## 3 Results
### Bioactive Properties of the Tested Rice Drinks  
#### 3.3.1 Polyphenol Content  
The studied beverages were characterised by a relatively low content of total polyphenols, ranging from 0.59 \(\pm\) 0.03 to 2.81 \(\pm\) 0.03 mg GAE/100 mL, with statistically significant (\(p<0.05\)) differences between the analysed beverages in terms of this parameter (Figure 1). The beverage RB_10 (0.59 \(\pm\) 0.03 mg GAE/100 mL) had the lowest total polyphenol content, while the beverages RB_6 (0.79 \(\pm\) 0.04 mg GAE/100 mL), RB_7 (1.03 \(\pm\) 0.03 mg GAE/100 mL), or RB_2 (1.14 \(\pm\) 0.02 mg GAE/100 mL) were significantly higher. Among the rice beverages tested in this study, the highest total polyphenol content was found in RB_5, with a polyphenol content of 2.81 \(\pm\) 0.0 mg GAE/100 mL. There are little data in the available literature for the content of total polyphenols in rice drinks. In the case of rice drinks obtained from white rice, the content of these bioactive ingredients was similar to the results obtained in our studies and amounted to less than 10 mg GAE/100 g of drink. In the case of rice drinks obtained from red and black rice, the content of total polyphenols was significantly higher, reaching approximately 40 mg GAE/100 g and 100 mg GAE/100 g, respectively, which the authors explained by significant differences in the content of these bioactive ingredients in the raw materials used to produce the drinks, i.e., white rice (less than 20 mg GAE/100 g), red rice (approx. 120 mg GAE/100 g), and black rice (just over 120 mg GAE/100 g). These authors also found slight differences in the concentration of total polyphenols in unpasteurised and pasteurized drinks (a slight decrease in total polyphenols content in pasteurized products) [31]. More  
Figure 1: The total polyphenol content of tested rice drinks (arithmetic mean \(\pm\) standard deviation; a-i—mean values in bars marked with different letters differ significantly (\(p<0.05\))). information can be found in the literature for the content of these bioactive compounds in other plant-based beverages used as milk substitutes. [PERSON] et al. (2020) [20] showed the highest content of total polyphenolic compounds in a hazelnut beverage (130.42 mg GAE/100 mL), and a much lower content in a soy beverage (8.79 mg GAE/100 mL) or in an almond beverage (0.12 mg GAE/100 mL). Comparing these results with those of our study, it can be concluded that the content of polyphenolic compounds in the rice drinks studied was most similar to the almond drink, as it averaged 1.40 \(\pm\) 0.62 mg GAE/100 mL for all the products analysed in the study. The authors also examined the content of polyphenolic components in the respective raw materials used to make the plant beverages and showed that the content of these bioactive components was significantly higher in the fresh material; for hazelnut it was 226 mg GAE/100 g, for soy 94.10-116.70 mg/100 g, and for almond 95.28 mg GAE/100 g. Although a high content of phenolic compounds characterized the fresh plant material, the processing of the respective raw materials resulted in a significant reduction of these bioactive components in the final products [20]. Studies by other authors also confirm that nuts and cereals, which are rich in protein, dietary fibre, fatty acids, and vitamins or phytonutrients, contain significantly more of these bioactive components than plant-based milk substitutes. For example, hazelnut's total phenolic compound content was reduced by about 42% when a milk substitute was produced from raw hazelnuts because the bioactive components were lost during processing [45]. Another reason for decreased total phenolic compounds observed in most plant-based dairy products may be the lower amounts of hydrophilic phenols [46]. According to the literature, the most minor loss in polyphenol content is caused by the microbial processes, thus plant-based beverages are increasingly produced using these processes [47].