Applied Colloids Surfactants

EURO FOOD CHEM XIII und Deutscher Lebensmittelchemikertag 2005

Hamburg September 19-23, 2005

Rapid stability assessment for liquid and paste-like foods with multisample analytical centrifugation

T. Sobisch, D. Lerche, S. Küchler, A. Uhl

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 down to 4 °C. Analytical centrifugation measures the inherent stability of the samples, but cannot foresee destabilizing processes which will happen in the future. In this respect a combination with common accelerated stability testing is the method of choice. The wide application potential of this approach is demonstrated by examples of measurements on typical food dispersions like beverages, emulsions, milk and milk based products.

A considerable fraction of food products are dispersions (emulsions, suspensions, suspoemulsions). Therefore, not only the microbiological and chemical stability matters, but the separation stability has also to be characterized. The development of new food formulations as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life prediction and stability determination. To this end the potential of multisample analytical centrifugation was evaluated as an accelerated test procedure.

Beiträge zur Geschichte der Kolloidwissenschaften

Herr Klaus Beneke arbeitet seit vielen Jahren an der Aufbereitung der Geschichte der Kolloidwissenschaften.
Die Internetseiten sind für an der Kolloidchemie und Wissenschaftsgeschichte Interessierte aufschlußreich.

Water and Wastewater.com Help Forum - Ferric chloride in water w/NaCl

besides there is no chemical interaction one has to consider the electrolyte effect on electrostatically stabilized colloids. Higher electrolyte concentrations cause the reduction of the electrostatic double layer thickness, i.e. reduce electrostatic repulsion. Therefore, the colloids can be more easily removed. On the other hand coagulation efficiency might be reduced due to a reduction of the effective surface of the coagulate.

Cosmetics chemical linked to birth defects

Long overdue to ban the phthalates from consumer goods. There was no reason to wait until it was proved that it has serious effects on humans, when these were already demonstrated on animals.

Irrespective responds of the industry body CFTA

'there appears to be ’potential technical uncertainties’ regarding the way the study was conducted and the conclusions it drew.' “To draw the broad conclusions being reported in the media from such preliminary findings is totally unsupportable from a scientific viewpoint,” the CFTA said in an official statement.

Only 'tested safe' substances should be used in cosmetic products

Mineral oil will not cause skin outbreaks, report claims

It seems logical that there is a difference in 'industrial grade' and 'cosmetic grade' mineral oil.

Paraffin oil is used as a standard pharmaceutical ingredient.

Water and Wastewater.com Help Forum - Coagulation vs. Flocculation

flocculation is mostly carried out with polymeric flocculants, in most cases with cationic polyelectrolytes, given that particle surfaces have a net negative surface charge.

Coagulation is a preferred method for water treatment, in wastewater treatment it is mostly used when finely dispersed colloids with lower mass concentration have to be removed. On the other end for sludge dewatering flocculation is preferred.

Poor settling, besides other operational parameters, might be caused by using the wrong flocculant, by under and overdosing as well.

Paper - at the 11th CID Conference June 22 - 24 Rom, Italy

Friday, June 24th , 2005

2.15-12.40 p.m
SOBISCH T., LERCHE D.
(L.U.M. GmbH, Berlin, Germany)
Rapid selection of dispersants and evaluation of emulsion stability by analytical centrifugation

Surface active additives are often applied to stabilize dispersions (emulsions, suspensions) and to modify surface properties. Selection of optimum additive concentration and composition is a crucial step in formulation and in design of technical applications. To this end, a lot of different laboratory methods have been developed, which are in part very sophisticated or on the other end may be very simple but strongly based on individual judgement and experience.

Up-to-date related investigations often require a lot of manpower without delivering clear-cut results.

A multisample technique based on analytical centrifugation is presented, which allows for an accelerated study of dispersion stability and determination of the velocity of destabilizing processes without dilution, thus avoiding changes of dispersion properties. The kinetics of separation are measured directly in-situ with high time and space resolution.

The efficiency of the method proposed for screening and in-depth studies is demonstrated by examples of selection of concentration and composition of additives as well as of preparation conditions for carbon black and lime dispersions. Examples related to emulsion characterization, emulsifier selection, and processing conditions are presented in more detail.

The multisample technique is very suitable for screening purposes, to investigate the influence of different preparation conditions and processes, for selection of the most efficient emulsifier or dispersant systems and for quality control. To trace slow destabilizing (aging) processes a combination with common accelerated aging tests is the method of choice.

Operation flexibility (centrifugal acceleration, measuring time, temperature) allows one to adapt the measuring conditions to a broad stability range and to investigate temperature effects.