## 3 Results and Discussion
### BA Content in Edible Mushrooms  
The content of separate BA (Figure 5a,b) and their sum (Figure 5c) in mushroom samples is shown in Figure 5. Histamine, tyramine, and spermine were not found in all samples. Phenylethylamine and spermidine were found in all fresh mushroom samples, the highest concentrations being found in _B. edulis_ (31.3 and 374 mg/kg, respectively). Putrescine was found in _B. edulis_ and _C. cibarius_ (445 and 35.2 mg/kg, respectively). In addition, cadaverine was established in fresh _C. cibarius_ (14.6 mg/kg). Comparing the sum of BA in fresh mushrooms, the highest was established _B. edulis_; that in _C. cibarius_ and _R. caperata_ was 7.3 and 7.2 times lower, respectively. In comparing thermally treated and ultrasonicated unfermethod mushroom groups, tryptamine was found in thermally treated and ultrasonicated _B. edulis_ (8.54 and 8.88 mg/kg, respectively). As in fresh samples, phenylethylamine and spermidine were established in all thermally treated and ultrasonicated mushrooms. Additionally, putrescine was found in both thermally treated and ultrasonicated _B. edulis_ and _C. cibarius_. However, the sum of BA in thermally treated and ultrasonicated samples was lower in treated samples of _B. edulis_ and _C. cibarius_ than in fresh mushrooms: 2.2 and 1.2 times lower, respectively, in thermally treated samples, and 1.9 and 1.2 times lower, respectively, in ultrasonicated samples. When comparing thermally treated and ultrasonicated fermented mushroom groups, tryptamine was found in ultrasonicated and fermented _B. edulis_ (75.5 mg/kg), and ca  
Figure 5: (**a**) The content of spermidine, phenylethylamine, and triptamine in edible mushrooms; (**b**) the content of cadaverine and putrescine in edible mushrooms; and (**c**) the sum of biogenic amines in edible mushrooms (BE—_Boletus edulis_; Ca—_Cantharellus cibarius_; Ro—_Rozites coperata_; thermal—thermally treated by boiling for 30 min; ultrasound—ultrasonated for 30 min; LUHS245—_fermented with _L. uvarum_ LUHS245). daverine was established in both thermally treated and ultrasonicated fermented _B. edulis_ samples (38.6 and 1542 mg/kg, respectively). Ultrasonication before fermentation, in comparison with thermal treatment before fermentation, increased the sum of BA in _B. edulis_ and _R. caperata_ samples (on average, by 15.3 and 2.4 times, respectively). In contrast, ultrasonication before fermentation reduced the sum of BA in _C. cibarius_ samples (on average, by 2.4 times). Microbial activities could lead to amino acid decarboxylation which induces BA formation. [55]. The amount and type of BA in food are closely related to the spoilage and fermentation processes and depend on the composition of food (mainly free amino acid content), microorganisms in it, and technological and environmental conditions [56]. Acidity parameters (especially pH) are also important factors for the formation of BA [57]. However, no correlation was found between the BA content and the pH of samples in our study. A moderate positive correlation was established between spermidine and the mould/yeast count in samples (r = 0.585, \(p\leq\) 0.0001). This could be explained by the fact that moulds and yeasts could also contribute to BA production [14]. However, it should be noted that the metabolic pathways available in LAB generate significant concentrations of BA in fermented foods [15]. Certain BA, such as histamine, tyramine, cadaverine, and putrescine, can be produced by LAB species in different fermented foods [14]. The routes available for this are the enzymatic production of putrescine from ornithine and/or from arginine via agmatine, followed by the transformation of agmatine to N-carbamoylputrescine, and then on to putrescine, which is converted to spermine and then to spermidine; cadaverine from lysine; 2-phenylethylamine from phenylalanine; tyramine from tyrosine; histamine from histidine; tryptamine from tryptophan; and trimethylamine from trimethylamine-N-oxide [16].