scholarly journals Physicochemical Properties and Antioxidant Activity of Pumpkin Polysaccharide (Cucurbita moschata Duchesne ex Poiret) Modified by Subcritical Water

Foods ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 197
Author(s):  
Guoyong Yu ◽  
Jing Zhao ◽  
Yunlu Wei ◽  
Linlin Huang ◽  
Fei Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Molecular Mass Distribution ◽  
Subcritical Water ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Great Influence ◽  
Cucurbita Moschata ◽  
Solution Treated ◽  
Linear Viscoelastic

In this paper, subcritical water (SCW) was applied to modify pumpkin (Cucurbita moschata Duchesne ex Poiret) polysaccharides, and the properties and antioxidant activity of pumpkin polysaccharides were investigated. SCW treatments at varying temperature led to changes in the rheological and emulsifying properties of pumpkin polysaccharides. SCW treatments efficiently degraded pumpkin polysaccharides and changed the molecular weight distribution. Decreases in intrinsic viscosity, viscosity-average molecular weight, and apparent viscosity were also observed, while the activation energy and flow behavior indices increased. The temperature of SCW treatment has a great influence on the linear viscoelastic properties and antioxidant activity of pumpkin polysaccharides. Pumpkin polysaccharides solution treated by SCW at 150 °C exhibited the highest emulsifying activity and antioxidant activity, which was probably due to a broader molecular mass distribution and more reducing ends exposed after treatment. Scanning electron microscopy showed that SCW treatment changed the microstructure of pumpkin polysaccharides, resulting in the exposure of bigger surface area. Our results suggest that SCW treatment is an effective approach to modify pumpkin polysaccharides to achieve improved solution properties and antioxidant activity.

scholarly journals Extraction, Characterization, and Molecular Weight Determination ofSenna tora(L.) Seed Polysaccharide

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Harshal A. Pawar ◽  
K. G. Lalitha
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Flow Property ◽  
Stability Study ◽  
Angle Of Repose ◽  
Molecular Weight Determination ◽  
Pharmaceutical Excipient ◽  
Accelerated Stability

The objective of the present work was extraction of polysaccharide fromSenna toraL. seed and its characterization as a pharmaceutical excipient. Polysaccharide extraction was based on mechanical separation of the endosperm of seeds ofSenna tora, water dissolution, centrifugation, and precipitation with acetone. Standard procedures were used to study the viscosity, micromeritic properties, and microbial bioburden. Accelerated stability study was carried out on isolated polysaccharide for six months at 40°C/75 RH as per ICH guidelines. The gum obtained fromS. toraseeds was an amorphous free flowing odourless powder with dull brown colour (yield = 35% w/w). The bulk density, tapped density, and angle of repose data reveal thatS. toragum possesses good flow property. The intrinsic viscosity obtained was 1.568 dL/g. The average molecular weight of purifiedS. toragum was found to be 198 kDa by intrinsic viscosity method. The results indicated that viscosity of gum solution increases with increase in temperature. FTIR study revealed the absence of degradation or decomposition of polysaccharide at accelerated stability conditions for six months. It has been concluded that extracted polysaccharide can be used as pharmaceutical excipient in terms of flow behavior, microbial properties, and stability.

A Composition Rule to Predict the Linear Viscoelastic Properties of Polybutadienes with Varying Microstructure

2006 ◽  
Vol 79 (5) ◽  
pp. 859-869 ◽  
Author(s):  
O. Robles-Vásquez ◽  
A. González-Álvarez ◽  
J. E. Puig ◽  
O. Manero
Keyword(s):  
Molecular Weight ◽  
Relaxation Time ◽  
Glass Transition ◽  
Viscoelastic Properties ◽  
Average Molecular Weight ◽  
Composition Rule ◽  
Narrow Molecular Weight Distribution ◽  
Plateau Modulus ◽  
Linear Viscoelastic ◽  
Rate Dynamic

Abstract A composition rule is proposed here to predict the glass transition temperature (Tg), the zero shear-rate dynamic viscosity (η0′), the plateau modulus (G0) and the terminal relaxation time (λ) of narrow molecular weight distribution (MWD) polybutadienes with various vinyl contents in solution and in the melt from the knowledge of the vinyl fraction, polymer fraction in solution and average molecular weight. The predictions of the composition rule are compared with data of a variety of narrow MWD polybutadienes with varying microstructure.

