## 1 Introduction  
Foodborne pathogens are a severe problem for the agri-food industry and a serious concern for public health on a global scale. The cost is divided between social aspects such as medical care, reduction in quality of life, mortality, and the agri-food industry, i.e., costs for regulation compliance, product recalls, and tracing back-contamination [1]. Specific bacterial pathogens may cause severe illness or even become life-threatening within a few days. Currently, among the most critical bacterial agents are _Listeria (L.) monocytogenes_,Salmonella spp., and the Shiga toxin-producing _Escherichia (E.) coli_ O157 [2]. _L monocytogenes_ is a Gram-positive, biofilm-forming, and ubiquitous microorganism that can grow at low temperatures, making it a serious health risk for the food industry. Moreover, listeriosis may induce abortion in pregnant women, showing a high mortality rate of about 13 to 34% [3]. It is estimated that listeriosis-related costs reach up to \(\ell\)245 million per year in the UK [3]. _Salmonella_ spp. cause acute gastroenteritis and are considered the leading cause of morbidity and mortality in developed and developing countries [4]. There are continuous increases in cases of salmonellosis in the EU related to the consumption of contaminated poultry [5]. _E. coli_ O157:H7 is a Shiga-toxin-producing pathogen (STEC) that may cause acute diarrhoea and severe kidney damage. Serotype O157 was associated with the most reported infection incidences in the EU in 2017 [6]. Moreover, methicillin-resistant _Staphylococcus (S.) aureus_ (MRSA) strains are of particular interest. They can cause severe infections in humans and animals and have shown resistance to other antimicrobial groups, raising serious concerns. Its transmission has been associated with community interaction, healthcare (i.e., in hospitals), and livestock (zoonosis) [6]. Therefore, rapid identification of pathogenic bacteria in food is paramount to making decisions in time. Selective culture followed by biochemical identification is used in conventional laboratories for identification. However, this path can take up to 6 days to complete [7]. Other methods provide more rapid and accurate identification, including PCR, serological, and surface protein identification using matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry [8]. However, these methods generally require the acquisition of high-cost equipment and reagents. Raman spectroscopy (RS) is a non-invasive and non-destructive spectroscopic technique based on the molecular vibrations derived from the interaction of photons from a laser source when they hit the molecules of a substance characterised by specific chemical groups [9]. It has the advantage that it can probe numerous biochemical compounds on the cell surface without needing a particular marker [10]. However, only 1 in 10\({}^{6}\)-10\({}^{8}\) scattered photons correspond to Raman scattering phenomena, producing a weak signal. Therefore, in addition to mathematical signal-to-noise data amplification by computational models, other techniques have been developed to increase Raman efficiency. For instance, surface-enhanced Raman scattering (SERS) significantly upturns Raman scattering efficiency, up to 10\({}^{6}\) times, compared to conventional Raman [11]. This consists of using metallic particles such as silver or gold as substrates that interact with the target molecules, increasing their signal intensity [10]. SERS has been reported to detect _E. coli_ on grounded beef within three hours [12] (p. 171) and _Pseudomonas_ from drinking water within 15 min of analysis time [13]. This promising technique allows for the rapid identification of culture-free and label-free microorganisms. Nevertheless, SERS requires expensive equipment and infrastructure, making it impractical for laboratories in limited-resource settings.