**3. Whey**

Whey is the remaining liquid that is produced after milk has been curdled and strained during the manufacturing of hard and semihard cheese. Depending on the process of casein precipitation, whey can be acid or sweet. Acid whey is formed when lactic acid bacteria are added to milk, and sweet whey is formed when the coagulation process is started by adding chymosin. Whey contains 90% of milk water and 50% of milk nutrients (**Table 2**). The major whey proteins are lactoglobulin, lactalbumin, serum albumin, immunoglobulins, and glycomacropeptide, while minor whey proteins include lactoperoxidase and lactoferrin among other proteins (**Figure 2**). These globular proteins are water soluble and contain all nine essential amino acids. **Tables 2** and **3**  show the composition and the vitamins present in whey, respectively. As it can see, whey is nutritional and, in spite of that, it is rarely used as such. One problem of using whey as a food is the high concentration of lactose that makes it difficult to digest especially for people intolerant to this carbohydrate (lactose intolerance). For lack of alternative uses, what happens is that it ends up being discarded as an effluent.

 The amount of discarded whey is difficult to quantify for obvious reason. The Food and Agriculture Organization (FAO) estimated that 40 × 106 l/day of whey are produced in South America, and the largest amount is discarded. In Argentina, the dairy industry produces around 11,338 × 106 l/year. Approximately, 41% is used for the production of cheese. This volume is equivalent to producing 4.015 × 106 l/year of whey. Fifty-five percent of that volume is used in part to feed animals and most of it is discarded as waste [4].

Whey has a negative environmental impact for both soils (due to mineral concentration) and water (due to lactose concentration) Although this is well known, what is observed in most cheese factories is that whey is discarded, without treatment or with a minimum treatment that fails to reduce the chemical oxygen demand (COD) to acceptable values (marcos murcia, personal communication). As a way to contribute to the search of solutions to this problem, our group seeks simple and economical alternatives to implement the use of whey. Below, two alternatives are discussed. First, we discuss the use of whey as a culture medium for yeast enriched in specific minerals and, second, a beverage elaboration carried out by a group of students from an agricultural school under our direction. This last experience, we believe, is important to visualize the problem and promote the local production.

## **3.1 Whey as a culture media to obtain selenium-enriched yeast**

The concentration of minerals present in the soil varies according to the geographical area. When a mineral is deficient in soils, livestock needs to be


**Table 2.**  *Whey composition [6].* 

#### **Figure 2.**

*Whey and curd protein composition.* 


#### **Table 3.**

*Vitamin concentration in whey [7].* 

supplemented. In the semiarid region, for example, a low concentration of selenium is observed [8]. Selenium is a cofactor of different enzymes such as glutathione peroxidase, which is involved in the antioxidant systems [9]. Also, selenium plays an important role in thyroid hormone synthesis [10]. Although the animal requirement for this mineral is low (300 μg/ dry matter) [11], selenium deficiency affects health and productivity. In cows, immunological suppression, placental retention, and decreased milk production have been reported associated with selenium deficient [12, 13]. In calves, diets deficient in selenium can cause a lethal condition called white muscle [14]. In order to find an alternative use to whey and at the same time offer a solution to the geographical areas that have selenium deficiency, we developed an economical culture using whey for the growth of yeast expressing lactase (Kluyveromyces DSM 11954). In this way, lactose is used to obtain seleniumenriched biomass. The whey-based culture medium (whey, (NH4)2SO4 and K2PO4) was supplemented with 20 μg/ml of Na2SeO3. At the end of the process, a total of 550 g wet cell weight (WCW) was equivalent to 85 mg/kg yeast selenium concentration. We then studied the effect of selenium-enriched yeast on calves. Six calves received 7 g of K. *marxianus* daily for 10 days (0.60 mg of selenium/animal/day). The supplement was offered individually to the animals, mixed in a small amount of grains. The animals showed no signs of rejection of the supplement. The level

of selenium in the blood was measured at Day 0 (before supplementation) and at Day 10 of treatment. The animals showed a significant increase in selenium blood (p < 0.005) (**Figure 3**) [6]. The use of whey as a culture medium is an inexpensive way to produce organic mineral supplements and at the same time reduces the environmental impact caused by the concentration of lactose in wasted milk by-product.

## **3.2 Whey as an isotonic, lactose-free beverage**

 Water footprint is the amount of direct and indirect water used to produce a product. It is estimated that a glass of milk (200 ml) requires 250 l of water (1 water l/1000 milk l) [15]. Taking into account that whey contains 90% milk water and is discarded without use, it is surprising that no further efforts are made to avoid the waste of such a volume of water. In addition to water, whey—as mentioned above—is a source of all essential amino acids. In Chapter 2 of this book, a fermented beverage process from whey is described. Here, whey is discussed as an isotonic drink. Whey has been promoted to be used as a sports drink as it contains all minerals to replace the electrolyte losses in sweat and carbohydrate [16, 17]. **Table 4** shows whey and commercial sport drinks mineral concentration. Isotonic drinks help prevent blood sodium dilution, a dangerous situation that occurs when athletes, especially in long distance events, drink water in excess [21]. Athletes need to replace water and minerals during and after an endurance event. Mineral losses by sweat include sodium, potassium, magnesium, chloride, and calcium. All of these minerals play important biochemical and physiological roles in the body. Another nutritional advantage of whey protein is that it has a high level of leucine (11.8% of total protein), which is important in sports supplementation when the objectives are muscle repair and growth. For example, Hamarsland et al. [22] reported higher blood leucine concentration and higher muscle protein rates after exercise when athletes consumed native whey, compared to milk or WPC-80. Reitelseder et al. [23] quantified labeled L-[1-13C] leucine in muscle and compared two different treatments: casein and whey ingestion. The authors observed no difference in protein muscle synthesis. These results are important because they valorize the use of whey compared to more costly technological processes. The point that must be emphasized is that the promotion of whey as a beverage will help reduce environmental pollution and develop a new commercial option to use a by-product that, otherwise, is considered a waste.

**Figure 3.** 

*Selenium blood levels (ppb) in calves before (Day 0) and the day after selenium-enriched yeast supplementation (Day 10).* 


#### **Table 4.**

*Mineral concentration in sweet whey, acid whey, and commercial sport drink Gatorade and Powerade.* 

 Keeping the idea of finding alternative products for whey, the authors of this chapter collaborated with students of Agriculture School (Escuela Agrotécnica Victorica, La Pampa, Argentina) to produce a lactose-free beverage based on whey. The students developed the product as part of their laboratory assignment for the Nutrition course. **Figure 4** shows the production flow, and **Figure 5** shows the final product. In this way, the students visualized and understood that with a simple process, what is considered a waste can be transformed into food.

**Figure 4.**  *Lactose-free whey beverage production flow.* 

#### **Figure 5.**

*Lactose-free whey beverage produced by students of Agriculture School Victoria (Escuela Agrotécnica Victorica, La Pampa, Argentina).* 
