Soro de Leite

Whey Milk

Dairy Milk

Whey milk is a by-product obtained after curdling of milk, being the majority attained in cheese production. Depending on the type of cheese, two types of whey are distinguished:

  • Sweet whey: produced during the rennet cheese making, such as cheddar. The concentration of proteins is about 6-10 g/L.
  • Acid whey: obtained as a co-product of the making of acidic dairy products, such as cottage cheese. The content in proteins rounds 6-8 g/L.

Whey, sweet and acid, dried physical-chemical characteristics. Amount per 100 g:

  Soro doce Soro ácido
Energy 353 kcal 339 kcal
Water 3.19 g 3,51 g
Protein in dried weight 12,9 g 11,7 g
Total lipid (fat) 1.07 g 0.54
Fatty acids, total saturated 0,684 g 0,342 g
Cholesterol 6 mg 3 mg
Ashes 8.35 g 10,8 g
Carbohydrate (by difference) 74.5 73,4 g
Fiber, total dietary 0 g 0 g
Sugars, total including NLEA 74,5 g 73,4 g
Calcium, Ca 796 mg 2050 mg
Iron, Fe 0,88 mg 1,24 mg
Potassium, K 2080 mg 2290 mg
Phosphorus, P 932 mg 1350 mg
Sodium, Na 1080 mg 968 mg

Source: USDA Food Data Central (1, 2)

Whey is characterized by its high concentration of proteins (whey proteins) and low-fat content, containing peptides, lactose, lipids, vitamins, and minerals. Its chemical composition depends on the type of animal which produces the milk. Cow whey has around 18% of proteins, mainly ß-lactoglobulin and š¯›¼ – lactalbumin.

Considering the high content of proteins, the industry commercialized three different classes of whey highly rich in proteins in powder:

  • Whey Protein Concentrate (WPC): contains a high content of lactose, and low proportion of fat and over 70% of proteins.
  • Whey Protein Isolate (WPI): the protein content ups to 90% after fat removal.
  • Whey Protein Hydrolysates (WPH): aimed to ease digestion, some proteins are partially digested. The protein content is around 70 – 80%.

Though the food industry has generally considered whey a waste, its potential uses have a rising interest due to its content of bioactive compounds. Regarding whey powder, their production was higher than 2M tons in 2019 in the EU (FAOSTAT) (3, 4).

Considering the relevance of proteins in whole milk, the main bioactive compounds in whey are the proteins obtained after ultrafiltration process.

The most abundant protein is ß-lactoglobulin, in a proportion upper than 50%. After that, š¯›¼ – lactalbumin is in a percentage of 20%. Apart from these two main proteins, immunoglobulins and lactoferrin are essential glycoproteins in whey proteins with bioactive activity (5).

Amino acids from whey and minerals promote the synthesis of muscle proteins, helping to avoid fat accumulation, as whey proteins promote bone formation by activating osteoblasts. On the other hand, whey proteins can increase HDL levels and decrease TGs and cholesterol. Furthermore, whey proteins proved to have anticarcinogenic activity in different clinical trials, resulting in the regression of the tumor by increasing glutathione levels in healthy cells and decreasing its level in cancer ones, and increasing the activity of NK cells.

One of the most relevant activities of whey proteins is enhanced immunity. It takes place by decreasing Ala-transferase activity and increasing glutathione levels in tissue. These functions are significant in antiviral and anticarcinogenic activities5,6. Moreover, their suppressive activity oxidative stress is a key factor in some viral infections, such as HIV and hepatitis B, where the increased oxidative stress is a characteristic sign (5, 7, 8).

Specifically, ß-lactoglobulin is a retinol carrier, binds fatty acids and has antioxidant capacity. š¯›¼ – lactalbumin is a Ca+2 carrier, has immunomodulatory and anticarcinogenic activity by inducing apoptosis of tumor cells (BAMLET: Bovine α-lactalbumin made lethal to tumor cell), as improves cognitive symptoms related to stress, depression, and anxiety. Lactoferrin has antimicrobial, antiviral, anticarcinogenic (when it is co-administrated with baicalein, a cytotoxic flavonoid commonly used in this aim, the anticarcinogenic potential increased over 13 folds), anti-inflammatory, antioxidant, antithrombotic, antitoxin and immunomodulation capacity, as well as it acts as wound healing. Besides, some of these bioactive compounds are also a precursor of molecules that can be bound to different receptors. For instance, š¯›¼–lactalbumin and ß-lactoglobulin are precursors of lactokinins, which have ACE inhibitory activity, one of the most common virus entrances in the human organism, including SARS-CoV-2 (7, 8, 9, 10, 11).

Whey proteins are lately used in pharmaceutical and food technology to elaborate drug delivery systems to protect the inner bioactive compounds and improve their bioaccessibility and bioavailability. WPC and WPI can bind hydrophobic bioactive compounds through gelation, emulsifying, and barrier properties.

In particular, the ß-lactoglobulin has three binding sites to attach molecules like vitamin D, retinol, polyphenols, and fatty acids. This binding capacity could increase with heat, resulting in an enhancement of the encapsulation capacity. In addition, this capacity is convenient for masking off-flavors or enhancing other desirable flavors.

Protein structure varies with application heat. The use of 100 ºC is effective in spray-drying. At this temperature, proteins are unfolded, contributing to the creation of more binding points.

Whey proteins can act as biosurfactants and bioplasticizers, valuable properties to elaborate emulsions, which allows for encapsulating hydrophobic bioactive compounds o/w emulsions, like vitamin E. Recently, nanoemulsions have gained relevance as encapsulating systems, due to their kinetic stability, enhanced inner loading, improved drug solubility and bioavailability, and controlled bioactive compounds release. In this aspect, whey proteins proved to be more effective than other well-known natural plasticizers, such as Arabic gum.

Another delivery system to encapsulate bioactive compounds is hydrogels. When WPI is heated at 60ºC in water solution, forming spherical particles containing molecules like caffeine.

Aside from the drug technological aspects, whey is helpful as soil fertilizer and in producing biofuel through bacteria fermentation, like ethanol, biobutanol, biofertilizers, biomethane, etc.

All these current applications and future trends aim to reach eco-friendly approaches within the circular economy concept (12 - 19).