In-line characterization of ground oilseeds concentration in solid-liquid dispersions in the food industry

- Dispersed powder concentration is well estimated by analysing near infrared spectra.
- In-line infrared spectroscopy can measure mixing homogeneity.
- Infrared spectra are sensitive to temperature and flow rate.
- Particle size distribution of dispersed powder affects instrumental noise.

Near infrared spectroscopy is proposed as a method for continuous characterization of ground oilseed concentration in diluted solid liquid dispersions. The effect of operational parameters, such as flow rate and temperature on the stability and reliability of the in-line measurement was investigated. Moreover, in order to widen the applicability of the approach to different materials, the variety of oilseed, the particle size distribution, and the chemistry of the suspending liquid carrier were all changed, and their influence assessed through principal component analysis. Simple multivariate techniques were efficiently used to regress spectral features against known values of dispersed solids concentration. The calibration, obtained after internal cross validation, proved to give values of coefficient of determination always higher than 0.95, ratio of performance to deviation higher than 4, and comparably reduced root mean squared error of cross validation. Instantaneous concentration prediction were characterized by oscillations much dependent on the dispersed solids particle size, being their amplitude lower in the case of finer particles. Those oscillations were characterized through the coefficient of variation that, at steady state, gave values small enough to constitute an effective parameter to tackle mixing end-point, hence constituting a novel way to assess homogeneity during powder incorporation in liquids.