###### Abstract  
This study aimed to evaluate the feasibility of incorporating natural mineral waters (NMW), including thermal water (TW) and bottled mineral water (BMW), into bread ('biju' type) to enhance its mineral content and explore their impacts on physicochemical, technological, biochemical, and chemical composition. NMW, rich in sodium, potassium, and magnesium, resulted in bread formulations with higher contents of these minerals and greater total mineral levels, thus potentially enriching food products. Proximate composition analysis showed no significant differences in moisture, proteins, carbohydrates, and energy, except for lipids and soluble sugars. Texture analysis revealed that water type influenced textural properties, with salt content affecting hardness, springiness, and cohesiveness. Viability analysis of _Saccharomyces cerevisiae_ showed consistent results across formulations, suggesting water pH and mineral content did not significantly affect fermentation. In addition, bread formulations without added salt were developed to assess the potential of sodium-rich NMW as a natural source of salt. For these samples, and considering the parameters assessed, except for salt and sodium content, the differences observed were slight compared to salt-added formulations, highlighting NMW's potential to produce low-salt bread. These findings not only enhance the value of local resources but also offer an innovative and sustainable strategy for utilizing NMW springs across Europe. natural mineral waters; bread; chemical composition; physical properties; minerals 202  
and vitamin B [3]. Therefore, due to its high consumption and accessibility, bread represents a good model for developing innovative, nutrient-enriched, value-added products. Natural mineral waters (NMW) originate from underground reservoirs, exhibiting specific microbiological features and, occasionally, health-promoting effects [4]. They differ from drinking water due to their spring purity and consistent mineral content, encompassing a spectrum of elements such as calcium, magnesium, potassium, sodium, and trace minerals [5]. Among different types of NMW, thermal water (TW) is also distinguished due to its unique mineral and oligo-element profiles, attributed to myriad therapeutic effects [4; 6]. TW receives this designation independently of the temperature at the source as long as it emerges inside a thermal resort and has therapeutic applications [6]. Portugal is one of the European countries richest in thermal sites, predominantly located in the northern region. Despite the well-recognized richness of NMW as a source of mineral compounds, the potential of this resource remains underexplored as an ingredient in food products. Notably, the potential of TW in food manufacturing has been thoroughly neglected. Thus, this study proposed that NMW be utilized beyond its conventional purposes and incorporated into a bread formulation, aiming to prospect the potential of this natural resource to enrich bread with mineral compounds, creating a nutritive and innovative product with distinct sensory flavors and characteristics. Additionally, NMW is typically abundant at its source but has limited practical applications. By demonstrating its feasibility in bread production, we introduce a novel approach to its utilization, serving as a model for sustainable exploration of NMW springs across Europe, which is paramount to promoting their valorization and local development. Importantly, the final quality of bread, including technological, biochemical, and nutritional aspects, may be strongly affected by the added components [7; 8], making it essential to evaluate the impact of incorporating novel ingredients on these parameters.