3 - 6 Oct. 2006, Lyon, France
Evaluation of long term stability of model emulsions by multisample analytical centrifugation
T. Sobisch, D. Lerche
L.U.M. GmbH, Stability & Particle Analysis,
F. Aguilar, G. G. Badolato, H. P. Schuchmann
The development of emulsion based products as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life evaluation and stability determination. Destabilisation processes in emulsions are very complex. Aging and
breaking of emulsions are the result of several processes – creaming or sedimentation, flocculation, coalescence, Ostwald ripening, phase inversion – which can occur separately or simultaneously. This is the main reason why the development of reasonable procedures for shelf life prediction is very difficult and always depends on the product which is subject to evaluation.
The multisample approach applied using analytical centrifugation allows an accelerated characterisation of any demixing processes (creaming, sedimentation, phase separation) as well as the quantification of time dependent structural alterations (e.g. flocculation, coalescence). The analytical centrifugation is very sensitive to small changes in the inherent stability, but also alterations due to slow aging can be revealed far faster than by simple visual assessment.
Model emulsions were designed exhibiting creaming, coalescence, flocculation or Ostwald ripening as the dominating mechanism for instability. Results obtained are compared with rheological measurements, particle size analysis by light scattering and common accelerated stability tests like freeze/thaw cycling and storing at 45 °C.
see google.docs
Evaluation of long term stability of model emulsions by multisample analytical centrifugation
Application of multisample analytical centrifugation for fast evaluation of long term stability and freeze/thaw stability of emulsions
L.U.M. GmbH, Stability & Particle Analysis,
The development of emulsion based products as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life prediction and stability determination. Freeze/thaw stability is often used as measure of long term stability. On the other hand high freeze/thaw stability is often required as property of the final product. To this end the potential of multisample analytical centrifugation was evaluated as an accelerated test procedure.
A new multisample approach is presented using analytical centrifugation, which allows for an accelerated characterization of destabilization processes (creaming, sedimentation, coalescence, phase separation). The kinetics of these destabilizing processes can be traced simultaneously for up-to 12 different samples with temperature control in the range between 4 and 45 °C. No dilution is necessary, which otherwise could lead to changes of dispersion properties.
Analytical centrifugation measures in a rapid way the inherent stability of the samples. Therefore, alterations due to slow aging may be investigated combining first a shorted common accelerated stability test like freeze/thaw cycling and second a rapid evaluation by analytical centrifugation.
The wide application potential of this approach is demonstrated by examples of measurements on cosmetic creams and on beverages.
see google.docsApplication of multisample analytical centrifugation for fast evaluation of long term stability and freeze/thaw stability of emulsions
Rapid emulsifier selection and evaluation of emulsion stability by analytical centrifugation
T. Sobisch, D. Lerche
L.U.M. GmbH, Stability & Particle Analysis,
Selection of emulsifiers and evaluation of emulsion stability is a frequent task. This relates to practical issues like formulation of emulsions, optimization of manufacturing, quality control, shelf life prediction and breaking of emulsions.
Results of investigations on emulsion stability behaviour as function of polarity of nonionic emulsifiers and preparation conditions are presented.
The investigations revealed that the method applied is very suitable for screening purposes, optimization of emulsion manufacturing and that time of investigation and centrifugal acceleration can be adapted to avoid conditions were centrifugal forces are the determining factor for phase separation.
SHELF LIFE PREDICTION OF LIQUID FOOD PRODUCTS BASED ON MULTISAMPLE ANALYTICAL CENTRIFUGATION (MAC)
Dietmar Lerche, Titus Sobisch and Stefan Kuechler
L.U.M. GmbH, Stability & Particle Analysis,
Rudower Chaussee 29, 12489
Many dispersions in industry and daily life are colloidal systems based on emulsions, partly containing additional solid particles to improve their performance. The long term stability of the “quality” of emulsion based products is crucial, as between the production date and the time of their use or consumption often weeks, month and even years are passed by. Shelf life depends directly on physical stability besides other phenomena like structural alterations due to aging or degradation phenomena by light. Centrifugation is the only method truly to accelerate physically sedimentation or creaming processes of emulsions and suspensions. In addition, analytical photocentrifugation is a very efficient tool to determine the separation/demixing velocity (SDV). In this paper we demonstrate that based on experimentally obtained SDV by MAC the shelf life may be determined directly. We present a SOP, how the influence of the elevated g-forces may be evaluated based on the analysis of a velocity versus g-force (centrifugal acceleration) dependency. Shelf life at gravity (1 g) can be confidently calculated based on linear or non-linear regression. Besides shelf life these studies reveal additional information regarding the structural (rheological) stability of emulsion based products.
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