Steady and Dynamic Shear Rheological Properties of Buckwheat Starch-galactomannan Mixtures

Silver-based gels for oral and skin infections: antimicrobial effect and physicochemical stability

Aim: To systematically evaluate the literature on silver (Ag) gels and their antimicrobial efficacy and physicochemical stability. Materials & methods: A search was performed in PubMed/MEDLINE, LILACS, Web of Science, Scopus, Embase and Google Scholar. Results: Gels were formulated with Ag nanoparticles, Ag oxynitrate and colloidal Ag and showed antimicrobial activity for concentrations ranging from 0.002 to 30%. Gels showed stability of their chemical components, and their physicochemical properties, including viscosity, organoleptic characteristics, homogeneity, pH and spreadability, were suitable for topical application. Conclusion: Ag-based gels show antimicrobial action proportional to concentration, with higher action against Gram-negative bacteria and physicochemical stability for oral and skin infection applications.

Physicochemical Properties of Starch Binary Mixtures with Cordia and Ziziphus Gums

The effect of gum Cordia (GC) and gum Ziziphus (GZ) on the physicochemical properties of wheat, potato, and chickpea starches was investigated. Native or acetylated gums were mixed with starch at 2% or 5%. Starches were analyzed using rapid viscoanalyzer (RVA), differential scanning calorimeter (DSC), texture analyzer, and rheometer. In the presence of gums, the data showed clear variations between the starch gels. The effects of gum acetylation on the starch characteristics were significant. According to the starch type, the peak viscosity of the gels increased depending on the gum type or concentration. With the exception of the potato starch, when gums were added, the gelatinization temperature of the starches increased. Gum acetylation significantly increased starch–gel elasticity (high G′), particularly at the 2% concentration. GC-starch gel hardness was ranked as follows: chickpea–5% native gum > wheat–5% native gum > potato–0% gum, whereas GZ followed the order of: chickpea–2% native gum > wheat–2% native gum > potato–2% native gum. Both the gums promoted reduction in syneresis for the wheat and chickpea starches. Although there was no clear trend, the Ea of the native starches was lowered overall as a result of the gums, indicating the limited effect of temperature on the rheological properties of the blends.

Effect of Hydrocolloid Gums on the Pasting, Thermal, Rheological and Textural Properties of Chickpea Starch

The study was planned to evaluate the effect of non-commercial gums as compared to commercial gums. The concentration dependent effect of two commercial (arabic, xanthan) and four non-commercial (cress seed, fenugreek, flaxseed, okra) polysaccharide gums on the pasting, rheological, textural and thermal properties of chickpea were investigated by rapid visco analyzer (RVA), hybrid rheometer, texture analyzer and differential scanning calorimetry (DSC). Blends were prepared by replacing chickpea starch at 0.5% and 2.0% with gums, whereas native chickpea starch was used as a control. RVA data showed that peak and final viscosities were dramatically increased with xanthan contrary to reduction with gum arabic, flaxseed and okra gums. Hybrid rheometer displayed that storage and loss moduli were increased as a function of angular frequency and dominance of elastic properties over viscous ones. Xanthan blend was less temperature dependent due to dramatic decrease in activation energy value as compared to control while other gums were more temperature dependent. The magnitude of this effect was reliant on the type and concentration of gum. After storage for 21 days at -20 °C, total syneresis was reduced with the incorporation of xanthan and cress seed and also with high levels of gum arabic, flaxseed and fenugreek gums. The gel hardness was increased after overnight storage at ambient temperature (23 °C) with fenugreek while reduction in hardness was observed with xanthan, flaxseed and okra gums. The presence of gums resulted in significantly higher onset and peak temperatures determined through differential scanning calorimetry.

Use of Hydrocolloid Gums to Modify the Pasting, Thermal, Rheological, and Textural Properties of Sweet Potato Starch

Effect of hydrocolloids (arabic, xanthan, cress seed, fenugreek, flaxseed, and okra gums) at 0.5 and 2.0% concentrations on sweet potato starch pasting, viscoelastic, textural, and thermal properties was studied. Rapid Visco Analyzer (RVA) measurements showed that the final viscosity was increased as a function of gum irrespective of their concentration except with cress seed gum. Dynamic rheological data revealed that the magnitude of the moduli was increased as a function of angular frequency and no crossovers were perceived among them. Consistency coefficient (k) was decreased by the addition of any gum and also with increasing concentration of gums except with xanthan gum at 25°C. Flow behavior index (n) data showed that starch gum blends possessed more pseudoplastic shear thinning behavior than those for the control at 25°C and pseudoplasticity was further increased with increasing concentration of xanthan, fenugreek, flaxseed, and okra gums. Texture analysis data displayed that after overnight storage of starch gels at room temperature, hardness was significantly increased by the addition of gums except for xanthan. Differential scanning calorimeter (DSC) profile showed that enthalpy was decreased by the inclusion of xanthan gum.

Dynamic rheological properties of corn starch-date syrup gels

The rheological, pasting, and gel textural properties of corn starch blended with date syrup (DS) or sugar (SG) were studied. The average amylose content of the starch was 27.8%. Corn starch gel is considered elastic since the elastic modulus (G') was much greater than the viscous modulus (G″). Different effect between DS and SG on corn starch gel was observed, where SG addition and DS replacement experiments exhibited the highest G'. The tan δ of all samples was in the range of 0.02-0.20 indicating elastic behavior since it is less than unity. The hardness of starch gel ranged from 13 to 146 g and 212-145 for DS replacement and DS addition, respectively. Unlike the replacement experiment, the addition experiment exhibited significant increase in peak viscosity, setback and pasting temperature (p > 0.05). The magnitude of the effect of DS on corn starch gel was more evident compared to SG. This was apparent by looking at the slopes of the linear regression of the log of G' or G″ versus the log of frequency. Based on the information provided here, date syrup application can expand to cover the baking and beverage industries.

Effect of Tara Gum Addition on Steady and Dynamic Shear Rheological Properties of Rice Starch Isolated from the Korean Rice Variety 'Boramchan'

The present study was performed to investigate the influence of tara gum (TG) addition on the steady and dynamic shear rheological properties of rice starch (RS) isolated from the Korean rice variety 'Boramchan' flour. From X-ray diffraction and Fourier transform infrared spectra of RS, it was found that RS was purely isolated. All RS+TG pastes (4.7:0.3, 4.5:0.5, and 4.3:0.7, w/w) showed shear-thinning fluid characteristics. Adding TG significantly increased the values of apparent viscosity and consistency index of RS. In the dynamic shear rheological analysis, the dynamic moduli and complex viscosity of RS+TG pastes were significantly greater than those of the RS paste, indicating that RS+TG pastes had significantly higher viscoelastic properties than the RS paste. Light microscopy images of RS+TG pastes showed that the addition of TG can inhibit the RS granule from swelling.