How are protein yogurts made? A Deep Dive into Production Methods

December 7, 2025 •

5 min read

The market for high-protein foods continues to grow, with protein yogurt emerging as a key player due to its nutritional benefits. So, how are protein yogurts made to achieve their thick texture and increased protein content? This is achieved through specific methods that concentrate or add protein to the yogurt base, diverging from the process for traditional yogurt.

Quick Summary

This article explores the two main methods for making high-protein yogurt, detailing the process of ultrafiltration and the addition of powdered protein concentrates. It covers the fermentation, straining, and fortification steps that distinguish these products, explaining how a higher protein content and thicker texture are achieved.

Key Points

Straining and Filtration: High-protein yogurts like Greek yogurt and skyr are often made by straining or filtering cultured milk to remove excess whey, concentrating the natural protein.
Protein Fortification: An alternative method involves adding concentrated protein powders, like skim milk powder or whey protein isolate, to the milk before fermentation to boost protein levels.
Ultrafiltration Technology: Modern dairy manufacturers often use advanced ultrafiltration membrane technology to achieve precise protein and fat concentration, creating a very smooth mouthfeel.
Flavor and Texture: Both the type and amount of protein fortification, as well as the heat treatment of the milk, significantly influence the final texture, viscosity, and sensory properties of the yogurt.
Acid Whey Management: The straining method produces a byproduct called acid whey, which requires proper management and disposal, a challenge avoided by the fortification method.
Clean Label Focus: The ultrafiltration method can allow for 'clean-label' products with fewer additives, while fortified versions might require stabilizers to achieve a comparable texture.
Protein Sources: Proteins can be concentrated from milk (casein) or whey, or come from alternative sources like plants, each imparting different functional and sensory properties.

Introduction to Protein Yogurt Production

High-protein yogurts, including varieties like Greek and Icelandic skyr, are popular for their thick texture and rich nutritional profile. While all yogurts are made by fermenting milk with live cultures, protein yogurt production involves additional steps to increase protein content beyond that of standard yogurt. This is typically done through one of two primary methods: concentrating the milk either before or after fermentation, or by fortifying the milk with additional milk protein powders. The choice of method significantly impacts the final product's texture, taste, and consistency.

Method 1: The Straining or Filtration Process

The most traditional and widely recognized method for making high-protein yogurt, like Greek yogurt and skyr, involves concentrating the yogurt after it has been cultured.

Fermentation and Concentration

Preparation of Cultured Milk: The process begins like standard yogurt. Milk is pasteurized at a high temperature (around 90°C for several minutes) to denature whey proteins, which helps create a smoother gel structure. The milk is then cooled to a fermentation temperature (40-45°C), and a starter culture of live bacteria, typically Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, is added.
Fermentation: The bacteria ferment the lactose (milk sugar) into lactic acid, causing the milk's pH to drop and the proteins to coagulate, forming the characteristic yogurt gel.
Concentration by Straining or Filtration: Once the desired pH is reached, the yogurt is cooled. To concentrate the protein, it undergoes a straining process to remove the excess liquid, known as whey. This can be done in several ways:
- Traditional Straining: In smaller-scale or homemade production, this involves straining the yogurt through a cloth or mesh bag for several hours.
- Modern Centrifugation: Large-scale manufacturers use mechanical separators, or centrifuges, to spin and separate the solids from the whey more efficiently.
- Ultrafiltration: Advanced dairy processors use membrane filtration, called ultrafiltration, to gently and efficiently remove water, lactose, and minerals while retaining most of the protein and fat.

The Result of Straining

Because straining removes a significant amount of water, the protein becomes more concentrated, resulting in a much thicker yogurt. This process can yield a product with a protein content of 10% or more, compared to the 3-4% in regular yogurt. The whey that is removed can be a costly waste product for manufacturers, though some have developed uses for it, such as in animal feed or energy production.

Method 2: The Protein Fortification Method

An alternative, and sometimes more cost-effective, way to produce protein-rich yogurt is by adding extra protein to the milk before fermentation.

Protein Enrichment and Fermentation

Milk Standardization: Milk is standardized for fat and total solids content. This is where extra protein is added to the milk base. Common ingredients include:
- Skimmed Milk Powder (SMP): A traditional method for increasing total solids and thickening yogurt.
- Milk Protein Concentrate (MPC) or Whey Protein Isolate (WPI): These highly concentrated protein powders or liquids can be added to significantly boost the final protein content.
- Casein-Containing Ingredient: Micellar casein can be added to raise the casein-to-whey protein ratio, which can result in a thicker, firmer product without straining.
Heating and Homogenization: The fortified milk is then heated and homogenized. The heating step is crucial for denaturing proteins, which improves the final yogurt's texture and water-holding capacity.
Fermentation: Similar to the straining method, the fortified milk is inoculated with cultures and fermented until the target acidity is reached. Because the milk already has a high protein content, no post-fermentation concentration step is needed.

