Development and performance evaluation of an automated continuous pasteurizer

Abstract

Thermal processing by pasteurization is regarded as a critical unit operation in the juice processing chain because it extends the juice's shelf life. The purpose of this study was to develop a novel automated low-viscous juice continuous pasteurizer with regeneration. The pasteurizer is equipped with three heat exchangers that operate on a counter current flow system. The raw juice is preheated in the regeneration section before being heated in the heating section to a specified pasteurization temperature. The juice is then held at pasteurization temperature in holding tubes for a set period of time before being cooled in the regeneration and cooling section. SolidWorks 2019 was used for modeling as well as simulation. Simulation of flow in the holding tube revealed that the fluid had relatively uniform velocity and temperature along the straight path, but with a reduction in fluid pressure. Stainless steel A304 grade was used during the construction of the machine. The performance was evaluated by (i) determining the optimal initial heating time for hot water, (ii) determining optimal product flow rate for effective pasteurization, (iii) modeling throughput and pasteurization efficiency, (iv) assessing the effect of product pumping rate on regeneration and pasteurization efficiency. With an initial heating time of 23 minutes, all product pump speeds over 792 rpm can yield a regeneration efficiency of about 50% with a throughput capacity of about 600 L/h. The machine is equipped with an automated control unit that allows for the adjustment of pasteurizing temperatures, allowing it to be utilized for a wide range of products foods with pasteurization temperatures ranging between 72°C to 88°C under HTST processing. The machine's pasteurizer efficiency was greater than 90%. The logarithmic model and the quadratic polynomial model were found to be the best fit for predicting throughput capacity and the pasteurization temperature, respectively. The results from the validation showed R2 values of 97.52% for the throughput capacity and 99.28% for pasteurization temperature. This implies that the logarithmic model and quadratic polynomial model are in good agreement with the observed values for throughput capacity and pasteurization temperature, respectively. Product pump speed did not affect the regeneration and pasteurization efficiency. The performance of the pasteurizer is therefore promising for use with low-viscous food products. The machine has potential to boost production among small-to-medium-sized processors by increasing capacity and lowering overall energy requirements.