Emulsions accelerated stability testing

Accelerated stability tests using the emulsion volume index (EVI) Accelerated aging procedure in which an emulsion in a microhematocrit tube is subjected to centrifugal force EVI = (length of emulsion phase/lolul length of column) (% fal/0.9) x 100. A higher EVI indicates a more stable emulsion under the conditions of the test. 

Keywords Accelerated stability test Droplet size distribution Emulsion stability Multisample analytical centrifugation Shelf life Viscosity... 

To estimate the oxidative stability or susceptibility of a fat to oxidation, the sample is subjected to an accelerated oxidation test under standardized conditions and a suitable end-point is chosen to determine appropriate levels of oxidative deterioration (Figure 7.1). Several parameters such as temperature (60-140°C), metal catalysts (5-100 ppm), oxygen pressure (3-165 psi), or variable shaking to increase reactant contact, are manipulated to accelerate oxidation and development of rancidity in oils and emulsions. The oxidation level used for an end-point varies widely according to the time desired to obtain stability data. For practical purposes, predictions of oxidahve stability in foods and oils based on measurements of induction period should be related to actual product shelf life, and the conditions used should be as close as possible to those under which the food is stored. To translate the induchon period obtained under accelerated conditions to the actual shelf hfe of a product, it is necessary to use an arbitrary factor based on prior experience with the desired product. Much effort has been devoted to more accurately eshmate the shelf hfe of foods... 

The main physico-chemical characteristics that need to be controlled in cosmetic emulsions are their formation and stability on storage as well as their rheology, which controls spreadability and skin feel. Most cosmetic and toiletry brands have a relatively short life span (3-5 years) and hence development of the product should be rapid. Consequently, accelerated storage testing is needed to predict stability and change of rheology with time. These accelerated tests represent a challenge to the formulation chemist. 

Diehl, K.C., Hamann, D.D., and Whitfield, J.K. 1979. Textural failure in selected raw fruits and vegetables. J. Texture Studies 10 371-400. Fligner, K.L., Fligner, M.A., and Mangino, M.E. 1991. Accelerated tests for predicting long-term creaming stability of infant formula emulsion systems. Food Hydrocolloids 5 269-280. 

Beyond the bottle/jars tests and their acceleration by centrifugation, other methods have been applied to the study of emulsion stability including [100-102] ... 

The simplest accelerated test consists of storing the emulsion at elevated temperature (at constant temperature usually 45 or 50 °C, and/or using a temperature cycle). From the results, stability is usually predicted using empirical rules. For example, a stability of 3 months at 45 °C corresponds to at least 6 months stability at room temperature [11]. 

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