Predicting product stability and shelf life

A manufacturer approached us concerned that a reduction in calorie content of their products' fillings could have a negative effect on the consumer's product experience. Here's how our accelerated testing strategy supported the successful and rapid development of low calorie/fat/sugar confectionery fillings.


The challenge


Our client was concerned that reformulating confectionery fillings to reduce calorie content would result in a negative consumer experience if their physical stability didn’t meet expectations. 


Sedimentation and phase separation can create an undesirable appearance, unappealing texture and cause leakage between product layers or out of the confectionery shell. So, identifying the optimum recipe formulation for each new filling was essential.


We responded by carrying out a series of accelerated physical stability tests. It meant we could provide our client with a clear understanding of which formulations would be the most stable and predict their shelf life, without having to wait for real time stability study observations.




We used the LUMiSizer, an analytical centrifuge combined with NIR light extinction measurement, to evaluate the stability of numerous reformulated fillings against the originals. This enabled us to track the development and movement of any phase interfaces, such as changes caused by sedimentation (see figure 1). 


From this data, we could then predict which of the new formulations would retain their intended structure for the longest.


Working with this centrifugal method also enabled us to run the entire test under the influence of multiple gravities and accelerate any physical instability processes – significantly reducing development time. We evaluated a 12-month shelf life in just four hours.



Figure 1. LUMiSizer tracking of sedimentation process, images adapted from




Numerous recipes could be screened initially in a designed experiment to optimise ingredient levels. This allowed the reformulation process to follow a more targeted approach and be completed in a shorter timeframe.



Fondant filling


One test formulation containing additional fibres (circled in pink) was found to match the stability of the original filling (circled in blue). See figure 2. However, the other seven concepts sedimented during shelf life into a hard, dense layer and low viscosity liquid layer.


Fat-based nut filling


The fat-based nut filling required a complete reformulation to reduce the calorie content, making use of a water-in-oil emulsion. We observed phase separation in all of the initial test formulations, where sedimentation of the emulsion water droplets created distinct fat and water liquid layers. By carrying out separate investigative analysis using laser diffraction, we were able to confirm that the large emulsion droplet size was the root cause of the instability.






Figure 2. LUMiSizer screening of test formulations for fondant fillings.



Our client used this data to tweak both the emulsifier concentration and homogeniser process parameters. At this stage, we repeated both analytical techniques. The results showed a successful reduction in emulsion droplet size (figure 3) and identified which of the new test formations would maintain emulsion stability for the desired product shelf life of one year (figure 4).




Figure 3. Laser diffraction droplet size analysis of initial emulsion test formulation (red), and final emulsion formulation (green).




Figure 4. LUMiSizer stability analysis (left) and interface tracking (right). Original filling (red), initial emulsion test filling (yellow), subsequent test emulsions (green, turquoise, blue – final emulsion formulation).



Find out how RSSL can support your shelf life studies

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