Abstract
Near infrared spectroscopy in combination with a transflection probe was investigated as inline measurement in a continuous flash pasteurizer system with a sugar-water model solution. Robustness and reproducibility of fluctuations of recorded spectra as well as trueness of the chemometric analysis were compared under different process parameter settings. Variable parameters were the flow rate (from laminar flow at 30L/h to turbulent flow at 90L/h), temperature (20 to 100°C) and the path length of the transflection probe (2 and 4mm) while the pressure was kept constant at 2.5bar. Temperature and path length were identified as the most affecting parameters, in case of homogenous test medium. In case of particle containing systems, the flow rate could have an impact as well. However, the application of a PLS model, which includes a broad temperature range, and the correction of prediction results by applying a polynomial regression function for prediction errors, was able to compensate these effects. Also, a path length of 2mm leads to a higher accuracy. The applied strategy shows that by the identification of relevant process parameters and settings as well as the establishment of a compensation strategy, near infrared spectroscopy is a powerful process analytical tool for continuous flash pasteurization systems.
Highlights
Pasteurization is one of the most important steps in the beverage production as it does affect biological stability and the quality of the product, and the energy expenditure
NIR spectra were investigated for their repeatability and robustness at different flow rates or rather current pattern and two different path lengths
The results for the variation coefficient (VC) vary unsystematically regarding the level of the flow rate
Summary
Pasteurization is one of the most important steps in the beverage production as it does affect biological stability and the quality of the product, and the energy expenditure. NIR measurements were undertaken in an adapted laboratory parameters, the precision in terms of reproducibility was investi- heat treatment system for high temperature short time treatgated, shown in the left work path of Figure 1. Based on previous research results, this study follows the hypothesis that during inline process control in a flash pasteurizer, various influencing variables affect the NIRS measurement. Five temperature levels (20, 40, 60, 80, and °C) were taken into calculation of the Re using an empirical mathematical model according to Swindells, Snyder, Hardy, and Golden (1958) to calculate the kinematic viscosity of the used low-concentrated sugar solutions (Schmidt, 2000) Another process characteristic considered, the pressure (in a range of 2 to 4 bar), neither showed an effect on NIR spectra nor on the chemometric data analysis (data not shown). Measured samples were water–sugar solutions in varying concentrations (0, 20, 40, and 60 g/L sucrose), which were prepared by dissolving crystalline sucrose in demineralized water
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