## 4 Discussion  
The analysis performed in this study revealed no negative effects of vacuum impregnation on the brewing process or on the final product quality. In our previous studies, vacuum impregnation did not cause significant changes in the germination efficiency of the tested cereals, i.e., barley, wheat and rye. It was found that the impregnation did not affect the internal structure of the grain [28]. Other authors noticed that the integrity of plant tissue cells is unaffected despite changes in microstructure caused by vacuum impregnation [7; 8].  
In the current study, a decrease in the pH of the congress word was observed during malting. Wort from malt obtained from vacuum-impregnated grain, under a pressure of 5 kPa, showed a greater decrease in pH. This has been confirmed in other studies that the optimum pH for \(\alpha\)-amylase is 5.6 to 5.8, and for \(\beta\)-amylase, it is 5.4 to 5.5. Higher pH values are considered unfavorable, in contradistinction to lower pH values. At a low pH, higher amounts of fermentable sugars are obtained, which results in an increase in the degree of fermentation [30]. The pH values of the word produced from malt, which was created from impregnated grain, were slightly lower than optimal. These low pH values do not cause enzyme inactivation and may only slightly slow down the starch saccharification process.  
The literature does not indicate the optimal extract content. It should be as high as possible. In the case of malt obtained from impregnated grain, the extract content was slightly lower, but at further stages of beer production, during beer brewing, the extract content can be increased [29; 30]. To produce high-quality beer, the malting industry requires malt with a high extract yield. Brewing barley is the primary raw material used in the production of beer, and its quality is critical. To meet these requirements, the barley must be able to germinate vigorously [33]. The extract is one of the most important malt quality parameters. During the mashing stage, it determines the amount of received soluble solids. The extract content slowly decreases at mash-in temperatures higher than 65 \({}^{\circ}\)C [34].  
Obtaining the word with the highest extract and the desired pH is the main goal of mashing. The pH value is crucial for the quality of the beverage produced. The lowest extract value was obtained in the word produced from 100% Special X malt, whereas the highest extract values were obtained from the word produced from 100% Vienna malt and 100% Melanoidin malt. Surprisingly, the combination of Caramel pils and Special X malt also resulted in the high extract of the word produced. The use of a mixture of Vienna malt, melanoidin malt and Special X malt resulted in the highest extract of the word produced from ternary mixtures. The pH values obtained by the researchers were very diverse and ranged from 6.5 to 8.4 [35].  
[PERSON] [36] states that the optimum pH of the word should be 5.6 \(\pm\) 0.2. Based on the results obtained, the optimal parameters of the word can be obtained by combining Vienna and Melanoidin malts in a 2:1 ratio.  
It is an issue of utmost importance to control the pH value within the desired range in the different phases of beer production. Mash pH is an important factor affecting the isomerization and solubility of \(\alpha\)-acids, yeast flocculation, enzymatic activity and extract yield. When it comes to beer, pH affects its flavor (acidity), flavor stability, non-biological stability and biological stability [37].  
Both the raw materials at the various stages of beer production and the final product should be tested for pH. Its value has a decisive influence on the taste, prevents the development of microorganisms and is a key factor influencing the maturation of beer, its stability and its durability [38; 39].