Whey is the by-product of cheese or paneer production and was viewed as a burdensome organic waste in dairy industries for a long time. It is estimated that whey contains more than half of the solids present in the original whole milk, including whey proteins (20% of the total protein) and most of the lactose, water-soluble vitamins and minerals. Thereby it is considered as a valuable by-product with several applications in the food and pharmaceutical industries.
In general, whey accounts for 85–95% of the milk volume and is characterised by chemical oxygen demand and biological oxygen demand ranging between 50–102 and 27–60 g L−1, respectively, which imposes very heavy burden of organic waste in the environment. Among the available treatment options, traditional activated sludge processing is economically not sustainable due to the high organic load of dairy effluents, and the consequent huge quantities of both oxygen required for aeration and excess sludge produced. Activated sludge treatment consumes an average of 900 kWh.d−1, including 100 kWh.d−1 for dewatering (using a filter press) and 800 kWh.d−1 for aerobic stabilization, accounting for 30% of the total energy required for aerobic treatment of dairy effluents. Thermo-catalytic treatment has also been proposed for whey valorisation, but the high temperature required (450-600°C) and the production of solids make such a process expensive.
That’s why biotransformation of such organic dairy wastes into value-added products is gaining interest owing to minimizing the overall waste of whey. The opportunities of development of whey based functional food, drinks and powder using the whey as major raw material have been explored by food industries during the past decade. The growing interest for whey and whey components is evident by the availability of a wide range of whey based value-added ingredients in energy drinks, infant formulas and protein concentrates in the market. Furthermore, the bio- utilization of whey is also gaining popularity at industrial scale for the microbial production of several value added products including lactic acid, biopolymers, bioethanol and vitamins e.t.c. Following are the examples of emerging trends for the utility of this valuable dairy waste.
1. Whey proteins as health supplements for humans
Whey protein is generally safe for most people to take, as long as they don’t have a dairy allergy. Thereby, addition of whey supplements in the diet is a healthy way to meet the nutritional requirements of the body. The whey protein consists of several beneficial milk proteins, including lactoglobulin, lactalbumin, immunoglobulins, bovine serum albumin, lactoferrin, lactoperoxidase, and glycomacropeptide e.t.c. Whey also include additional proteose-peptone components and low-molecular weight products formed by the enzymatic degradation of the caseins during the curdling of milk. Whey protein contains all essential amino acids, and it is a rich and balanced source of the sulphur amino acids that serve a critical role as antioxidants. It contains three to four times more bioavailable cysteine than other proteins. The presence of these health promoting components provide multiple benefits to the consumer. Here are some examples of health benefits of whey consumption that are supported by scientific studies:
1.1 Antimicrobial and Antiviral Activities
Whey contains several components which may protect against toxins, bacteria, and viruses. These components include immunoglobulins, lactoferrin and its peptide derivative, lactoferricin, lactoperoxidase, glycomacropeptide and sphingolipids. Furthermore, antimicrobial peptides may be generated from whey protein by proteolysis during gastrointestinal transit that protect us from harmful pathogens.
1.2 Immune Modulating Activity
Whey contains bioactive components that may enhance immunity and protect against some infections. In particular, three whey peptides are known to boost the immune system by increasing production of glutathione (lactoglobulin, lactalbumin and lactoferricin). Some growth factors are also present in whey that promote gut health and wound healing in the intestine.
1.3 Cardiovascular Health
Some of whey protein peptides exhibits anti-hypertensive effects. Thereby, these peptides help in lowering of high blood pressure. Fermented milk with whey protein concentrate could also lower triglyceride levels in the blood and improves vascular function in overweight and obese individuals.
1.4 Physical Performance
Whey protein is a rich source of branched chain amino acids, containing the highest known levels of any natural food source. Branched chain amino acids are important for athletes since unlike the other essential amino acids, they are metabolized directly into muscle tissue and these are the first ones used during periods of exercise and resistance training. Furthermore, whey protein are equally effective in stimulating muscle protein synthesis in elderly individuals also.
