## 3 Results
### Physico-Chemical Parameters of the Tested Rice Drinks  
3.2.1. pH, Soluble Solids Content, and Osmolality  
The rice drinks tested in this study showed a pH close to neutral (ranging from 6.3 to 7.4). The results obtained are confirmed by the studies of other authors, who reported similar pH values in rice drinks ranging from 5.21 to 6.10 [13]. In the study by [PERSON] et al. (2023) [24], the authors obtained slightly higher values for this parameter (depending on the type of rice used for the production of plant drinks), ranging from 5.94 \(\pm\) 0.01 to 6.22 \(\pm\) 0.01 (for white rice), from 6.17 \(\pm\)0.01 to 6.25 \(\pm\) 0.01 (for black rice) and the highest for red rice (from 6.22 \(\pm\) 0.01 to 6.27 \(\pm\) 0.01). Nevertheless, these values remained similar to the results obtained in this study. Cow's milk has a pH of 6.5 to 6.7 [34], so the pH values of the tested beverages were similar to that of cow's milk. Determining variables such as the pH of milk or its plant-based substitutes is an important factor in determining, among other things, the growth of microorganisms in food. In addition, pH also improves protein extraction, which occurs more quickly and efficiently in a slightly acidic environment [35]. The pH value in the vegetable beverages could have been influenced by the base composition, the additivesused in the industrial production of these beverages, and the production methods of these products [20]. The tested rice drinks had similar soluble solids content, ranging from approx. 9% to 13%. The main factor determining the soluble solids content of the studied rice drinks was the content of sugars and carbohydrates; the rice drinks RB_8, RB_7 and RB_3, with the highest soluble solids content (average 12.44 \(\pm\) 0.30%), was also characterised by a high content of carbohydrates (average 11.00 \(\pm\) 0.00 g/100 mL), including sugars (average 5.67 \(\pm\) 1.15 g/100 mL). In addition, it is noteworthy that beverage RB_8, characterised significantly (\(p\) < 0.05) by the highest soluble solids content (12.67 \(\pm\) 0.29%), was also characterised by the highest percentage of rice content at 15%. In contrast, the rice content of beverage RB_10, with significantly the lowest total extract content (8.67 \(\pm\) 0.29%), was 12%. The results of our study were confirmed in the study of [PERSON] et al. (2020) [20], where a soluble solids content of 12.9% was obtained for the tested rice beverage. In turn, [PERSON] et al. (2023) [12], in their research on rice drinks produced based on various types of rice, showed a much lower content of soluble solids, i.e., 0.4 \(\pm\) 0.05% (for white rice), 0.8 \(\pm\) 0.05% (for black rice), and 0.9 \(\pm\) 0.05% (for red rice), with no impact of the pasteurisation used in the tests on this parameter. The osmolality of the tested drinks averaged 324.73 \(\pm\) 70.17 mOsm/kg H\({}_{2}\)O, showing significant (\(p\) < 0.05) variation in this parameter (Table 3). The highest osmolality was recorded for drinks RB_6 and RB_8 (average 423.83 \(\pm\) 6.49 mOsm/kg H\({}_{2}\)O) and was significantly lower in drinks RB_7 and RB_4 (average 363.33 \(\pm\) 2.16 mOsm/kg H\({}_{2}\)O) or drinks RB_3, RB_9, and RB_2 (average 317.89 \(\pm\) 9.31 mOsm/kg H\({}_{2}\)O). The drink with the significantly (\(p\) < 0.05) lowest osmolality was RB_10 (193.33 \(\pm\) 1.53 mOsm/kg H\({}_{2}\)O). Thus, some of the tested beverages with osmolality > 330 mOsm/kg H\({}_{2}\)O can be classified as hypertonic. These beverages contained a high amount of carbohydrates (average 10.65 \(\pm\) 0.70 g/100 mL), which probably influenced their higher osmolality level. The remaining drinks, on the other hand, with osmolality < 270 mOsm/kg H\({}_{2}\)O, can be classified as hypotonic ones. They have a lower osmolality than body fluids and can therefore be used to rehydrate the body effectively [36]. There are no data in the available literature on the osmolality of rice drinks. Osmolality depends on the concentration and activity of solute molecules and the concentration and activity of water molecules.