## 3 Results and Discussion
### Effect of Pulsed-Light Treatment on Spoilage Microorganisms and Campylobacter
#### 3.2.2 _Campylobacter_  
The samples inoculated with _Campylobacter jejuni_ presented counts of 4.9 \(\pm\) 0.01 log cfu/g (Table A1). On treatment 3 (3 cm and 2828 V) with a higher energy dose of 9.68 \(\pm\) 0.15 J/cm\({}^{2}\), the _Campylobacter_ counts were significantly lower (4.5 \(\pm\) 0.01 log cfu/g, \(p<\) 0.05). However,  
Figure 4: Effect of PL treatment over _Enterobacteriaceae_ counts (**a**, blue shadow = dispersion of data /blue square = average, “–” = median) and according to fluence (J/cm\({}^{2}\)) (**b**). Figure 3: Effect of PL treatment energy dose on psychothropic counts. this slight reduction inferior to 1 log shall not have an impact on _Campylobacter_ control on poultry meat. Overall, the counts on poultry meat samples treated with PL were not significantly different when compared to those of contaminated samples not treated (Figure 5a). According to the model presented in Figure 5b, when the fluence increases, there is not a significant effect on _Campylobacter_ counts. While for Gram-negative group _Enterobacteriaceae_, the pulsed-light photochemical and/or photophysical (without photothermal influence) actions can be the main mechanisms that affected them with a significant count decrease. For _Campylobacter_ bacteria, it seems that it was mainly the photothermal action with a respective increase of temperature that induced some bacteria lethality when the fluence was higher. PL will be more effective only when a concomitant temperature increases, inducing a higher denaturation of essential proteins and enzymes. [PERSON] et al. (2019) reported that for the same fluence, the intensity of the energy related to the distance of the sample to the source of light could influence the antimicrobial action of pulse light. In addition, in a study with higher intensities of near-ultraviolet/visible (NUV-vis) light, it was reported that the combination of more extended treatment times (5 min) and reduced distance (3 cm) resulted in significant temperature increases (over 65 \({}^{\circ}\)C) with the greatest reductions for C. _jejuni_ (2.62 log\({}_{10}\) cfu/g on the raw skinless chicken fillet) (S  
After PL treatments (Figure 6), the poultry meat samples became slightly lighter, redder, and yellower than meat not treated. The PL treatment did not influence colour parameters, L* and b*, when the irradiance increased, and only a* was significantly influenced. Additionally, authors reported that chicken breasts exposed to high doses of UV light were shown to be redder with a slight increasing of yellow colouration [41]. However contrary to what was obtained in this study, the chicken breasts were slightly darker but without statistical significance. The meat colour is dependent on the myoglobin oxidation state. The L* value remains constant during pigment meat oxygenation and oxidation [42]. Nevertheless, the muscle proteins could be oxidized, and the photothermal action of UV light could change their conformation [43], which could explain a higher reflection of the light and increased values of L*. Usually, the oxidation of myoglobin in meat is translated to a decrease of a* and b* values [42]; however, in this study, we had a significant increase of a* in poultry samples PL treated; this observation was also supported by [PERSON] and [PERSON] [41]. Moreover, an increase of a* was described in irradiated poultry meat by [PERSON] et al. [44]. Lipid oxidation was pointed out as the primary cause of flavour deterioration and development of \"warmed-over flavour (WOF)\" in poultry meat, known as oxidized flavours. Usually, storage and cooking are the main factors inducing the formation of WOF. The application of UV light on meat was mentioned as a pro-oxidant factor developing off-flavours due to photochemical effects on the lipid fractions of the meat or caused by the absorption of ozone and oxides of nitrogen [45]. Some aldehydes are lipid oxidation products in poultry flavour [46; 47]; thus, changes in the aldehyde profile of PL-treated poultry samples could result from lipid oxidation.