Predicting Processing and Filling Equipment with Complex Food Rheology

Sammanfattning: As a food processing lines manufacturer with diverse product complexity, an understanding of fluid dynamics in a pipe system corresponding to the rheological properties and flow behavior is substantial. This will be beneficial to design suitable equipment and prevent processing-related issues, i.e. lowering filling performance, over-dimensioning pumps, excess energy consumption, etc. Therefore, the objectives of this study were (1) to obtain a better understanding of the time-dependent behavior consisted of thixotropy and rheopexy of liquid products with different complexities, (2) to predict the pressure drop in the straight pipe by using the rheological parameters, and (3) to investigate the correlation between the rheological parameters of liquid food products and their filling behavior responses systematically. This study consisted of three main parts involving different complexity of liquid food products, i.e. orange juice concentrate, fermented milk or yoghurt, and tomato puree. First, rheology measurement by using a rotational rheometer to investigate time-dependent behavior through hysteresis loop, breakdown, and build-up test. The second part included pressure drop measurement by using a pressure drop rig, pressure drop prediction calculated from the rheology measurement, and comparison of the experimental and calculated pressure drop values. The last part was a filling experiment to correlate between rheology parameters of fermented milk products and filling behavior responses such as splashing, drippings, and filamentation. The time-dependent behavior of the three liquid food products could be investigated through the hysteresis loop, breakdown, and build up test. Naturell lätt yoghurt had the highest thixotropy properties, followed by orange juice concentrate, and tomato puree with a slight rheopexy behavior at a certain shear rate range. The build-up test captured a clear structural recovery especially by the products with the time-dependent behavior. Furthermore, the pressure drop experiment reported that the generated rheological parameters could predict the actual pressure drop to some extent. The determination of the model to predict pressure drop must be based on the product’s rheological properties. It was due to the challenges from different product’s properties and behavior. The orange juice concentrate had a better pressure drop prediction than Naturell lätt yoghurt and tomato puree due to its rheology simplicity. However, two other products had more complexity that complicated the rheological measurements in different ways as reflected in the pressure drop experiment. Yoghurt had an obvious thixotropy behavior, while tomato puree had both thixotropy and rheopexy behavior with an oscillatory effect during measurement. Lastly, the filling prediction and correlation experiment have shown that systematic rheological parameters can be generated by using a different proportion of Långfil and Naturell lätt yoghurt and the Power Law prediction model. The result of correlation analysis has proven the possibility to correlate between rheology parameters, which are consistency index (K-value) and flow behavior index (n-value), and filling behavior responses (splash outside of the package and impact splash distance in the package) from the five systematic blends with R2 >0.75. However, the particle addition in the ambient drinking yoghurt did not cause any significant differences in the filling behavior responses. Above all, these three parts of the study would contribute to the pressure drop prediction from rheological characteristics and to the development of the filling behavior indicator (rheological parameters) for manufacturer application in the filling machine.