## 3 Results and Discussion  
### Antioxidant and Antihypertensive Properties  
For all beverages, pH, antioxidant capacity and antihypertensive activity are shown in Table 2. The antioxidant capacity was measured against peroxyl radical using ORAC assay, and the antihypertensive activity by the beverages' ability to inhibit ACE. Additionally, Table 2 includes data regarding the beverages' degree of proteolysis measured as an amount of free amino groups and expressed as L-Leu equivalents. Since no significant differences in antioxidant capacity, ACE-I activity and degree of proteolysis were determined between beverages of the same type (i.e., kefir, ryazhenka, amasi and mmahewu) but from different manufacturers, in the following text all data regarding the same beverage type were pulled together and reported as mean \(\pm\) standard deviation. The pH values of kefir, ryazhenka and amasi were in the range 4.4-4.5, while the pH value of mmahewu was substantially lower and comprised approximately 3.5, which is consistent with previously reported data for these products [4; 5; 6]. Generally, the antioxidant capacity of the studied beverages decreased in a row: amasi > kefir = ryazhenka > mmahewu, while ACE-I activity decreased (i.e., IC\({}_{50}\) increased) in a row: mmahewu > amasi > kefir = ryazhenka. At the same time, the degree of proteolysis decreased in a row: amasi > kefir > ryazhenka > mmahewu. It is well known that antioxidant and ACE-I properties of fermented products are primarily attributed to bioactive peptides produced through the action of the cell envelope proteinases (CEPs) of starter cultures [27]. Since for dairy-based beverages both antioxidant capacity and ACE-I activity correlated with the degree of proteolysis, it can be proposed that kefir, ryazhenka and amasi starters produced almost similar bioactive peptides, and their amounts are primarily responsible for the observed overall activities. In the case of mmahewu, having the lowest degree of proteolysis, this beverage demonstrated the lowest antioxidant activity and the highest ACE-I activity among all studied beverages. This situation can be explained by the different source of bioactive peptides in this beverage. While in dairy-based fermented beverages the primary release source of bioactive peptides is caseins [28], in corn-based fermented beverages it is zein and glutelin [29]. The activities of bioactive peptides are determined by both their amino acid compositions and sequences, and the ACE-I peptides are more sequence-specific than antioxidant ones [30]. Hence, while the lowest antioxidant activity of mmahewu is a result of the lowest amount of peptides in this beverage, the highest ACE-I activity suggests the presence of some peptides with very strong ability to perform competitive inhibition at the catalytic site of ACE. Currently, a number of scientific studies have confirmed the probiotic potential and the health benefits of kefir. It has been shown that the regular consumption of kefir improves digestion, leads to a decrease in blood glucose in patients with type 2 diabetes, improves lipid profile, lowers blood cholesterol, normalizes blood pressure, leads to a decrease in the concentration of free radicals in the blood and has a number of other health-promoting effects [31]. In contrast, studies confirming the health-promoting effects of ryazhenka, amasi and mmahewu are currently absent; however, due to the presence of probiotic strains of lactic acid bacteria in the starter cultures, these products are defined as beneficial to health [4; 32; 33]. In the presented study it was demonstrated that ryazhenka and mmahewu possess antioxidant capacity comparable to kefir, while the antioxidant capacity of amasi was significantly higher. As for the ACE-I activity, in ryazhenka it was slightly lower than in kefir, and in amasi and mmahewu it was approximately 1.6 and 3 times higher, respectively.