How Pretreatment Transforms Whey Nutrition
For centuries, whey was considered little more than a waste product in cheese production—often discarded down the drain or used as animal feed. Today, this liquid remnant has undergone a remarkable image transformation, becoming a valuable reservoir of nutritional compounds used in everything from infant formula to sports nutrition. But what determines the quality of this increasingly precious byproduct? The answer lies in an often-overlooked factor: how the cheese milk is treated before coagulation.
Approximately 160 million tons of whey are produced globally each year as a byproduct of cheese manufacturing 6 .
Recent research has revealed that pretreatment processes applied to milk before cheesemaking significantly alter the composition and functionality of the resulting whey. This discovery has substantial implications for the nutritional quality of whey-based products and represents a fascinating intersection between food science, technology, and nutrition. As whey continues to gain popularity as a functional food ingredient, understanding these relationships becomes crucial for both producers and consumers alike 3 6 .
Whey is the liquid fraction that remains after milk coagulation during cheese production. It represents approximately 85-95% of the original milk volume and contains about 55% of the milk's nutrients, including soluble proteins, lactose, vitamins, and minerals. There are two main types of whey: sweet whey (pH 5.9-6.6) from rennet-coagulated cheeses like cheddar or gouda, and acid whey (pH ~4.3-5.0) from acid-coagulated products like cottage cheese or fresh cheeses 6 9 .
Whey proteins are particularly valued for their high nutritional quality and functional properties. The major protein components include:
Additionally, whey contains caseinomacropeptides (CMP), which are released from κ-casein during renneting and comprise about 20-25% of the protein in sweet whey. Approximately half of CMP is glycosylated (GMP), giving it unique biological activities 2 6 .
| Component | Sweet Whey | Acid Whey |
|---|---|---|
| pH | 5.9-6.6 | 4.3-5.0 |
| Protein (g/L) | 6-10 | 6-8 |
| Lactose (g/L) | 46-52 | 44-46 |
| Minerals (g/L) | 2.5-4 | 4.3-7.2 |
| Fat (g/L) | 5-6 | 5-6 |
Cheesemakers employ various pretreatment methods to increase cheese yield, but these methods significantly impact the resulting whey:
Heating milk to temperatures above normal pasteurization (often 80-100°C) causes partial denaturation of whey proteins. These denatured proteins interact with casein micelles and are retained in the cheese curd rather than passing into the whey. This results in whey with reduced protein content but elevated levels of non-protein nitrogen 1 4 .
This membrane process concentrates all milk proteins by removing water and some low-molecular-weight compounds. UF increases the protein density of cheese milk, leading to enhanced coagulation kinetics and higher cheese yield. The resulting whey has elevated whey protein content since proteins are retained in the retentate, but reduced non-protein nitrogen as some is lost in the permeate 2 3 .
Using slightly larger pore membranes than UF, MF selectively increases the casein content of milk while allowing some whey proteins to pass through to the permeate. This results in whey with reduced volume and altered protein composition, including an increased ratio of caseinomacropeptides to total protein 2 3 .
| Pretreatment | Effect on Whey Protein Content | Effect on Non-Protein Nitrogen | Effect on Caseinomacropeptides |
|---|---|---|---|
| High Heat (HH) | Significant reduction | Elevated | Slight increase |
| Ultrafiltration (UF) | Elevated | Reduced | Minimal change |
| Microfiltration (MF) | Significant reduction | Variable | Significant increase |
The pivotal research conducted by Outinen and colleagues examined how these pretreatment methods affect whey composition and functionality on an industrial scale. The team produced demineralized whey powders from milk that underwent different pretreatments: partially high-temperature heat-treated (HH), ultrafiltered (UF), ultrafiltered high-temperature heat-treated (UFHH), and traditional pasteurization as a reference (REF) 1 3 .
The experiments were conducted using Edam cheese production processes at a pilot plant with 1200 L vats. The protein concentration of the milk was standardized to ensure comparable conditions—34 g/kg for REF and HH milk, and 42 g/kg for UF and MF milks to increase cheese yields. The quantity of total protein in each vat was adjusted to the same level to ensure consistent cheese making conditions 2 .
