# Functional Yogurt: Types and Health Benefits
## 2 Functional Yogurt Types
### Probiotic  
Probiotics are live microorganisms that provide beneficial effects on health, primarily by supporting the digestive system [39; 61]. The consumption of these microorganisms, defined as live microbial food supplements, is generally considered safe [67]. Probiotics can modulate the gut microbiota, enhance digestive health, and support the immune system [64]. Studies have demonstrated that food products must contain a minimum of between \(10^{6}\) and \(10^{7}\) CFU/mL probiotics to benefit from these advantages [56; 60]. _Lactobacillus_ and _Bifidobacterium_ species are prevalent in yogurt production [47; 59]. _Streptococcus salivarius_ subsp. _thermophilus_ (_S. salivarius_ subsp. _thermophilus_ and _L. delbrueckii_ subsp. _bulgaricus_ are commonly used as starter cultures in yogurt production [125]. During fermentation, they facilitate the conversion of lactose into lactic acid through processes such as glycolysis, lipolysis, and proteolysis. This starter culture promotes the viscous texture of the products [126]. Studies have investigated the use of diverse probiotic species in yogurt production [63]. The probiotic strains used in production affect the properties of yogurt. Therefore, the choice of probiotic is a crucial parameter for production [4]. Live probiotics in yogurt are referred to as bioyogurt because of their effects. Probiotics not only provide health benefits but also improve the physicochemical, textural, and sensory properties of the main product [57]. This is primarily due to the exopolysaccharides (EPS) produced by the probiotics, as well as the starter cultures [65; 127]. These polysaccharides, which are secreted outside the cells by probiotics, positively affect the textural properties of the yogurt, including viscosity, gel structure, stability, and smoothness, as well as the sensory properties such as mouthfeel, taste, and aroma [106; 127]. The probiotics generally used in fermented food production support the structure of functional yogurt by producing EPS [86]. Commonly, yogurt products have high acidity and low pH values, making it unlikely that they provide suitable conditions for the viability of probiotics during passage through the digestive system [36]. Using the yogurt matrix for probiotic delivery and ensuring probiotic viability and stability is essential [55]. The survival of these bacteria during the digestive process demonstrated that they can contribute to beneficial bacterial populations in the digestive system. A recent study assessed the effects of _Lentilactobacillus kefranofaciens_ (_L. kefranofaciens_) and _Kluyveromyces marxianus_ (_K. marxianus_), probiotic microorganisms isolated from kefir grains, on yogurt fermentation as mono- and cocultures [57]. The results of yogurt production demonstrated that, when only _L. kefranofaciens_ was used in a monoculture, the yogurt produced tended to have a low viscosity. Consequently, these yogurt samples presented weaker gel structures and greater whey separation. On the other hand, co-culture with both microorganisms increased microbial aggregation, biofilm formation, and exopolysaccharide production, increasing nutritional stability. Additionally, it resulted in yogurt with higher viscosity, strengthening the gel structure and reducing whey separation. Additionally, _L. kefranofaciens_ and _K. marxianus_ exhibited similar survival rates in digestive fluids when used alone and together, indicating that these bacteria could be effective as probiotics. A study by [PERSON] et al. aimed to examine a new yogurt production method by adding the probiotic bacterium _Lacticaseibacillus rhamnus_ (_L. rhamnus_) to conventional yogurt and to compare the antioxidant capacity, performance during storage, and sensory properties of this yogurt [55]. The probiotic yogurt was more acidic than conventional yogurt, but there was no significant difference at the end of the storage period. _S. salivarius_ subsp. _thermophilus_ and _Lactobacillus delbrueckii_ subsp. _bulgaricus_ (_L. delbrueckii_ subsp.