Yeast-Based Bio-Valorization of Whey for Sustainable and Functional Bread Development: A Step Toward Next-Generation...

Two indigenous strains of Saccharomyces cerevisiae (GP4 and 11815), isolated from traditional fermented products of the Northwestern Himalayas, together with a lactose-utilizing yeast, Kluyveromyces marxianus (MH6), and two commercial S. cerevisiae (dry and compressed), were comparatively evaluated for their suitability in producing sustainable whey-based bread. All yeast strains were assessed for critical baking-relevant characteristics, including growth kinetics, acid tolerance, maltose utilization, invertase activity, and latency period, along with quality parameters such as texture profile and color. K. marxianus (MH6) was identified as the most effective strain for whey fermentation due to its lactose-utilizing capability, S. cerevisiae (GP4) was selected for dough fermentation owing to its better baking traits, maltose metabolism, and favorable bread quality attributes. Based on the biochemical profiling (3.3 °Brix, 8.4% total sugars, 2.9% reducing sugars, 0.21% soluble protein, pH 5.5) during fermentation, 22 h at 28°C was standardized as the working fermentation time and temperature for whey fermentation. From the standpoint of physicochemical profiling and nutritional composition, bread prepared using S. cerevisiae (GP4) and fermented whey demonstrated the highest overall quality. In addition, processing parameters for fermented whey-based bread production were standardized to a yeast inoculum level of 4% (w/w); a primary proofing time of 1.5 h for commercial yeasts and 2.5 for GP4; a secondary proofing period of 30 min; a baking temperature of 200°C; and a baking time of 25 min. Breads formulated with fermented whey and GP4 yeast exhibited a shelf life of up to 4 days under ambient storage conditions. PRACTICAL APPLICATIONS: This study provides a sustainable and cost-effective valorization protocol for dairy whey utilization in bread production through yeast fermentation. Fermented whey can be incorporated into a bread formulation that would enhance the protein content, loaf characteristics, texture, and shelf life. Additionally, it will also help to refrain whey disposal into the environment, which can cause water hazards. The addition of Kluyveromyces marxianus to help reduce lactose further increases the lactose-free suitability of whey-based products for lactose-sensitive consumers and helps in altering the acid profile of the bread. Furthermore, the baking performance of the indigenous Saccharomyces cerevisiae GP4 strain was found to be superior to that of commercial baker's yeast, which suggests that the indigenous yeast is a potential alternative starter culture in the bakery industry. This study also standardised the process (whey fermentation conditions, bread inoculum concentration and proofing conditions, and baking conditions), providing a practical protocol for bakeries and dairy processors to utilize surplus whey to develop whey bread that can be used by small to medium dairy and bakery businesses to turn a low-value by-product into a value-added functional food.