## 4 Conclusions  
This study provides a comprehensive evaluation of the fermentation performance of various LAB strains and their contributions to the quality of fermented products, especially fermented dairy products. The findings underscore the significant role of each strain's unique metabolic capabilities in shaping the organoleptic, rheological, and functional characteristics of the final products. The _L. acidophilus_ demonstrated a remarkable balance between lactic acid production and sensory acceptance, making it a prime candidate for enhancing the flavor and overall preference of fermented milk products. _B. bifidum_ stood out for its ability to produce high viscosity, attributed to its exopolysaccharideadic production, and its distinctive aromatic profile. These traits highlight its potential in developing texturally rich and flavor-intense fermented products. Furthermore, the observed differences in organic acid and sugar metabolism across strains provide valuable insights into tailoring fermentation processes to achieve specific quality attributes. For instance, the high lactose consumption by the _L. helveticus_ and its moderate rheological impact suggest its suitability in applications where enhanced textural properties are desired. As for aroma profiles, it is thought that the phenethyl alcohol, 3-methyl-1 butanol, and ethanol compounds are associated with the _B. bifidum_; the hexanoic acid and 2-methylbutanal compounds are associated with the _L. acidophilus_; the hexanoic acid, 2-methylbutanal, 2-furanmethanol, and acetaldehyde compounds are associated with the _L. bulgaricus_; and the hexanoic acid, 2-methylbutanal, and 2-heptanone, in addition to the acetoin and d-limonene, are associated with the _L. casei_. On the other hand, it is thought that the _L. helveticus_ strain is associated with hexanoic acid, 2-methylbutanal, and 2-heptanone, as well as benzaldehyde compounds. The _S. thermophilus_ strain is associated with hexanoic acid, hexanol, as well as acetoin, 2,3-pentanedione, 1-butanol, and 3-methyl-2-butanone compounds. Especially fruity aroma properties from aroma profiles were associated with the _L. casei_ and the _L. helveticus_ strains. This research also emphasizes the importance of selecting strains not only for their health-promoting attributes but also for their capacity to optimize product quality. By combining the functional benefits of these microorganisms with desirable sensory profiles, this study offers a pathway to develop innovative, consumer-preferred fermented products. The unique metabolic capacities of these prominent cultures have been revealed to play an important role in determining the aroma, organic acid content, viscosity, and overall quality of the products as a whole. Therefore, the findings of this study can provide the right strain selection for a fermented dairy product or a different non-dairy-based fermented product according to the desired functional properties. It also can provide a preliminary guide for inoculation in the right ratios as an adjunct culture or co-culture for a desired property. Limitations of this study are that the combined use of strains may produce different reactions and therefore different results, especially in terms of aroma profiles. Future research can explore the synergistic or antagonistic interactions of LAB strain combinations and their stability under different storage conditions. Additionally, investigating their effects on plant-based milk alternatives could provide insights for non-dairy fermentation. Optimizing vitamin production, bioavailability, and prebiotic interactions may further enhance the functional properties of fermented products. These studies can contribute to the development of tailored probiotic formulations for diverse food applications. These areas can provide valuable insights for optimizing LAB strains in various food production applications. Conceptualization, T.K.T. ; Methodology, F.E.D. and E.C.D. ; Validation, F.E.D. ; Formal analysis, N.O. and E.C.D. ; Investigation, T.K.T. and N.O.