Early-stage inactivation of Alicyclobacillus acidoterrestris: A UV-C LED and peracetic acid approach

Alicyclobacillus (ACB) spp. are thermoacidophilic spore-forming bacteria responsible for the spoilage of fruit-based products by producing off-flavours that compromise sensory quality and consumer acceptance. While ACB spores are known to withstand pasteurisation and germinate during storage, vegetative cells are typically assumed to be inactivated by heat and, therefore, excluded from alternative disinfection studies. However, this assumption may underestimate the true resilience and spoilage potential of ACB. In this study, exponentially growing Alicyclobacillus acidoterrestris DSM 3922T cells were exposed to high temperatures and showed post-treatment recovery under optimal conditions, despite their initial heat sensitivity, supporting the need to consider both vegetative cells and spores when validating preservation strategies. To better control these resilient bacteria, an early-stage disinfection strategy using the combination of ultraviolet-C (UV-C) light-emitting diodes (LEDs) with peracetic acid (PAA) was evaluated. UV-C LEDs (280 nm) were first assessed as a standalone non-thermal disinfection strategy under two contamination scenarios (cells in suspension and on surfaces). Across the fluences tested (40 mJ/cm 2 , 160 mJ/cm 2 , and 640 mJ/cm 2 ), UV-C LEDs achieved > 3-log reductions, although higher fluences were required to fully prevent ACB regrowth. When combined with PAA, to simulate a two-step industrial washing process (PAA in wash water followed by surface UV exposure), post-treatment recovery was prevented at fluences ≥160 mJ/cm 2 for both ACB forms. This integrated approach could provide a practical early-stage intervention to reduce ACB entry and propagation along the production line, supporting improved product quality, extended shelf-life, and reduced spoilage-related losses. • Spores and exponentially growing cells showed post-heat recovery • 280 nm UV-C LEDs achieved >3-log reductions in suspensions and on surfaces • Recovery after UV exposure was fluence-dependent • Peracetic acid + UV prevented recovery at ≥160 mJ/cm 2 • A two-step early-stage strategy is proposed for fruit processing