Heat resistance of bacterial spores isolated from plant-based matrices: Consequences for food safety and quality

Plant-based drinks are processed using methods like Ultra High Temperature treatment to guarantee their safety and quality by targeting heat resistant endospores of aerobic and anaerobic spore-formers. However, the spore heat resistance of bacterial isolates obtained from relatively new plant-based ingredients is yet to be determined. This study aims to benchmark the heat resistance of spores isolated from these ingredients to available inactivation data. D-values were collected from literature for spores of Bacillus cereus, B. subtilis, B. licheniformis, Geobacillus stearothermophilus, Paenibacillus spp., Clostridium spp., and other spore-forming species encountered in plant-based ingredients. Based on the temperature needed to reach a decimal reduction time (D-value) of 1 min, spores of G. stearothermophilus showed the highest heat resistance, followed by C. sporogenes, B. subtilis (high heat resistant subgroup), C. perfringens, Paenibacillus (high heat resistant subgroup), proteolytic C. botulinum, B. licheniformis, B. subtilis (low heat resistant subgroup), B. cereus, Paenibacillus (low heat resistant subgroup), and non-proteolytic C. botulinum. For a total of 96 strains isolated from plant-based ingredients, spores were heated for 30 min at 100 or 105 °C to screen for their heat resistances. For a selection of these isolates, in-depth heat inactivation experiments were carried out in phosphate buffered saline (pH 7.4) and the outcomes were benchmarked against the retrieved literature data. Experimental log₁₀D-values of analyzed spores from plant-based ingredients fell within the 95 % prediction intervals of meta-analysis data, indicating that the overall spore heat resistance aligns with published data for similar species. This study supports the design of effective thermal processing strategies for plant-based dairy alternatives, which is essential for ensuring safety and stability of this growing and sustainable food category.