1.5 Weight Management
Whey proteins are the best protein for fat loss during energy restricted diets, when combined with exercise. It improves body composition and reduces waist circumference.
1.6 Bone Health
Milk basic proteins present in the whey protein fraction which increases serum osteocalcin concentrations. The active component in the whey protein also plays an important role in bone formation by activating the osteoblasts.
It is also observed that whey could improve the imbalance in brain serotonin levels and could possibly control the negative effects of chronic stress, fatigue, and delirium. In addition, whey protein is an excellent protein choice for the expectant mother who needs increased amounts of protein.
2. Whey as cattle feed
Studies has shown that ruminates can take in up to 30% of their intake of dry matter as liquid whey with good results. Whey can be fed to animals in a variety of forms, such as: Liquid whey, condensed whey, dried whey (partially delactosed whey) or as dried whey products. Liquid whey can also be added to straw at ensiling as a rehydration medium. Feeding of such whey to farm animal results in a savings of about one-third of the farmers’ total feed bill as well as improved health of the animals. Whey can also improve the feed palatability, texture, and dust control of feedlot rations. It provides a balanced nutrition of energy, protein, minerals, and a safety factor to compensate for poor or variable quality diets. Various scientific studies have demonstrated that when whey is given to lactating cows, milk yield, milk calcium and magnesium increases and the technological properties of milk improved.
3. Bio-utilization of whey in other industries
Whey and permeates contain all the minerals and trace elements required for the growth of micro-organisms. They also contain water-soluble vitamins, and thus constitute an excellent basal medium for any type of culture required by the fermentation industry, whereas it appears to be difficult to produce a culture medium with wide applications from plant based starchy materials without a preliminary treatment. Additionally, the main advantage of whey is its constant composition arising from its animal origin. Its competitors are plant products with composition varying according to the cultivar, the harvest date, the annual climatic variations, and pest attacks, as well as subsequent treatments and storage conditions. Moreover, whey is an industrial by-product which is immediately available, which does not require additional investment for production.
Different processes have been described for the fermentation of whey for the industrial scale production of food grade components including single cell protein (i.e. yeast), lactic acid, galactose, bacterial and yeast enzymes, proteins and vitamins. Besides, the production of bioethanol by the fermentation of whey lactose has also been developed in various biorefineries. It is also demonstrated that ethanol production from cheese whey is competitive against chemical synthetic processes; in addition, there is a 30-40% net energy gain. Another important area has opened up in the last few years for the production of bacterial biopolymers using whey fermentation. The biopolymers including Polyhydroxyalkanoates (PHA), polylactic acid (PLA), poly butylene succinate (PBS) are biodegradable or biobased polymers with at least one monomers produced by microbial conversions or microbial industrial biotechnology. The large scale application of PHA as a low biodegradable plastic has been hampered by its higher production cost. Hence, the utilization of whey as the growth media for industrial production provides a sustainable solution for producing diverse biopolymers with a low cost.
4. Whey protein as food packaging material
Whey proteins are proven to be an effective alternative coating and film for packaging applications. Whey continues to be a widely available and underused by-product from cheese- making, containing around 13% protein in dry matter. The whey-protein-based coatings are formulated using whey protein isolate as well as bio-based plasticizers and/or reactive additives, such as urea, to enhance thermoformability. The whey formulation is subsequently coated on a plastic substrate and dried. In this process step, the protein is denatured to form a
crosslinked network. The coated film is laminated into the final structure. The whey coating is highly environment friendly due to both bio-based and biodegradable properties.
Undoubtedly this dairy waste product is an untapped goldmine which could provide great economic advantages to the dairy farmers and dairy industries.
Lakhwinder Singh, Namita RokanaDepartment of Dairy Microbiology, College of Dairy Science and Technology,
Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana