Developing a shelf-stable protein beverage is more difficult than simply adding protein to a beverage. Functional RTD beverage formulation involves precise management of protein composition, pH, stabilization and thermal treatment to maintain proper texture, taste and shelf stability throughout shelf life. This article will help beverage producers who are trying to develop high-protein beverages by outlining some factors of formulation and processing that should be considered to formulate RTD beverages successfully.
Ready-to-Drink (RTD) Protein Beverage Formulation: Shelf-Stable Guide
Developing a shelf-stable protein beverage is more difficult than simply adding protein to a beverage. Functional RTD beverage formulation involves precise management of protein composition, pH, stabilization and thermal treatment to maintain proper texture, taste and shelf stability throughout shelf life. This article will help beverage producers who are trying to develop high-protein beverages by outlining some factors of formulation and processing that should be considered to formulate RTD beverages successfully.
What Is a Functional Ready-to-Drink (RTD) Beverage?
A functional RTD beverage is any ready-to-drink beverage formulated in such a way that, besides quenching thirst provides health benefits, like protein, fibre, vitamins, minerals or electrolytes. RTD protein beverages have moved from sports nutrition to health and convenient nutrition areas, making protein beverage product development an active area of innovation.
In 2026, continued interest in protein is creating opportunities in dairy, plant-based, and wellness beverages. Effective protein beverage formulation must consider such factors as protein concentration, solubility, viscosity, flavour, mouthfeel, processing, and shelf life. [1]
How to Choose the Right Protein Ingredient for RTD Beverages
Protein selection is an important factor in protein beverage product development and should be guided by the target pH and thermal processing. RTD beverages in general can be categorised into two classes: acidic beverages (pH ≤ 4.6) and low acid beverages (pH > 4.6).
Examples of proteins used in high-protein RTD drink ingredients include:
- Whey Protein Concentrate (WPC), Whey Protein Isolate (WPI) and milk whey
- Milk Protein Concentrate (MPC), Milk Protein Isolate (MPI) and Micellar Casein
When choosing a protein, manufacture should consider the following factors:
- Solubility and dispersibility
- Heat and pH stability
- Protein concentration
- Taste and texture profile
- Protein aggregation/sedimentation propensity
- Compatibility with other ingredients
A whey protein isolate beverage can deliver a high amount of protein along with a low amount of fat and lactose but requires proper hydration, pH and stabilisation. [2]
Whey vs Milk Protein: Which Works Best in RTD Formulations?
Whey and milk proteins have different behaviors during processing. The most suitable option depends upon pH, thermal process, texture, and shelf-life considerations.
Table 1. Protein Selection and Formulation Considerations for RTD Beverages
|
Protein Type |
Best-Suited Application |
Key Advantage |
Main Consideration |
|
WPC |
Acidic beverages |
High protein with varying lactose, minerals and fat |
Controlled hydration and processing |
|
WPI |
High-acid beverages |
High protein, low fat and lactose |
Hydration, pH adjustment and stabilisation |
|
MPC |
Neutral or low-acid beverages |
Casein and whey fractions; creamy profile |
Hydration and heat stability |
|
MPI |
Neutral or low-acid beverages |
Milk-derived casein and whey proteins |
Stabilisation to reduce aggregation |
|
Milk-derived whey |
Protein RTDs requiring clean flavour |
Fat-free, clean flavour profile |
Process stability must be validated |
In whey protein beverage processing, controlled hydration before heat treatment is key. Milk proteins usually need more hydration and careful shear control; stabilizers like pectin may minimize aggregation. [2] [3]
How Does pH Affect Protein Stability in Shelf-Stable Beverages?
pH is an important factor in shelf-stable protein beverage formulation, as it affects the solubility, aggregation, flavour, microbiological safety, and thermal stability of proteins. High-acid beverages have an equilibrium pH of 4.6 or less upon completion of processing, while low-acid beverages have a higher pH than 4.6.
As pH approaches the protein’s isoelectric point, it may increase the risk of protein aggregation. Variations during processing can also impact RTD beverage protein stability via the Maillard reaction protein beverage pathway. Therefore, pH-stabilizing RTD drink methods could involve acidulants, buffers, mineral control and stabilizers.
High Acid vs Low Acid RTD Beverages: Key Formulation Differences
High acid vs low acid processing decisions influence protein choice, stabilization, thermal processing and shelf-life requirements. [4]
Table 2. Key Formulation Differences Between High-Acid and Low-Acid RTD Beverages
|
Formulation Factor |
High-Acid RTD Beverages |
Low-Acid RTD Beverages |
|
pH |
Generally, 4.6 or below |
Generally, above 4.6 |
|
Protein selection |
Whey proteins can be suitable when thermal stability is validated |
Milk proteins can be suitable with careful control of protein-mineral interactions |
|
Formulation focus |
Acidulants, protein solubility and heat stability |
pH stabilisation RTD drink, buffering, mineral management and stabilisation |
|
Processing |
May use hot-fill or another validated thermal process |
Requires a validated process to achieve commercial sterility |
|
Shelf stability |
Depends on pH, formulation and validated process |
Requires stringent thermal and process controls |
What Happens to Protein at 140°C During RTD Processing?
At high temperatures in some systems at or above 140°C, proteins could denature and react with other ingredients in the beverage. Based on the type of protein, its pH level and heating period, the protein may undergo aggregation, changes in viscosity, sedimentation, or flavour changes.
