## 3 Results and Discussion
### In Vivo Experiment  
#### 3.3.1 Photodecontamination of _A. flavus_ on Maize  
The combination of 1000 \(\upmu\)M of curcumin in propylene glycol and 102.4 J\(\cdot\)cm\({}^{-2}\) was selected according to the in vitro results which had showed to inactivate _A. flavus_ spores (Section 3.2). The average initial spore's load in popcorn, yellow and white maize were 5.78,  
Figure 4: Scanning electron micrographs of _Apergillus flavus_ spores after different treatments (\(\times\)1000; scale bar = 20 \(\upmu\)m). (**a**) P\({}^{\text{o}}\)L\({}^{\text{o}}\) = control; (**b**) P\({}^{\text{o}}\)L\({}^{\text{+}}\) = light; (**c**) P\({}^{\text{+}}\)L\({}^{\text{o}}\) = photosensitizer; (**d**) P\({}^{\text{+}}\)L\({}^{\text{+}}\) = photosensitization. Arrows in the SEM micrographs indicate cell wall deformation.  
5.44 and 5.61 log CFU\(\cdot\)g\({}^{-1}\), respectively. The viability of spores was not affected (\(p>0.05\)) by curcumin or light treatment. Moreover, up to 0.39 \(\pm\) 0.06 log CFU\(\cdot\)g\({}^{-1}\) reduction was obtained through 25% propylene glycol application on maize kernels (Figure 5), which corresponds to the concentration of the solvent in 1000 \(\mu\)M of curcumin. On the other hand, _A. flavus_ colonies were not observed in the experiments with photosensitized maize kernel extract, suggesting that photosensitization completely removed the spores from the kernel surface, which was in contrast to the in vitro results, where only 2.3 log CFU\(\cdot\)mL\({}^{-1}\) reduction was achieved. The immersion of kernel in curcumin solution for 5 min before illumination might have washed the spores on its surface, reducing the microbial load before illumination. Consequently, the initial concentration of spores on the maize surface may have been lower than that used in vitro. Complete decontamination of food through curcumin-mediated photosensitization has also been reported in oysters inoculated with _Vibrio parahaemolyticus_[45].  
Contrary to our results, several studies have reported lower photoinactivation efficiency on food surface than in vitro [46; 47], which have been attributed to the irregularity and different light-reflecting properties of the food under illumination [48]. In a study reported by [PERSON] et al. [22], nearly 2 log CFU\(\cdot\)g\({}^{-1}\) reduction was achieved on maize kernel and flour through the combination of curcumin and light, against 3 log CFU\(\cdot\)g\({}^{-1}\) reduction achieved in vitro. This divergence of the results by [PERSON] et al. [22] and those reported in the present study might be related to the use of different light doses, 60 J\(\cdot\)cm\({}^{-2}\) ([PERSON] et al.) vs. 102.4 J\(\cdot\)cm\({}^{-2}\) (present study). In addition, the illumination source used by [PERSON] and co-workers [22] was unidimensional, and though the kernels were constantly turned over during illumination, the light may have been distributed irregularly, reducing the effectiveness of the treatment. Nevertheless, these are mere assumptions, and further studies are necessary to explore the effect of the maize matrix on the efficiency of photosensitization.  
Figure 5: Photodecontamination of _A Aspergillus flavus_ spores on three maize varieties (popcorn, yellow and white). S = solvent (propylene glycol); PO\({}^{+}\) = light; P\({}^{+}\)L\({}^{o}\) = photosensitizer; P\({}^{+}\)L\({}^{+}\) = photosensitization. Data are means \(\pm\) SE (\(n=3\)); means with different letters in the same column are significantly different (\(p<0.05\)).