Heidy den Besten (Wageningen University)

Summary of presentation:
Introduction
Plant-based ingredients are a source of a wide diversity of microbial contaminants, and their control is of utmost importance in new plant-based value chains. However, the heat resistance of spores of plant-based isolates have not been quantified yet, while this is needed to develop safe-by-design product formulations and processes.
Methods
D-values were collected from literature for spores of Bacillus cereus, B. subtilis, B. licheniformis, Geobacillus stearothermophilus, Clostridia spp. and the more unknown Paenibacillus spp., to determine the variability in heat resistances as function of temperature. Also, inactivation of 96 isolates from plant-based ingredients, including Brevibacillus and Aneurinibacillus strains, was assessed after heating for 30 min at 100°C or 105°C. For 14 strains that produced heat resistant spores, inactivation kinetics were determined. Instead of using the D-value at a reference temperature to compare the species and strains, the temperature was determined to attain a set D-value (i.e., logD-value = 0). This simple approach allowed for a comparison of species when heat resistances vary largely.

Results
The spore heat resistance of the various strains fell within the 95% prediction intervals of the literature data, indicating that their heat resistance aligns with established data for similar species under comparable conditions. A sterilization process (3 min at 121°C), and an ultra-high-temperature process (4 s at 140°C) were used to estimate the survival of common and more unknown spore-forming contaminants.

Conclusion
This study informs the design of thermal processing strategies for plant-based foods to ensure the safety and stability of this growing food category.