Some Aspects of the Relationship between Molecular Structure and Flow Behavior of Polymer Melts

1969 ◽  
Vol 42 (3) ◽  
pp. 823-834 ◽  
Author(s):  
L. L. Blyler
Keyword(s):  
Molecular Structure ◽  
Activation Energy ◽  
Molecular Weight ◽  
Molecular Mechanisms ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Melt Fracture ◽  
Flow Activation Energy ◽  
Shear Dependent Viscosity ◽  
Dependent Viscosity

Abstract The shear dependent viscosity and related properties of a number of ethylene polymers of differing molecular structure have been characterized using a capillary extrusion rheometer. The structural aspects of interest were average molecular weight, branching, and the presence of strong intermolecular secondary forces. It was found that average molecular weight influences the degree of shear dependence of the viscosity, branching affects both flow activation energy and the nature of the observed “melt fracture” phenomenon, and intermolecular hydrogen bonding enhances viscosity and activation energy and leads to increased shear dependence of flow behavior. The results are interpreted in terms of specific molecular mechanisms.

scholarly journals Study on Preparation of Water-Soluble Chitosan with Varying Molecular Weights and Its Antioxidant Activity

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Dang Xuan Du ◽  
Bui Xuan Vuong
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Dose Range ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Chitosan Solution ◽  
Water Soluble ◽  
Molecular Weights ◽  
Ph Level ◽  
The One

The preparation of water-soluble chitosan (WSC) with various molecular weights by gamma Co-60 irradiation of chitosan solution (5%) in the presence of hydrogen peroxide (1%) combined with acetylated reaction was carried out. The average molecular weight (Mw) of chitosan was measured by gel permeation chromatography (GPC). The chemical structure and the crystallinity of chitosan and WSC were characterized by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD), respectively. The antioxidant activity of WSC and chitosan was investigated using the free radical 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS•+). Obtained results showed that chitosan with Mw of 18–90 kDa could be efficiently prepared by this technique in the dose range from 10 to 24.5 kGy. After the acetylated process, the resulting WSC possesses good solubility in a wide pH level of 2–12, and WSC with low molecular weight exhibited significantly higher antioxidant activity than the one with high molecular weight. In detail, the antioxidant activity was 14.7%, 70.5%, 84.2%, 89.4%, and 97.5% for WSC samples prepared from chitosan with Mw of 140.2 kDa, 91.4 kDa, 51.2 kDa, 35.3 kDa, and 18.1 kDa, respectively, at the same reaction time of 90 min. Moreover, the antioxidant activity of WSC was higher than that of chitosan. Thus, WSC prepared by gamma Co-60 irradiation and acetylated process can be potentially applied as a natural antioxidant agent.

Rheological Properties of Polybutadienes Prepared by n-Butyllithium Initiation

1965 ◽  
Vol 38 (4) ◽  
pp. 881-892
Author(s):  
J. T. Gruver ◽  
Gerard Kraus
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Polymer System ◽  
Newtonian Flow ◽  
Newtonian Viscosity ◽  
Long Chain Branching ◽  
Shear Rates ◽  
Molecular Weights

