How to measure performance and textural properties of personal care products

CREAMS, EMOLLIENTS & SHAMPOOS

Rheological properties of semisolids are highly important physical parameters in both technical (manufacturing, filling, storage) and aesthetic terms.

The evaluation of semisolid emulsion structure and consistency is therefore essential in order to determine, adjust, and possibly predict the corresponding product performance. The emulsifier concentration in the formulation of the cream and the manufacturing temperature are just two variables that can effect the flow and viscoelastic properties as well as the resistance to deformation.

Measuring Consistency

When formulating products such as moisturising creams, lotions, shampoos and conditioners, the materials to be used will depend largely upon the required end product consistency. A thin lotion or shampoo for easy pouring will require the addition of different ingredients or quantities than that required for a thick cream or conditioner. A product developer may wish to create a product that squeezes out of a tube and breaks sharply after squeezing.

These consistencies can be assessed by either a Forward Extrusion test (simulating the force required to extrude the sample by the consumer) or a Backward Extrusion test (both shown in Figure 11) which will give an indication of product physical failure and consistency/cohesiveness.

Backward extrusion tests are often preferred, as the product may be tested directly from the container in which it was originally dispensed, thereby avoiding disruption of the sample and potential changes of properties prior to testing. 

When the back extrusion disc’s lower surface is in full contact with the product, the disc proceeds to penetrate to a user-defined depth into the container. At this point (most likely to be the maximum force), the probe returns to its original position. The ‘peak' or maximum force is taken as a measurement of firmness - the higher the value, the firmer is the sample. The positive area of the curve is taken as a measurement of consistency - the higher the value, the thicker the consistency of the sample. 

The negative region of the graph, produced on probe return, is as a result of the weight of sample which is lifted primarily on the upper surface of the disc on return – i.e. due to back extrusion – and hence gives  an indication of consistency/resistance to flow off the disc. The maximum -ve force is taken as an indication of the cohesiveness of the sample - the more negative the value, the more resistance to withdraw the probe, and hence the more ‘cohesive' is the sample.  

There is a Texture Analysis test for virtually any physical property. Contact Stable Micro Systems today to learn more about our full range of solutions.

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For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

No-one understands texture analysis like we do!

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Watch the video below to see a summary of the types of testing possibilities that are available for the measurement of cosmetic and skincare products.



You can also visit our website's Cosmetics and Skincare Applications page...