1
History of Whey Production and Whey Protein Manufacturing

Mingruo Guo1, 2 and Guorong Wang1

1 Department of Nutrition and Food Sciences, University of Vermont, Burlington, USA

2 College of Food Science, Northeast Agriculture University, Harbin, People's Republic of China

1.1 Types of Whey

Milk is a complex of colloidal suspension that is comprised of fat globule, casein micelle colloidal and serum or whey phase (Figure 1.1). Whey (sometimes called milk serum) is a yellowish to greenish clear solution strained from milk curd coagulated by either rennet or acid. Whey components are those small molecules that are not involved in the milk curdling and are able to be strained out. The typical whey solid components include lactose, protein (mainly whey protein), and minerals as illustrated in Table 1.1. Whey liquid contains over 50% of whole milk solids, including the majority of minerals, and nearly all whey proteins and lactose.

Figure 1.1 Milk is a complex suspension system comprised of fat globules, casein micelles, and the serum/whey phase. Whey proteins, lactose, and minerals are presented in the serum/whey phase.

Table 1.1 Analytical data of whole milk and whey.

Source: Data adapted from Smithers (2008).

Milk coagulated by different method resulted in different types of whey. In general, it can be categorized into sweet whey and acid whey. There is no clear definition between sweet and acid whey, but typically cut off at pH of 5.6. Sweet whey has a pH higher than 5.6, while acid whey is below pH 5.6. Sweet whey is usually from cheese manufacturing (rennet coagulated) and sometimes also called as cheese whey. Acid whey is that from coagulation by fermentation (lactose converted to lactic acid, such as Greek yogurt manufacturing) or by adding acid (acid casein production) (Tunick 2008). The compositional difference between sweet and acid whey is listed in Table 1.2.

Table 1.2 Comparison of sweet and acid whey components.

Source: Data adapted from Tunick (2008).

1.1.1 Cheese Whey

Mammals such as cattle, sheep, and goat have been domesticated for over 10 000 years (Clutton-Brock 1999; Beja-Pereira et al. 2006). With the DNA technology, it can be dated back to 17 000 years ago (Troy et al. 2001; Beja-Pereira et al. 2006). Besides milk, cattle and other mammals were also domesticated for traction, wool, or meat. Eastern Asian and Central Africa domesticated cattle as early as other regions, but with no tradition of milking (Clutton-Brock 1999). Until today, people from those regions still have more lactose intolerance than people from other regions like Northern Europe and Near East. The practice of milking a critical step during the prehistoric period because it made a sustainable and nutritious food supply without slaughtering the precious livestock. Making cheese was a milestone of the human civilization history. Cheese, as a preserved food, is much easier to keep than fresh milk. The cheese making during ancient times shares much common as the modern technology, typically including natural fermentation, cooking, straining, and drying.

It is believed that the first cheese was probably produced in a ruminant stomach that is used as a storage vessel for milk (Smithers 2008). The enzyme called rennet naturally presented in the stomach curdled the milk into cheese. The milk curd was further strained to remove the whey. This was probably the first whey disposal even we do not know when and where it took place. The archeological evidence of early milking (usually in the form of a pottery milk/cheese residue) have been disclosed across the world (Evershed et al. 2008; Salque et al. 2013; Scott, Robinson, and Wilbey 1998; Yang et al. 2014). The earliest evidence of cheese making in northern Europe was of the sixth millennium BC (Salque et al. 2013), which is a fragment of a pottery sieve that was used for straining whey (Figure 1.2). The reconstructed sieve vessel (Figure 1.2b) was very similar to the modern cheese sieve from Haute-Loire, France, dating back to the beginning of the twentieth century (Briggs 2012).

Figure 1.2 (a) The reconstructed sieve vessel; (b) the sieve fragment (7000 years old) found in the region of Kuyavia, Poland; and (c) a modern pottery colander that can be used for cheese straining.

Source: Modified from Salque et al. (2013).

A typical cheese production includes a rennet addition to cleave the casein micelle hair (?-casein hair), thus collapsing the micelle structure and then curdled milk (O'Callaghan et al. 2002). The milk serum phase is able to be strained out by cutting and pressing the milk curd. The rennet coagulation process is depicted in Figure 1.3. Rennet is a complex of enzyme produced in ruminant stomachs. The functional component called chymosin is a protease that can cut off the ?-casein hair (a casein protein that stabilizes the micelle structure), thus curdle the casein micelles (Daviau et al. 2000). Fat globules is trapped or emulsified by the casein curd while the serum phase can be strained out which is so called sweet whey or cheese whey. When 1 part of cheese is made, there is 9 parts of liquid whey generated. The ?-casein fragment cut from the micelle by rennet called glycomacropeptide () (Brody 2000) commonly presented in sweet whey products. Rennet does not work on lactose into lactic acid, therefore, sweet whey has a more neutral pH. Due to the huge volume of cheese making in the world, sweet whey from cheese making is the major commercial available whey today.

Figure 1.3 Rennet coagulated milk curd and sweet whey.

1.1.2 Acid Whey

Acid whey is a byproduct of acid coagulated milk including acid casein and Greek yogurt. At neutral pH, casein micelle is stabilized by ?-casein hair (via electrostatic repulsion) and colloidal calcium phosphate () (de Kruif and Holt 2003). The acid coagulation mechanism is depicted in Figure 1.4. When pH drops, the ?-casein electrostatic repulsion was neutralized and cause the micelle hair layer shrinks (de Kruif 1997). On the other hand, CCP which binds casein molecules is solubilized into the serum phase (Le Graët and Gaucheron 1999). The casein micelle lost it stability, and coagulated into milk curd (Lucey 2003). The whey strained from the acid coagulated milk curd is called acid whey. The acidification can be induced by adding inorganic or organic acid (such as HCl and lactic acid) and/or fermentation (lactose converted to lactic acid).

Figure 1.4 Acid coagulated milk curd and acid whey.

Due to the different coagulation mechanisms induced by rennet or acid, acid whey and sweet whey demonstrated different physicochemical properties. Besides the pH difference, acid whey typically does not contain GMP (lack of rennet ?-casein cleave), high in ash (calcium released from micelle into serum phase), and perhaps slightly low in lactose (some of lactose converted into lactic acid) compared to sweet whey. For Greek yogurt acid whey, due to the heat treatment before fermentation, some of the whey protein (especially ß-lactoglobulin) interact with ?-casein via disulfide-thiol interaction (Lucey 2002; Lu et al. 2013) and become part the milk curd resulting in lower protein content in the acid whey.

1.2 Whey Utilization

Whey was considered as the waste for most of the time, especially when modern industrial mass production of cheese started in the nineteenth century. Whey waste is considered as the most polluted waste of dairy industrial with a biochemical oxygen demand () between 35 and 45 kg m-3 and chemical oxygen demand () of 60-70 kg m-3 (Mawson 1994). Untreated whey has been prohibited from direct disposal in the most regions of the world. Whey is a nutrient dense product, which contained about 50% of milk solids. The history of whey utilization is an excellent example of turning a gutter to a gold...