The Result of Fortification

This method avoids the issue of acid whey disposal and can be more efficient, especially for producing specific formulations. The resulting yogurt's texture and sensory properties can be different from a strained product, and may involve functional additives to ensure a desirable texture.

Comparison of Production Methods


Feature	Straining/Filtration Method	Protein Fortification Method
Processing Step for Protein Boost	Occurs after fermentation via physical separation of whey.	Occurs before fermentation by adding protein powders or concentrates.
Protein Source	Natural concentration of proteins already present in the milk.	Additional protein sources (e.g., SMP, MPC, WPI) are explicitly added.
Texture	Very thick, dense, and creamy due to the physical removal of liquid.	Can be thick, but may rely on additional stabilizers or specific protein types for texture.
Yield	Lower yield per gallon of milk, as whey is removed.	Higher yield per gallon of milk, as solids are retained.
Waste	Produces a byproduct of acid whey that requires disposal or treatment.	Minimizes or eliminates the production of acid whey.
Clean Label Potential	Excellent clean label potential, as fewer or no additives are needed for texture.	Potentially requires more additives to achieve desired texture and stability.

Other Factors Influencing Protein Yogurt

Several other factors are critical to producing high-quality protein yogurt:

Starter Cultures: The choice of bacterial culture affects the fermentation speed, final pH, and flavor profile. Different strains can produce a milder or tangier taste.
Heat Treatment: The pasteurization temperature and duration are carefully controlled. Higher heat treatments, such as 90°C for an extended period, are often used to denature whey proteins, which increases the yogurt's firmness and reduces syneresis (whey separation).
Flavoring and Additives: After fermentation and concentration, flavorings such as fruit, vanilla, or other sweeteners are added. Stabilizers like pectin or starches may be used in fortified yogurts to improve texture and prevent syneresis, though many brands opt for a cleaner label by relying solely on milk solids.

Conclusion

Creating protein-rich yogurt is a sophisticated process that goes beyond simple fermentation, allowing for a concentrated and nutrient-dense product. Whether through advanced ultrafiltration technology or the strategic addition of protein concentrates, manufacturers have multiple paths to achieve the high protein content and thick texture that consumers demand. Each method presents different advantages related to efficiency, yield, and the final product's characteristics, highlighting the innovation within the dairy industry. The result is a diverse market of products, from traditionally strained Greek yogurt to fortified and creamy alternatives, all designed to deliver a protein boost.

For further reading on industrial membrane filtration in yogurt production, see the Tetra Pak article: The magic of yoghurt filtration.

Frequently Asked Questions

The main difference is concentration. Greek yogurt is a strained yogurt, meaning the whey (liquid) is removed after fermentation, resulting in a thicker, denser product with a higher protein content. Regular yogurt is unstrained.

Not necessarily. While some flavored protein yogurts may have added sugars, the high-protein varieties themselves do not inherently contain more sugar. In fact, concentrating the yogurt through ultrafiltration can even reduce the lactose content.

Skyr is a traditional Icelandic cultured dairy product that is technically a fresh cheese, not a yogurt, though it's consumed similarly. It is thicker than Greek yogurt due to more extensive straining and is made from skimmed milk, while Greek yogurt is often made from a variety of milk fats.

Yes, you can make protein yogurt at home by starting with regular yogurt and straining it through a cheesecloth-lined sieve to remove the whey until it reaches your desired thickness. The longer you strain, the thicker and more concentrated it becomes.

Ultrafiltration is a modern manufacturing technique that uses a semi-permeable membrane to separate milk components. It allows water and lactose to pass through while retaining proteins and fats, thus concentrating the milk before or after fermentation to achieve a higher protein content and thicker texture.

Manufacturers add protein powder, such as milk protein concentrate or whey protein isolate, to increase the protein content of yogurt efficiently without the need for a straining process. This can result in a higher yield and avoids the disposal of acid whey.

Heating the milk to a high temperature before fermentation denatures whey proteins, which allows them to integrate into the casein network during fermentation. This process improves the final yogurt's texture, firmness, and water-holding capacity, preventing whey separation.