# The Fermentation of Orange and Black Currant Juices by the
## 1 Introduction  
Fermented beverages from ancient times offer essential nutrients crucial for human health, fostering physical and mental well-being while aiding in disease prevention and management. Recently, there has been a surge in consumers' interest in functional foods that not only provide essential nutrition but also offer specific benefits to bodily functions. Examples include foods rich in bioactive compounds like oligosaccharides, dietary fiber, and beneficial microbes that support gut health. Alongside established functional ingredients such as trace elements, vitamins and probiotics represent a growing category of active components, alongside probiotics, contributing to overall health and vitality [1]. Live microorganisms that, when administered in adequate quantities, confer health benefits upon the host are called probiotics. Except for lactic acid bacteria, there is significant interest in isolating yeast strains possessing probiotic potential, with _Saccharomyces cerevisiae_ var. _boulardii_ emerging as the yeast species demonstrating clinically significant effects and verified probiotic efficacy. Initially isolated from litchi fruits by French microbiologist [PERSON] in the 1920s, _Saccharomyces cerevisiae_ var. _boulardii_ (known earlier as _Saccharomyces bouldarii_) has been employed as a probiotic yeast since the 1950s, predominantly within the pharmaceutical industry, often in lyophilized form for the prevention and treatment of diarrhea. Research on commercial varieties of _S. cerevisiae_ var. _boulardii_ revealed morphological and physiological similarities with other _Saccharomyces cerevisiae_ strains, thereby contributing to a deeper understanding of its probiotic characteristics [1; 2; 3; 4]. Multiple investigations have demonstrated the efficacy of _S. cerevisiae_ var. _boulardii_ against diverse enteric pathogens. This effectiveness is attributed to multifaceted mechanisms, such as hindering bacterial adherence and translocation within intestinalepithelial cells, generating substances that counteract bacterial toxins, and the gut cells' response to pro-inflammatory reactions during bacterial infections [1; 4; 5]. In addition to its well-known metabolic conversion of sugars into ethanol, yeast manifests other advantageous properties, notably its capacity for phytate biodegradation. This compound is known to form insoluble complexes with essential divalent minerals such as zinc, iron, calcium, and magnesium, which poses challenges by reducing the bioaccessibility of these ions. Moreover, phytate can adversely impact the functional and nutritional characteristics of proteins, including their susceptibility to enzymatic digestion [6]. Another notable function of yeast is folate production. Foldes, indispensable cofactors in nucleotide biosynthesis, are vital for cellular proliferation and development. Mammals lack the folate biosynthetic pathway and require an adequate dietary supply, whereas plants and yeast possess this ability. It is well established that folate is important in the prevention of neural tube defects during fetal development. Folate consumption is linked to lowered risks of cardiovascular disease, cancer, and neurodegenerative disorders. Additionally, yeast strains contribute positively to the decomposition of mycotoxins [6; 7; 8]. The examination of yeast viability demonstrates that probiotic _S. cerevisiae_ var. _boulardii_ withstands the elevated alcohol levels generated during fermentation and subsequent vacuum distillation processes [9; 10; 11]. Fruit juices contain many compounds, including ascorbic acid, vitamin E, beta-carotene, and phenolic compounds, renowned for their antioxidative properties, which are crucial for neutralizing free radicals. The importance of these antioxidants extends to health maintenance, disease prevention, and age-related degenerative conditions [12; 13; 14].