Polarized light based scheme to monitor column performance in a continuous foam fractionation column

<p>Abstract</p> <p>Background</p> <p>A polarized light scattering technique was used to monitor the performance of a continuously operated foam fractionation process. The <it>S</it>₁₁and <it>S</it>₁₂parameters, elements of the light scattering matrix, combined together (<it>S</it>₁₁<it>+S</it>₁₂) have been correlated with the bubble size and liquid content for the case of a freely draining foam. The performance of a foam fractionation column is known to have a strong dependence on the bubble size distribution and liquid hold up in foam. In this study the enrichment is used as a metric, representative of foam properties and column performance, and correlated to the <it>S</it>₁₁<it>+S</it>₁₂parameter.</p> <p>Results</p> <p>Three different superficial gas velocities (6.9, 7.5, and 10.6 cm/min) and four different pH values (4.8, 5.5, 6.5, and 7.5) are tested for the foam fractionation of a dilute solution of bovine serum albumin (0.1 mg/ml). As a result, at scattering angle of 125° the magnitude of <it>S</it>₁₁<it>+S</it>₁₂is higher as the pH increases. When the bubble sizes are small with a larger liquid content, the foam is strongly back scattering resulting in lower values of <it>S</it>₁₁<it>+S</it>₁₂(at 125°) at pH = 4.8. The light scattering data and the enrichment values are measured over a period of 90 minutes and correlated using a linear model. The predictive power of the model was found to be statistically significant.</p> <p>Conclusion</p> <p>The time average <it>S</it>₁₁<it>+S</it>₁₂shows a direct proportionality with the enrichment value, indicating that polarized light should be a valuable technique for monitoring foam fractionation columns. Additional knowledge of the nature of dependence between foam properties and <it>S</it>₁₁<it>+S</it>₁₂combined with models relating the enrichment to the bubble size and liquid hold up is needed to develop an accurate diagnostics tool for monitoring enrichment utilizing <it>S</it>₁₁<it>+S</it>₁₂measurements.</p

Effect of Fat and Casein Particles in Milk on the Scattering of Elliptically Polarized Light

In this article, we present an experimental approach to determine the milk fat content using scattered light intensity profiles. The elements of the scattering (Mueller) matrix have been shown to provide valuable information about variation of the optical properties of scattering particles. The scattering behavior of fat and casein in terms of the scattering matrix elements was experimentally determined for milk with varying fat levels ranging from 0.05 wt% (skim) to 3.20 wt% (whole). Three of the scattering Mueller matrix elements, specifically S11, S12/S11, and S33/S11, were found to be sensitive to the number of fat particles in milk. These results indicate that it should be possible to develop a reliable sensor based on the measurement of these scattering elements, which will allow for the development of a robust, in-line sensor to be used in food processing. In addition, an attempt was made to model the phenomena using a relatively simple approach based on single scattering with a size distribution. The disagreement between the model and experiments suggests that a more comprehensive model is needed which can account for multiple scattering