## 3 Results  
### Extraction Yield and Chemical Composition  
Three different extraction conditions were used for each mushroom species, resulting in a total of nine different extracts. The results for the extraction yield of each extraction are presented in Table 1. The results show that extraction M1 presented the highest yield in all mushroom species; however, it was not statistically significant in the case of _P. ostreatus_ and _P. eryngii_ compared to the respective M2A extraction. Extraction M2B showed the lowest yield for all mushroom species, with the _P. eryngii_ M2B extract providing the lowest extraction yield of all nine extracts. The protein and total glucan content results are also shown in Table 1. The results show that all extracts presented a high amount of protein. Among them, extracts M1 and M2A from _P. eryngii_ yielded the lowest protein contents with 14.61 and 12.09 g/100 g of dry extract, respectively. In contrast, extract M2B from _A. cylindracea_ showed the highest protein content at 32.97 g/100 g of dry extract. The results show that these aqueous extraction approaches were able to extract a high quantity of protein from frozen mushrooms. Hence, these extracts have a high potential for use in the food industry as rich protein ingredients. The results suggest that extract M2B is the most adequate for producing functional ingredients rich in protein since, for all mushrooms, they had a higher amount of protein than M1 and M2A. Regarding mushroom species, the results indicate that _A. cylindracea_ was the best option for protein extraction in the conditions studied since the amount of this nutrient in extracts M1, M2A (excluding _P. ostreatus_), and M2B was higher than in the same extracts from the other two mushrooms. It is known that edible mushrooms have high nutritional value and are a good source of protein [26]. The protein contents obtained from the present aqueous extracts were in line with protein contents reported by other studies for these mushroom species. For instance, different studies have reported protein contents for _P. ostreatus_ ranging from 17 to 42 g/100 g of dried fruit bodies [27]. For _P. ervggii_, protein contents also range from 21.33 to 24.08 g/100 g of dried fruit bodies [28]. Regarding _A. cylindracea_, there are studies reporting protein contents ranging from 34.17 to 44.94 g/100 g of dried fruit bodies as well as 14.09 to 27.24 g/g of dried extract, depending on the origin/location of the mushrooms and the substrate used for their growth [26; 29]. In terms of total glucans, extract M2B from _P. eryngii_ showed the highest content (48.57 g/100 of dry extract). Due to insufficient extract mass, it was not possible to determine the glucan content for the _P. eryngii_ M2A extract. The _A. cylindracea_ extract showed the lowest content of total glucans, especially M2A and M2B, with 12.69 and 14.19 g/100 of dry extract, respectively. Hence, when an ingredient rich in glucans is desired for the desired final product, _A. cylindracea_ seems less sustainable than _P. eryngii_ and _P. ostreatus_. In terms of total glucans, the present _P. ostreatus_ extracts yielded a lower amount than what has been reported in other studies for this mushroom. For instance, [PERSON] et al. [30] reported 44.2 to 90 g/100 g of dry matter for different _P. ostreatus_ water extracts. In the same study, glucans for _P. eryngii_ water extracts ranged from 33.6 to 66.4 g/100 g of dry matter, which are in line with the results of the present study. All extracts were a better source of \(\beta\)-glucans than \(\alpha\)-glucans, which is corroborated by several previous studies [11; 12]. It is important to underline that the total glucan content as well as the \(\alpha\)-glucan and \(\beta\)-glucan ratio varies strongly within and between mushroom species depending on extraction methodology, mushrooms' development stage, the composition of the growth subtract, and the parts of mushrooms analyzed (e.g., cap versus stalk), among others [11; 12; 13].