# Quality Parameters of Wheat Bread with the Addition of Untreated Cheese Whey
## 1 Introduction  
Whey is defined as the milk serum remaining after separation of the cheese curd, resulting from the coagulation of milk proteins through the use of either acid or proteolytic enzymes [1]. Whey, a by-product of cheese making, is distinguished into sweet whey (from the precipitation of casein by rennet) and acid whey (coagulation of proteins through the addition of acid) [2]. Whey is composed of lactose (70-72% of the total solids), whey proteins (8-10%), and minerals (12-15%) on dry basis [1].  
Due to its high biological oxygen demand (BOD) and chemical oxygen demand (COD) content, whey causes an enormous amount of environmental pollution [2]. However, it comprises an excellent source of functional proteins and peptides, lipids, vitamins, minerals, and lactose [3]. Consequently, discarding whey constitutes a significant loss of potential nutrients and energy [1]. Moreover, compelling evidence in the literature supports the exceptional nutritional quality of whey protein compared to common dietary protein sources. The Biological Value of whey proteins exceeds that of egg protein (reference protein) by ca. 5%, due to its content of essential amino acids and specifically of the branched chain amino acids (leucine, isoleucine, and valine) [3].  
Whey is widely used in the production of whey cheeses, many of which have distinct names based on the region or country of origin such as Myzithra, Manouri, Ricotta, etc. It is also used to commercially produce whey protein bars and beverages used as dietary supplements by athletes, resulting in maximum physical performance [4]. According to USADEC [4], concentrated whey can be used for texture enhancement in meat and poultry products, color enhancement in bakery and confectionery products substituting the action of milk or eggs, etc.  
Bread constitutes one of the most important staple foods, being a good source of macronutrients (carbohydrates, proteins) and micronutrients (vitamins, minerals). However, it is susceptible to mold growth and has a short shelf life (typically of 3-7 days) when stored at room temperature due to its high moisture content (about 40%) and water activity (about 0.94-0.97) [5]. For this reason, several additives (mainly sorbate and propionate salts) are added in order to increase bread shelf life and prevent its microbiological spoilage [6].  
The time-dependent loss of bread quality (deterioration of texture, taste, and aroma) is described as \"staling\". This phenomenon has been mostly attributed to the retrogradation of starch, but it is also related to moisture loss. Both starch retrogradation and moisture loss equally contribute to bread staling and result in the hardening of bread texture [7].  
Flavor, on the other hand, comprises an equally significant sensory parameter for the acceptability of bread by consumers. A large number of volatile compounds are responsible for the aroma of fresh bread including alcohols, aldehydes, esters, pyrazines, pyrrolines, etc. [8].  
To the best of our knowledge there are no data available in the literature involving the direct use of untreated cheese whey for the production of leavened wheat bread. Therefore, the objective of the present study was to evaluate, on a qualitative and quantitative basis, commercial wheat breads prepared by replacing water with untreated cheese whey. At the same time, the proposed application comprises a novel use of cheese whey contributing to the solution of the whey disposal problem.