## 3 Results
### Biogenic Amine Profile of the Mushroom Samples
Histamine was the most abundant, ranging between 0.15 and 1.23 mg/g, constituting 28% of the total biogenic amine content (Appendix F). It was present in all fermented samples except the blanched ones, with notably high levels (1.23 mg/g) observed in the HHP-pretreated fermented samples. Tyramine was the second most abundant biogenic amine (0.08-4.1 mg/g), representing 48% of the total biogenic amine content. It was detected in all of the fermented samples except the blanched and microwave-pretreated ones, with an exceptionally high amount (4.1 mg/g) in the UV-light-pretreated fermented sample. Spermidine ranged between 0.12 and 0.21 mg/g across the six pretreatments but was undetectable in the HHP-pretreated samples. Putrescine (0.01-0.27 mg/g) was present in all samples except the blanched ones, contributing an average of 9.1% to the total biogenic amine content. Cadaverine accounted for 3.0% of the total biogenic amine content, with the highest concentration observed in the HHP-pretreated fermented samples (0.15 mg/g). Spermine was only detected in the fresh fermented samples (0.48 mg/g), while agmatine (0.08 mg/g) was only found in the HHP-pretreated fermented samples. In a study on button mushrooms, three biogenic amines, spermidine, putrescine, and tyramine, were identified. Putrescine (ranging from 0.58 to 10.11 mg/kg) and tyramine (ranging from 1.44 to 69.04 mg/kg) were only present in fermented mushroom samples, while histamine was not detected in [PERSON] et al. 's study [46]. The biogenic amine profile of mushroom samples was also evaluated using a principal component analysis, as shown in Figure 12. The first two principal components accounted for 75.7% of the variance, representing the majority of the dataset's variation. In Figure 12, the upper-right quadrant contains markers corresponding to the fresh fermented and UV-light-treated fermented mushrooms, forming a distinct cluster differing from the other sample groups, indicating similarities in their biogenic amine profiles. The lower-right quadrant features markers only for the HHP-pretreated fermented samples, located far from all the other sample groups, suggesting a unique biogenic amine composition. The markers for the oven-treated fermented and steamed fermented samples are located near the center of the plot, indicating that their biogenic amine profiles closely resemble the overall dataset average. The lower-left quadrant includes all of the pretreated samples along with the blanched fermented and microwave-treated fermented samples. This distinct clustering of pretreated samples highlights the minimal impact of pretreatments on their biogenic amine profiles, which are predominantly characterized by spermidine and show an absence of other biogenic amines. Notably, the blanched fermented and microwave-treated fermented samples exhibit similar profiles, suggesting that fermentation had a limited effect on altering their biogenic amine composition, in contrast to the fresh fermented, UV-light-treated fermented, and HHP-treated fermented samples, which showed more pronounced changes. The arrows represent the biogenic amines' contribution to the principal components. The fresh fermented and UV-light-treated fermented samples are positioned further along the positive PC 2 axis, indicating elevated levels of biogenic amines such as putrescine, spermine, and notably tyramine in the UV-light-treated fermented samples. In addition to agmatine being exclusively detected in the HHP-pretreated fermented samples, histamine was also most abundant in these samples, a factor that influenced their distinct positioning on the plot.