfully prepared. The bubble size of the microfoam could be controlled by solution viscosity, gas and liquid flow rate, temperature, and backpressure. The bubble size of microfoam decreased and became uniform with the increase of solution viscosity, total flow rate, and backpressure. The bubble size increased slightly and became non-uniform with the increase of temperature, while the concentration of foaming agent had little effect on the bubble size when above 5000 mg/L. The xanthan gum in the solution increased the viscosity and thickness of liquid membrane, so xanthan gum-stabilized microfoam maintained better stability within microconfined media than common microfoam under condition of 160 g/L salinity, 90°C, and 6 MPa backpressure.     

Effect of Ziziphus and Cordia Gums on Dough Properties and Baking Performance of Cookies

The influence of 2% and 5% Cordia (CG) and Ziziphus (ZG) gums on dough characteristics and cookie quality was investigated. Micro-DoughLab, a texture analyzer (TA), a rapid viscoanalyzer (RVA), and solvent retention capacity were used to examine the effect of CG and ZG gums on dough physicochemical parameters (SRC) and cookie quality. The diameter, thickness, spread, and sensory evaluation of cookies were evaluated. With the addition of CG and ZG, dough softness, mixing time, and mixing tolerance index (MTI) increased, whereas stability and water absorption decreased. TA data showed that adding gums resulted in softer and less sticky doughs than the control, whereas RVA data showed that adding CG resulted in a significant increase in peak viscosity, but no change in flour gel setback. In comparison to the control and CG samples, the ZG samples exhibited the most dough extensibility. The thickness and diameter of the cookies increased but the spread decreased, due to the added gums. The gum-containing cookies had a lower overall acceptability by panelists than the control, although only by a small margin. Gum-containing cookies, on the other hand, can deliver up to 5% soluble fiber.     

Mechanism analysis of hydroxypropyl guar gum degradation in fracture flowback fluid by homogeneous sono-Fenton process

An effective hybrid system was applied as the first report for the successful treatment of key pollutants (hydroxypropyl guar gum, HPG) in fracturing flowback fluid, and the synergistic index of the hybrid system was 20.45. In this regard, chemical oxygen demand (COD) removal ratio was evaluated with various influencing operating factors including reaction time, H₂O₂ concentration, Fe²⁺ concentration, ultrasonic power, initial pH, and temperature. The optimal operating parameters by single-factor analysis method were: the pH of 3.0, the H₂O₂ concentration of 80 mM, the Fe²⁺ concentration of 5 mM, the ultrasonic power of 180 W, the ultrasonic frequency of 20–25 kHz, the temperature of 39 ℃, the reaction time of 30 min, and the COD removal rate reached 81.15 %, which was permissible to discharge surface water sources based on the environmental standards. A possible mechanism for HPG degradation and the generation of reactive species was proposed. Results of quenching tests showed that various impacts of the decomposition rate by addition of scavengers had followed the order of EDTA-2Na < BQ < t-BuOH, therefore OH radicals had a dominant role in destructing the HPG. Based on the kinetic study, it was concluded that Chan Kinetic Model was more appropriate to describe the degradation of HPG. Identification of intermediates by GC–MS showed that a wide range of recalcitrant compounds was removed and/or degraded into small molecular compounds effectively after treatment. Under the optimal conditions, the sono-Fenton system was used to treat the fracturing flowback fluid with the initial COD value of 675.21 mg/L, and the COD value decreased to 80.83 mg/L after 60 min treatment, which was in line with the marine sewage discharge standard. In conclusion, sono-Fenton system can be introduced as a successful advanced treatment process for the efficient remediation of fracture flowback fluid.