High temperatures during the process can also play a role in initiating the Maillard reaction in protein-beverages where there is interaction between the proteins and the reducing sugar. The aim would be to manage the changes such that the beverage is still considered to be of acceptable quality.
Thermal Processing Methods for Shelf-Stable RTD Drinks: UHT vs Retort
The choice of thermal processing will depend on the pH, type of protein, formulation, packaging and shelf life of the beverage.
H3 Table 3. Comparison of UHT and Retort Processing for Shelf-Stable RTD Beverages
|
Factor |
UHT |
Retort |
|
Process |
High temperature for a short time, followed by aseptic filling |
Thermal treatment of the sealed package |
|
Protein impact |
Shorter heat exposure can help limit protein changes |
Longer exposure can increase aggregation, viscosity and flavour changes |
|
Packaging |
Requires compatible aseptic beverage packaging |
Requires heat-resistant packaging and reliable seals |
|
Focus |
Protein stability, pH and aseptic compatibility |
Protein stability, thermal tolerance and package integrity |
UHT beverage processing or retort should be selected alongside formulation development because the process can influence protein, stabiliser, pH and packaging requirements.
How to Select Stabilisers for Protein RTD Beverage Formulation
Stabilizers such as pectin and gellan gum may be used to help manage aggregation, sedimentation, viscosity, and mouthfeel properties. This depends on the nature of the protein, pH, ionic strength, process parameters and texture desired.
In the case of shelf-stable protein beverage formulation, too much stabilizer will give a gummy texture, while insufficient stabilizer will lead to sedimentation and separation. Proper use of the stabilizers is required by regulatory bodies in the relevant markets. [5]
Packaging Selection for Aseptic and Retort RTD Beverages
Package selection should go together with beverage formulation and thermal processing method. The Aseptic beverage packaging should be able to keep its contents sterile after the filling process, whereas the one for retort products should withstand the thermal process.
Key considerations include thermal resistance, seal integrity, oxygen and light protection, material compatibility, distribution conditions and target shelf life. [4]
Functional RTD Beverage Formulation: Development Approach
Workflow can facilitate transition of manufacturers from formulation to a validated RTD beverage:
- Target identification: Consumer, protein level and functionality profile.
- Selection of ingredients: Protein, sweeteners, flavours, minerals and functional ingredients.
- Establishment of parameters: pH, hydration, stabilizers and buffer systems.
- Pilot processing validation: Thermal processing and protein stability.
- Product evaluation: Viscosity, sedimentation, sensory evaluation and packaging compatibility.
- Shelf-life validation: Microbiological, stability and shelf-life studies before scale-up.
The functional beverage formulation guide illustrates the importance of laboratory formulation followed by pilot scale validation and shelf-life validation.
Conclusion
Successful functional RTD beverage formulation relies on protein selection, pH, stabilisation, thermal processing, packaging and shelf-life validation. Validation at pilot scale allows manufacturers to obtain stable RTDs with high protein content and uniform nutritional and sensory qualities.
Food Research Lab offers beverage product development services, facilitating development and optimization of RTD beverages for formulation, processing, sensory evaluation, packaging and shelf-life performance.
Frequently Asked Question
A functional RTD beverage is formulated to provide benefits beyond hydration, such as protein, vitamins, minerals, probiotics or energy.
There are WPC, WPI, MPC, MPI, and micellar casein. It is common for whey protein to be used in acidic formulations while milk proteins and casein can be incorporated in neutral and low-acid beverages depending on the formulation.
It influences protein solubility, aggregation, flavour, heat resistance and microbiological safety of the product. Therefore, proper pH control is important for RTD beverage stability.
Common methods include UHT with aseptic filling technology, retort process, and if necessary, hot fill or pasteurization processes. The choice will depend on pH, formula, packaging, and shelf life.
Maillard reaction takes place between reducing sugars and amino acids during processing or storage of products. In protein RTD beverages, it may cause browning and decrease of product quality.
References
- Panou, A., & Karabagias, I. K. (2025). Composition, properties, and beneficial effects of functional beverages on human health. Beverages, 11(2), 40. https://doi.org/10.3390/beverages11020040
- Rovai, D., Watson, M. E., Barbano, D. M., & Drake, M. A. (2025). Consumer acceptance of protein beverage ingredients: Less is more. Journal of Dairy Science, 108(2), 1392–1407. https://doi.org/10.3168/jds.2024-25679
- Vogel, K., Carter, B., Cheng, N., & Barbano, D. M. (2021). Ready-to-drink protein beverages: Effects of milk protein concentration and type on flavor. Journal of Dairy Science, 104. https://doi.org/10.3168/jds.2021-20522
- Singh, R., Rathod, G., Meletharayil, G. H., Kapoor, R., Sankarlal, V. M., & Amamcharla, J. K. (2022). Invited review: Shelf-stable dairy protein beverages—Scientific and technological aspects. Journal of Dairy Science, 105, 9327–9346. https://doi.org/10.3168/jds.2022-22208
- Li, J., Ru, S., Zhu, L., Lu, Y., Wang, J., Zhang, Y., Dong, L., & Wang, S. (2026). Enhancing stability of vitamin-fortified protein beverages: Optimization of stabilizer type and concentration and screening of natural antioxidant combinations. Foods, 15(8), 1392. https://doi.org/10.3390/foods15081392
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