## 1 Introduction  
Salmonellosis is a disease caused by _Salmonella_, which infects humans by the consumption of contaminated foods or can be transmitted through pets. The continuing cases of foodborne outbreaks due to _Salmonella_ in low-water activity (a\({}_{\rm w}\)) foods such as pet food kibble, breakfast cereals, spices, dried coconuts, etc. [1; 2; 3], is a major concern. _Salmonella_ can contaminate dried food products in any stages of their preparation and can survive in low-a\({}_{\rm w}\) foods for over a year [4; 5; 6]. They develop resistance to the conventional decontamination methods such as heat treatments or use of oxidizing chemicals in the food industry by developing certain defense mechanisms such as accumulation of compatible solutes in the cell to maintain their turgor pressure in stress conditions [7; 8; 9]. This necessitates the need for exploring alternative decontamination technologies for low-a\({}_{\rm w}\) foods.  
Light-emitting diode (LED) technology has gained attention due to several advantages, including cost-effectiveness, ease of incorporation into the existing processing lines, monochromatic light, small size and absence of warm-up time [10; 11; 12]. This technology can produce antibacterial effects by photodynamic inactivation (PDI), which involves the generation of reactive oxygen species (ROS) upon the absorption of light by chromophores such as porphyrin compounds in the presence of oxygen. This triggers cytotoxic responses in cellular components such as deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, etc., eventually leading to cell death [13].  
Several mechanisms attributed to the inactivation efficacy of LED treatments have been reported in high-\(\mathrm{a_{w}}\) conditions, especially in cell suspensions [14; 15; 16; 17; 18; 19; 20]. For instance, LEDs emitting light of wavelengths 260 and 280 nm showed inactivation efficacy against _E. coli_ suspension by inducing DNA and RNA damage [15]. In addition, the 365 nm (ultraviolet-A) LED treatment of _E. coli_ DH5\(\alpha\) suspension showed DNA damage, DNA oxidation and generation of hydroxyl radical and hydrogen peroxide in the bacterial cell [14]. Similarly, the LEDs emitting blue light (~460 nm) have shown significant oxidative stress and loss of cell membrane integrity in bacteria, when combined with exogenous photosensizers such as curcumin and riboflavin [21; 22].  
In low-\(\mathrm{a_{w}}\) foods, drying can provide stress conditions to the bacteria but could also result in survival of these bacteria [23]. Increases in the accumulation of compatible solutes and in oxidative stress resistance under stress conditions increase the bacterial resistance to lethal intervention processes such as heat and pressure [24; 25]. For example, decreasing the \(\mathrm{a_{w}}\) of the dry bacteria (_Salmonella enterica_) resulted in improvement in their survival ratio [26]. LED technology has shown its antibacterial efficacy in low-\(\mathrm{a_{w}}\) food systems, also. For instance, LED emitting light of wavelength 405 nm previously showed its inactivation efficacy against _E. coli_ and _Salmonella_ in shelled almonds [27]. Our previous studies reported the antibacterial effect of 365 (UV-A), 395 (NUV; near ultraviolet-visible) and 455 nm (blue) LEDs against _Salmonella_ in low-\(\mathrm{a_{w}}\) foods such as wheat flour and pet food kibble [28; 29; 30; 31]. However, studies focusing on understanding the antibacterial mode of action of light pulses emitted from LEDs in low-\(\mathrm{a_{w}}\) conditions are limited. This study focused on understanding the _Salmonella_ inactivation mechanisms of 365, 395 and 455 nm light pulses emitted from LEDs in the low-\(\mathrm{a_{w}}\) environment.