The liquid remaining after removal of the fat and casein from milk by
isoelectric or rennet-induced coagulation of the casein is called whey. The whey
contains about 90 % of the water of milk, ~98 % of the lactose, ~25 % of the protein
and ~50 % of the inorganic salts.
Whey definition: Liquid remaining after removal of fat and casein from milk by:
- Isoelectric coagulation (acid) → acid whey
- Rennet-induced coagulation → sweet (rennet) whey
Milk serum:
- Obtained by ultracentrifugation of skimmed milk (100,000 g, 1 h).
- Contains aqueous phase of milk with small casein micelles.
- Represents milk without structural changes.
Types of Whey
- Sweet Whey (Rennet Whey)
- Produced during rennet coagulation (e.g., Cheddar cheese).
- pH: 6.2–6.6
- Contains κ-casein-derived macropeptides and small amount of fat.
- Lower calcium and phosphate content than acid whey.
- Acid Whey
- Produced during acid coagulation (e.g., paneer, lactic casein).
- pH: ~4.6
- Higher in calcium, phosphate, citrate due to dissolution of milk salts.
- Essentially fat-free if made from skim milk.
Composition
| Component | Whole Milk | Rennet Sweet Whey | Cheddar Sweet Whey | Lactic Acid Whey | Mineral Acid Whey |
|---|---|---|---|---|---|
| Total solids (g/L) | 122.5 | 66.0 | 67.0 | 64.0 | 63.0 |
| Total protein (g/L) | 33.0 | 6.6 | 6.5 | 6.2 | 6.1 |
| Non-protein nitrogen (g/L) | – | 0.37 | 0.27 | 0.30 | 0.40 |
| Lactose (g/L) | 47.0 | 52.0 | 52.0 | 47.0 | 44.0 |
| Milk fat (g/L) | 35.0 | 0.20 | 0.30 | 0.30 | 3.0 |
| Minerals / Ash (g/L) | 7.5 | 5.0 | 7.5 | 7.9 | 5.2 |
| Calcium (g/L) | 1.2 | 0.40 | 1.6 | 1.4 | 0.50 |
| Phosphate (g/L) | 2.0 | 0.50 | 2.0 | 2.0 | 1.0 |
| Sodium (g/L) | 0.5 | 0.50 | 0.51 | 0.50 | 0.53 |
| Lactate (g/L) | – | 2.0 | 6.4 | – | – |
| pH | 6.7 | 6.4 | 6.4 | 4.7 | 6.4 |
Importance
- Once considered waste, now an important by-product due to:
- Valuable lactose and whey proteins.
- Used in production of whey powder, whey protein concentrate, lactose, infant formula, etc.
- World whey production ≈ 200 million tonnes/year containing:
- ~9 million tonnes lactose
- ~1.4 million tonnes whey proteins
Clarification of Whey (Pre-processing Step)
Clarification of Whey – Key Points
- Removal of curd fines:
- Curd fines are tiny bits of curd in whey.
- Methods: vibrating screen or centrifugal clarifier.
- Use: fines can be returned to cheese curd or processed cheese.
- Purpose: Removing fines makes further processing (like ultrafiltration) easier.
- Fat removal:
- Bulk whey usually contains ~0.3% fat.
- After clarification, fat is reduced to ~0.07%.
- Whey cream (~50% fat) is obtained and used to make whey butter, often for processed cheese.
- Phospholipids / lipoproteins:
- Come from milk fat globule membrane.
- Can block ultrafiltration membranes, reducing flux.
- Not removed by centrifugation alone.
- Removal methods: aggregation with CaCl₂, pH adjustment (~7.5), followed by sedimentation, centrifugation, or microfiltration.
- These lipoproteins have good emulsifying properties and are useful in food applications.
- Clarified whey products:
- Can be processed into beverages with:
- Good amino acid profile
- Isotonic nature (similar to blood)
- Flavoured with fruit juices or fermented into whey wine
- Can be processed into beverages with:
Utilization
- Whey proteins: Concentrated or isolated (e.g., WPC, WPI).
- Lactose: Used in pharmaceuticals, infant food, and as base for derivatives.
- Oligosaccharides (OS): New focus area – purified from whey for functional food use.
1. Whey Beverages
- Base: Clarified whey (isotonic with blood, rich in amino acids).
