Biopolymers have received much attention in recent years due to their unique rheological properties, their bioavailability, biocompatibility and biodegradability. They can be divided in three main groups:
For almost every kind of application, a suitable biopolymer can be found. They can be used alone and can show important sensitivity to temperature, pH or salt addition. Some biopolymers show synergistic effects with other biopolymers. They have thickening, viscosifying and gelling effects. Some do not form gels, whereas others form gels as a function of concentration, temperature, salt or change in pH.
In some cases, the frontier between viscosifying and gelling systems is not so clear, but may be important for the application.
All these systems can be qualified and quantified thanks to microrheolgy, and Rheolaser MASTER is the only ready-to-use solution to do so.
Food industry faces a great challenge nowadays due to people’s demand of low-fat and low-sugar content products. Healthy products are moved to the center of attentions, and the industry continuously adapts the recipes. One of the solutions is to replace part of the fat content by water, which is texturized with biopolymers. The biopolymer has of course to be chosen carefully, in order to match textural and sensorial properties of the original product.
Rheolaser MASTER provides several advantages to handle this issue. Its six measurement positions enable studying up to six different recipes at a time and comparing them simultaneously by running a unique experience. Moreover, the optical technique allows characterizing these fragile products at rest, with no shear and/or denaturation.
This technique is also well-suited for any weak gel or fragile products, such as yogurt or cheese formation, by measuring the gel time and the final strength of the structure.
Rheological studies of some materials can have unwanted side- effects. For example, surface activating gels with corrosives compounds can degrade the metal geometries of conventional rheometers. Another problem can be the toxicity of samples, e.g. cross-linkers which are used for the curing of epoxy resins are often harmful. Moreover, the cleaning can be difficult when the resin has cured completely.
In contrast, Rheolaser MASTER provides a clean and simple solution with disposable measurement cells. After the 1-click measurement is performed, the glass tubes are simply thrown away, which decreases user time.
Rheolaser MASTER can answer to end-users need in various cases:
RHEOLASER MASTER enables the measurement of the evolution of viscosity and elasticity, in bulk samples, without any mechanical stress. The measurement is performed at rest, allowing to monitor sample evolution, such as gelation, rheology ageing, or samples stability. The measurement is performed in a closed glass cell, preventing any evaporation or drying, and making it safe to operate at all time.
Our microrheology analyser use MS- DWS (Multi-Speckle Diffusing Wave Spectroscopy) principle of measurement. It corresponds to Dynamic Light Scattering extended to concentrated dispersions. It measures the particles Brownian motion, which depends on the viscoelastic structure of the sample. This technique consists in sending a coherent laser beam into the sample, leading to interfering waves which create a speckle pattern captured with a video camera detector. The variations of this speckle image are directly linked to the particles Brownian motion, their speed and the distance they explore.
Brownian motion of the particles is reported as the particle Mean Square Displacement (MSD) versus time. This MSD curve enables the characterization of the viscoelastic properties of the sample. The particles MSD in a purely viscous fluid grows linearly with time, while in a viscoelastic fluid the particles are limited in their displacement as they are trapped in the 3 dimensional microstructure network leading to a plateau in the MSD curve.
> Mean Square Displacement (MSD)
The Mean Square Displacement is the average distance travelled by the particles in the media (unit: nm2). This value grows linearly with time in a purely Newtonian sample, while there is a plateau in a visco-elastic fluid.
When the plateau is getting lower (shorter distance), the elasticity in the product is higher (tighter network), while if the curves get longer (longer times), the viscosity in the product is higher.
Rheolaser MASTER enables to measure MSD curves as a function of time or temperature, allowing to monitor stability, or gelling process...
> Time cure superposition (TCS)
Acquisition of particles MSD as a function of the gel variable enables the monitoring of any sol-gel process. A rescaling process (Time Cure Superposition) can then be applied to determine gel point and gel strength with a great accuracy.
This enables to monitor any kind of gelling process, no matter the gel variable:
> Quantitative parameters (elasticity & viscosity)
> Rheolaser Master
A PRECIOUS TOOL TO CHARACTERIZE VISCOELASTICITY AND ITS EVOLUTION
A state-of-the-art instrument, dedicated to monitoring evolution of the rheological properties, such as viscoelasticity change versus aging time, or sol-gel transition with high accuracy thanks to the Time Cure Superposition method.
|Light source||650 nm|
|Cell Volume||4 or 20 ml|
|Temperature control||RT to 90°C|