Abstract The flow behavior of n-butyllithium-polymerized polybutadienes was investigated as a function of molecular weight, temperature, and shear rate. At low shear rates these polymers exhibit Newtonian flow up to molecular weights of several hundred thousand so that “zero shear” Newtonian viscosities can readily be determined without the risk of long extrapolation. Above 10,000 molecular weight the Newtonian viscosities obey the well-known 3.4 power dependence on weight-average molecular weight. The entanglement spacing molecular weight is estimated at 5600. The temperature dependence of viscosity is substantially independent of molecular weight and shear stress and can be represented analytically by functions proposed in the literature. The apparent activation energy for viscous flow is not constant, but decreases with rising temperature. The flow of the polymers becomes increasingly non-Newtonian with the product of shear rate, molecular weight and Newtonian viscosity. However, the departure from Newtonian behavior is apparently less than for any polymer system whose flow behavior has been described in the literature. The indications are, therefore, that sharp molecular weight distribution and freedom from long chain branching favor Newtonian flow and that the n-butyllithium initiated polybutadienes represent some of the most perfectly linear, narrow distribution polymers known.

scholarly journals Effect of γ-irradiation on the structure and antioxidant activity of polysaccharide isolated from the fruiting bodies of Morchella sextelata

2020 ◽  
Vol 40 (9) ◽  
Author(s):  
Chuan Xiong ◽  
Ping Li ◽  
Qiang Luo ◽  
Jinyan Yan ◽  
Juan Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Antioxidant Activities ◽  
Average Molecular Weight ◽  
Radical Scavenging ◽  
Fruiting Bodies ◽  
Γ Irradiation ◽  
Irradiation Treatment ◽  
Chemical Groups ◽  
Thermal Stability Of

Abstract The molecular weight of the polysaccharide and the chemical groups it contains has an important influence on its biological activity, relatively low molecular weight polysaccharides may have better antioxidant activity. Polysaccharides isolated from the fruiting bodies of Morchella sextelata (MSP) were treated by γ-irradiation at 10, 100 and 1000 kGy doses, and the physicochemical properties and antioxidant activity of irradiated MSP were investigated. Microscopic observation under a scanning electron microscope (SEM) showed that breakage and pores appeared on the surface of the irradiated polysaccharide. As the irradiation dose increased, the average molecular weight of MSP decreased significantly, while the particle size and thermal stability of MSP first increased at 10 and 100 kGy doses and then decreased at 1000 kGy doses. The antioxidant activities, measured by free radical scavenging tests and protective effect on PC12 cells injured by H2O2, were all increased after irradiation, especially when the concentration of MSP was low (50 and 100 μg/ml). Therefore, irradiation treatment was an effective method to enhance the activity of polysaccharides.

Studies on the selection of domestic viscosity additives for multi-grade hydraulic oils HVLP

2020 ◽  
Vol 05 ◽  
pp. 45-49
Author(s):  
L. A. Radchenko ◽  
◽  
Yu. A. Morshanskaya ◽  
A. V. Beskova ◽  
M. A. Zhumlyakova ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Mass ◽  
Molecular Mass Distribution ◽  
Average Molecular Weight ◽  
Weighted Average ◽  
High Technology ◽  
Base Oil ◽  
Optimal Quality ◽  
Selection Of

At the present time, imported viscosity additives purchased abroad are used to produce premium multi-grade hydraulic oils in Russia. The high technology production such oils is entirely dependent on the import of these additives. At the JSC "MidVolgaNIINP" conducted research on the development and selection of domestic viscosity additives is not inferior to foreign analogues in the composition of hydraulic oils of the HVLP. For select the domestic viscous additive of optimal quality were studied three laboratory samples of polyalkyl methacrylate additives in physicochemical and operational properties in base oil. The results obtained were selected a domestic viscosity additive with a narrow molecular-mass distribution (2.19 Р) and a minimal weighted average molecular weight (34983 Da) that allows hydraulic oils to meet the requirements DIN 51524-3 and OEM. Studies had found that the quality of thickened oils is affected by the content viscous additive. The optimal contents of domestic additives for obtaining oils of viscosity levels ISO VG 32 and ISO VG 46 have been determined. The results are used in further research on the development of multi-grade hydraulic oils HVLP.

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

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