- Processing: Flavored with fruit juice or fermented → Whey wine.
- Status: Small-scale commercial production.
2. Concentrated and Dried Whey Products
(a) Non-hygroscopic Whey Powder
- Problem: Lactose (~70% of whey solids) crystallizes poorly → powder becomes sticky (hygroscopic).
Solution:
- Concentrate whey to 50–60% total solids.
- Seed with lactose crystals → induce crystallization.
- Dry → non-hygroscopic whey powder (stable storage).
(b) Demineralized Whey Powder
- Use: Infant formula (to match human milk composition).
- Process: Removal of salts using electrodialysis or ion-exchange.
- Reason: Bovine whey has 3–4× more minerals → causes renal load in infants.
(c) Delactosed or Delactosed–Demineralized Whey Powder
- For protein-rich whey powders:
- Crystallize and remove lactose by centrifugation/filtration.
- Optionally demineralize before spray drying.
Read More: Get more News from Dairy Sector
3.Lactose and Its Derivatives
Properties of Lactose
- Unique to milk; has:
- Low solubility, low sweetness, low hygroscopicity (if crystallized properly).
- Tendency to form supersaturated solutions.
- Problems → controlled crystallization essential in dairy powders.
Production
- Whey concentrated to 50–60% solids → seeded with crystals → lactose separated by centrifugation or filtration.
- High-purity lactose → recrystallization.
Major Derivatives
| Derivative | Process | Application |
|---|---|---|
| Lactulose | Isomerization of glucose to fructose (alkali) | Laxative, prebiotic, promotes Bifidobacteria |
| Lactitol | Reduction of lactose → sugar alcohol | Low-calorie sweetener, anti-cariogenic, emulsifier |
| Lactobionic acid | Oxidation of lactose | Sweet acidulant, used in organ preservation |
| Tagatose | Conversion of galactose → tagatose (alkali) | Low-calorie sweetener, prebiotic, GRAS status |
| Glucose–Galactose Syrup | Enzymatic hydrolysis by β-galactosidase | Sweetener (limited commercial use) |
| Galacto-oligosaccharides (GOS) | Enzymatic transgalactosylation | Prebiotic promoting Bifidobacteria |
| Fermentation Products | Fermentation of lactose/UF permeate | Ethanol (biofuel or beverage), lactic acid, yeast biomass |
| Indigenous Milk Oligosaccharides | Naturally present; isolated from whey | Functional ingredient for infant formula |
4.Whey Proteins
Major Components
- β-Lactoglobulin (~50%)
- α-Lactalbumin (~20%)
- Serum albumin, immunoglobulins, lactoferrin, enzymes (trace).
Forms & Products
| Product | Protein % | Process | Use |
|---|---|---|---|
| Lactalbumin | ~70 | Heat denaturation | Low solubility; food fortification |
| Whey Protein Concentrate (WPC) | 30–80 | Ultrafiltration/Diafiltration | Functional ingredient (foams, gels, emulsions) |
| Whey Protein Isolate (WPI) | 90–95 | Ion-exchange chromatography | Nutritional supplement |
| Fractionated Proteins | Variable | Ion-exchange or membrane separation | Nutraceutical and pharma applications |
Important Bioactive Proteins
- Lactoferrin: Iron-binding, antimicrobial, immune-enhancing.
- Lactoperoxidase: Antibacterial system (H₂O₂ + SCN⁻).
- Caseinomacropeptide (CMP): Anti-adhesive, antiulcer, bifidogenic, phenylketonuria-safe.
5.Whey Cheese
Principle: Recover whey proteins as cheese by heating whey + milk (pH 6, 90°C).
Examples:
- Ricotta (Italy), Anari (Cyprus), Manouri (Greece).
- Mysost / Gjetost (Scandinavia): caramelized sweet whey cheese (due to Maillard reaction).
Technology:
Centri-Whey process – denatured whey proteins recovered & added to next cheese batch.
UF pre-concentration – improves soft cheese yield.
Conclusions
Whey, which contains about 50 % of the total solids of milk and which was regarded
as a waste stream until recently, can serve as the raw material for the production of
a wide range of food products and food ingredients . Some of these are being produced profitably on a commercial scale. It is very likely that as new technologies are
developed, new and improved food ingredients derived from or based on whey will
be developed.
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