# Techno-Functional Properties and Recent Advances in the Manufacturing of Whey Beverages: A Review
## 1 Introduction  
The dairy industry is perpetually increasing its production, resulting in the substantial production of whey as a valuable by-product. Hence, proper processing of whey is crucial, as its composition may present a risk to the environment if not disposed of appropriately. Inappropriate disposal of whey may alter the physicochemical characteristics of the soil, potentially diminishing crop yield. Moreover, the discharge of whey into wastewater may reduce dissolved oxygen levels, consequently endangering aquatic ecosystems [1, 2]. Bovine milk is widely regarded as one of the most versatile foods for humans, either consumed in its natural form or as an ingredient in various dairy products. Nowadays, a range of products are derived from milk, including liquid milk, cheese, yogurt, powdered milk products, and various additives such as protein-rich products and lactose. Additionally, fermented milk, butter, and cream-based products are also popular. In 2020, Europe produced nearly 148 million tons of milk, with close to 50% of this amount allocated for cheese [3, 4]. During cheese production, up to 90% of the milk volume is converted to whey. Additionally, whey is divided into two main groups--sweet and acid whey, respectively. Sweet whey is primarily generated during cheese production, whereas acid whey is predominantly developed in the production of quark cheese (acid-coagulated cheese) or yogurt. Sweet whey, in particular, has become the largest volume by-product in the dairy industry and contains valuable components with nutritional and technological properties, such as proteins, lactose, and minerals. Advances in technology have further enhanced the value of sweet whey, expanding its applications in the food industry [3, 5, 6]. Furthermore, whey is widely recognised as a valuable source of highly nutritious and biologically active proteins, along with other organic compounds. Notably, whey protein accounts for approximately 20% of the total protein content in bovine milk. Theseproteins possess exceptional functional properties (foaming, emulsification, water-binding, and gelation properties). Due to these unique characteristics, whey protein products are increasingly sought after as food additives [7; 8; 9]. Recent advances in whey processing technologies, such as ultrafiltration, microfiltration, and enzyme treatments, have unlocked new potentials for whey utilisation. These innovations allow for the production of high-purity whey protein isolates (WPI) and other specialised products, catering to a growing market demand for whey-based ingredients [10]. However, whey is often regarded as a production waste and, in many cases, is combined with water from cleaning processes before being discharged to wastewater treatment plants and may be associated with serious environmental problems [11]. It is reported that only 50% of the sweet whey produced is further processed for food production. Fifty percent of this amount is used directly in liquid form, for example, in the production of ricotta cheese and whey-based fermented beverages. Approximately 30% of the processed whey volume is converted into powder, which can be used for producing infant formula; 15% is purified and sold as lactose and its by-products, while the remaining portion is utilised for whey protein concentration or isolation [11; 12; 13]. As the dairy industry expands, the environmental and economic challenges associated with whey disposal and management become increasingly significant. This review explores not only the functional and nutritional properties of whey but also recent innovations that address these challenges. In particular, this review will examine the techno-functional properties of whey, discuss the latest manufacturing methods and technologies, and explore recent trends in the development of whey beverages.