# Functional Yogurt: Types and Health Benefits
## 2 Functional Yogurt Types
### Prebiotic  
Prebiotics that have a nondigestible function and are selectively fermented in the intestine contribute to maintaining, balancing, and promoting the development of the gut microflora when added to yogurt production [70; 71]. In addition to their health benefits, they also help improve the rheological and sensory properties of the product [73]. The generally used prebiotics include fructooligosaccharides (FOSs), galactooligosaccharides (GOSs), inulin (INU), polydextrose (PDX), and xylooligosaccharides (XOS) [81]. Adding one or more of these factors enhances the functional properties of the product [72]. Determining which prebiotics to integrate and at what dosage are parameters that influence and need optimizing for product characteristics. Additionally, researchers have conducted numerous studies to evaluate food byproducts from fruits, vegetables, and grains as health-supporting food additives, supporting zero-waste policies [70].  
INU and PDX were added to yogurt to examine their physicochemical and sensory properties in a study conducted by [PERSON] et al. [71]. While no significant difference in texture was observed in the yogurt prepared with PDX, those with added INU showed a decrease in texture properties during storage. Similarly, in sensory evaluation, PDX-added products were perceived similarly to the control, whereas those with INU were rated lower in acceptance levels. Conversely, when probiotic survival was evaluated, the yogurt with INU presented increased probiotic survival during storage, whereas overall, all of the yogurts maintained minimum probiotic survival throughout the storage period.  
In a recent study by [PERSON] et al., FOS, GOS, INU, PDX, and XOS prebiotics were added to yogurt in equal dosages to investigate their effects on the textural and rheological properties of products [130]. INU, XOS, and PDX had the strongest influence on the rheological, textural, and water-holding characteristics of yogurt, whereas GOS and FOS had less of an impact on these properties. These varied effects highlight the importance of careful selection when adding prebiotics to yogurt.  
When developing prebiotic-added yogurt, the type and dosage of the added prebiotics are crucial. For example, one study investigated the physicochemical and sensory properties of yogurt supplemented with different amounts (3%, 6%, 9%, 12%, or 15% \(w/w\)) of INU [75]. The results showed that, as the amount of INU increased, the total acidity of the product decreased, whereas the pH increased. These findings indicate that, while INU supplementation enhances the nutritional value of yogurt, the optimal dosage needs to be optimized.  
Under the zero-waste policy, components derived from food waste and byproducts can be utilized as prebiotics in functional yogurt production [45]. One study evaluated the prebiotic properties of byproducts obtained from guava fruit and their utilization in yogurt production [70]. Enzymatically processed guava byproducts significantly promoted the growth of _Lactobacillus_ spp. in prebiotic-supplemented yogurt, demonstrating that _Lactobacillus_ spp. are suitable nutrient sources for probiotic bacteria. Additionally, guava byproducts were found to enhance the textural properties of yogurt. This study serves as a significant example for the evaluation of food byproducts.  
In summary, the addition of prebiotics to yogurt products enhances both their rheological and sensory properties to support health. Additionally, the materials derived from food waste and byproducts can serve as prebiotic sources, contributing to zero-waste policies.