Modeling Geobacillus stearothermophilus spores inactivation in plant-based drinks to design UHT processing

This study provides predictive models for G. stearothermophilus spores inactivation in four plant-based drinks, half-skimmed bovine milk and Brain Heart Infusion (BHI) broth and while also evaluating of matrix effect on inactivation. Heat inactivation was performed using the capillary tube method within the temperature range 115-127 °C. Geeraerd's model - which incorporates initial level, shoulder duration, inactivation rate and tailing - was fitted to the data. Secondary models were developed on the logarithm of the D-values with validation at 130 °C. The Z_T values in the different matrices ranged between 7.93-9.98 °C and log₁₀D_121°C between 0.43-0.55. Statistical tests revealed no significant differences among the plant-based drinks enabling a general model for the four of them. However, the heat resistance was significantly higher in the bovine milk compared to plant-based drinks. The time to achieve a 5-log reduction under a UHT regime, was different, ranging from 4.28 s to 10.08 s at 140 °C for the six matrices. These differences indicate the importance of considering the food matrix in thermal processing. The findings of this study provide insights on designing thermal processes and support the development of data-driven risk assessments for these products.