Whey, Waste or Value?

The dairy industry has effluents of different characteristics, according to the product obtained (yogurt, cheese, butter, milk, ice cream, etc.). By-products contain various valuable nutrients; thus, their reuse in the production process allows efficient exploitation of all nutrients available in raw milk. The processing of dairy products becomes a complex network of interrelated production processes. Often, production of a certain dairy product results in an additional residual dairy flow by-product. For instance, production of cheese results in additional production of whey and cream; production of butter results in additional buttermilk [1]. The cheese manufacturing industry produces vast volumes of aqueous wastes. It can be referred that for the production of 1 kg of cheese, 10 kg of milk are needed, originating 9 kg of cheese whey [2]. Whey is the major by-product of the dairy industry and its disposal without expensive sewage treatments represents a major source of environmental pollution due to the bulk quantities and its high organic load. Lactose, the major component of whey solids, contributes to its high biochemical and chemical oxygen demand (BOD, COD). It is 175-fold higher than the typical sewage effluent [3]. With increasingly strict environmental regulation of disposing of whey as waste has become difficult and costly. The growing societal focus on circular economy and the environmental pressure has forced the dairy industry to manage its whey side stream. Cheese whey is simultaneously an effluent with strong organic and saline content and nutritional value. Whey contains valuable substances that are possible to valorise, including functional proteins and peptides, lipids, vitamins, minerals and lactose [4]. In recent decades Dairies around the world have developed technologies, processing capacities, products and new business models for utilising these substances. The rapid growth in global markets for food ingredients, including whey-based protein powders, which are ‘among the winners of several new nutrition trends and food developments’ [5]. Thus, whey has become an important nutritional and functional ingredient for high-quality foods [6] and the global whey protein industry has been estimated to grow by 12–14% per year [7]. This strong market trend is strongly driven by the rise of ‘functional nutritionism’, which refers to the increased engineering and reengineering of food in coevolution with changing corporate strategies, trends in food, diets and health, and new food and nutrition policies [5,8,9]. An indication of this trend is the large and growing market for functional food ingredients, i.e. probiotics, proteins and amino acids, phytochemical and plant extracts, prebiotics, fibres and specialty carbohydrates, omega-3 fatty acids, carotenoids, vitamins, and minerals. In 2018 these were estimated at US$ 68.6 billion worldwide, rising to US$ 94.2 billion by 2023 [10].