The researchers employed sophisticated analytical methods to characterize the resulting whey and whey products:
The research yielded several fascinating discoveries about how milk pretreatment affects whey:
HH treatment significantly elevated the quantity of non-protein nitrogen in total protein but reduced the whey protein content of the resulting whey. The combination approach (UFHH) produced whey with significantly reduced volume and total solids compared to reference and HH wheys, though the chemical composition was relatively comparable 1 .
UF treatment increased the whey protein content in whey, while MF resulted in whey with distinctly different composition—most notably, an increased ratio of caseinomacropeptides to total protein. This is significant because while caseinomacropeptides are not inherent whey proteins, they represent a substantial portion of the nitrogenous compounds in whey 2 3 .
Perhaps most importantly, the research found no significant differences in the protein and amino acid compositions of whey products obtained by HH, UF and UFHH. However, whey obtained by ceramic and polymeric MF showed an inferior amino acid profile compared to traditional whey, particularly regarding essential amino acids important for infant nutrition 3 8 .
When it came to the functional performance of whey powders, the study revealed:
| Functional Property | High Heat | Ultrafiltration | Microfiltration | Reference |
|---|---|---|---|---|
| Viscosity | No significant difference | No significant difference | No significant difference | Baseline |
| Water-binding capacity | No significant difference | No significant difference | No significant difference | Baseline |
| Emulsifying capacity | No significant difference | No significant difference | No significant difference | Baseline |
| Heat stability | Moderate increase | Significant increase | Slight decrease | Baseline |
The findings from this research have significant implications for manufacturers of nutritional products, especially infant formula. Since MF whey was found to have an inferior amino acid profile compared to traditional whey, its use in infant nutrition may be limited. This is particularly important for essential amino acids like tryptophan and threonine, which play crucial roles in infant development 3 8 .
For other applications such as sports nutrition or general food processing, the functional similarities between whey from differently pretreated milk suggest that manufacturers may have flexibility in selecting whey ingredients based on availability and cost, without sacrificing performance in products like protein bars, beverages, or baked goods.
With approximately 160 million tons of whey produced globally each year as a byproduct of cheese manufacturing, the valorization of whey has important environmental implications 6 . Whey has high biological oxygen demand (BOD) and chemical oxygen demand (COD), meaning that if discarded improperly, it can cause significant water pollution. The findings from this research help dairy processors make informed decisions about milk pretreatment methods that will optimize both cheese yield and whey valorization potential.
For small and medium-sized dairy enterprises that lack the infrastructure to process whey into refined products, these findings highlight the importance of considering the entire production system—not just the primary cheese product but also the secondary whey stream—when implementing new technologies 6 .
The research enables dairy processors to optimize pretreatment methods for both cheese yield and whey quality, enhancing economic viability while reducing environmental impact.
Proper whey utilization prevents water pollution by reducing BOD and COD levels in wastewater, contributing to more sustainable dairy processing practices.
The groundbreaking work on milk pretreatment effects on whey composition has opened several promising avenues for future research:
Further investigation into how different pretreatments affect the bioactivity of specific whey components like lactoferrin, immunoglobulins, and glycosylated caseinomacropeptides.
Developing combined pretreatment approaches that maximize both cheese yield and whey quality, perhaps through sequential or integrated processing strategies.
While MF whey may be less suitable for infant nutrition, research could identify valuable applications where its unique composition provides functional or nutritional advantages.
Exploring how pretreatment methods affect the environmental footprint of cheese and whey production, potentially leading to more sustainable dairy processing practices.
As food scientists continue to unravel the complex relationships between milk processing, cheese yield, and whey quality, one thing becomes increasingly clear: the once-humble whey has transformed from a waste product into a sophisticated nutritional ingredient worthy of careful consideration throughout the cheese production process. This research exemplifies how modern food science can simultaneously address technical, nutritional, and environmental challenges to create a more sustainable and health-conscious food system 3 6 9 .
The next time you enjoy a protein shake or read the label on infant formula, remember that behind these modern nutritional products lies a fascinating science of transformation—where how we treat the milk fundamentally shapes the nutritional value of the whey it produces.