Particle Size Distribution of Chocolate

Particle sizes that are present within chocolate and various chocolate products have a considerable effect on the feel of the chocolate product when it enters a consumer’s mouth. For example, a small particle size will produce a very ‘smooth’ feeling.

To meet the selected standards of quality and smoothness within the chocolate, it is essential to thoroughly test final products but, more importantly, it is vital to monitor the actual production process.

Analysis of Three Different Chocolate Types

In the example shown here, particle size distributions of several types of high quality chocolate (from the same producer) have been measured with a FRITSCH ANALYSETTE 22. Before measuring, the samples were pre-dispersed in an organic solvent.

The image below displays the cumulative curve distribution Q3(x) (top) and the histogram dQ3(x) (bottom).

The volume share per particle size interval is observable for all three types of chocolate and as can be seen, the chocolate with a cocoa share greater than 99% will deliver a very intense taste with a mouth feel that is practically ‘sticky’.

Visible Differences

Clear and noteworthy differences can be seen: for example, the chocolate that has a greater portion of cocoa will have a finer particle size distribution than something like, for example, milk chocolate, therefore resulting in a smooth texture and a sticky sensation with an intense flavor.

Wherever chocolate has a greater sugar content – for example within milk chocolate – particle size distribution will generally be shifted to favor bigger particles. In the example’s density distribution, there is a clear dominant peak at around 20 µm, but still over 95% of the sample has particles that are smaller than 30 µm.

Sugar crystals present in the chocolate will increase the higher upper limit of the particle sizes, though this is less important for the mouth feel of the chocolate as these quickly dissolve as the chocolate is eaten.

Analysis of Identical Samples

Reproducibility is very important when measuring particle size distributions. The image below shows the cumulative curve distributions Q3(x) of 5 consecutive measurements of a sample obtained from a milk chocolate production process of as a way of controlling the conching process.

In this example, around 5 g of chocolate was added to a beaker then pre-dispersed in an organic solvent by using an external ultrasonic bath. Once this was done, ten separate measurements were acquired by placing a small amount of sample material in the ANALYSETTE 22’s small volume wet dispersion unit.

Additionally, the dispersion unit was flushed, and then the system was refilled with solvent after each measurement.

Conclusion

The example above demonstrates a small but noticeable variation in particle size distribution between the measurements - this was mainly due to the sampling process.  When taking a small amount of material from the beaker glass the actual distribution will very likely differ, though this can be addressed by averaging results over several measurements.

It is very important that a suitable solvent be utilized when measuring chocolate samples. If this is not the case, the chocolate samples’ high fat content will rapidly contaminate the measurement cell glass, affecting future measurements.

This information has been sourced, reviewed and adapted from materials provided by FRITSCH GMBH - Milling and Sizing.

For more information on this source, please visit FRITSCH GMBH - Milling and Sizing.

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