The manufacture of bottled soft drinks involves the use of flavoring emulsions. These emulsions must consist of droplets of a uniform size that prevent Oswald ripening or agglomeration, both of which can cause unwanted “neck rings” within the bottle or cause “breaking” of the emulsion. The neck rings can be detected in initial stages since the process is gradual.
Although there are a number of methods used for ascertaining the mean droplet size of emulsions, they are unsuitable for investigating small quantities of oversized material that cause a neck ring. Methods related to sizing and counting individual particles are suitable for this type of analysis where even small quantities of outliers are counted and sized in the process.
This article demonstrates the capabilities of the AccuSizer single particle optical sizing (SPOS) system used for determining oversized outlier particles in an emulsion.
Overview of AccuSizer
The AccuSizer determines the oversized outlier particles in the tail of emulsion where the main population is below 1µm. The SPOS system measures particles one by one while passing through a narrow measurement chamber, and it has high resolution and sensitivity to detect the individual particles eliminated from the main distribution. The determination of counts and size of the outlier particles enables the identification of emulsions that are likely to form a sediment or neck ring.
Based on the incorporated sensors, the AccuSizer can be used for an extensive operating range from 0.15 to 400µm. Figure 1 shows the system consisting of the standard LE400 light extinction and scattering sensor that provides automated dilution of the sample to the optimum concentration for effective measurement.
Figure 1. Schematic of AccuSizer AD
Figure 2 shows the results of the sample pre-diluted in 1:200 ratio, with a total count of 213,432 particles/ml greater than 1µm.
The tail denotes 0.623% of the total sample volume. Since the volume of sample measured and the starting volume is known, multiple emulsions can be compared with overlaying sample runs as shown in Figure 3.
Figure 4 shows the results of the six different soft drink emulsions. Clear differences in the size and amount of the oversized particles were also observed. The AccuSizer SPOS single particle counting method allows zooming in for a clear view of the X and Y axes.
Emulsions with large number of particles having a size of over 1µm indicate the presence of a neck ring. The stability of the emulsion can be determined by counting the number of particles that are over 1µm and the volume fraction is higher than 1 µm.
Table 1. shows the data demonstrating the decline of the stability of the product and formation of neck ring as the number of particles greater than 1µm increase.
Figure 2. Pre-diluted flavor emulsion
Figure 3. (a) Graph illustrating the comparison of multiple emulsions with overlaying sample (b) Results of the six different soft drink emulsions
Table 1. Stability forecast
||Particles /mL > 1 µm
||Volume Fraction > 1 µm
||1.4 x 108
||No Neck Ring/Sedimentation
||2.1 x 108
||No Neck Ring/Sedimentation
||1.2 x 108
||6.2 x 108
||2.6 x 108
||5.4 x 108
||Extreme Neck Ring
The AccuSizer features high sensitivity and resolution required to calculate the number of particle counts over 1µm, which are proportional to the formation of neck ring and stability of the emulsion.
This information has been sourced, reviewed and adapted from materials provided by Entegris
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